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Book of Abstracts
3rd Structural Integrity Conference
and Exhibition
(SICE 2020 e-Conference)
11-13 and 18-20 December 2020
Indian Institute of Technology Bombay, Mumbai, India
http://sice2020.in/
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Platinum Sponsor
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Platinum Sponsor
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Platinum Sponsor
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Gold Sponsor
Gold Sponsor
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Silver Sponsor
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Sr. No. Contents Page
No. 1. SICE2020 e-Conference Committees 8 2. Message from Indian Structural Integrity Society 9 3. ABOUT SICE 2020 10 4. Technical Theme and Symposia 11 5. Acknowledgements 12 6. Schedule 13-20 7. Plenary talks [PN] 21-27 10. Key note talks [TSXX_KNXX] 28-44
Themed symposium talks: Invited Talk [IN] Contributed[CN]
11. TS01 Structural Integrity of Additive Manufactured 45-47 12. TS02 Applications of Data Science 48-53 13. TS03 Creep and High Temperature Failure 54-62
14. TS04 Fracture and Fatigue in Materials and Structures 63-79 15. TS05 Fracture Mechanics at Multiple Length Scales 80-91 16. TS06 Fracture and Fatigue of Structural Adhesives 92-98 17. T07+TS26 Integrity of Concrete Structures Against Blast and Ballistic
Loading and Construction materials, and concrete and steel structures 99-101
18. TS09 Material Behaviour Characterization using Miniature Specimens 102-109
19. TS10 Material Behaviour Characterization Under High Strain Rate Loading 110-122
21. TS12 + TS16 Multiscale Modelling of Plasticity, Creep, Fracture, and Fatigue and Role in Material and Structural Integrity
123-140
22. TS13 Non-destructive Testing and Evaluation for Structural Integrity Assessment
141-143
23. TS14Nuclear Reactor Safety, Radiation and other Extreme Conditions 144-149
24. TS15+TS23 Reliability of coatings + Thin Film Deformation and Failure 150-158
25. TS17+ TS25-Reliability Aspects in Medical Devices and Implants Other - Biomechanics
159-165
26. TS20-Structural Integrity of Weldments and Welded Structures 166-169
27. TS21-Structural integrity of Gas Turbine Engine Materials 170-174
28. TS22-Damage and Failure modelling in Composite Materials 175-181
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SICE2020 e-Conference Committees
National Steering Committee:
• Dr. Ravi Chona, AFRL, USA
• Prof. Amol Gokhale, IIT Bombay, India
• Prof. Vikram Jayaram, IISc, India
• Dr. Vikas Kumar, DMRL, India
• Prof. Raghu Prakash, IIT Madras, India
• Dr. Karthik Prasad, DMRL, India
• Prof. Ashok Saxena, University of Arkansas, USA
• Dr. Ramasubbu Sunder, ITW-India, India
Local Organizing Committee – IIT Bombay
• Prof. Krishna Jonnalagadda (Convener)
• Prof. Alankar Alankar (Convener)
• Prof. Tanmay Bhandakkar (Convener)
• Prof. Nagamani Jaya Balila (Convener)
• Prof. Prasad Manepalli
• Prof. Prakash Nanthagopalan
• Prof. Anirban Patra
• Prof. Amber Shrivastava
• Prof. Parag Tandaiya
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Message from Indian Structural Integrity Society
Structural Integrity is at the core of any endeavor associated with safety critical engineering effort. The increasingly interdisciplinary nature of this discipline is well reflected in SICE2020, the third such Conference organized under the aegis of the Indian Structural Integrity Society and hosted by the Indian Institute of Technology, Bombay at Powai, Mumbai.
The first two meetings in 2016 in Bangalore and 2018 in Hyderabad were a resounding success, with more than 400 participants from over 15 countries between them. When IIT Bombay took up the organization of SICE2020, no one could have imagined the challenge that would be thrown up by a tiny virus that attacks structural integrity at the scale of human organism. Nevertheless, the dynamic team at IIT under the joint chairmanship of Profs. Krishna Jonnalagadda, Nagamani Jaya Balila, Alankar Alankar and Tanmay Bhandakkar have put together a rich conference programme.
SICE 2020 brings together well over a hundred participants from 7 countries, including 22 plenary speakers, over 40 invited speakers and close to 80 contributed papers. These will be presented across as many as 20 specialist symposia in line with the Conference theme aligned with Structural Integrity at Multiple Scales. Peer reviewed submissions will appear as a dedicated Springer publication.
To overcome the unforeseen challenge posed by COVID-19, SICE 2020 is organized across as many as five parallel on-line sessions spread across 6 days over the evening hours in India that should suit most global participants. And, to convert the unexpected problems posed by the pandemic into a virtual advantage, the Organizers have opened up the internet infrastructure to permit extended interaction between participants that extend beyond the formal sessions. All this at a Registration Fee that should be attractive to one and all.
SICE2020 may not have had the grandeur of its original venue, the Victor Menezes Convention Centre. But this appears more than made up by the eminent scientists from the world over and by a large number of participants from industry, academia and national laboratories, who have been brought together by the Indian Institute of Technology.
Please sign up if you haven’t done so, register, and enjoy SICE2020.
R. Sunder
President, Indian Structural Integrity Society
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ABOUT SICE 2020
The Structural Integrity Conference and Exhibition (SICE), is a flagship conference of the Indian Structural Integrity Society (InSIS). The 3rd edition of the regular conference was suppovsed to be conducted at IIT Bombay campus in December 2020. However, due to the existing COVID19 pandemic situation, it was decided to postpone the regular conference to a better time in near future. Considering that the 2nd SICE was conducted in 2018, the organizers at IIT Bombay in consultation with InSIS Executive Board (EB), have decided to conduct a ‘limited’ version of the conference, virtually, through video conferencing. Since, this decision, with the help of many colleagues and friends, the evolution of the conference has been interesting journey. The current program of the conference consisting of invited and contributory talks, and e-Posters, has come to fruition, due to the hard work and enthusiasm shown by Symposium Organizers, InSIS-EB members, Conference Organizers at IIT Bombay, and more importantly speakers and authors, who accepted our request at a short notice. In addition, the timely advice and support provided by Prof. Amol Gokhale (IIT Bombay), and InSIS-EB members, especially, Dr. R. Sunder (President, InSIS) and Prof. V. Jayaram (Vice-President, InSIS), has helped us shape this conference. Finally, the staff and student volunteers, have been working towards a smooth execution of this conference, and we hope that all the participants will have a great experience, in attending this virtual event, from the safety and comfort, of their respective locations. On a positive note, the advantage of this virtual conference is in its reach for those who cannot afford to attend and travel a regular conference.
We also take this opportunity, to thank all the members of the structural integrity community, who through their contributions have made this conference possible. We thank all the symposium organizers, InSIS international steering committee, IIT Bombay organizing members and authors, to make this conference a reality (albeit virtual!) in these unusual times. A few important names behind SICE2020 are listed below:
• Prof. Amol Gokhale – IIT Bombay
• Prof. Vikram Jayaram – Indian Institute of Science
• Dr. Ramasubbu Sunder – BISS, ITW
• Prof. Ashok Saxena – WireTech Cylinders LLC
• Dr. Vikas Saxena – Defense Metallurgical Research Laboratory
• Dr. Dheepa Srinivasan – Pratt & Whitney
• Prof. Raghu Prakash – IIT Madras Symposium Organizers:
• Dr. Dheepa Srinivasan
• Prof. Srikanth Gollapudi
• Prof. Ravishankar Kottada
• Prof. Viswanath Chintapenta
• Prof. Naresh Datla
• Prof. Prakash Nanthagopalan
• Prof. Manish Kumar
• Dr. Zafir Alam
• Prof. Eswar Korimilli
• Prof. Gaurav Tiwari
• Prof. Pritam Chakraborthy
• Prof. Anup Keshri
• Prof. Abhay Kumar Kuthe
• Prof. Amber Srivastava
• Prof. Anirban Patra
• Prof. Chandra Sekhar Yerramilli
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Technical Theme and Symposia
The technical theme of the conference for this edition is “Structural Integrity at Multiple Length Scales”. It is recognized that the integrity and failure are associated with the nucleation, growth and propagation of ‘defects’ in various materials and structures. The length scale at which these ‘defects’ dominate the response of a solid, small or large, determines its integrity. Therefore, the current conference includes, symposia that span a wide range of length scales from small crystal lattice to large structural components. Under such a broad theme, the conference includes the following symposia, which are ably led by our symposium organizers, listed next to the technical symposium name.
• Structural Integrity of Additive Manufactured Components – Dr. Dheepa Srinivasan
• Applications of Data Science – Prof. Alankar Alankar • Creep and High Temperature Failure – Prof. Srikanth Gollapudi • Fracture and Fatigue in Materials and Structures – Prof. Viswanath Chintapenta
• Fracture Mechanics at Multiple Length Scales – Prof. Nagamani Jaya Balila
• Fracture and Fatigue of Structural Adhesives – Prof. Naresh Datla
• Integrity of Concrete Structures Against Blast and Ballistic Loading AND
Construction materials, and concrete and steel structures – Prof. Prakash Nanthagopalan and Prof. Manish Kumar
• Material Behaviour Characterization using Miniature Specimens – Dr. Zafir Alam
• Material Behaviour Characterization Under High Strain Rate Loading – Prof. Eswar Korimilli, Prof. Krishna Jonnalagadda and Prof. Gaurav Tiwari
• Multi-scale Modelling of Creep, Fracture AND
Fatigue and Role of Multiscale Plasticity in Material and Structural Integrity Prof. Alankar Alankar and Prof. Pritam Chakraborty
• Non-destructive Testing and Evaluation for Structural Integrity Assessment - Prof. Krishna Jonnalagadda
• Nuclear Reactor Safety, Radiation and other Extreme Conditions – Prof. Alankar Alankar • Reliability of coatings – Prof. Anup Keshri • Reliability Aspects in Medical Devices and Implants and Biomechanics – Prof. Abhay Kumar
Kuthe
• Structural Integrity of Weldments and Welded Structures – Prof. Amber Shrivastava
• Structural integrity of Gas Turbine Engine Materials – Prof. Anirban Patra
• Damage and Failure modelling in Composite Materials – Prof. Chandra Sekhar Yerramalli
We hope that you enjoy the virtual talks and interactions, by speakers and participants.
From Conference Convenors:
Krishna Jonnalagadda Alankar Alankar Tanmay Bhandakkar Nagamani Jaya Balila
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Acknowledgements
We would like to take this opportunity to thank the president, vice-president and all the members of the
executive board of the Indian Structural Integrity Society for giving IIT Bombay the opportunity to host the
3rd Structural Integrity Conference and Exhibition-SICE 2020. They have constantly helped us with their inputs
and experience, in between their busy schedules for which we are grateful.
This conference would not be having the impressive list of invited speakers across more than 8 countries and
more than 100 contributed presentations/posters that we can boast of, without our symposium organizers.
We would like to thank them immensely for the time and resources that they have spared in bringing all the
people together, reviewing abstracts and conducting this conference smoothly, as well as being patient and
understanding with our lapses. We would like to express our sincere gratitude to all the Plenary, Keynote and
Invited speakers for taking time off their busy schedules to deliver their talks, while adjusting to the time
schedules of an online conference. Our students and colleagues will immensely benefit from their presence
and participation at SICE 2020.
We would like to thank all the authors who submitted their papers for consideration at SICE 2020.
Congratulations to those who were selected for full paper presentations as well as e-posters and we look
forward to listening to you all. No conference is a success without its attendees’ active participation. We would
like to thank all the participants for registering for SICE 2020 and joining us here.
No event can run without sufficient finances, not even an e-conference. While it has been a difficult year for
all, our industry friends have supported us immensely. In addition to best presentation and poster prizes, we
were able to offer free registrations to students for listening in to the conference talks. This is all because of
the generosity of our sponsors. We were also able to reach out to a larger audience because of them. They
have enriched our program by contributing technical talks and demonstrations in place of physical exhibits,
along with content on our webpage at: http://sice2020.in/exhibitors/. We would like to thank our Platinum
sponsors: Bruker Industron, Micro Materials, Dassault Systems, Gold sponsors: Zwick-Roell, BISS-ITW, Silver
Sponsors: DTS-Gleeble, for their generous contributions.
With the changed circumstances of this year and the entire conference going online, we could not have pulled
this through without an efficient team of website design and management. We would like to thank Mr Ulhas
Joshi, PowerSoft.Inc for providing us a platform for the same. We would also like to thank Mr Bansode and
SBI IITB for helping us with accounts. When the physical conference was being planned the IITB Administration
helped us in booking the venue and readying other logistics, which we unfortunately could not utilize.
Nevertheless, we are grateful for their support. We would also like to thank our publishing partner Springer, for
publishing the conference proceedings of SICE 2020. We are sure the authors will benefit immensely from this
opportunity.
While the planning for SICE 2020 started a while ago, it was the army of student volunteers who pitched in
during the last two weeks. This event would be an impossibility without them rising to the occasion and helping
us out with every task including registrations, scheduling, abstract booklets, poster lists and online session
coordination. We would like to thank each and every one of them here: Ashwini K Mishra, Soudip Basu,
Tanmayee More, Vaishali Garud, Mahavir Singh, Prakash Kumar Sahu, Pilla Kartheek, Deepesh Yadav, Tejas
Chaudhari and Hrushikesh Sahasrabuddhe.
On behalf of local organising committee, SICE 2020 Krishna Jonnalagadda Alankar Alankar Tanmay Bhandakkar Nagamani Jaya Balila
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Schedule
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Plenary talks
1. John Hutchinson 11th Dec 2020
2. Arun Shukla 12th Dec 2020
3. Huajian Gao 13th Dec 2020
4. K. Ravi-Chandar 18th Dec 2020
5. Rhys Jones 19th Dec 2020
6. Ioannis Chasiotis 20th Dec 2020
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Plenary Lecture-1
Dent imperfections in shell buckling: the role of geometry, residual stress
and plasticity
John W. Hutchinson
School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
Departures of the geometry of the middle surface of a thin shell from the perfect shape have long
been regarded as the most deleterious imperfections responsible for reducing the shell’s buckling
capacity. Here systematic simulations are conducted for both cylindrical and spherical metal shells
whereby, in the first step, dimple-shaped dents are created by indenting a perfect shell into the
plastic range. In the second step, buckling of the dented shell is analyzed, in axial compression for
the cylindrical shells and under external pressure for the spherical shells. Three distinct buckling
analyzes are carried out: 1) elastic buckling accounting only for the geometry of the dent, 2) elastic
buckling accounting for both the dent geometry and the residual stresses, and 3) a full elastic-plastic
buckling analysis accounting for both the dent geometry and residual stresses. The three analyzes
reveal the relative importance of the dent geometry and the residual stress, and they suggest a clear
indicator of whether plasticity is important in establishing the buckling load of the dented shells.
This work has been performed in collaboration with Prof. Simos Gerasimidis, Civil and Environmental
Engineering Department, University of Massachusetts, Amherst, MA 01003.
John Hutchinson received his undergraduate education in engineering mechanics at Lehigh University and his graduate education in mechanical engineering at Harvard University. He joined the Harvard faculty in the School of Engineering and Applied Sciences in 1964 and is currently the Abbott and James Lawrence Professor of Engineering Emeritus. Hutchinson and his collaborators work on problems in solid mechanics concerned with engineering materials and structures. Buckling, structural stability, elasticity, plasticity, fracture and micro-mechanics are all relevant in their research. Examples of ongoing research activities are: (1) efforts to extend plasticity theory to small scales, (2) instabilities in soft materials and shell structures, (3) fracture mechanics of tough ductile alloys, and (4) the mechanics of thin films, coatings and multilayers. Hutchinson is a Fellow of the ASME, a member of the US National Academy of Engineering and the US National Academy of Sciences, and a foreign member of the Royal Society of London. Further information and publications can be downloaded at http://www.seas.harvard.edu/hutchinson .
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Plenary Lecture-2
Dynamic Instability and Fluid Interaction in Underwater Structures under
Complex Loading Conditions
Arun Shukla
Simon Ostrach Professor
Co-Director, National Institute for Undersea Vehicle Technology
Department of Mechanical, Industrial and Systems Engineering
University of Rhode Island, Kingston RI 02881, USA
This talk will present recent experimental results on the dynamic structural integrity of designed
composite cylinders under complex loading conditions. Experiments are conducted to study the
mechanics of implosion of single hull and double hull structures with and without confining
conditions. Experiments are also performed to investigate sympathetic implosions and interaction
of an imploding cylinder with a nearby structure. State of the art pressure vessel facilities are used
to study the implosion process. These pressure vessels are outfitted with several windows to allow
the use of the 3D Digital Image Correlation (DIC) technique. The pressure histories generated by the
implosion event are captured from dynamic pressure transducers mounted close to the specimen
in all the experiments. These pressure histories are then related to real time deformations and
velocities occurring on the shells. High speed images are captured for better understanding of the
deformation mechanisms and collapse modes of the structures during the experiments. 3D-DIC
technique is utilized in conjunction with high speed photography to get quantitative information on
the deformation of the collapsing cylinders. Displacements, velocities, and variations in the pressure
profile are correlated to key stages of the collapse event to improve understanding of the failure
process during the implosion of underwater structures.
Dr. Shukla was elected to the Russian Academy of Engineering in 2015 and the European Academy of Sciences and Arts in 2011. He is a Fellow of the American Society of Mechanical Engineers, American Academy of Mechanics, Society for Experimental Mechanics (SEM) and Fellow of the Society for Shock Wave, India. He has received the Murray, Taylor, Frocht, Lazan and Tatnall Awards from SEM. In 2003 he served as the President of SEM. He was the Technical Editor of the international journal Experimental Mechanics and currently serves on the Editorial Boards of key engineering journals. Dr. Shukla served on the National Research Council on the United States National Committee on Theoretical and Applied Mechanics for eight years. Recently, he also served as member and the Chair of the Executive Committee of the Applied Mechanics Division of ASME. Dr. Shukla has received the Distinguished Alumnus Award from his alma mater, IIT Kanpur. In 2011, he served as the Clark B. Millikan Visiting Professor at Caltech and in 2019 as the Satish Dhawan Visiting Professor at IISc Bangalore. Along with his many Ph.D. and M.S. students, he has published more
than 400 papers in refereed journals and proceedings. Dr. Shukla has
authored and edited 10 books and has delivered numerous plenary and
keynote lectures.
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Plenary Lecture -3
Engineer metals with internal interfaces for enhanced mechanical
performance Huajian Gao
Distinguished University Professor
Nanyang Technological University
Email: [email protected]
Gradient microstructures with internal interfaces exist ubiquitously in nature and are increasingly
being introduced in next generation engineering materials with unprecedented mechanical
properties. Here we discuss some recent studies on engineering metals with nature-inspired internal
interfaces and gradients. First, metals typically suffer from cumulative, irreversible damage to
microstructure during cyclic deformation, leading to limited fatigue life along with cyclic responses
that are unstable and history-dependent. Through atomistic simulations and variable-strain-
amplitude cyclic loading experiments at stress amplitudes lower than the tensile strength of the
metal, we report a history-independent and stable cyclic response in bulk copper samples with
microstructures mimicking the highly oriented nanoscale twin boundaries in conch shells. We
demonstrate that this unusual cyclic behaviour is governed by an unusual type of dislocations called
correlated ‘necklace’ dislocations (CNDs). Furthermore, we show that introducing gradient
nanotwinned structure in metals results in extra strengthening that defies the classical rule of
mixture theory. This phenomenon is attributed to another new type of dislocations called bundles of
concentrated dislocations(BCDs).
Huajian Gao received his B.S. degree from Xian Jiaotong University of China in 1982, and his M.S. and Ph.D. degrees in Engineering Science from Harvard University in 1984 and 1988, respectively. He served on the faculty of Stanford University between 1988 and 2002, where he was promoted to Associate Professor with tenure in 1994 and to Full Professor in 2000. He was recruited to become Director at the Max Planck Institute for Metals Research between 2001 and 2006, and then Walter H. Annenberg Professor of Engineering at Brown University from 2006-2019. At present, he is one of 6 Distinguished University Professors at Nanyang Technological University and Scientific Director of the Institute of High Performance Computing in Singapore.
Professor Gao’s research has been focused on the understanding of basic principles that control mechanical properties and behaviors of materials in both engineering and biological systems. He is the Editor-in-Chief of Journal of the Mechanics and Physics of Solids, the flagship journal of his field. He has been elected to US National Academy of Sciences, US National Academy of Engineering, American Academy of Arts and Sciences, German National Academy of Sciences, Chinese Academy of Sciences and Academia Europaea.
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Plenary Lecture-4
Exploring the mechanical behavior of materials through experiments Krishnaswamy Ravi-Chandar
M.C. (Bud) and Mary Beth Baird Chair
University of Texas at Austin
The most exciting role of experimental mechanics is in discovery – the uncovering and
understanding of phenomena. Such discovery experiments require careful attention both to
the design of experiments and to the development of appropriate tools for diagnostics. Of
course, the basic ideas go all the way back to Galileo. In this presentation, I will describe
three examples of this process through clean experiments related to constitutive and failure
behavior of materials: (i) dynamic strain localization and fragmentation under high strain-
rate loading in ductile materials; (ii) multiscale experiments on damage nucleation and
failure under quasistatic loading in polycrystalline metallic materials; (iii) nucleation and
growth of cavities and cracks in elastomers
Professor Krishnaswamy Ravi-Chandar holds the M.C. Bud and Mary
Beth Baird Endowed Chair at the Department of Aerospace Engineering
and Engineering Mechanics at the University of Texas at Austin. He is the
Editor-in-Chief of the International Journal of Fracture (2000 – present).
He served as President of the International Congress on Fracture (2005-
2009), and the American Academy of Mechanics (2011-2012), and as
Chair of the Applied Mechanics Division of the ASME, and the US National
Committee for Theoretical and Applied Mechanics (2019-2020). He
received the Murray Medal from the Society for Experimental Mechanics
in 2004, the Drucker Medal from the American Society of Mechanical
Engineers in 2015, and the Prager Medal from the Society of Engineering
Science in 2020. He is a Fellow of the American Society of Mechanical
Engineers, Society for Experimental Mechanics, the American Academy
of Mechanics, the International Congress on Fracture and the Indian
Structural Integrity Society
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Plenary Lecture-5
On the Mechanics and physics of AM and COLD spray build parts and their
use in limited life UAV structures and as airframe replacement parts Rhys Jones
Emeritus Professor
Department of Mechanical and Aerospace Engineering, Monash University, Clayton
One of the challenges in aircraft sustainment is to develop AM replacement parts for legacy
aircraft. This is particularly important to increase aircraft availability, to minimize logistics
problems, and for fixed and rotary wing aircraft that operate in aggressive environments, i.e.
in a marine environment, off carriers, etc. Such parts can be certified under the “limited life”
approach outlined in the US Joint Services Structural Guidelines JSSG2006, Structures
Bulletin EZ-19-01, and MIL-STD-1530D. The USAF have also adopted the concept of using
AM to rapidly deploy limited-life unmanned air platforms (attritable aircraft). Unfortunately,
crack growth in AM and cold spray built materials can be dependent on the build direction,
the fabrication process, and post processing. This paper reveals how to account for these
effects in a fashion that is consistent with both the fundamental physics of the problem and
with the governing crack tip parameter. We then illustrate how to perform the durability
analyses required in USAF Structures Bulletin EZ-19-01 for the airworthiness certification of
limited life parts. In this context, the damage tolerance and durability analyses presented in
this paper suggests that AM and cold spray built parts are attractive both for use as
replacement parts for legacy aircraft, and for attritable unmanned aerial vehicles (UAV’s).
The raises the potential for assessing the trade off between: Weight, cost of fabrication,
choice of AM process, choice of the post processing options, and their effects on the
economic life of the airframe.
Professor Rhys Jones AC is a Companion of the Order of Australia: “For eminent
service to mechanical and aerospace engineering, and to education as an
academic, researcher and author, particularly in the area of aircraft structural
mechanics, corrosion repair and airworthiness”. The Order of Australia replaced
a “Knighthood” in the Australian Honours systems. It is the highest honour that
can be given to an Australian Citizen. In 2008 his seminal paper on thermo-
elasticity was chosen as one of the Top Ten Defence Science publications in the
period 1907-200
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Plenary Lecture-6
Engineered Multifunctional Interfaces
Ioannis Chasiotis
Caterpillar Professor of Aerospace Engineering
Aerospace Engineering, University of Illinois at Urbana-Champaign
Engineered micro and nanostructured interfaces enable new forms of macroscale material
behavior, which are not possible through monolithic materials. For instance, compliant
interfaces comprised of nanowires or nanotubes alleviate thermal mismatch stresses while
introducing system-level functionalities, such as control of permittivity and impedance,
enhanced heat and charge transfer, energy storage, etc. In the context of microthermal
interfaces, films of dense and orderly arrays of Cu nanosprings provide tunable mechanical
compliance combined with high thermal conductivity. As a result, such nanoarchitected Cu
films, fabricated via Glancing Angle Deposition (GLAD), possess the compliance of
polymers but orders of magnitude higher thermal conductivity than polymers. This unique
combination of mechanical and thermal properties makes it possible to populate the largely
empty space in the materials selection chart of thermal conductivity vs. elastic modulus.
Control of the geometric features and materials comprising such discrete interfaces is an
effective means to design traction-separation laws of interfaces in a variety of applications.
For instance, the orientation and geometry of GLAD nanostructures in interlayers between
elastomeric substrates and hard coatings can be utilized to control surface wrinkling and
impart wrinkling anisotropy which is not attainable in isotropic material systems. Finally, the
application of Si-based GLAD nanospring layers as multifunctional films for embedded
power and stress control in high capacity Li+ anodes will be presented.
Ioannis Chasiotis is the Caterpillar Professor of Aerospace Engineering at the
University of Illinois at Urbana-Champaign and the editor-in-chief of Experimental
Mechanics. He received his Ph.D. and M.S. degrees in Aeronautics from the California
Institute of Technology, and his Diploma in Chemical Engineering from the Aristotle
University in Thessaloniki, Greece. His research focuses on mechanics of materials
and interfaces at small length scales. He is a recipient of the NSF Presidential Early
Career Award for Scientists and Engineers (PECASE), the Society of Engineering
Science Young Investigator Medal, the ASME Thomas J.R. Hughes Young
Investigator award, the Society for Experimental Mechanics A.J. Durelli award, etc.
He is a fellow of the American Society for Mechanical Engineers and the Society for
Experimental Mechanics.
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Keynote Talks
1. Michael Gorelik
11th Dec
2. Sunder Atre
11th Dec
3. Atul Chokshi
11th Dec
4. Raman Singh
12th Dec
5. Christoph Kirchlechner
13th Dec
6. Abass Bramiah
18th Dec
7. Vikas Tomar
11th Dec
8. Ghatu Subhash
12th Dec
9. C. S. Upadhyay
19th Dec
10. Ashok Saxena
12th Dec
11. B. K. Dutta
12th Dec
12. Sanjay Sampath
18th Dec
13. Vikram Deshpande
13th Dec
14. Sankara Narayanan
13th Dec
15. B. V. A. Patnaik
20th Dec
16. Anthony Waas
19th Dec
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TS01 Keynote Lecture
Lessons Learned” for Structural Alloys and Implications for Metal
Additive Manufacturing F&DT Considerations
Dr. Michael Gorelik
Chief Scientist, Fatigue and Damage Tolerance
Federal Aviation Administration, USA
Metal Additive Manufacturing (AM) is still a relatively new technology, with very limited
full-scale production and field experience in Aviation. The expanding use of AM, heading
towards the safety-critical applications, prompts F&DT considerations, both to ensure
product safety and to meet certification requirements. Most of the current “lessons
learned” for AM are based on either academic R&D, or industry development work (the
latter typically being proprietary). While such work is very important and helps with
identification of AM-specific properties and attributes and the means of addressing them
in the context of Q&C, it cannot replace decades of production and field experience for
more conventional forms of structural alloys, e.g. castings, wrought products, powder
metallurgy etc. Thus, examining some of the relevant lessons learned for such legacy
alloy systems can help with shaping the appropriate F&DT framework for metal AM
materials. These considerations, illustrated by specific examples, will be discussed in
the presentation.
As the Chief Scientist for Fatigue and Damage Tolerance at the FAA, Dr. Gorelik supports various certification programs, development of advisory materials and rule making activities across the Agency, training of FAA personnel, R&D and evaluation of new technologies, and engagement with aerospace industry, SDOs and government agencies. His prior industry positions included Engineering Fellow and Life Methods Manager at Honeywell Aerospace, and Six Sigma Master Black Belt at GE.
Dr. Gorelik has over 25 years of experience in the areas of fracture mechanics, fatigue, damage tolerance, additive manufacturing, characterization and modeling of material behavior, probabilistic methods, prognostics and health management. He currently serves as the Chair of the Structures and Dynamics Committee of IGTI (ASME) and Co-Chair of Emerging Technologies Task Group of MMDPS.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS01 Keynote Lecture
Metal Fused Filament Fabrication of Ti-6Al-4V: Materials, Processing &
Design Sundar V. Atre
Endowed Chair of Manufacturing & Materials
University of Louisville
Building end-use functional metal parts from metal fused filament fabrication (MF3) is an
emerging extrusion process in additive manufacturing. MF3 involves extrusion of polymer
filaments that are highly filled with metal powder to print three-dimensional parts, followed by
debinding and sintering to eliminate polymer and get a fully dense metal part. Material properties, part design and processing conditions have a significant influence on the quality of printed MF3
parts. Part distortion and dimensional variations are significant quality challenges that hinder the
acceptance of printed parts in potential functional applications. However trial-and-error
experiments to find the best conditions for defect avoidance are time-consuming and expensive.
Hence, computational simulation and design solutions are required for MF3. This paper
investigates the quantitative influence of material properties on printed part quality using a
thermo-mechanical simulation platform for MF3. The simulation results of a Ti-6Al-4V filled
polymer were compared to experiments to effectively explore the material-process-geometry
space
Sundar V. Atre is the Endowed Chair of Manufacturing & Materials at the University of Louisville where he is Director of the Additive Manufacturing Institute of Science & Technology (AMIST). Sundar obtained his PhD degree in Materials Science and Engineering from the Penn State University, following a B.Tech. degree in Chemical Engineering from the Indian Institute of Technology, Madras. Sundar’s research focuses on the interactions between materials, manufacturing and design and has generated over 200 publications, 7 issued and licensed patents, and over 20 intellectual property filings. Sundar has led a start-up company and helped establish 8 other new businesses during the last 18 years. One company, Home Dialysis Plus, focusing on portable kidney dialysis, received over $185 million in private investment.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS03 Keynote Lecture
Current understanding of creep in polycrystals: Extension to advanced
ceramics, nanocrystals and high entropy alloys Atul H. Chokshi
Department of Materials Engineering, Indian Institute of Science, Bangalore 560 012
The time-dependent plastic deformation of materials, termed creep, is an important limitation for structural applications at high temperatures. The scientific studies on creep can be traced back to over a century. The phenomenological and micromechanisms based approaches have led to a good understanding of factors influencing creep. Experimental values of n, p and Q (the activation energy related to diffusion) are compared with those predicted by theoretical models to identify possible creep mechanisms, together with appropriate microstructural characterization. Diffusion creep mechanisms which depend on the grain size, such as Nabarro-Herring and Coble creep are associated with n=1, and p= 2 and 3, respectively. In contrast, intragranular deformation processes such as dislocation glide and climb involve p=0, and n=3 and 5, respectively. The general understanding of creep will then be extended to three different classes of advanced materials: ceramics, nanocrystals and high entropy alloys. In ceramics, the need to consider charge neutrality may involve the process of ambipolar diffusion, where diffusion creep is controlled by the slower moving species diffusing along the faster path. There is not much information available on creep in nanocrystals, with grain sizes below 100 nm, where potentially new mechanisms can be activated. High entropy alloys are a new class of multiple element concentrated solid solution alloys. Recent experimental results and possible new approaches to understanding creep in such materials will be discussed.
Prof. Atul Chokshi received his Bachelor of
Technology degree in Metallurgical Engineering
from Indian Institute of Technology, Madras, in
1980. Subsequently, he received M.S. and Ph.D.
degrees from University of Southern California, Los
Angeles in 1981 and 1984, respectively. He is
currently a Professor with the Department of
Materials Engineering, Indian Institute of Science,
Bangalore. His main research interests are in
engineering mechanical properties of materials
and he is well known for his pioneering research in
the area of mechanical behavior of nanocrystalline
materials, deformation mechanisms in
superplasticity and creep of ceramics.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS04 Keynote Lecture
Understanding Corrosion and Corrosion-assisted Cracking of Magnesium
Alloys for their Innovative Use as Bioimplants
Raman Singh (R.K. Singh Raman)
Department of Mechanical & Aerospace Engineering
Department of Chemical Engineering
Monash University (Melbourne), VIC 3800
Magnesium (Mg) alloys possess great potential for their use as temporary implants such as pins,
wires, screws, plates. Use of Mg alloys will completely avoid the cumbersome procedure of second
surgery (which is required when such implants are constructed out of traditional materials such as
titanium alloys or stainless steels). However, Mg also has limitations as a temporary implant
material, viz., their unacceptably high corrosion rates and concurrent hydrogen evolution, and stress
corrosion cracking (SCC) and/or corrosion fatigue (CF) under the simultaneous action of the
corrosive human-body-fluid and the mechanical loading. The presentation will provide an overview
of SCC and CF of different Mg alloys in simulated body fluid (SBF) and the associated fracture. The
presentation will also discuss the need of investigations under such mechano-chemical conditions
that appropriately simulate the actual human body conditions, and present new data generated
under such conditions in the presenter’s research group.
Professor Raman Singh’s primary research interests are in the relationship of
Nano-/microstructure and Environment-assisted degradation and fracture of
metallic and composite materials, and Nanotechnology for Advanced Mitigation
of such Degradations. He has also worked extensively on use of advanced
materials (e.g., graphene) for corrosion mitigation, stress corrosion cracking,
and corrosion and corrosion-mitigation of magnesium alloys. His professional
distinctions and recognitions include: Editor of a book on cracking of welds,
Editor-in-Chief of two journals, member the Editorial Boards of a few journals,
leader/chairperson of a few international conferences and regular
plenary/keynote lectures at international conferences, over 225 peer-reviewed
international journal publications, 15 book chapters/books. He has supervised
49 PhD students.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS 05 Keynote Lecture
Why are nanotwinned systems damage tolerant? Insights from in situ
nanomechanics Christoph Kirchlechner
Professor – Head of the IAM-WBM
Institute for Applied Materials, Karlsruhe Institute of Technology (KIT), Germany
Nano twinned (NT) materials are known for their high strength and ductility, i.e. damage
tolerance. The fundamental origin of the damage tolerance of NT systems is yet not fully clear.
To shed light on the damage tolerance we (i) measured the stress for dislocation slip transfer
through a single coherent Σ3 twin boundary in copper (N Malyar et al. Acta Mater 2017) and (ii)
we extend this knowledge to multiple coherent Σ3 twin boundaries in Ag (MK Kini et al. Acta
Mater. 2020). While the slip transfer behaviour can explain the high strength, it is not suited to
explain the high ductility in NT materials. Hence, to understand this damage tolerance we (iii)
finally look into the role of dislocation nucleation from twin boundaries. The later study might
unravel the origin for damage tolerance in NT systems.
The talk will introduce experimental nano- and micromechanics comprising pillar compression
in the SEM, synchrotron Laue diffraction as well as pop-in statistics using spherical
nanoindentation
Christoph Kirchlechner studied material science
and received his PhD at the University of Leoben in
Austria. Subsequently, he held an Assistant
Professor position at the University of Leoben
(2012-1018) and was group leader for in situ nano-
and micromechanics at the Max-Planck-Institut für
Eisenforschung in Düsseldorf, Germany (2013-
2020). Since 2020, he is head of the Institute for
Applied Materials – Materials- and Biomechanics
(IAM-WBM) at the Karlsruhe Institute of
Technology. His research focusses on a
mechanism-based understanding of plasticity,
fatigue and fracture at the micron scale,
particularly at single interfaces. For this purpose,
he is using electron microscopy as well as
advanced synchrotron techniques. He was
awarded with a promotion sub auspiciis
praesidentis rei publicae (Austrian President) and a
Heinz Maier-Leibnitz prize (German Research
Foundation).
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS07 Keynote Lecture
Contact Explosion Effects on Reinforced Concrete Columns. Abass Braimah
Vice Chancellor, Tamale Technical University, Ghana
The vulnerability of reinforced concrete columns to explosion effects and the attendant
likelihood of progressive collapse has seen increased research activity on the response of
columns to blast loading. Most of the research has however concentrated on the response of
columns to far-field explosion effects with many researchers investigating the effects of
explosions on columns through numerical modelling techniques.
This presentation will highlight the dearth of experimental research data on the response of
columns to near-field explosion effects and present an experimental and numerical modelling
program to investigate the response of reinforced concrete columns to contact explosion
effects.
Abass Braimah is the Vice Chancellor of Tamale Technical University in Ghana. Before his appointment as
Vice Chancellor he was a Professor of Blast Load Effects and Extremely Load effects on Critical
Infrastructure in the Department of Civil and Environmental Engineering (Infrastructure Protection and
international Security Program), Carleton University, Canada. He completed his PhD at Queen’s University
at Kingston and worked in Structural Engineering consulting and at the Canadian Explosives Research
Laboratory (CERL).
His research interest is in the area of critical infrastructure protection, especially extreme load effects on
structures. He is particularly interested in research on the response of reinforced concrete columns and
reinforced concrete walls to close-in explosions; blast risk assessment and vulnerability assessment of
critical infrastructure systems. He is also interested in the use of advanced composite materials in
structural engineering; especially the use of advanced composite materials for retrofit of structures
subjected to extreme loading.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS 10 Keynote Lecture
Interface Level Shock Regime Rate Dependent Mechanical Properties and
Related Implications in Larger Material Architecture Settings
Abhijeet Dhiman1 and Vikas Tomar2 1Graduate Research Assistant, 2Lead Investigator
Purdue University, West Lafayette, IN-47907, USA [email protected], [email protected]
Role of interfaces at high strain rates approaching shock loading in materials is a challenging
problem to solve. Under shock loading one can use an equation of state to describe overall
homogeneous material behavior. At non-shock high strain rate loads one can use viscoplasticity
driven constitutive models to describe material behavior. However, as one dives deeper into
analyzing a material response to high strain rate loading, at the localized scale of interfaces local
strain rates and strains are significantly different from globally applied strain rates. As such
locally material can deform in significantly different and unexpected ways than what is expected
using a localized homogeneous equation of state or a viscoplasticity model. This issue bears
significant attention when one might want to change localized chemistry/chemical composition
of materials to change overall response to impact loading. Interfacial Multiphysics Lab (IML) at
Purdue has been performing time resolved interface level stress and thermal measurements
under impact loading using nanomechanical Raman spectroscopy coupled with numerical
advancements in the molecular simulations at experimental strain rates. This presentation
presents key insights obtained from interface level stress wave measurements during shock
loading of energetic materials. A new material viscosity model that considers shock level local
loading is Presented
Prof. Tomar started as an assistant professor in January 2006 after
graduating from Georgia Tech with PhD in mechanical Engineering in
December 2005. He was promoted to full professor in 2016 at Purdue
University.Professor Tomar has published 110 international journal
publications (h-index 28), filed 6 research patent/disclosures (awarded
2 patents), written 45 international reviewed proceeding articles and
book chapters. Professor Tomar’s excellence in research has been
recognized by a number of awards including VAJRA award from Govt of
India, AFoSR young investigator award for high temperature interface
thermomechanics, American Society of Mechanical Engineers (ASME)
Orr early career award for excellence in fracture and fatigue, The Mineral,
Metal, and Materials Societies (TMS) early career faculty fellow-
honorable mention award for materials research, inaugural Elsevier
Material Science and Engineering journals’ early career young researcher
award for interface mechanics, Purdue’s Seeds for Success Awards
(2017, 2018, 2020), Purdue’s CT Sun Research award, Purdue’s
University Faculty Scholar Award, and multiple other best paper awards.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS 10 Keynote Lecture
Mechanics of Dynamic Tension, Compression and Shear Response of Visco-
Hyperelastic Materials
Ghatu Subhash*, Kshitiz Upadhyay**, and Douglas Spearot
Mechanical and Aerospace Engineering
University of Florida, Gainesville, FL 32611 USA
**Johns Hopkins University, USA
Soft materials such as biological tissues, elastomers and hydrogels, exhibit large elastic
deformations as well as nonlinear strain-rate dependent stress-strain response that is also
microstructure sensitive. In this research, a combined experimental and theoretical framework
based on fundamental continuum thermodynamics principles to study the constitutive behavior of
these materials is presented.
First, a generalized thermodynamic stability criterion is presented to formulate constitutive
inequalities for hyperelastic constitutive models. It is shown that all three primary deformation
modes (compression, tension and shear) should be considered to ensure a physically reasonable
model for 3D stress state. Quasi-static experiments in compression, tension, and shear on agarose
hydrogel at a range of gel concentrations are then conducted to formulate a concentration
dependent extended generalized Rivlin model. In the second step, we explore the time-dependent
mechanical behavior by conducting novel split-Hopkinson pressure bar (SHPB)-based experiments
for the shear and tensile characterization of soft materials under large deformations and in a wide
strain rate range. Full-field digital image correlation (DIC) and piezoelectric force sensing methods
are used to extract steady-state material response. Finally, a novel viscous dissipation potential is
proposed to model time-sensitivity using visco-hyperelastic framework, which can capture both
linear and nonlinear large deformation behaviors over a wide range of strain rates. By implementing
the proposed model to capture deformations of human patellar tendon and brain gray matter, a good
fitting accuracy in capturing 3D response is observed.
Professor Ghatu Subhash obtained his PhD from University of California San Diego in 1991 and conducted his post-doctoral research at
California Institute of Technology. He is currently the Newton C Ebaugh Professor in Mechanical and Aerospace Engineering at University
of Florida, Gainesvlle, FL. His research focusses on multiaxial behavior of advanced ceramics, metals, composites, gels and biological
materials. He has developed novel experimental methods which have been patented and widely used. He has co-authored 200 peer
reviewed journal articles (7800 citations in Google Scholar, h-index=47), 85 conference proceedings, 2-books, and 6 patents. He has given
numerous keynote and invited lectures at major international conferences. He has graduated 35-PhD students and is currently advising
6-PhD students and one post-doctoral fellow. Many of his students have received awards at student paper competitions from professional
societies and fellowships from NSF, DOD, and DOE. His former students are employed at major Universities in US and abroad, and national
laboratories including SNL, ORNL, PNNL and ARL. He is a Fellow of ASME, Society of Experimental Mechanics (SEM), and the American
Ceramic Society (ACerS). He is the Editor-in-Chief of Mechanics of Materials and Associate Editor of Journal of the American Ceramic
Society. He has received numerous awards, including the SEM Lazan Award (to receive in 2021) for innovative contributions to
experimental mechanics and development of in-depth understanding of multiaxial dynamic response of ceramics and soft materials, SEM
‘Frocht Award’ (2018) in recognition of outstanding achievements as an educator, ‘Best Paper’-Journal of Engineering Materials and
Technology (2016), ‘Significant Contribution Award’ for development rapid processing scheme of ceramic nuclear fuels, from the
American Nuclear Society. ‘Technology Innovator Award’ from University of Florida, ASME Student Section Advisor Award’, ‘SAE Ralph R.
Teetor Educational Award’, and ‘ASEE Outstanding New Mechanics Educator’ award. He has also served as the National Academies of
Engineering Panel Member.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS12+TS16 Keynote Lecture
Towards predictive damage models – some recent experience
Chandra Shekhar Upadhyay
Professor
Department of Aerospace Engineering, IIT Kanpur
The need to predict onset and progression of failure mechanisms has inspired intense
investigation of micro-level behaviour of different materials. The seminal work of Kachanov-
Rabotnov on progressive continuum damage has led the way to creation of damage models,
over length-scales, representing the behaviour of different progressively damaging
materials. The GTN and Lemaitre models were successful in capturing damage in ductile
metals. All these models rely on a single damage variable. Extension of these ideas to
modelling progressive damage in composites has led to several phenomenological and
micro-mechanics inspired models. The progressive damage models in composites aim to
capture all the distinct underlying damage mechanisms through multiple damage variables
and appropriate stiffness reduction and damage evolution models.
The talk will present some micro-mechanics inspired damage models for both metals and
composites, emphasizing the need for a consistent thermodynamic frame-work. Further, the
modelling approach will seek to create models that are physically justifiable and robust.
Some examples from practical applications will also be discussed.
Professor CS Upadhyay is an Aerospace Engineer by training, with a B.Tech
degree from IIT Kharagpur (1991), MS (1993) and PhD (1997) from Texas A&M.
After a short-stint as a post-doctoral fellow at TICAM (now ICES) at UT Austin, he
joined the department of Aerospace Engineering at IIT Kanpur in 1997. At IIT
Kanpur he has developed and taught courses on continuum mechanics, linear and
nonlinear finite element method, composite structures, structural integrity and
solid mechanics. He researches in the domains of material modelling, damage,
design and numerical analysis, in which he has published more than 120 papers
in international journals and conferences
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS13 Keynote Lecture
Integrity Assessment and Design of Pressure Vessels for Storing Hydrogen
Ashok Saxena
President
WireTough Cylinders, LLC
Cost-effective, pressure vessels for use in ground storage of hydrogen in refueling stations
require vessels that can safely store up to 750 liters of gaseous hydrogen at 875 bars or
87.5 MPa. This paper addresses fracture mechanics analysis to assist in the design and
structural integrity of a Type 2 pressure vessel to meet this need.
Metal cylinders have been used for storing hydrogen for several decades but are limited to
pressures of 55 MPa due to hardenability of the material and the ability to reliably inspect
for flaws. The designs must also meet safety requirements of standards such as the ASME
PVP Section VIII- Division 3 codes. Using the time-tested, metal cylinders as liners and
wrapping them with high strength steel wires that are 2 GPa or higher in strength is an
effective approach for increasing the pressure capability and fatigue life of these metal
composite cylinders. The wire-wrapped cylinders are further subjected to an autofrettage
process in which they are subjected to pressures high enough to plastically deform the inner
liner, but the wire jacket remains elastic. Upon release of the autofrettage pressure, the inner
liner is left with high residual compressive hoop stresses. This process decreases the
maximum tensile hoop stress in the liner under the operating pressure and can thus enhance
the fatigue life of the vessel very significantly. This paper will address several aspects of
design considerations such as materials selection, inspection capabilities and allowable
design stresses to meet the need of the users in the form of user design specifications in a
more wholesome design approach to ensure structural integrity.
Dr. Saxena currently serves as the President of WireTough Cylinders, LLC, a company located in Bristol,
VA, USA. He also serves as Emeritus Distinguished Professor and Dean in the Department of
Mechanical Engineering at the University of Arkansas and as an Adjunct Regents’ Professor at Georgia
Tech in Atlanta. In the past he served as the provost and vice-chancellor of academic affairs, dean of
engineering and the founding head of the Department of Biomedical Engineering at the University of
Arkansas. He also held the 21st Century Endowed Graduate Research Chair in Materials Science (2003-
2007), Irma and Raymond Giffels’ Endowed Chair in Engineering (2007-2012), and the George and
Boyce Billingsley Endowed Chair (2014-2015). Prior to University of Arkansas, he served as a Regents’
Professor and Chair of the School of Materials Science and Engineering at Georgia Institute of
Technology in Atlanta.
Dr. Saxena has primarily worked in linear and nonlinear fracture mechanics within the disciplines of
mechanical engineering and materials science and engineering.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS 14 Keynote Lecture
Mechanical properties of irradiated two nuclear materials using small punch
test data
B.K.Dutta1 and S.R.Ghodke 1Institute Chair Professor
Homi Bhabha National Institute
The small punch test (SPT) is an alternative method to assess the mechanical properties of nuclear
materials where the limited quantity of available irradiated material is insufficient to conduct
conventional standard tests. SPT specimens of two nuclear materials, OFE copper and Titanium, are
irradiated in electron accelerator up to various levels of irradiation dose. These SPT specimens are
then tested to obtain load v/s displacement data. Using experimental data and existing correlations
from literature, yield stress, ultimate stress, bi-axial fracture strain, specimen energy at fracture and
fracture toughness are calculated as a function of irradiation dose. The yield and ultimate stresses
are also used to obtain complete stress-strain curves at different doses of irradiation.
Prof. B.K.Dutta, former Distinguished Scientist and Dean HBNI, contributed
significantly in basic and applied research in structural and material
mechanics. He has guided eight PhD students, fifteen MTech. students and
presently associated with the doctoral programs of six students. He is the
author of 300+ publications, which includes 125+ peer reviewed journal
papers. He has been associated with the Homi Bhabha National Institute
right from its inception and served the institute in various capacities. He was
president of International Association for Structural Mechanics of Reactor
Technology (USA) and presently lifetime advisory board member. He is a
fellow of Indian National Academy of Engineering.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS 15 Keynote Lecture
Structurally Integrated, Damage Tolerant Coatings Sanjay Sampath
Distinguished Professor and Director
Center for Thermal Spray Research
Stony Brook University, Stony Brook, NY, USA
Thermal spray coatings are used extensively for the protection and life extension of
engineering components exposed to harsh wear and/or corrosion during service in
aerospace, energy, and heavy machinery sectors. Cermet coatings applied via high-velocity
thermal spray are used in aggressive wear situations almost always coupled with corrosive
environments. In several instances (e.g., landing gear), coatings are considered as part of
the structure requiring system-level considerations. In addition, spray based
remanufacturing of worn components is also expanding with the advent of high velocity
spray technology and here the integration of the restored and parent material from a
structural point of view is of importance. Despite their widespread use, the technology has
lacked generalized scientific principles for robust coating design, manufacturing, and
performance analysis. Advances in process and in situ diagnostics have provided
significant insights into the process–structure– property–performance correlations
providing a framework-enhanced design. In this overview, critical aspects of materials,
process, parametrics, and performance are discussed through exemplary studies on
relevant compositions. The underlying connective theme is understanding and controlling
residual stresses generation, which not only addresses process dynamics but also provides
linkage for process-property relationship for both the system (e.g., fatigue) and the surface
(wear and corrosion). The anisotropic microstructure also invokes the need for damage-
tolerant material design to meet future goals. This presentation will provide an overview of
emerging concepts of structurally integrated coating design and structural remanufacturing
of engineering components. In addition to traditional methods of coating evaluation, new
methods of integrated characterization of coating and structure is contemplated. Using
these principles approaches to enhancing applications will be presented.
Dr. Sanjay Sampath, is currently Distinguished Professor of Materials Science at Stony
Brook University (SUNY) and director of the Center for Thermal Spray Research
(www.sunysb.edu/ctsr) an interdisciplinary industry-university partnership in the field of
thermal spray materials processing and surface engineering. CTSR was created in 1996
through the National Science Foundation’s Materials Research Science and Engineering
Centers program. He received his B.Tech from IIT-BHU and Ph.D. from Stony Brook in
1989. He established Industrial Consortium for Thermal Spray Technology comprising of
35 leading companies aimed at knowledge transfer from fundamental research to
applications. Dr. Sampath has 220 journal publications to his credit, 15 patents and winner
of several best paper awards
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS21 Keynote Lecture
Hydrogen embrittlement in steels: why does it occur?
Vikram Deshpande
Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK.
One of the recurring anomalies in the hydrogen induced fracture of high strength steels is the apparent
disconnect between the toughness and tensile strength. For example, the toughness of a high strength steel
is typically reduced from approximately 100 MPam to about 20 MPam in the presence of hydrogen while
concurrently the strength reduces from 2 GPa to about 400 MPa. Traditional fracture mechanics then suggests
that quasi-brittle fracture under uniaxial tension occurred by the growth of a pre-existing flaw of size ≈1600
μm. There is no evidence of the presence of such large pre-existing flaws in high quality steels. This raises the
question as to what is the hydrogen-mediated fracture process that reduces the strength of such steels?
Here we propose, supported by detailed atomistic and continuum calculations, that unlike macroscopic
toughness, hydrogen-mediated tensile failure is a result of a fast-fracture mechanism. Specifically, we show
that failure originates from the fast propagation of cleavage cracks that initiate from cavities that form around
inclusions such as carbide particles. The failure process occurs in two stages. In stage-A, hydrides rapidly
form around the roots of stressed notches on the cavity surfaces with hydrogen fed from the hydrogen gas
within the cavity. These hydrides promote cleavage fracture with the cracks propagating at >100 ms-1 until
the hydrogen gas in the cavity is exhausted. Predictions of this hydrogen-assisted crack growth mechanism
are supported by atomistic calculations of binding energies, mobility barriers and molecular dynamics
calculations of the fracture process. Typically, cracks grow by less than 1 μm via this hydrogen-assisted
mechanism and thus insufficient to cause macroscopic fracture of the specimen. However, this stage is then
followed by a stage-B process where these fast propagating cracks can continue to grow, now in the absence
of hydrogen supply, given an appropriate level of remote tensile stress. This is surprising because the fracture
energy is now that of Fe in the absence of H and cleavage fracture requires opening tractions on the order of
15 GPa to be generated. Thus, fracture is usually precluded due to plasticity around the crack-tip. Here we
show via macroscopic continuum crack growth calculations in a rate dependent elastic-plastic solid with
fracture modelled using a cohesive zone that cleavage is possible if the crack propagates fast enough. This
is because strain-rates at the tips of fast propagating cracks are sufficiently high for the drag on the motion
of dislocations resulting from phonon scattering to limit plasticity. This combined atomistic/continuum model
is used to explain a host of well-established experimental observations including (but not limited to): (i)
insensitivity of the strength to the concentration of trapped hydrogen; (ii) the extensive microcracking in
addition to the final cleavage fracture event and (iii) the higher susceptibility of high strength steels to
hydrogen embrittlement.
Prof. Vikram Deshpande joined the faculty of Engineering at the University of Cambridge as a lecturer in October 2001 and was promoted to a professorship in Materials Engineering in 2010. He has written in excess of 270 journal articles in experimental and theoretical mechanics solid mechanics with an h-index of 71. He serves on the editorial boards of a number of journals in mechanics and biomechanics including Journal of the Mechanics and Physics of Solids, Modelling and Simulation in Materials Science and Engineering and the Proceedings of the Royal Society, London. He has awarded the Philip Leverhulme Prize, the William Hopkins medal, the 2020 Rodney Hill Prize in Solid Mechanics and has been elected Fellow of the Royal Society, London
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS21 Keynote Lecture
Probabilistic design and uncertainty quantification for structural integrity Dr. Sankar Narayanan
Technical Expert,
Siemens Technology, Bangalore, India.
For the structural design of rotating machineries, the conventional deterministic approaches engage
assumed minimum or maximum values of material-properties, operating variables like temperature,
stress etc., and hence oftentimes are conservative in nature. Probabilistic approaches on the other
hand account for uncertainties in the aforementioned random variables, by statistically harnessing
the available data and via appropriate statistical formulations based on the physics of the failure
mechanisms involved. As a result, a risk level associated with a certain failure mode or a
combination of several modes, can be quantified. These statistical formulations facilitate the
integration of risks for an entire component or an engineering system, which helps transcend from
a local deterministic approach to a robust integrative risk quantification. Probabilistic design
enables a reliable risk quantification in engineering design, allowing for appropriate service
decisions, including recertifications and life-time extensions. It allows for a reliable flexible operation
of energy components critical for the energy transition including intermittent renewable energies. In
my talk, I will give an overview of probabilistic design for structural integrity, the underlying
technologies, and computational schemes for implementation on actual components.
Dr. Sankar Narayanan is a Technical Expert at Siemens Technology, Bangalore,
India and specializes in technology development in the field of probabilistic
design and analytics. His academic background and expertise are in
computational mechanics, multiscale material modelling and statistical
modelling. He received his PhD in Mechanical-Engineering from Georgia
Institute of Technology, USA, in 2014. .
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS 21 Keynote Lecture
Structural Integrity Aspects of Gas Turbine Parts Shri BVA Patnaik
Technology Director, Gas Turbine Research Establishment, Bangalore
Structural integrity of a Gas Turbine is the ability of structure/system to perform its intended function without failure under all operating conditions for a specified life. Achieving very high specific workout put as a means of producing large power with minimum possible size of Gas turbine aero engine was the target of aero thermodynamic engineers for a long time. This required development of high pressure ratio compressors and development of Turbines which can withstand Turbine Entry Temperatures of the order of 1900K.The evolution of Titanium alloys as a replacement to steels and development of high temperature super alloys have brought tremendous advantage of designing the aerodynamic flow paths required besides meeting long life requirements. The critical parts undergo various failure modes like High Cycle Fatigue (uniaxial and multiaxial) due to phenomenon like resonance, aeroelastic interactions, Low Cycle Fatigue and thermal fatigue due to start stop and transient operations. The combination of extreme mechanical and high temperatures experienced by these components often result in significant amounts of plasticity and cyclic time dependent plasticity which makes the structural analysis and life prediction a challenging job. This requires exhaustive material characterisation and structural simulation techniques.
Subsequent to the design and life prediction it is equally important to assess the residual life due to operational usage in order to ensure safe and economic exploitation. The life of critical components of the engine is declared based on the flight envelope consisting of various mission cycles and the corresponding operating environment of the component & failure modes.
The Low cycle fatigue life is declared in terms of number of 0-Max-0 cycles. This fatigue life can always be correlated to equivalent damage cycles with respect to actual mission profile by summing up the damages due to minor sub cycles and the major cycle of the mission profile. The life of the cold parts is dictated by Low Cycle Fatigue behavior with respect to mission cycle whereas the components for which the operating temperatures are high (hot parts) the life is dictated by combination of Creep & thermal fatigue.
In order to ensure that the components in service have not exhausted the equivalent declared safe life, it is essential to assess the damages incurred in these components during engine operation. The cyclic exchange rate for the mission profiles in terms of hours are generally defined by apportioning speed excursion ranges in to predominant speed ranges. However more accurate damage consumptions are to be evaluated so that life potential of the critical components is exploited very effectively. Diagnostics, Prognostics play vital role in ensuring integrity and economic life exploitation (Including life extension) of the Gas Turbine parts.
Shri BVA Patnaik is M.Tech. in Aerospace Engg from IIT Khargpur and presently
working as Technology Director at, Gas Turbine Research Establishment, Bangalore
. His area of specialization is Structural analysis ,Life prediction and Life monitoring,
Material Charactertisation of Gas turbine critical parts.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS22 Keynote Lecture
Modeling Progressive Damage and Failure of Fiber Reinforced Laminates
Anthony M. Waas
University of Michigan, Ann Arbor, MI, 48109
High-strength and high-stiffness carbon fiber-reinforced polymer composite laminates (CFRP)
arEbeing increasingly used for primary load bearing structures in many industries. The most
common material system used is based on thermoset resins (matrix material), which come in the
form of convenient prepreg tapes allowing high flexibility and productivity using advanced
automated manufacturing technologies. Engineers must provide mechanics based models for the
deformation response and failure of these materials and structures. The mechanisms responsible
for progressive damage accumulation and failure are (intralaminar) matrix cracks, which can lead to
delamination initiation and spreading resulting in ultimate failure. Interlaminar fracture in CFRP,
referred to as delamination, is defined as an out-of-plane discontinuity between two adjacent plies
of a laminate.
Delamination behavior has been studied by many researchers and now can be characterized in a
standardized manner. Fracture properties of Mode I, Mode II, and mixed-mode (between Mode I and
Mode II) delamination can be obtained from ASTM standard tests in conjunction with finite element
analysis (FEA). In a CFRP structural component, the intralaminar and interlaminar modes of failure
can interact and therefore, developing a computational model to accurately replicate the
failure mechanisms and their interaction has been challenging. In this presentation, a series of
experimental results that delineate the different mechanisms of failure will be presented. Based on
these results, a validated model will be presented, resulting in a progressive damage and failure
modeling framework that can be used for assessing the structural integrity and damage tolerance
of CFRP structures.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS01
Structural Integrity of Additive Manufactured
Components
Organizer
D. Srinivasan, Pratt & Whitney
11th Dec 7-10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
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Invited Speakers
Large Part Additive Manufacturing using Direct Metal Deposition (DMD®)
Dr. Bhaskar Dutta
President DM3D Technology
As additive manufacturing (AM) is emerging as a main stream manufacturing technology,
demand for large part manufacturing is getting stronger. Direct Metal Deposition (DMD) is
a DED technology based on laser and powder metal application using a closed-loop-
feedback control system. This presentation will give an overview of the DMD technology
highlighting its capability to scale up to large size parts. Challenges, such as high throughput
and associated distortion control to build large parts weighing more than 1000 lbs will be
discussed along with potential solutions. Finally, DMD’s capability of large part
manufacturing will be demonstrated through case studies from component manufacturing
for rocket engines.
Bhaskar Dutta is president and chief operating officer of DM3D Technology, United States, an
additive manufacturing company. Dr. Dutta has almost 30 years of experience in the field of
metallurgy and metal processing including 16 years in the AM industry. He has been directly
involved in AM research and technology development as well as commercial product
development using AM. Dr. Dutta has several patents, multiple technical publications and
presentations in the field of AM, and authored several books and book chapters on AM.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Accelerating Additive Manufacturing parts certification
Dr Sergey Mironets Collins Aerospace, Poland
Certification of parts produced by Additive Manufacturing techniques is one of the most
critical challenges that enables transition to production especially in the aerospace market.
Often, the cost for quality control and part certification is more expensive than printing a
part. The certification process may include in-situ monitoring, on the plate testing and final
inspection. The importance of developing a robust on the plate techniques for 3D print
certification will be discussed.
Sergey Mironets has 10 years of Additive Manufacturing experience and over 30
years of combined experience in fields of Powder Metallurgy and Composites, Heat
Treatment and Fusion Welding. As an Advanced Technology Leader at Pratt &
Whitney Additive Manufacturing Group Sergey played a significant role in the
development of various Additive Manufacturing prototypes for NGPF jet engines. At
Collins Aerospace Sergey has been active developing Additive Manufacturing
Strategy, selecting components for manufacturing cost reduction utilizing Powder
Bed Fusion and Direct Energy Deposition technologies. Sergey has over 35 patents
either awarded or in the application process. Sergey is an active member of ASTM
F42.05, ISO/TC 261, SAE AMS AM and America Makes ANSI Additive Manufacturing
committees contributing to development of standards for various Additive
Manufacturing materials and processes. Sergey is actively involved in collaborating
with RTRC on Additive Manufacturing modeling efforts. He serves as Additive
Manufacturing advisor to University of Connecticut Graduate Student Projects.
Sergey received a Mechanical Engineering degree from National Transport University
(Kiev, USSR), completed Powder Metallurgy and Composite Materials PhD course
work from Institute for Problems of Material Science (Kiev, USSR) and received MBA
from Rensselaer Polytechnic Institute.
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS02
Applications of Data Science
Organizer
A. Alankar, IIT Bombay
18th Dec 4-6 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
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Invited Speakers
A Deep Learning Approach for Development of Virtual Sensors to Compute
Responses for Structures Under Dynamic Loading Conditions
Dr. Giri R Gunnu
Suprabhash Sahu, and G. R. Gunnua
Tardid Technologies Pvt. Ltd. Bangalore, India.
Measurement of dynamic responses plays an important role in structural health monitoring, damage
detection and other fields of research. With current technology, the number of sensors is often
limited and the locations may also be inaccessible for instrumentation. To obtain the desired
responses using limited physical measurements, virtual sensing techniques have developed rapidly
in the last decades. Recently, considerable attention has been focused on Artificial Intelligence (AI)
which has been proven to be a powerful response modeling tool and approximator. An approach
based on virtual sensor techniques based on the Convolutional Neural Network (CNN) to estimate
the dynamic responses of a structure given measurements at some locations, where real sensors
are placed is implemented in this work. As proof of concept, a beam simply-supported at both ends
was modelled for training, testing and subsequent validation. Loading Condition: A random load
populated by Gaussian white noise was applied at one/multiple points on the beam. A script on
MATLAB was written implementing the dynamic time-history response of the beam using the
Newmark-Beta Method. A virtual sensor network was developed based on the data created. A
functional Convolutional Neural Network was used with varying number of convolutional layers,
hidden layers and fully connected layers based on the implementation. The model takes the
geometric and material properties of the beam as an input and also allows flexibility to change the
loading conditions, allowing us to use random loads, sinusoidal loads and other loads based on
mathematical functions. Moreover, point of application of loads can be changed to one/multiple
points. The CNN was exhaustively inclusive of all intrinsic beam parameters, loading conditions and
support types. Based on all these specified parameters, the CNN give an accurate time-history
response of the acceleration, velocity and displacement for the beam, effectively capturing the
underlying physics, while simultaneously decreasing the computation time by a factor of a thousand.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Statistical Learning for Infrastructure Vulnerability Assessment under
Natural Hazards
Jayadipta Ghosh Assistant Professor
Indian Institute of Technology Bombay
Infrastructure systems, such as highway bridges constitute the socio-economic backbone
of any nation that aids the safe transport of pedestrians and traffic. Adequate functioning
of these key elements of the transportation network are particularly relevant in the aftermath
of natural hazards, such as earthquakes, to ensure post relief and recovery operations.
Consequently, the vulnerability assessment of highway bridge structures in the wake of
natural hazards becomes imperative for highway authorities and disaster mitigation
agencies.
The assessment of structural integrity under extreme events, however, must be
conducted while acknowledging uncertainties from a multitude of sources, such as hazard
characteristics, structural parameters, and often the environmental effects on bridge
component deterioration. This talk will focus on the application of modern statistical
learning algorithms for seismic fragility assessment of highway bridges. Of relevance will
be the prediction of seismic response of critical bridge components for lateral load
resistance and the mutual interdependence of component behaviour that dictates bridge
system-level behavior. Parallels will be drawn with traditionally adopted naïve Monte Carlo
simulations to highlight the efficiency in vulnerability assessment with significant
reductions in computer runtime.
Dr. Jayadipta Ghosh is an Assistant Professor in the Department of Civil
Engineering at IIT Bombay. He obtained his Ph.D. degree from Rice University, TX,
USA following which he worked in portfolio-level seismic loss assessment in AIR
Worldwide in Boston. He joined IIT Bombay in 2014 where his primary research
focuses on efficient methods for vulnerability estimation of civil engineering
systems. Several of his research articles have been selected as the ‘Editor’s Choice’
papers in the American Society of Civil Engineers.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Machine Learning Applications in Contact Problems
Sachin Singh Gautam Assistant Professor
Department of Mechanical Engineering, IIT Guwahati, 781039
Machine learning has recently attracted a lot of attention in various fields. The field of computational
mechanics has also found application of machine learning in areas such as constitutive modelling,
fracture mechanics, fatigue failure etc. Computational contact mechanics is one such field where
the machine learning algorithms are been applied. Artificial neural network (ANN) is one of such
highly accurate machine learning methods that has been used in various engineering problems to
analyse discrete nonlinear data and find complex interrelations therein. After forming sophisticated
interrelation with non-linear data, ANN is widely used to predict the system output set corresponding
to single or multiple input set. Backpropagation neural network (BPNN) is a kind of multi-layer
artificial neural networks (MLANNs) where sensitivity of weights is back-propagated from output to
input layer via one or more hidden layers. In the present talk, the BPNN is applied to two contact
problems – gecko adhesion and fretting damage. First, the Bayesian regularization (BR) based
BPNN model is employed to predict some aspects of the gecko spatula peeling such as the variation
of the maximum normal and tangential pull-off forces and the resultant force angle at detachment
with the peeling angle. The input data is taken from finite element peeling results. The neural network
is trained with 75% of the FE dataset while the remaining 25% is used to predict the peeling
behaviour. The training performance is evaluated for every change in the number of hidden layer
neurons to determine the optimal network structure. The relative error is calculated to draw a clear
comparison between predicted and FE results. It is observed that BR-BPNN models have significant
potential to estimate the peeling behaviour. In the second problem, BPNN models are considered to
predict Ruiz parameters (F1) for the nominal and optimized liner geometries in diesel engines.
Overall, good correlation is observed in terms of the predicted F1 results using 2D FEA, full factorial
DOE, BR-BPNN and 3D FEA.
Dr. Sachin Singh Gautam is currently an Assistant Professor in the Department of
Mechanical Engineering, Indian Institute of Technology Guwahati. His research
interest is in computational mechanics specifically isogeometric analysis, contact
problems, GPU computing. Recently, he has started to explore machine learning
applications in contact problems. He has published 23 journal papers, 12 books
chapters, and made more than 50 conference presentations. He has supervised 3
PhDs, 17 master students and many bachelor students. Currently he is supervising 7
PhD students and 4 master students. Dr. Gautam is currently involved in development
of contact and isogeometric modules for FEAST® software being developed by VSSC,
ISRO.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Contributed Speakers
Detection of Fretting Fatigue Using Machine Learning Algorithms
Khizr Mohammad Khan, IIT Guwahati
Khizr Muhammad Khan, Sachin Singh Gautam
Department of Mechanical Engineering, Indian Institute of Technology Guwahati
Abstract
Fretting is very common in machines that experience relative movement among mechanical
components resulting in wear, corrosion, and fatigue especially in parts experiencing
vibrations such as in aircraft, turbine/blades etc. The main purpose of the paper is to
develop a classification model that can predict fretting fatigue by using different machine
learning algorithms. To make any machine learning model the first most important aspect
is to collect the data as much as possible by experiments or by some other means. Recently,
there has been some attempt to predict the life of the specimen by using artificial neural
networks. The main objective of this work is to develop a classification model to determine
whether the specimen will pass or fail, using the experimental dataset available in the
literature and transforming the data to make it suitable for classification. In the experiments,
the specimen which crosses a million cycles is considered to safe and said to be run-out
and the specimen which does not cross a million cycles is considered to be a failure. The
data points which show a million cycles greater than 107 are categorized as 1 (runouts) and
the data points which are showing a million cycles less than 107 are categorized as 0
(failed). The classification model is trained by splitting the whole dataset into 80% training
data and 20% test data. The dataset is imbalanced as there are more number of data points
showing failure than the data points showing the run-out. To balance the dataset Synthetic
Minority Oversampling Technique (SMOTE) is used. The result is validated using the
performance metrics like precision, recall, and F1 score. Results show that classification
models are working well on test data
Keywords: Fretting Fatigue, Machine Learning Algorithms, SMOTE, F1 score.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Debond detection in metallic stiffened plate by estimating mahalanobis
distance
Abhijeet Kumar, IIT Bombay
Abhijeet Kumar1, Anirban Guha1, Sauvik Banerjee2
1 Department of mechanical engineering, Indian Institute of Technology Bombay, Mumbai,
400076, India 2 Department of civil engineering, Indian Institute of Technology Bombay, Mumbai, 400076,
India
Abstract
In this study, the feasibility of statistical technique Mahalanobis square distance (MSD) with
combination vibration-based approach is examined to debond detection and quantification
in metallic stiffened plate structure. The numerical simulated and experimental model
displacement data is used as damage sensitive feature vector. For debond identification,
the undamaged feature vector set as baseline data, the MSD, a covariance weighted
distance is calculated on any future data to discriminate the damaged or undamaged state
structure. The sensitivity of technique is first examined to set the threshold with numerical
simulated data there after the experimental data is processed to validate the technique. It
is observed that, MSD estimation-based damage detection technique has quite significant
capacity for debond detection and quantification with numerical as well as experimental
data.
Keywords: Structural health monitoring, Debond Detection, Mahalanobis distance,
Vibration-based
3rd Structural Integrity Conference and Exhibition – SICE2020
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TS03
Creep and High Temperature Failure
Organizers
S. Gollapudi, IIT Bubhaneswar
R. Kottada, IIT Madras
11th Dec 5-10 pm
20th Dec 4-6.30 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
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Invited Speakers
Creep and high temperature deformation behaviour of Al0.2 CoCrFeNiMo0.5
high entropy alloy
Rajesh Korla, IIT Hyderabad Rajesh Korla, Yasam Palguna
Indian Institute of Technology, Hyderabad [email protected]
Continuous decrease of fossil fuels along with rapid increase in carbon foot print pushing towards increasing the efficiency of thermally operated systems such as thermal power plants. One way of increasing the efficiency is to increase the operating temperature which can be possible only with the development of new structural materials with enhanced high temperature strength, creep resistance and oxidation resistance. In this direction, studies in last decade showed that high entropy alloys (HEAs) exhibiting better properties compared to conventional steels and super alloys. One of the interesting observations with high entropy alloys, as observed recently, is that many of these high entropy alloys retaining their high strength even at temperatures above 700oC . Further, some of these alloys exhibit good corrosion resistance which make these alloys a suitable candidate as high temperature material especially for the present generation advance ultra-super critical thermal power plants.
Present work investigated the high temperature strength and creep behavior of Al0.2CoCrFeNiMo0.5 high entropy alloy. Alloy was prepared through vacuum induction route followed by thermo-mechanical process and further, precipitation hardening and the structural stability at high temperature was studied using Iso-thermal annealing experiments. High temperature tensile experiments were performed on the peak aged samples at different temperatures along with the post deformed microstructural studies. Preliminary results on the creep behavior will be discussed.
Dr. Rajesh Korla is an Assistant Professor in the department of Materials Science and
Metallurgical Engineering at Indian Institute of Technology, Hyderabad. He obtained his M.E.
and Ph.D. Degree from IISc Bangalore. He worked as Post-Doctoral fellow at Oxford
University. His research interest is in mechanical behaviour of materials and creep
3rd Structural Integrity Conference and Exhibition – SICE2020
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Physics based versus empirical models for creep
Ramkumar Oruganti Principal scientist
GE Research
While there is a constant effort to deepen understanding of high temperature mechanical behavior and create better physics-based models, the industry prefers to use methods that are simple and time tested. In most cases at the practical level there is an unshakeable reliance on hard data. Where behavior has to be extrapolated beyond the range of available data, the tendency is to use empirical methods and equations. This talk will cite examples of these scenarios and outline reasons for why this situation persists. We will also try to provide directions on how this gap might be addressed.
Obtained Ph.D in materials science from University of Michigan, Ann Arbor in 2002. Working with GE Research since then. Areas of focus include high temperature mechanical behaviour, constitutive modelling, superalloys, steels, novel non-destructive methods for microstructure
3rd Structural Integrity Conference and Exhibition – SICE2020
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Multiscale modelling and prediction of high temperature mechanical
response – are we there yet?
S. Karthikeyan
Associate Professor
Materials Engineering, Indian Institute of Science, Bangalore
The past several decades has seen an exponential growth in the application of
computational tools to a variety of engineering disciplines, including materials engineering.
While there has been reasonable success in usage of these modelling tools towards alloy
design and processing, prediction of mechanical response remains a challenge. These
efforts have remained largely academic and limited to idealised situations. In my talk, I will
review the state-of-the-art on various computational approaches to predicting high
temperature strength and failure of engineering alloys. I will present specific results from
our multiscale modelling efforts combining first principles calculations with FEM and
dislocation dynamics to predict the high temperature behaviour of Ni- and Co-base
superalloys. I will discuss some novel computationally inexpensive yet accurate models that
we have developed that enables high throughput prediction of properties relevant to high
temperature strength, not just in model systems but in multicomponent engineering alloys
and at operating temperatures. I will close the talk by highlighting the current challenges in
the applicability of these tools to engineering problems.
Prof. S. Karthikeyan’s interests are in mechanical response of metals and intermetallics
under extreme conditions of strain rate and temperature. The experimental activities in
his group include creep testing, high strain rate testing and electron microscopy, while
the computational activities include atomistic simulations, electronic structure
calculations, phase field methods and FEM.
3rd Structural Integrity Conference and Exhibition – SICE2020
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New Insights into Creep in the So-Called Harper-Dorn Creep Regime
Praveen Kumar Praveen Kumar, Shobhit P Singh,Michael E Kassner
Associate Professor
Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)
Creep response of pure materials at very low stresses (<10-5 G, where G is the temperature
compensated shear modulus of the material) and very high temperatures (>0.9 Tm, where
Tm the melting temperature of the material) is not fully understood. After the classic work
of Harper and Dorn, in 1957, on high purity Al in this “stress-temperature” regime, this creep
test regime is often called the Harper-Dorn regime. Although the creep response is
conventionally characterized by dominance of dislocation-climb, a creep stress exponent, n,
of 1 and a stress independent dislocation density, several studies did not observe a
transition to n = 1 in the Harper-Dorn regime. This study aims to provide some insights into
creep behaviour in this regime that may help resolve the debate. Here, creep responses of
pure LiF and Al single crystals were examined. After long term (~ one year) annealing at
high temperatures (>0.9Tm), a frustration dislocation density was observed in these crystals.
This frustration density restricts any further coarsening of the dislocation network. Hence,
a stress independent dislocation density might be observed in the Harper-Dorn regime.
However, crystals initially grown with dislocation density lower than this frustration limit can
show a stress dependence at such low stresses, and then n can be close to 3 in the Harper-
Dorn creep regime. Overall, n can be in between 1 and 3, depending on the initial dislocation
density. A model, which is based on the higher dependence of dislocation climb velocity on
the applied stress, is developed to explain the effect of dislocation density variation on the
stress exponent observed in the Harper-Dorn as well as “five”-power law regime. A
consensus is now building that Harper-Dorn creep is most likely a special case of “five”-
power law.
Praveen Kumar received his Bachelor of Technology degree in Mechanical
Engineering from Indian Institute of Technology, Kanpur, in 2003. Subsequently, he
received M.S. and Ph.D. degrees in Mechanical Engineering from University of
Southern California, Los Angeles in 2005 and 2007, respectively. He is currently an
Associate Professor with the Department of Materials Engineering, Indian Institute
of Science, Bangalore. His main research interests are mechanical behaviour of
materials, with particular emphasis on studying effects of electric current,
temperature and sample length scale, and constructive usage of electromigration,
both in solid and liquid metals.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Transition from dislocation to diffusion dominant plastic flow in nanolayered
thin films
Dr. Rejin Raghavan, IISc Bengalore
R. Raghavana, J.M. Wheelerb, T.P. Harzerc, V. Chawlad, S. Djaziric, B. Philippic, C.
Kirchlechnere, J. Wehrsf, J. Michlerf, G. Dehmc aDepartment of Materials Engineering, Indian Institute of Science, Bangalore
bLaboratory for Nanometallurgy, Department of Materials Science, ETH Zürich cStructure and Nano-/Micromechanics of Materials, Max-Planck-Institut für
Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany dInstitute Instrumentation Centre, Indian Institute of Technology Roorkee
eInstitute of Applied Materials, Karlsruhe Institute of Technology fEmpa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for
Mechanics of Materials and Nanostructures, Feuerwerkerstrasse
Email address: rejinr@ gmail.com
This presentation highlights the transition from dislocation to diffusion dominant plastic flow
observed during the deformation of mutually immiscible, nanolayered systems at moderately
elevated temperatures. Three different systems of nanolayered thin films consisting of varying sub-
100 nm thick Cu layers sandwiched between TiN, W, and Cr layers were studied. Diffusion barriers
such as W or TiN prevent Cu diffusion into the Si during synthesis and service. On the other hand,
do supersaturated Cu-Cr alloys supersede nanolayered Cu-Cr films of the same average
composition irrespective of the layer thickness?
The mechanical response of 2 μm (Cu-Cr system) & 4-5 μm (Cu-W & Cu-TiN) nanolayered
films up to 400 oC was studied by compressing focused ion beam machined micropillars in situ SEM
using an Alemnis® indenter modified for high temperature testing. Shearing and tearing by
separation of the columnar Cr, W & TiN layers across the layers was observed up to ~100 oC. But,
lateral flow or plastic flow perpendicular to the load direction of Cu was observed at ~0.35
homologous temperature in all three systems. The confined layer slip model captures the trend of
the yield strength as a function of Cu layer thickness at 25 oC well. At elevated temperatures, the
applicability of existing stress-assisted diffusion plasticity models is considered.
Dr. Rejin Raghavan is working on the high temperature mechanical behavior of NiAl with
Pt and Pd additions as a Research Associate under the supervision of Prof. Vikram
Jayaram in the Materials Engineering department at IISc (Bangalore, India). He had joined
MPIE after working as a Scientist/Post-doc at Empa, Swiss Federal Laboratories for
Materials Science and Technology (Thun, Switzerland) in the department of Dr. Johann
Michler (Laboratory for Mechanics of Materials and Nanostructures) for five years. He is
the recipient of the Prof. K. P. Abraham medal Best thesis award for his PhD thesis on
“Effect of free volume on the fracture and fatigue of amorphous alloys”.
3rd Structural Integrity Conference and Exhibition – SICE2020
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Impression creep and its application to magnesium alloys and magnesium
composites
Dr. Ashok Kumar Mondal, Assistant Professor,
Department of Metallurgical Engineering, Indian Institute of Technology (BHU) Varanasi,
Varanasi - 221005, India.
Email: [email protected]
Impression creep test is a special type of indentation creep test. It uses a cylindrical indenter
to impress the specimen surface, and the depth of penetration is recorded as a function of
time. The technique is useful for studying the creep behaviour of many materials. The
impression creep test has been employed successfully to investigate the creep behaviour
of several magnesium alloys like AE42, MRI230D, AZ91, AZ91+Ca, AZ91+Sb, AZ91+Bi,
AZ91+Ca+Sb, AZ91+Ca+Bi, and AZ91+Bi+Sr alloys as well as several magnesium alloys-
based composites and nanocomposites. The values of stress exponent (n) and activation
energy of creep (Q) have been calculated using the impression creep tests to determine the
dominant creep mechanisms operating in these magnesium alloys, composites and
nanocomposites. The creep behaviour of some of these materials has also been evaluated
using the conventional tensile and compression creep tests for comparison. The results
obtained using the impression creep test are in good agreement with that produced by the
conventional creep tests. In this talk, a brief introduction on impression creep will be
provided. In addition, the results obtained on some magnesium alloys, composites and
nanocomposites using impression creep tests and their comparison with the results
produced by conventional creep tests will be discussed.
Dr. Ashok Kumar Mondal obtained his B.E. from the Department of Metallurgical
Engineering, Bengal Engineering College Shibpur (Presently IIEST) in 2001. He
completed his M.E. in 2003, and Ph.D. in 2009 from the Department of Materials
Engineering, Indian Institute of Science, Bangalore. He served the Metallurgical Quality
Control, Bharat Forge Limited, Pune from August 2009 to July 2011. He then worked
as the Associate Professor at the Department of Metallurgical and Materials
Engineering, National Institute of Technology Rourkela from August 2011 to May 2018.
Dr. Mondal is presently working as the Assistant Professor at the Department of
Metallurgical Engineering, Indian Institute of Technology (BHU) Varanasi.
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Contributed Speakers
Compositionally graded nanosize precipitates at grain boundaries of
directionally solidified GTD444
Richa Gupta, IIT Bombay
Richa Gupta*, M.J.N.V. Prasad and Prita Pant
Department of Metallurgical Engineering and Material Science, IIT Bombay
*Email- [email protected]
Abstract
Minor addition of boron as a grain boundary strengthener improves the creep rupture
properties of the Ni-based superalloys. However, the existence of boron in the
multicomponent system remains questionable. The role of boron in altering the grain
boundary chemistry has been investigated in directionally solidified GTD444. DS GTD444 is
a grade of General Electric (GE) suitable for later stage gas turbine buckets. The samples
from the airfoil were characterised extensively by time of flight-secondary ion mass
spectrometry (ToF-SIMS), transmission electron microscopy (TEM) in conjunction with
energy dispersive X-ray spectroscopy (EDS). The investigation suggests that most of the
boron presents at the γ-γ' interface lies along the grain boundary in the form of nanosize (~
80-90 nm) precipitates. These particles are further confirmed as (Cr, W, and Mo) borides.
Presence of borides suppresses the agglomeration of mostly reported M23C6 carbides at
the grain boundaries of GTD444. An elemental partitioning within the borides is also
observed which suggests that they are at their initial stage of forming. Such type of
compositionally graded nanosize precipitates is not reported in superalloy systems so far.
Keywords: Grain boundary borides, Nanosize precipitates, Time of flight- secondary ion
mass spectrometry (ToF-SIMS), Transmission electron microscopy (TEM), Energy
dispersive X-ray spectroscopy (EDS).
3rd Structural Integrity Conference and Exhibition – SICE2020
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Residual stress analysis in large water quenched stainless steels
S. Hossain, Military Technological College, Oman
S. Hossain1,*, A.M. Shirahatti2
1. Department of Aeronautical Engineering, Military Technological College, Al Matar Street,
PO Box 262, PC 111, Muscat, Sultanate of Oman
2. Jain College of Engineering, Visvesvaraya Technological University, India
*Corresponding author email: [email protected]
Abstract
Age related degradation mechanisms in nuclear plants are crucially dependent on the
magnitude and distribution of weld residual stress. Earlier studies focussing on
measurements of residual stresses in thick section welded components revealed there is
sufficient driving force for the creation of creep damage, in particular during high
temperature operation. Detail of how the presence of residual stress influences creep
degradation need to be investigated. The main aim of the research programme is to assess
how stresses act as a driving force for creating creep damage. To numerically predict creep
damage using finite element analysis (FEA), it is required to accurately model the stress
distribution and validate the stresses experimentally. Quenching is a practical means of
introducing residual stress field in laboratory specimens in a controlled manner.
Residual stresses measured deep into metal parts using neutron diffraction (ND) technique
with the application of a novel ENGIN-X stress instrument are presented. A time-of-flight
method developed at ISIS facility at Rutherford Appleton Laboratory was used to measure
residual stress distributions in type 316H stainless steel specimens of large size. The
specimens included two cylindrical bars of diameter 60mm, length 160mm and a cylinder
of diameter 60mm, length 60mm. Residual stresses were introduced into the specimens by
rapid spray water quenching. This study was part of a research motivated by a need to
model and understand creep in ageing power plant. An extensive finite element analysis
was carried out to predict the residual stress following water quenching. Overall, an
excellent correlation existed between the measured and FEA simulations for both residual
strains and stresses.
Keywords: quenching, residual stress, finite element analysis, neutron diffraction
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63
TS04
Fracture and Fatigue in Materials and Structures
Organizers
V. Chintapenta IIT Hyderabad
D. Mahajan, IIT Ropar
12th Dec 4-9 pm
20th Dec 4-9 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
64
Invited Speakers
Relation between strain localization and micro-void coalescence in ductile
fracture
Shyam Keralavarma
Associate Professor
Department of Aerospace Engineering, IIT Madras
The ductility of structural metals is often limited by strain localization phenomena, such as
necking and shear banding. A criterion for the onset strain localization, viewed as an
instability in the incremental constitutive response of the material, was developed by Rice
and co-workers (1975, 1976). However, application of Rice's theory to ductile metals
obeying classical porous plasticity models leads to predictions of unrealistically large
strains to failure compared to experiments. In this study, we show that this discrepancy can
be addressed by accounting for alternative "inhomogeneous" modes of yielding at the meso-
scale of the voids. At sufficiently large porosities, localized yielding of the ligaments
between neighbouring voids leads to void coalescence and crack initiation/propagation. It
is shown that Rice's instability criterion combined with a recently developed model for void
coalescence can yield realistic predictions for the strain to failure in ductile materials as a
function of the loading path. The predictions of the new model are compared with numerical
estimates of the strain to failure, obtained using finite element cell model simulations of
void growth under proportional loading paths, and good quantitative agreement is
demonstrated. The advantages of the new model via-a-vis existing ductile fracture criteria
in the literature are discussed.
Shyam Keralavarma obtained his Ph.D. from the department of Aerospace Engineering
at Texas A&M University, USA, in 2011. After a short stint as a post-doc at Brown
University, USA, and EPFL, Switzerland, he joined the faculty of the Aerospace
Engineering department at IIT Madras in 2013. His research interests are in the broad
area of mechanics of materials, with emphasis on problems in the micromechanics of
plastic deformation and fracture.
3rd Structural Integrity Conference and Exhibition – SICE2020
65
Snap-buckling and failure analysis of CFRP laminate with embedded circular
delamination subjected to four-point bending load
Dr Gangadharan
Lala Bahadur Andraju, Gangadharan Raju*, M Ramji
Department of Mechanical and Aerospace Engineering, Indian Institute of Technology
Hyderabad, India
Snap-buckling of delaminated carbon fiber reinforced polymer (CFRP) composite laminate
under pure bending load may lead to critical failure, which needs to be understood for
damage tolerant design. In this work, a multi-angle CFRP composite beam specimen with
embedded circular delamination is studied under four-point bending. Experimental
techniques like digital image correlation (DIC) and acoustic emission (AE) are used to
evaluate the strain at which the snap-buckling of sub-laminate happens and the subsequent
delamination propagation in the beam specimen. Detailed fractography studies are carried
out on the post-failed specimens to get insights on the various damage modes.
Subsequently, a three-dimensional finite element model is developed in the Abaqus
software to model the beam specimen with delamination for simulating the snap-buckling
of the sub-laminate and the associated damage modes in the laminate. The cohesive zone
model technique is used to model the delamination failure, and a continuum damage model
employing user material (UMAT) subroutine is implemented to model the fiber, matrix, and
fiber-matrix shear failures in the laminate. The sub-laminate buckling strain and damage
evolution results predicted by the numerical is compared with experimental observations.
The developed numerical models can aid in the design of damage tolerant composite
structures under bending loads.
3rd Structural Integrity Conference and Exhibition – SICE2020
66
Adhesion Durability of Interfaces in Photovoltaic Module
Naresh V Datla Associate Professor
Mechanical Engineering, IIT Delhi
The photovoltaic (PV) module is a multi-layered structure that is expected to work under
prolonged outdoor exposure with consistent power output. The loss of integrity at the
interfaces of the module due to service loads and environments adversely affects the
module efficiency. An understanding on how water diffuses within the module and how it
affects the fracture toughness will help us to assess and prevent the long-term degradation.
This talk shall show by both experiments and simulations on how fracture toughness of
encapsulant-glass adhesion changes with service life. Methods developed to corelate
fracture with water exposure and characterize water diffusion will be presented. These
methods will be used to predict spatial and temporal loss of adhesion in PV module.
Naresh V. Datla is an Associate Professor in the Department of Mechanical Engineering
at IIT Delhi. He received his B.Tech. from NITW in 2002, M.E. from IISc in 2004 and Ph.D.
from Univ. of Toronto, Canada, in 2011. He worked as a postdoctoral fellow at Temple
University, Philadelphia, and as a scientist at ISRO Bangalore. His research concerns
deformation and failure of materials using both experimental and numerical techniques.
His current research activities include work on tissue biomechanics, composite joints,
nanocomposites, and photovoltaic modules.
3rd Structural Integrity Conference and Exhibition – SICE2020
67
Contributed Speakers
Multiaxial Fatigue Behavior of Near Alpha Titanium Alloy for Aeroengine
Applications
Adya Charan Arohi, IIT Kharagpur
Adya Charan Arohi1, Vikas Kumar2, N. Narasaiah3
1Department of Metallurgical and Materials Engineering, Indian Institute of Technology,
Kharagpur, India
2Defence Metallurgical Research Laboratory, Hyderabad, India
3Department of Metallurgical and Materials Engineering, National Institute of Technology,
Warangal, India
Email of corresponding author: [email protected]
Abstract
Titanium alloys are considered as an attractive material for the aerospace applications
owing to their unique characteristics such as high specific strength, good ductility and better
corrosion resistance. IMI 834 alloy is a near α Ti -alloy which is used in the compressor discs
and blades of turbine engines. These components rotate at very high RPM and often
experience the combined effect of axial and centrifugal stress. Most of the times, the failure
of these components occurs due to the cyclic loading during its normal operation. Hence,
the aim of the present study is to evaluate the tensile and multiaxial fatigue behavior of IMI
834 alloy at room temperature. Tensile tests are performed at a strain rate of 6.67 x 10-4 s-
1. Fully reversed pure axial, pure torsion, and combined axial torsion fatigue experiments are
conducted on the tubular specimen in in-phase loading condition at a frequency of 0.3 Hz.
Hysteresis loops are determined for all the fatigue tests at half of the fatigue life. Cyclic
stress response curves are generated and noted that the alloy tends to show neither cyclic
hardening nor cyclic softening during the pure axial fatigue. On the other hand, it shows
cyclic softening for the case of pure torsion and combined axial torsion fatigue.
Subsequently, fatigue life is correlated to Von Mises equivalent stress and strain under
various loading combinations. The alloy exhibits lowest fatigue life under pure axial and
highest life under pure torsion fatigue. It is noteworthy to observe that the effect of torsion
is more dominant under the combined axial torsion fatigue. Fractography is also carried out
to understand the fracture micro mechanism with respect to loading conditions.
Keywords: IMI 834, multiaxial fatigue, tubular
3rd Structural Integrity Conference and Exhibition – SICE2020
68
Use of Compression-bending Fracture Geometry to Study the Effects of
Stoichiometry on Fracture Toughness of NiAl
Devi Lal, IISc Bengaluru
Devi Lal a, Ananya Tripathi a, Abhijit Ghosh a, b, Ravi Bathe C, Praveen Kumar a and Vikram
Jayaram a
a. Department of Materials Engineering, Indian institute of Science, Bengaluru 560012
b. Department of Metallurgy Engineering and Materials Science, Indian Institute of
Technology Indore
c. Centre for Laser Processing of Materials, International Advanced Research Centre for
Powder Metallurgy and New Materials (ARCI), Hyderabad
E-mail: [email protected]
The study of fracture in hard materials requires a stable test geometry that eliminates the
need for fabricating a large number of samples. Compression-bending fracture is an old
technique in which compressive loads on a pre-cracked sample induce bending moments
that lead to mode I conditions at the crack tip1 2. Since this geometry shows stable crack
growth, it is useful for studying crack propagation and associated processes, such as crack
bridging and microstructural and compositional inhomogeneity induced variation of fracture
toughness and R-curve behaviour. In addition, due to the relative ease of sample fabrication,
handling as well as of performing tests, this geometry has recently been re-discovered for
studying the fracture behaviour of hard coatings 3. In the present work, we apply this
technique to the study of toughness in -nickel aluminides which constitute the principal
component of bond coats used to protect superalloys from oxidation. We have further
developed some mechanistic details of this geometry to understand the effect of friction
between pillars and loading punch and geometry dimension on stress distribution and
fracture behaviour using finite element (FE) analysis. We have prepared compression
fracture samples from two compositions of NiAl alloys: Ni-50Al, Ni-40Al. Herein, 20 mm
diameter disks of NiAl of desired composition were arc melted and homogenized for 100 h.
Post homogenisation, composition, grain size and grain orientation were analysed. Fracture
samples were prepared from the cast alloy using electro-discharge machining, followed by
femtosecond laser ablation to create a sharp notch in the range of dimensions in which
fatigue pre-cracking or focused ion beam machining are difficult to implement. Fracture
toughness and hardness were measured at room temperature.
Key words: Compression bending fracture Geometry, FEM, NiAl, Fracture toughness
3rd Structural Integrity Conference and Exhibition – SICE2020
69
Multiaxial cyclic test response of low C-Mn steel under proportional/ non-
proportional conditions and constitutive material equations aspects
Punit Arora, BARC
Punit Arora*, Suneel K. Gupta, M.K. Samal and J. Chattopadhyay
Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
*Email of corresponding author: [email protected]
Tel.: +91 22 2559 7139; Fax: +91 22 2550 5151
The piping and vessel components in Nuclear Power Plants (NPP) are generally subjected
to multiaxial state of cyclic stresses/ strains owing to their complex geometries/ loading
conditions. Depending on variation of stress (or strain) components, multiaxial loading can
be categorized as ‘Proportional’ with fixed principal stress axes and ‘Non-Proportional (NP)’
with varying principal stress axes. In general, the damage caused under these two loading
categories is significantly different. Non-proportional cyclic condition results in higher
hardening in material as compared to corresponding proportional case resulting is
reduction of fatigue life. Most of the commercial Finite Element (FE) softwares are not
equipped with advanced material models which are capable of simulating higher hardening
under NP loading. This is due to the reason that these models are mainly based on
associative flow rules and Armstrong-Frederick family of kinematic hardening rules.
In this view, recently a large number of multiaxial tests have been performed on primary
piping material (low C-Mn steel) of Indian Pressurized Heavy Water Reactor (IPHWR) under
uniaxial, proportional and non-proportional multiaxial conditions to determine cyclic
response of material. The material follows Masing idealization with a linear shift along
elastic line under uniaxial and proportional conditions. The uniaxial and proportional
responses are attributed to be modelled by combined kinematic and isotropic hardening
rules with von-Mises yield function and associative flow rule of Prandtl-Reuss. However,
tests hysteresis loops under NP loading conditions have brought out that material does not
follow associative flow equations for von-Mises yield equation. Material once subjected to
90° out-of-phase axial-torsion conditions, does not bring back stress state in elastic regime
even after several un-loadings of axial/ shear strain cycles.
This study mainly highlights some of the key test observations in connections with material
constitutive equations, generally used to model cyclic stress-strain behaviour.
3rd Structural Integrity Conference and Exhibition – SICE2020
70
Effect of notch configurations on geometric factor solutions of an SENW
fracture test geometry.
Hrushikesh Sahasrabuddhe, IIT Bombay
Hrushikesh Sahasrabuddhe*, Abu Zubair, Tejas Chaudhari, Nagamani Jaya Balila
Department of Metallurgical Engineering and Materials Science,
Indian Institute of Technology Bombay, Mumbai 400076, India
Abstract
Materials in fiber or wire form are used at several length scales, sometimes bunched into
cables and at other times reinforced into composites. Knowledge of fracture toughness of
these wires is critical in life prediction. The influence of wire aspect ratio on the Mode I
geometric factor solutions of a straight fronted notch in a wire specimen was recently
established [1]. The present study extends the contem-porary physical understanding to the
modelling of asymmetric notches vis. a vis. convex, concave,chevron, and angled chevron,
as well assymmetric notches vis. a vis. circumferential and double-edged. Multi-parametric
mode I geometric factor solutions as a function of relative crack depth, wire aspect ratio
and location on the crack front have been computed using extended finite element method
(XFEM). Dependence of geometric factor on wire aspect ratio is explained in terms of the
change in stress state ahead of an asymmetric notch and the boundary conditions that
result out of the axial con-straints of a tension test. Additionally, the double-edged-notched
wires are shown to provide the re-quired geometric stability for controlled crack growth in
brittle materials, enabling the measurement of R-curves and cyclic crack growth.
Experimental validation of the geometric factor solutions is obtained through mode I notch
toughness measurements on a brittle linear elastic polymeric material - Poly (me-thyl
methacrylate).
Keywords: Finite Element Analysis, Mode I geometric factor, notch configurations, stable
crack growth
3rd Structural Integrity Conference and Exhibition – SICE2020
71
Effect of pre-strain on fatigue life of DP600 steel in presence of stress
concentrators
Puja Ghosal, IIT Patna
Puja Ghosala, Surajit Kumar Paula, Bimal Dasa, Manaswini Chinarab, K.S. Arorab
a Mechanical Engineering Department, Indian Institute of Technology Patna, Bihar, Patna -
801106, India
b R&D, Tata Steel Limited, Jamshedpur, India
[email protected], [email protected]
Abstract
This study investigates the influence of pre-strain on high cycle fatigue behavior of DP600
steel for a center hole notch specimen. Uniaxial monotonic pre-strain of 12.5% is imposed
along the rolling (RD) and transverse (TD) direction of DP600 steel blank. The center hole
notch specimen is fabricated from the pre-strained blank along parallel and transverse to
the initial pre-strain direction. Monotonic and fatigue performances are assessed for as-
received, parallel, and orthogonal pre-strain conditions. An increase in yield and tensile
strength are noticed after pre-straining. The presence of stress concentration at the notch
tip results in the lower plastically deformed zone for pre-strained specimens relative to as
received specimens. Pre-strain results in negligible influence on the notch fatigue limit.
Advancement of stress-concentration with pre-straining nullified the increased yield stress
and fatigue limit for the notched specimen.
3rd Structural Integrity Conference and Exhibition – SICE2020
72
Static and Dynamic Fracture Toughness Properties of HSLA Steel for Naval
Application
Jeetesh Kumar, NIT Warangal
Jeetesh Kumar*,@, Adya Charan Arohi* ,Jalaj Kumar#, G. Brahma Raju* and Vikas Kumar#
* NIT, Warangal; # DMRL, Hyderabad
@ Corresponding author
Email: [email protected]
Abstract
In the present investigation, static and dynamic fracture toughness properties of HSLA
steel have been evaluated. Standard fracture mechanics CT (compact tension) type
specimens for static fracture toughness, CVN (Charpy V-notch) specimens for dynamic
fracture toughness have been extracted from the industrial plate in LT and TL directions.
Elasto-plastic fracture toughness tests (JIC) have been performed using single specimen
unloading compliance technique. For the dynamic elasto-plastic fracture toughness (JID)
tests, CVN samples have been fatigue precracked to different crack lengths levels.
These samples are further tested under impact loads in an instrumented impact
machine. Crack initiation energies have been deduced from dynamic load-deflection
curves. Subsequently, JID have been evaluated using these energies. No significant
difference is observed in the dynamic fracture toughness properties w.r.t. orientations.
However, the dynamic fracture toughness values are lower than static fracture
toughness. This may be due to higher strength of materials under dynamic conditions
which is known to lower the fracture toughness values. Further, SEM based
fractographic analysis have been performed on all the tested samples to identify various
fracture micromechanisms.
Keywords: JIC; JID; HSLA steel
3rd Structural Integrity Conference and Exhibition – SICE2020
73
Effect of deformation and aging on hardening behaviour of Maraging Steel
250
Kevin Jacob, IIT Bombay
Kevin Jacob a, Saurabh Dixit b, Anton Hohenwarter c, B. Nagamani Jaya a
a Department of Metallurgical Engineering and Materials Science, Indian Institute of
Technology Bombay,Mumbai, Maharashtra, India - 400076
b Mishra Dhatu Nigam Ltd. (MIDHANI), Hyderabad, Telangana, India - 500058
c Department of Materials Science, Chair of Materials Physics, Montanuniversität Leoben,
Jahnstraße 12, 8700 Leoben, Austria
Abstract
Plastic flow of materials is dependent on the ability of dislocations to move along specific
crystallographic planes under the application of an external stress. Hindrances encountered
to this flow will result in a higher stress required to facilitate this movement, leading to the
overall hardening of the material. The activation of the different slip planes along which the
dislocations move are governed by Schmids law. In certain situations however dislocations
prefer to move along a single plane in a condition called as planar slip, the occurrence of
which leads to an overall softening of the material. Maraging steels are one such class of
materials where in their as-solutionised condition, majority of slip is planar. Upon ageing,
they acquire a diverse microstructure with the presence of lath boundaries, precipitates and
reverted austenite each of which has a different effect on the overall hardening behaviour
of the material. In the current study the extent of different strengthening or softening
mechanisms is quantified as a function of applied deformation strain through High Pressure
Torsion (HPT) and ageing parameters. The stages of hardening and their mechanisms are
identified for both the as-received and HPT processed maraging steels. HPT processing
leads to an increase in strength by nearly 70% along with a change in the morphology and
distribution of the precipitates. On the flip side, the structural integrity of these steels suffers
from poor ductility. The precipitate morphology, distribution and spacing has been
characterised using Atom Probe Tomography (APT). The effect of the change in
morphology of the precipitates has been studied through finite element modelling to
understand the distribution of stresses around the differently shaped precipitates that act
as stress concentrators for early onset of fracture.
3rd Structural Integrity Conference and Exhibition – SICE2020
74
Remaining Life of Fastener Joints under Bearing and Bypass Fatigue
Loading
I Syed, Jain University
I Syed, B. Dattaguru and A.R. Upadhya
School of Aerospace Engineering, Jain (Deemed-to-be University)
Bengaluru
Abstract
Fastener joints are widely used in aircrafts to connect different parts in primary and secondary
structures. These create a non-permanent joint, unlike the case of welded or adhesive bonds and
also allow easy assembly and dismantling. However even though fastener joints provide easy
access to inspect, they cause stress concentrations and are susceptible to damages such as cracks
under overload and/or fatigue. Such cracks could grow to the critical sizes under aircraft flight loads
during service life. It becomes necessary that such a fastener joint is analysed suitably to ensure
safety. In normal joints the life of the joints is estimated using the S-N curve whereas critical joints
are designed based on the damage tolerance approach. This paper presents both approaches for a
few typical joints under bearing and bypass loading.
In this paper, the fatigue life of lap joints between rectangular plates with one to three bolts in series
is estimated numerically. Marginal clearance is used in the bolts to represent a practical
configuration. The current analysis is for metallic plates, but the approach is also applicable to
composite plates. A 2-dimensional non-linear contact stress finite element model (FEM) is used to
study the stresses and strains around the bolt holes in the upper plate of the joint. The FE model is
validated with the results in the literature on similar configurations. The variation in stress
concentration is studied with varying bearing to bypass load ratios. The reduction in strength of joint
due to the presence of cracks is also investigated. For damage tolerance analysis, initiation of
cracks is assumed to be at the stress concentration points. In the initial studies, constant amplitude
(CA) fatigue loading is applied and these cracks are grown till failure. The life, in terms of such CA
cycles, is presented in this paper. The Modified Virtual Crack Closure Integral (MVCCI) technique is
used to compute the strain energy release rate in mode – I of the crack. Crack growth life is
computed using the Paris law with Elber correction. Finally, the fatigue analysis loading is carried
out using variable amplitude FALSTAFF standard flight load spectra for typical fighter aircraft. Rain
flow cycle counting is used to extract the damage causing cycles. Results are presented in a way
that remaining life can be estimated at any stage of operational loading. This type of prognostic
approach helps in scheduling maintenance operations. The study presented in this paper is a prelude
to the development of a computational model as a part of a digital twin for structural joints.
Keywords: Lap joint . Fatigue life . Crack . Prognosis
3rd Structural Integrity Conference and Exhibition – SICE2020
75
Viscoplastic Constitutive Parameters for Inconel alloy-625 at 843K
S.C.S.P. Kumar Krovvidi, IGCAR S.C.S.P. Kumar Krovvidi1*, Sunil Goyal2, J. Veerababu1, A. Nagesha1, A.K. Bhaduri1
1Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India. 2Nuclear Fuel Complex, Kota Project, Rawatbhata- 323305, India
Abstract
Inconel alloy-625 is one of the candidate materials for high temperature bellows in sodium-
cooled fast reactor (SFR) systems. Typical temperature in SFR systems is around 843K at
which failure modes such as creep and creep-fatigue interaction are significant.
Viscoplastic analysis gives the combined strains due to fatigue including stress relaxation
during hold time. This paper presents the estimation and validation of the parameters of
Inconel alloy-625 for Chaboche and Rousselier viscoplastic constitutive model at 843K. A
set of low cycle fatigue and creep-fatigue interaction tests were carried out. The parameters
defining the isotropic and kinematic hardening of the material were estimated from the LCF
tests. The viscous parameters were estimated from the stress relaxation data obtained
from the CFI tests. Validation of the parameters of the viscoplastic constitutive parameters
was carried out by successfully predicting the hysteresis loops and the stress relaxation
behaviour exhibited by the alloy.
Keywords: Inconel alloy-625; SFR systems; visco-plastic; isotropic hardening; kinematic
hardening; finite element analysis.
3rd Structural Integrity Conference and Exhibition – SICE2020
76
Mechanical behavior of PEM membrane under uniaxial tension
Kartheek Pilla, IIT Bombay
Kartheek Pilla, Aakash Tanwar, Krishna N Jonnalagadda
Department of Mechanical Engineering, Indian Institute of Technology Bombay
Abstract
Polymer electrolyte membrane (PEM) based fuel cells have numerous advantages
over conventional power generation sources owing to their low operating noise, higher
efficiency compared to diesel or gas engines, and negligible pollution. These positive
factors have contributed to the demand of PEM based fuel cells. PEM membrane is a crucial
component of a fuel cell, whose reliability limits the life of the fuel cell. In this work, the
fracture toughness of the PEM membranes under tensile loading at room temperature was
investigated. Nafion-212 was the PEM polymer chosen for this work. Under operating
conditions, Nafion is highly ductile. In this work, the methods available to compute fracture
toughness of ductile polymers in thin film form were reviewed. Depending on the
constitutive behaviour of the polymer under tensile loading, suitable methods for fracture
toughness measurement were also suggested. Fracture toughness was calculated through
in-situ experiments on the thin films of Nafion-212. The essential work of fracture method
was employed, and its applicability as a measure of fracture toughness was verified. Digital
image correlation technique was employed for the validation of EWF as well as computation
of J-integral. The equivalence between EWF and J-Integral calculation methods was also
established. The effect of notch preparation had significant effect on the essential work of
fracture value due to the varying crack tip root radius.
Keywords: Polymer Electrolyte Membrane (PEM); Essential work of fracture (EWF); Fracture
of thin films; Digital image correlation.
3rd Structural Integrity Conference and Exhibition – SICE2020
77
Investigation into hydrogen induced blister cracking and mechanical failure
in pipeline steels
Vishal Singh, IIT Ropar
Vishal Singh*, Dhiraj K. Mahajan
Ropar Mechanics of Materials Laboratory, Department of Mechanical Engineering, Indian
Institute of Technology Ropar, Rupnagar, Punjab, 140001, India
Abstract
This work aims to investigate the role of hydrogen-induced blisters on tensile and fatigue
damage of pipeline steels (X65 and X80). The electrochemical method of hydrogen charging
is employed to simulate hydrogen-induced blister formation. Similar hydrogen charging
conditions result in different sizes, shapes, and number of blisters in both types of steels.
DIC analysis coupled with in-situ tensile/fatigue investigations confirmed the blisters as
potential stress concentration sites. Synergistic action of hydro-gen and stress
concentration around these blister type notches intensify the overall mechanical damage of
material under hydrogen atmosphere. Morphology and relative positioning of blisters is
confirmed to affect overall tensile and fatigue behavior significantly.
Keywords: Hydrogen embrittlement, blisters, pipeline steels, fatigue damage
3rd Structural Integrity Conference and Exhibition – SICE2020
78
Analysis of a turbofan engine bearing failure
Swati Biswas, DRDO
Swati Biswas, Jivan Kumar, Satish Kumar VN
Materials Group, Gas Turbine Research Establishment
Defence Research & Development Organization, Bengaluru, India
Structural integrity of the rotor support systems of the turbofan engines in aircraft
propulsion system application is of utmost importance as they constrain the relative motion
between the rotating elements at a speed close to 50,000rpm. Premature failure of a ball
bearing was encountered during ground testing of a turbofan engine leading to seizure of
shaft rotation.
Dis-assembly of the engine components revealed severe distress in one of the bearings.
The bearing cage was fractured, a portion was melted and few balls were stuck to the outer
race with the cage material. The inner race, all the rolling elements (balls) and outer race
were found to be covered by a golden layer which was subsequently found to be the cage
material. The fractured surface of the bearing cage was examined visually, macroscopcially
using stereo-binocular microscope and microscopically under scanning electron
microscope. Lower magnification view of the fractured surface reveled crack front
emanating from the ball pocket surface of the cage. Higher magnification observation
revealed striations on the fractured surface indicating fatigue failure of the cage. The
fractured surface was found to be oxidized. Other cage pieces collected from the failure
location showed solidified structure indicating melting and re-solidification of the cage
material.
Examination revealed that failure of the cage in the ball bearing of the engine was
associated sequentially with cage failure, seizure of cage and ball motion, cage melting,
flow and subsequent solidification, and inner race shift with respect to the outer race
towards the front face. Failure of the cage appeared to be the first event in this case. The
fatigue failure of the cage resulted in restricted cage movement, impeding the ball
movements which in turn resulted in huge frictional heat thereby melting the cage material.
The melt re-solidified later when the temperature cooled down.
Key words: ball bearing, inner race, outer race, rolling elements, fatigue
1Corresponding author, e-mail: [email protected]
3rd Structural Integrity Conference and Exhibition – SICE2020
79
Evaluation Of Cyclic Properties Of 50Ni-24Cr-20Co-0.6Mo-1Al-1.6Ti-2Nb
Alloy At Advanced Ultra Supercritical Steam Temperature
Ashmita Patra Banerjee, Midhani
Ashmita Patra Banerjee, Rajasekhar Kondabolu
Research & Development, Mishra Dhatu Nigam Ltd
Abstract
50Ni-24Cr-20Co-0.6Mo-1Al-1.6Ti-2Nb alloy is a candidate material for superheater tubes
and turbine rotors operating at 750°C in proposed A-USC power plant. Present study aims
to estimate cyclic strength and creep fatigue interaction behavior at operating steam
temperature. Strain controlled LCF tests are carried out within the strain range of 0.2%-1%
at RT and 750°C to evaluate effect of temperature on endurance limit. Substantial hardening
at all temperatures, which becomes more evident with increasing strain amplitude, is
attributed to the cumulative effects of dislocation tangle formation with their mutual
interaction and to the immobilization of dislocation by fine γ' precipitates. Deformation
mechanisms influencing the endurance limit as a function of strain rate are identified. Hold
times upto 500s are introduced at 750°C to evaluate creep fatigue interaction behaviour,
one of the primary damage mode in this case. Effect of direct aging on cyclic properties also
comes under the scope of present study.
Keywords: Ultra supercritical, Low cycle fatigue, Alloy 740
3rd Structural Integrity Conference and Exhibition – SICE2020
80
TS05
Fracture Mechanics at Multiple Length Scales
Organizer
N. J. Balila, IIT Bombay
13th Dec 4-6 pm, 7-10.30 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
81
Invited Speakers
Load Interaction in Fatigue Crack Growth – Cracking a Lasting Controversy
R. Sunder
ITW-India (P) Ltd
100th years of Griffith’s Theory and fifty years of regimented application of
Linear Elastic Fracture Mechanics into engineering practice have seen notable
improvements to residual life of safety critical structures. Residual life
estimates rely on the ability to estimate the duration of service usage
associated with the growth to critical proportions of a fatigue crack that may
have been too small to detect at the previous inspection.
A striking anomaly in research on fatigue crack growth has been its focus on
constant amplitude loading even if there is hardly any case of engineering
application that is essentially constant amplitude by nature. As a
consequence, even after more than fifty years of awareness of load interaction
effects that cause significant variation in crack growth rate from what one
may expect under constant amplitude loading, controversy continues to
persist about what exactly causes such variation. One school of thought
attributes load interaction and stress ratio effects to the phenomenon of crack
closure in the wake of the crack tip. Another school of thought attributes these
effects to the response of the material ahead of the fatigue crack tip.
This talk describes an essentially local research effort that appears, finally, to
resolve contradictions between the two contradictory schools of thought by
coming up with irrefutable empirical evidence backed up by simple and
transparent analytical modeling that together explain how the two load
interaction mechanisms actually operate in concert. The results of the
ongoing study open new avenues for path breaking research to improve the
quality of residual fatigue life estimates in engineering application, including
development of a new testing practice, emerging opportunities in additive
manufactured components and design of fatigue critical components.
Dr. R Sunder obtained his M.Tech. and Ph.D. from Kiev Institute of Civil
Aviation. He is currently research director at Instron Centre of Excellence,
Bangalore. He founded Bangalore Integrated System Solutions (P) Ltd (BISS)
in 1992, a developer and manufacturer of mechanical test systems. BISS now
operates as an amalgamated Division of Instron, a world-leader in mechanical
test systems. He is a fellow of Indian Academy of Sciences . He is President
at Indian Structural Integrity Society
3rd Structural Integrity Conference and Exhibition – SICE2020
82
Role of Photoelasticity in Advancing Fracture Mechanics Education and
Research
K. Ramesh Professor
IIT Madras
Photoelasticity has had a significant influence in the development of fracture mechanics
ever since the experimental work on running crack by Post and Wells, and the fringe
interpretation by Irwin. The importance of higher-order terms in crack-tip stress field
equation has been beautifully illustrated by Sanford and his co-workers. With developments
in digital computers and progresses made in image processing, use of statistical methods
for data processing, digital acquisition of fringe data has been perfected over the decades
to evaluate stress field parameters reliably. This has enabled solving complex problems
involving multi-axial loading with interacting cracks in mechanical and thermal loadings as
well as in the presence of residual stresses. Hybrid photoelastic-FE analysis has helped in
improving boundary conditions for numerical analysis. Crack-growth prediction is also
influenced by higher-order terms as revealed by photoelasticity. The talk would trace these
developments and also highlight the educational and processing tools available for
researchers.
K. Ramesh is currently the K Mahesh Chair Professor at the Department of Applied
Mechanics, IIT Madras and formerly a Professor at the Department of Mechanical
Engineering, IIT Kanpur. He has authored 175 technical papers, two books, two e-
books and three book chapters and four video courses in NPTEL. He is a Fellow of the
Indian National Academy of Engineering and has received the Zandman award from
Society for Experimental Mechanics, Distinguished alumnus award from NIT Trichy.
He has developed several educational software and processing software that are
copyrighted. Member of the Editorial boards of Strain and Optics and Lasers in
Engineering
3rd Structural Integrity Conference and Exhibition – SICE2020
83
Hydrogen Behaviour in Rail Steel during Steel Manufacture
Dr G Balachandran Vice-President (R&D)
JSW Steel, Vijayanagar
The damage associated with hydrogen in steel may be divided into environmentally assisted
damage and those which are due to other reasons. In the former category, the damages
include Hydrogen embrittlement, stress corrosion cracking and corrosion fatigue. The latter
category of damage is associated with the hydrogen that dissolves in the steel during
manufacture that ends up in severe damage during service. The hydrogen dissolved in the
steel during manufacture manifests as hydrogen flaking of the steel, that leads to what is
popularly called as shatter cracks or Tache Ovales in Rail steels. There can be other
damages in this category, which are blow hole or pin hole formation, fish-eye formation and
longitudinal cracking. Rail steels are very sensitive to hydrogen pick up during the
manufacture and it has potential to generate damage in service, in spite of passing through
all the initial inspection stages. The Hydrogen flaking event has not yet been successfully
timed. Hence, every precaution is taken to prevent the hydrogen pick up during the
manufacture of the steel. Every 1 ppm H, if it freely evolves in a solid steel, it has potential
to generate 9% by volume void. The present study deals with two rail steel grades VAR89S
(typically, 0.70%C–0.3%Si–1.1%Mn–0.015%S) and VAR101 (typically, 0.80%C–0.42%Si–
1.01%Mn–0.65%Cr–0.005%S) manufactured at JSW Steel Ltd for application in Euro Rail in
Italy. The hydrogen distribution in the steel varies from surface towards the core associated
with the phase transformation. This also explains the reason why hydrogen flaking takes
place towards the mid-section of a wrought steel product. In the present study, the hydrogen
levels were tracked in 15 heats produced right from the melting stage to rail making stage.
In one heat, where a higher level of hydrogen content was identified, the steel was hot rolled
and a series of anti-flaking heat treatments was carried out to reduce the hydrogen levels.
The removal of hydrogen by anti-flaking heat treatment was explained using a Fick’s Law
based model. The presentation deals with the damages caused by hydrogen in steel during
steel making and the measures needed to mitigate the same during manufacture.
Dr G Balachandran has done his M Tech from IIT Kanpur and PhD from IIT Bombay. He
has served as a scientist for over 20 years with DMRL, Hyderabad. He served later nearly
2 years with Ashok Leyland, Chennai. Subsequently, he served for more than 6.5 years at
Kalyani Carpenter Special Steels Ltd., Pune. He was a visiting faculty with IIT, Madras close
to a year. During the past more than 3 years, he is with JSW Steel Ltd. and has served in
the Salem unit and presently working in the Vijayanagar unit.
3rd Structural Integrity Conference and Exhibition – SICE2020
84
Structural Integrity of ship hull structures
K. Sridhar Scientist, Naval Materials Research Laboratory (NMRL),
Defence Research Development Organisation (DRDO), Ambernath
email : [email protected], [email protected]
Metals are widely used for the fabrication of various marine engineering components and
therefore their protection in aggressive seawater environments is of prime concern to marine
designers, engineers and constructors. Generally the choice of materials and the protection
methods depend on life cycle cost, regular maintenance required during the life of the component,
criticality of the component etc. Other factors of importance include strength, expected functional
performance, availability of materials and capital cost. Hull structures and its appendages of naval
ships are constructed by joining numerous assemblies/sub-assemblies / sub-systems made of
HSLA steel, primarily by various welding processes. This being the most critical structural member,
its structural integrity is of prime importance due to varying type of loads experienced by it due to
operating machinery inside as well as due to impacting sea waves from outside.
During service, the ship’s hull structure is subjected to external loading by impacting sea wave
from outside, whose amplitude and frequency depends on the sea state. The hull is also subjected
to fatigue loads due to operating machinery inside the ship. Thus the steel, its weldments & heat
affected zone (HAZ) are subjected to a complex spectrum of loading in an aggressive chloride
environment, which are both dynamic and static. This leads to initiation of crack at highly stressed
critical regions either from externally formed pits on the hull surface and from intrinsic defects in
the material such as porosities / blowholes /inclusions.
In this talk, the conjoint effect of fatigue loading and aggressive seawater environment effect on
the corrosion fatigue crack growth rates (CFCGR) are presented for two different types of
shipbuilding steels are presented. The mechanism of corrosion fatigue process, the various
parameters affecting the crack growth rates and the effect of environment and the loading frequency
on the fracture morphology will be delivered. The methodology adopted for fatigue life estimation
of hull structures based on the analytical approach and the experimental determined parameters will
be dealt with. Further the futuristic in-situ fatigue life prediction of ship hull structures estimation
based on sensors and AI/ML will be highlighted.
Dr.K.Sridhar has done his Ph.D. in Corrosion Science and Engg, from I.I.T, Bombay. His field of
interest includes Surface Engineering using HVOF and laser processing for marine corrosion
resistant coatings, Localized corrosion, Cathodic protection, Stress corrosion cracking, Corrosion
fatigue and Failure Investigation. He has done his postdoctoral fellowship from Boston University,
USA on PVD coatings and published 40 papers (national & international) including 3 chapters in
ASM handbooks & 2 in books and granted 4 patents. He is a reviewer for 6 international journals
published by Elsevier and Taylor & Francis, USA.
3rd Structural Integrity Conference and Exhibition – SICE2020
85
Elastic-plastic fracture mechanics at micrometer scale: Requirement,
Challenges and possible solutions
Prof. Ashish Kumar Saxena
Assistant Professor
School of Mechanical Engineering, Vellore Institute of Technology Vellore
In the current era of miniaturization, it necessary to understand the materials behaviour and
reliability at application length scale. For brittle materials the linear elastic fracture
mechanics is well established, but for semi-brittle materials linear elastic fracture
mechanics cannot be used to determine the fracture toughness of micro length scaled
material volume due to relatively large plastic zone size compare to sample size. In these
case the elasto-plastic fracture mechanics (EPFM) using J-integral method have to be used
to determine the fracture behaviour. There are still many challenges exist even application
of EPFM at micrometer length scale. In the talk, these challenges as well as possible
solution for reliable estimation of fracture toughness of elastic-plastic materials will be
presented.
Dr. Ashish Kumar Saxena, is currently working as Assistant Professor in School of
Mechanical Engineering, VIT Vellore. Before joining current position, he worked on elasto-
plastic fracture mechanics in Mac-Planck Institute for Eisenforschung Germany as Mac-
Planck Post-Doctoral Research Fellow. He also works briefly in Materials Modelling lab
of GE Global Research Centre. His research interest are micromechnics of materials,
microstructure property correlation and materials processing.
3rd Structural Integrity Conference and Exhibition – SICE2020
86
Contributed Speakers
FRACTURE EVALUATION OF A HIGH-PRESSURE GAS BOTTLE BY J-
INTEGRAL BASED FAILURE ASSESSMENT DIAGRAM USING ANSYS
K. Anjali Raj, MBCET
K. Anjali Raj1, A. K. Asraff2,Viswanath V.2, Vivek S.2 and Aneena Babu1
1 Mar Baselios College of Engineering and Technology,
2 Mechanical Design & Analysis Entity, LPSC/ISRO
Abstract
Metallic pressure vessels are used in launch vehicles in the form of propellant tanks, high pressure
gas bottles, water tanks etc. Different metals like Titanium alloys, Aluminium alloys, steels etc. are
used for the fabrication of these pressure vessels. These structures may contain cracks or crack
like defects, either inherently present in the base material or introduced during fabrication processes
such as welding. These crack-like defects have the potential to propagate rapidly under tensile
stresses during pressure testing or during service condition loadings leading to its catastrophic
failure. It is required to study the effect of these crack-like defects in pressure vessels through the
application of linear elastic as well as elastic-plastic fracture mechanics principles. The Failure
Assessment Diagram (FAD) concept is used to evaluate whether a crack may cause structural
failure. The FAD technique accounts for both brittle and ductile failure modes of the cracked
structure using two ratios: Load ratio (Lr) and Brittle fracture ratio (Kr). In this work, the variation of
fracture parameters such as stress intensity factors and J integral values along the crack front in a
high-pressure gas bottle containing part through crack used in an ISRO developed satellite launch
vehicle has been studied using ANSYS/Workbench (Version 18.1) general purpose finite element
analysis code. The objective of this paper is to ensure the structural integrity of the above gas bottle
using J integral based FAD. Both elastic and elasto- plastic fracture analysis of the gas bottle has
been done, the latter being done using multilinear kinematic hardening plasticity model. The ultimate
pressure carrying capacity of the structure in the presence of a specific crack has been calculated
directly from the FAD. The mode of failure of the structure, whether brittle or ductile, is also predicted
from the above diagram.
Keywords: Failure Assessment Diagram; Stress Intensity Factor; J integral; part through crack.
3rd Structural Integrity Conference and Exhibition – SICE2020
87
Clamped Beam Bending for Mixed Mode and Interface Fracture Toughness
Measurements
Ashwini Kumar Mishra, IIT Bombay
Ashwini Kumar Mishra*, Neha Kumari, Balila Nagamani Jaya
Department of Metallurgical Engineering and Materials Science,
Indian Institute of Technology Bombay, Mumbai, 400076, India
Abstract
Clamped beam geometry is successfully used for evaluation of mode-I fracture toughness on micro
and bulk scale[1][2]. The present study explores a combination of mode I and mode-II fracture
toughness by changing the position of the loading point with respect to notch, and of angular
notches with respect to the bending axis. Mode-II stress intensity factor is computed as a function
of different position of loading point and relative crack length using the finite element method. Using
this information, mixed mode fracture trajectory is predicted, which is relevant for evaluation of
fracture behavior of multilayered and composite structures. Systematic study of interface fracture
energy in bi-material composite structures is also performed using finite element method and a
compliance based solution is proposed, which is applicable for various extents of elastic mismatch.
This will broaden the scope of the clamped beam as a generalized fracture toughness testing
technique for brittle systems.
Keywords: Mixed mode loading, interface fracture energy, finite element method, clamped beam
bending
3rd Structural Integrity Conference and Exhibition – SICE2020
88
Deformation of Polycrystalline Copper during Mode-I Loading
Ashutosh Rajput, IIT Patna
Ashutosh Rajput, Surajit Kumar Paul*
Department of Mechanical Engineering, Indian Institute of Technology Patna, Bihar, Patna -
801106, India
[email protected],* [email protected], [email protected]
Abstract
Molecular Dynamics simulation is carried out to analyses the effect of crack in arranged
polycrystalline copper under mode-I loading. The orientation of centre grain is [100] [010]
[001], and surrounding grains are oriented randomly and kept 200,400, and 600 with respect
to the centre grain. Higher stress concentration has been observed at the crack tip, and
nucleation of dislocation is noticed at the triple point junction. The centre grain produces a
continuous generation of dislocations, which gives rise to a slow and stable transgranular
failure of polycrystalline copper during subsequent mode-I loading.
3rd Structural Integrity Conference and Exhibition – SICE2020
89
Implementation of phase-field model for fracture in functionally graded
brittle materials for various material property gradations
Aravind R, IIT Madras
Aravind R a,b, Ratna Kumar Annabattula a, Jayakumar K b
a Department of Mechanical Engineering, Indian Institute of Technology, Madras
b Vikram Sarabhai Space Centre, Thiruvananthapuram
Abstract
Modelling fracture failure using conventional techniques based on discrete modelling is very
complex as it requires continuous tracking of discontinuities in the displacement field.
Phase field model based on variational frame work replaces sharp crack surfaces by a
damage variable which is diffused onto the crack surface. The crack diffusion is controlled
using a regularization parameter. The phase field approach offers the advantage of
modelling crack where multiple crack nucleation, crack branching and crack coalescence
can be captured without prior knowledge of the crack path. In this investigation, phase field
model is applied to simulate crack growth characteristics in Functionally Graded Materials
(FGMs) for various material property gradations for standard reference cases. Functional
gradation of material property can be controlled from point to point by varying volume
fractions in a controlled manufacturing processes. For determining effective properties,
several models like Voigt Scheme, Mori-Tanaka Scheme, Sigmoid Scheme, Exponential
Scheme etc are employed. The phase field model for brittle fracture is implemented in a
commercial finite element software using user defined UEL and UMAT subroutines.
Numerical simulations show that the crack growth significantly varies for FGMs under
various material gradation laws.
Keywords: Phase Field Method (PFM), Crack Propagation, Functionally Graded Materials
(FGM).
3rd Structural Integrity Conference and Exhibition – SICE2020
90
On the role of secondary voids in the mechanics of plane strain ductile
fracture – A numerical study
A. K. Dwivedi
A. K. Dwivedi, I.A. Khan, J. Chattopadhyay
Reactor safety division, BARC, (HBNI)
Abstract
Ductile fracture in metals occurs due to the nucleation, growth and coalescence of
microscopic voids, resulting in the formation of a macroscopic crack. These voids often
originate at different length scales as a result of cracking of larger size inclusions or
decohesion at second phase particles.
In several structural alloys like carbon-manganese steels, secondary voids play a vital role
in the growth and coalescence of the primary voids. The existing literature on ductile
fracture suggests that for a given initial void volume fraction, the spatial distribution of the
secondary voids in the intervoid ligament between the primary voids has a significant
influence on the fracture ductility. A systematic study analyzing the effect of orientation,
clustering and the shape of secondary voids, however, has yet not been performed. In the
present study, cell model based finite element analyses are performed to understand the
role of secondary voids on the growth and coalescence of the primary voids at mesoscale.
Both the primary and secondary voids are modelled explicitly and an elastic-plastic
response is assumed for the matrix. A double periodic array of primary voids subjected to
different magnitudes of applied stress tri-axiality is analyzed assuming plane-strain
condition. The numerical results obtained from explicit modelling of primary and secondary
voids are compared with the case where a homogenized response of the latter is simulated
using the Gurson model. The initial void volume fraction is the same in the two cases. Our
numerical studies reveal that the orientation of secondary voids relative to primary voids
may change the mode of coalescence from internal necking to void-sheeting and vice-versa.
Clustering of secondary voids, for the same initial void volume fraction, leads to onset of
primary void coalescence at lower magnitudes of nominal strain. It is observed that the
shape of the secondary voids also influences the fracture ductility of the material.
Keywords: Ductile fracture, Porous plasticity, Secondary voids, Flow localization.
3rd Structural Integrity Conference and Exhibition – SICE2020
91
Nonlocal diffused approach to model delamination in composites
D. Pranavi
D. Pranavi*, A. Rajagopal
Department of Civil Engineering, IIT Hyderabad, 502285.
Abstract
Delamination is a critical failure mode in composites as its constituents get separated due
to the weakening of the interface between the layers of such composites. Manufacturing
defects, sites of stress concentrations, free edge effects are causes for delamination. Upon
loading of such composites the delamination can grow and also mitigate between layers,
finally leading to the structural failure. In order to assess structural integrity, the material
parameters especially of the interface that governs the delamination growth should be
determined. In the present work, a nonlocal diffused approach, is proposed to model the
delamination. Nonlocal approaches helps in understanding the complex mechanisms of
delamination growth and mitigation and operates at a material length scale. The
performance of the proposed formulation is illustrated through representative numerical
examples.
Keywords: Delamination, Composite, Nonlocal approach, Interface.
3rd Structural Integrity Conference and Exhibition – SICE2020
92
TS06
Fracture and Fatigue of Structural Adhesives
Organizer
N. Datla, IIT Delhi
18th Dec 7-8 pm, 9-10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
93
Invited Speakers
Fatigue behaviour of polymer nanocomposites
CM Manjunatha Chief Scientist and Head
Structural Integrity Division, CSIR-National Aerospace Laboratories
Bangalore 560017, India
In this presentation, improved fatigue properties of polymer nanocomposites
containing various types of nano fillers such as carbon nano tubes, graphene, silica
nano particles etc., is reviewed. It has been observed that over 10-100 times
improvements in fatigue life could be obtained in polymer composites by addition of
nano fillers. In particular, the constant amplitude fatigue behavior of a glass fiber
reinforced silica nano particle modified epoxy composite is described in detail. Further,
it is shown that significant spectrum fatigue life enhancement could also be obtained
in GFRP nanocomposites. The underlying mechanisms for such fatigue life
improvements in nanocomposites are discussed. Also, fatigue life prediction
methodology under spectrum loads is discussed with examples. With such
enormously improved fatigue resistance, nanocomposites could well be developed as
fatigue immune structural materials in the near future.
Dr. CM Manjunatha obtained his B.E. (NITK) in 1988, M.E. (IISc.), in 1991 and Ph.D.
(Cambridge Univ., UK) in 1995. He was a post-doctoral fellow at Imperial College,
London, UK in 2008. He is a recipient of Gold medal for first rank in B.E. (1988),
Cambridge-Nehru Scholarship (1991), ORS award from CVCP London (1991-1994) and
UKIERI research fellowship (2008), NAL outstanding award for project execution-2013
and NAL best innovation award- 2017. He has over 150 publications to his credit in
international journals, conferences and seminars. He is founder secretary of InSIS and
member of many professional societies
3rd Structural Integrity Conference and Exhibition – SICE2020
94
Adhesively bonded joint in scarf jointed composite structures
M. Ramji Professor and Head
Department of Mechanical and Aerospace Engineering
In this talk focus is on the mechanical behaviour of both single and double tapered scarf
adhesively bonded joint of Carbon fibre reinforced polymer (CFRP) adherend subjected to
tensile loading. The layup sequence of the CFRP adherend having unidirectional (UD) [0°]16
and quasi [+45/−45/0/90]2S are considered. The adhesive used here is Araldite 2015 supplied
by Huntsman which is a two-part epoxy system of intermediate toughness grade. Here, 2D
digital image correlation (DIC) technique is used for capturing the whole field longitudinal,
peel and shear strain distribution over the adhesive bond line of the CFRP specimen. In
addition, 2-D finite element analysis (FEA) of scarf joint model is carried out for validating
the DIC results. In the finite element model, cohesive zone elements are used for the
modelling of both adhesive layer and inter/intra laminar interface of the composite laminate.
To verify the proposed numerical model, joint's initial stiffness, failure load and
corresponding displacement obtained from FEA are compared with the experimental load
– displacement results.
He obtained his Ph.D. Degree from Applied Mechanics Department, IIT Madras in the area
of digital photoelasticity and graduated in Dec 2007. After his PhD, he worked as Engineer
in General Electric, JFWTC, Bangalore in the area of stress analysis of GenX engine till
March 2009. Currently, he is Professor and Head, Mechanical Engineering Department at
IIT Hyderabad. His areas of interest are material characterization, experimental solid
mechanics, composite structures, and fracture mechanics.
3rd Structural Integrity Conference and Exhibition – SICE2020
95
Contributed Speakers
Fracture R-curve and Cohesive Law of Aged CFRP Composite Adhesive
Joints
Mohd. Tauheed, IIT Delhi
Mohd. Tauheed*, N.V. Datla
Department of Mechanical Engineering, Indian Institute of Technology Delhi, Hauz Khas,
New Delhi, 110016, India
*Corresponding author: Mohd. Tauheed ([email protected])
Abstract
R-curve behaviour of brittle epoxy adhesive was studied using CFRP/epoxy adhesive joints.
Moreover, we studied the variation in cohesive law between crack initiation and steady state
part of the R-curve. Double cantilever beam (DCB) specimens were made of composite
adhesive joints to determine the mode I fracture toughness. The adherends are made of
CFRP laminates and adhesives used are AV138/ HV998 (brittle adhesive). The mode I
tractions-separation relations were extracted with the help of digital image correlation (DIC)
of the crack tip images. AV138 showed independence of G on crack length with initiation
and steady-state fracture toughness. The fracture R-curves of a brittle adhesive that was
aged under the ageing environment of 40 °C and 82 % relative humidity. The adhesive layer
was then dried before fracture testing in order to measure the effects of irreversible
degradation (i.e., without the reversible, plasticization effect of absorbed free water). The
cohesive parameters were used in the FE modelling using ABAQUS to predict the joint
strength numerically.
Keywords: ageing, cohesive law, R-curve, CFRP joint
3rd Structural Integrity Conference and Exhibition – SICE2020
96
Mode-I fracture behavior of carbon nanofiber reinforced epoxy adhesive
joints
Amit Chanda, IIT Delhi
Amit Chanda, Sujeet Kumar Sinha, Naresh Varma Datla*
Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi-
110016
Email: [email protected]
Abstract
Adhesives are increasingly used in joining structural components owing to its high specific strength,
ability to join intricate shapes and capability of better stress transfer capability. Epoxy adhesives are
the commonly used structural adhesives, which are used to bond components in aerospace,
automotive and marine industries. Though epoxy has good mechanical properties, chemical stability
and adhesive properties, it has very low fracture toughness and impact resistance. Fracture
toughness of epoxy can be increased by fillers, specially carbon-based nanofillers. In this study,
epoxy was modified using carbon nanofiber (CNF) and the effect of CNF was checked on mode I
fracture toughness (GIC) of epoxy.
Carbon nanofibers were dispersed into epoxy using ultrasonication method. P2-etched aluminum
adherends were bonded using pure and CNF modified epoxy to fabricate double cantilever beam
(DCB) specimens. Fracture tests were conducted with these DCB specimens to assess and evaluate
the mode-I fracture behavior. Modified beam theory was used for fracture toughness calculation.
Presence of CNF was observed to increase the GIC value significantly. Improvement ~ 300 % were
found when 0.5 wt% CNF was added. Fractured surfaces were studied under SEM to understand the
toughening mechanisms. Cohesive zone model with bilinear traction separation law was used in this
study to predict load displacement behavior of pure epoxy and CNF/epoxy joints. Obtained results
from finite element analysis were found to be in good agreements with experimental results.
Keywords: Carbon nanofiber/epoxy, DCB joint, fracture toughness, cohesive zone modeling
3rd Structural Integrity Conference and Exhibition – SICE2020
97
A MACRO-MECHANICAL STUDY OF THE EFFECT OF CIRCULAR
DELAMINATION ON FATIGUE LIFE CYCLE OF A COMPOSITE STRUCTURE
Jnanakshi Snigdha B, Sagar University
Shubha Javagal1, Shashidhar Naik H.G.2, Jnanakshi Snigdha B. 1*, Premkumar B.2
1Dept. of Mechanical Engineering, Dayananda Sagar University, Bangalore, Karnataka, India
2Compressors Global Department, QuEST Global Pvt. Ltd., Bangalore, Karnataka, India.
Composite materials are radically replacing metals in various structural applications due to
their high performance and adaptability. Composites have better load bearing capacities
and resistance to failure compared to metal structures. In order to quantify this, the damage
tolerance mechanisms of composites are studied extensively. One of the methods of failure
in composites is fatigue. The structural composites are subjected to various types of fatigue
loads, i.e., static and variable amplitude failure loads during service.
Although composites are believed to have better fatigue resistance compared to
conventional materials, it is necessary to study the effect of internal damages in the
structure on the fatigue life cycle. Delamination being one of the major types of damage in
polymer composites, can cause catastrophic failures. It causes stress concentration in load
bearing laminates and a local instability leading to a further growth of delamination which
results in a comprehensive failure of the laminate. This paper aims to study the fatigue life
cycle of a Carbon Fibre Reinforced Polymer (CFRP) specimen with a circular delamination.
A square plate specimen is assumed to contain a circular delamination due to barely visible
impact damage at the centre. A quasi-isotropic arrangement of Carbon fibre polymers is
considered and modelled. The material properties of the carbon fibre are taken from existing
literature. A commercially available Finite element software is used to carry out the analysis.
A low cycle fatigue load is applied on the specimen and analysis is carried out to generate
a suitable S-N curve for the considered case. The S-N curve further acts as an input to study
the onset of delamination in the specimen. The number of cycles required for the specimen
to fail under fatigue is be determined and the corresponding Strain Energy Release Rate will
be computed using Virtual Crack Closure Technique (VCCT). This study is further carried for
various delamination sizes and thru thickness locations of the delamination.
Keywords: Fatigue, CFRP, Virtual Crack Closure Technique, Strain Energy Release Rate.
3rd Structural Integrity Conference and Exhibition – SICE2020
98
Field-Induced Poynting Effect in Magneto-Active Polymers in Simple Shear
Krishnendu Haldar Department of Aerospace Engineering, Indian Institute of Technology Bombay, Mumbai
400076, India [email protected]
Magneto-Active Polymers (MAPs) are polymer-based composites with micro-magnetic particles em bedded in an elastomeric matrix material. The presence of magnetic particles provides strong tunability properties to the stiffness and damping of the polymeric composite under the magnetic field. It is a common observation that during simple shear deformation, conventional elastomers exhibit positive Poynting effect, i.e., the shearing planes tend to expand, and compressive stress is required to maintain a shear deformation. However, certain polymers exhibit a negative or reverse Poynting effect. In many biomedical applications, e.g., artificial muscles or magnetic gels, such a reverse Poynting effect for coiling, torsional, or shear deformation, is of fundamental interest. We solve a coupled simple shear problem with a specific constitutive equation and found that the magnetic field shows a significant influence on the Poynting effect and its sign.
Keywords: Magneto-active polymers, field-induced shear deformation, Poynting effect
3rd Structural Integrity Conference and Exhibition – SICE2020
99
T07+TS26
Integrity of Concrete Structures Against Blast and
Ballistic Loading and Construction materials, and
concrete and steel structures
Organizer: P. Nanthagopalan, IIT Bombay
18th Dec 6-8 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
100
Invited Speakers
High strain rate behavior of concrete
Dr. Manmohan Dass Goel
Assistant Prof., Department of Applied Mechanics, Visvesvaraya National Institute of
Technology (VNIT), Nagpur, India.
Although, effect of strain rates on materials behaviour is not a new area but with the
advancement in technology and innovations in experimental techniques are leading to
understand the effect of strain rates on deformation behaviour of materials in different
ways. This is an area, particularly in India, research is gaining momentum in recent time in
different engineering disciplines. A structural design engineer deals with different types of
materials to be used in buildings and structures and thus understanding their behaviour
under extreme loading condition such as blast, impact and earthquake becomes utmost
important. Hence, it is necessary to characterize these materials at high rate of loadings to
design and use these materials efficiently. In this talk, focus will be on concrete material
and its behaviour under high strain rates. It is well acknowledged that concrete behaves
differently under dynamic loading conditions than static loading. Further, enhancement in
the compressive strength of the concrete material is observed due to the increased strain
rates under dynamic loading conditions. This strength enhancement can be determined by
experiments using Split Hopkinson Pressure Bar (SPHB) device. The discussion on SHPB
and its working will also be presented.
Dr. Manmohan Dass Goel completed his bachelor of engineering from Yeshwantrao
Chavan College of Engineering at Wanadongri, Nagpur under the then Nagpur
University in 2000. He was awarded three gold medals by Nagpur University for
academic excellence. He pursued master of technology (M. Tech.) in offshore
engineering from Indian Institute of Technology (IIT) Bombay, Mumbai till 2003. He
completed his Ph. D. from Department of Civil Engineering, Indian Institute of
Technology (IIT) Delhi and University of Federal Armed Forces, Munich. Awards:
Surendranath Mukherjee Memorial Medal, Innovative Student Project Award 2013,
CSIR Young Scientist Awards-2014, IGS-HEICO Biennial Award- 2017, Young Engineer
Award.Currently he is serving as Assistant Professor, Department of Applied
Mechanics, Visvesvaraya National Institute of Technology (VNIT),
3rd Structural Integrity Conference and Exhibition – SICE2020
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Contributed Speakers
Dynamic performance of RC slabs under combined blast and impact loading
Akshaya Gomathi
Akshaya Gomathi K1, A Rajagopal2
Department of Civil Engineering, Indian Institute of Technology Hyderabad
The development of numerical tools for efficiently modelling the Reinforced Concrete (RC)
structures subjected to high velocity blast and impact has been one of the major recent
study in military and research, with the increased terrorist attacks. Even with advanced
development of finite element tools for modelling and analyzing of the complicated
structural behavior, it is difficult to understand the structural and material behavior of RC
structural components under dynamic loading. There are various literatures available for
understanding the complex behav ior of structure under blast or impact loading separately.
The analysis shows that under dy namic loading the RC structures show very complex
behavior. The concrete is exposed to rap idly changing stress state and material shows
strain rate sensitivity. The damage mechanism and deformation is different under dynamic
loading condition, failure in tension with increase in dynamic tensile strength, crushing of
concrete caused by compaction of material, flow stress and ductility increases with higher
strain rate. Failure is concrete is caused by the formation of micro cracks and it develops to
form fracture process zone. In this paper the failure mechanics and the dynamic response
of RC slab subjected to combined blast and impact dynamic loading is studied by
numerically implementing in explicit software LS-DYNA. The validation is done separately
for RC slabs subjected to impact and blast loading. Then the response of RC slabs is
analyzed by varying the sequence of application of loads. Blast fol lowed by impact loading
and impact followed by blast loading. The time lag between the load initiation. It is seen that
the RC slabs subjected to impact loading followed by blast, shows more severe damage and
spallation because of the flexural and shear failure caused by impact load before the
subsequent blast load application. The numerical analyzes is carried out using in-built
models in LS-DYNA and the performances are compared. Performance based on crack
development and propagation, maximum displacement, acceleration-time and
displacement time responses were plotted and investigated. The parametric study is carried
out by analyzing the mechanical and damage response by var ying the slab depth,
reinforcement ratio by giving single and double reinforcement, velocity and the distance of
impact and blast loading. It is seen that the better performance can be ob tained for the slab
with increased thickness and doubly reinforced.
Keywords: Failure mechanisms, Dynamic response, Blast loading, Impact loading
3rd Structural Integrity Conference and Exhibition – SICE2020
102
TS09
Material Behaviour Characterization using Miniature
Specimens
Organizer: Z. Alam, DMRL
18th Dec 4.30-8 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
103
Invited Speakers
Length Scale Effects on Power Law Creep of Materials: Cases of Uniform
and Graded Stress Fields
Praveen Kumar
Praveen Kumar (Other authors: Vikram Jayaram, Syed Idrees Afzal Jalali)
Associate Professor
Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)
revealed once the smallest dimension of the specimen decreases below a threshold value. In this
talk, the effect of sample dimensions on power law creep, which is controlled by dislocation climb, will be discussed, in context of uniaxial testing and cantilever bending. Experimental observations
suggest the existence of a surface affected region (SAR), wherein the dislocation substructures are significantly coarser than those formed in the interior. The origin of SAR lies in the classic
phenomena of dislocations escaping the sample through the surface, and its expanse is determined
by the applied stress, with its maximum value limited by the grain size. As the fraction of SAR in the
sample increases with a decrease in the sample size, the steady-state strain rates tend to increase and the “apparent” creep stress exponent registers a decrease, thereby clearly showing a sample
size effect on the observed creep behaviour of material. These variations, which are clearly observed in uniaxial loading, can be rationalized using the iso-strain composite model with SAR and interior
as two constituents. In bending, the strengthening effect of geometrically necessary dislocations associated with strain gradients, which increases with a decrease in the sample dimensions, gets
coupled with the “softening” effect of SAR, thereby producing a plethora of interesting cases, ranging from strengthened to “uniaxial-like” softened responses; these can be mapped using digital image
correlation. From induction, one may envision a cross-section in the cantilever wherein the strain
gradient and SAR effects perfectly balance each other. This extraordinary condition allows obtaining bulk creep response from miniaturized cantilever samples. Accordingly, this also enables accurate
assessment of the residual life of an in-service component using small volume specimens, which
can be scooped out from the component without disrupting its usual functioning.
Praveen Kumar received his Bachelor of Technology degree in Mechanical
Engineering from Indian Institute of Technology, Kanpur, in 2003. Subsequently, he
received M.S. and Ph.D. degrees in Mechanical Engineering from University of
Southern California, Los Angeles in 2005 and 2007, respectively. He is currently an
Associate Professor with the Department of Materials Engineering, Indian Institute of
Science, Bangalore. His main research interests are mechanical behaviour of
materials, with particular emphasis on studying effects of electric current,
temperature and sample length scale, and constructive usage of electromigration,
both in solid and liquid metals.
3rd Structural Integrity Conference and Exhibition – SICE2020
104
Mechanical properties of multi-phase complex concentrated alloys
Koteswararao V. Rajulapati*
School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad
500046, India.
*E-mail: [email protected], [email protected]
In a quest to develop new materials with enhanced properties, a novel class of material
systems called as “high-entropy alloys (HEAs)/ complex concentrated alloys (CCAs)” have
emerged recently, challenging the conventional alloy making principles. This concept gives
a “near-infinite” compositional space for exploration which was untouched till now.
Therefore it is also expected that unprecedented properties would be exhibited by these
materials. Our efforts at University of Hyderabad, India include development of various
classes of these materials by adding different alloying elements in equiatomic/ non-
equiatomic proportions and understanding the resultant mechanical properties vis-à-vis
structural/microstructural features. Ball milling coupled with spark plasma sintering (SPS)
as well as vacuum arc melting have been used to fabricate various multi-phase HEA
systems. Ball milling has resulted in either single/dual phase structures whereas multi-
phase structures have been realized while heating the samples as part of
sintering/homogenization. These multi-phase structures have resulted in interesting
mechanical properties w.r.t. hardness, strain rate sensitivity, activation volume, fracture
toughness etc. Development of some of our HEA systems was inspired by conventional
superalloys such as IN 718/ IN 617/Haynes 188. Detailed characterization has been done
using X-ray diffraction and electron microscopy. Mechanical properties were evaluated by
microindentation and high throughput nanoindentation at room temperature. This talk
would address the relationship between microstructural features and the corresponding
indentation based mechanical properties of different HEA systems investigated. It was
broadly observed that a multi-phase structure is desirable to have a balanced mechanical
properties in various alloy systems.
Dr. Koteswararao V. Rajulapati had his academic training in Metallurgical and
Materials Engineering and obtained his PhD, M. Tech. and B. Tech. degrees from
North Carolina State University, Raleigh, USA (2006), IIT-Kharagpur, India (2002) and
JNTU-Hyderabad, India (2000) respectively. He did his postdoctoral work in the
University of Michigan, Ann Arbor (2007) and the University of Southern California
(2008), Los Angeles, USA. He has been with the School of Engineering Sciences and
Technology, University of Hyderabad from 2009 onwards and is currently a Professor
here. His research interests include nanomechanics, high-entropy materials, friction
stir welding/processing, additive manufacturing, advanced high strength
steels/superalloys etc.
3rd Structural Integrity Conference and Exhibition – SICE2020
105
In-Operando Nanomechanical Testing and its applications
S.A. Syed Asif
Industron Nanotechnology
Understanding the mechanical response and properties of materials at multiple length, time
scales, and the test conditions are becoming very important to optimize the performance
and develop materials with unique properties. Materials science community has been
coming out with new materials with outstanding properties and for applications at normal
and extreme conditions. For the underlying research effort, recent instrumentation for
structure property correlation has played a critical role. In recent two decades, depth
sensing nanoindentation emerged as not only a tool to measure hardness and modulus of
materials but other important properties such as viscoelasticity , creep resistance, fracture
resistance etc.. at depths as shallow as a few nanometers and temperatures as high as
1000oC. The measurement techniques that were believed not possible a decade ago are
becoming possible now with much superior resolutions and accuracies. Besides
indentation, today’s nano- and micromechanical methods include compression, tension
bending, fracture, fatigue and creep tests. This talk will demonstrate this capability of
structure property correlation from results on the in-operando nanomechanical testing of
various engineering materials. The results will be reported and the physical insight regarding
the deformation mechanisms will be discussed. The main focus will be on the
instrumentation techniques to improve the research efforts, and develop fundamental
understanding of deformation mechanisms of materials
Key Words: In-Operando, Nanoindentation, Hardness, Creep
3rd Structural Integrity Conference and Exhibition – SICE2020
106
Contributed Speakers
Length Scale Effects on Power Law Creep of Materials: Cases of Uniform
and Graded Stress Fields
Syed Idrees Afzal Jalali
Syed Idrees Afzal Jalali, Vikram Jayaram and Praveen Kumar
Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)
E-mail: [email protected]
Mechanical properties of materials are sensitive to specimen dimensions, which are readily
revealed once the smallest dimension of the specimen decreases below a threshold value.
In this talk, the effect of sample dimensions on power law creep, which is controlled by
dislocation climb, will be discussed, in context of uniaxial testing and cantilever bending.
Experimental observations suggest the existence of a surface affected region (SAR),
wherein the dislocation substructures are significantly coarser than those formed in the
interior. The origin of SAR lies in the classic phenomena of dislocations escaping the
sample through the surface, and its expanse is determined by the applied stress, with its
maximum value limited by the grain size. As the fraction of SAR in the sample increases
with a decrease in the sample size, the steady-state strain rates tend to increase and the
“apparent” creep stress exponent registers a decrease, thereby clearly showing a sample
size effect on the observed creep behavior of material. These variations, which are clearly
observed in uniaxial loading, can be rationalized using the iso-strain composite model with
SAR and interior as two constituents. In bending, the strengthening effect of geometrically
necessary dislocations associated with strain gradients, which increases with a decrease in
the sample dimensions, gets coupled with the “softening” effect of SAR, thereby
producing a plethora of interesting cases, ranging from strengthened to “uniaxial-like”
softened responses; these can be mapped using digital image correlation. From induction,
one may envision a cross-section in the cantilever wherein the strain gradient and SAR
effects perfectly balance each other. This extraordinary condition allows obtaining bulk
creep response from miniaturized cantilever samples. Accordingly, this also enables
accurate assessment of the residual life of an in-service component using small volume
specimens, which can be scooped out from the component without disrupting its usual
functioning.
3rd Structural Integrity Conference and Exhibition – SICE2020
107
In-Situ Mechanical Behavior of Multi-layered Steel at Mesoscale
Mahavir Singh
Mahavir Singh, Krishna N Jonnalagadda
Department of Mechanical Engineering, Indian Institute of Technology Bombay
Abstract
The layered mixture of dissimilar materials to achieve the multi-functional properties has
widen-up their application in the fields of transportation, energy, infrastructure etc. The
structural steel industry has also seen advancement by various structural changes and
mixing of different phases; the layered structure is being one the most popularly used. In
this study, the multi-layer steel sheet fabricated by cold pressing of alternate layers of
martensitic (high strength) and austenitic (high ductility) nature was analysed to understand
its in-depth mechanical behaviour. The samples were cut by using wire EDM, polished and
etched to see the grain boundary structure and interfaces of the two phases. Subsequently,
they were fabricated again to obtain dog-bone tensile geometry. The uniaxial tensile loading
at the quasi-static rate was applied along the longitudinal direction to generate the iso-strain
loading for individual layers. High-resolution images were captured and processed by digital
image correlation (DIC) technique to obtain the full-field behaviour at mesoscale. The
heterogeneity in the intralayer region and across the interfaces was investigated to correlate
the same with the structural positioning and microstructure. The microstructure was
analyzed using scanning electron microscopy. The results obtained showed potential in
further growth by controlling the microstructure and variation in the thickness of individual
layers to obtain a tailored behaviour between high ductility and high strength.
Keywords: Multi-layered Steel, Digital Image Correlation, High Resolution.
3rd Structural Integrity Conference and Exhibition – SICE2020
108
Finite Element Modelling of Deformation and Fracture Behaviour of Barium
Titanate Thin Films
Nidhin George Mathews
Nidhin George Mathews*, N Venkataramani, Nagamani Jaya Balila
Department of Metallurgical and Materials Engineering,
Indian Institute of Technology Bombay, Mumbai-400076, India
Abstract
Barium Titanate (BTO) is a widely accepted lead-free piezoelectric ceramic used at micron
length scales and in thin film forms in applications. It is important to estimate mechanical
response of a material in the length scale of its real application as the mechanical properties
are different from their bulk values due to size effects. Here we study the mechanical
behaviour BTO thin film systems using different micromechanical experiments and finite
element modelling (FEM). Damage tolerance of the film-substrate is not dependent on the
applied loads alone but also on other parameters such as film thickness, residual stresses,
grain sizes, nature and number of interfaces. Nanoindentation is a high throughput
technique for measuring the deformation and fracture response of thin films. It has not been
exploited fully due to the complex stress-state that results underneath an indenter tip.
Stress-strain response of thin films estimated from nanoindentation experiments are
therefore compared to uniaxial microscale experiments on single crystals for
benchmarking. FEM models are used to eliminate substrate effects to obtain actual
response from the film. Microcantilever fracture measurements revealed that thin film
showed a 60% lower KIC than bulk due to the weak inter-columnar boundaries. Changing the
interlayer material and/or substrate type varies the residual stresses in the film and this will
in turn control their fracture resistance. These effects of residual stresses, film thickness,
and material anisotropy on the fracture toughness are estimated from different FEM
models. Fracture toughness from microcantilever experiments are compared with
indentation fracture toughness value to determine the effect of different stress states. An
insight to improve the damage tolerance of thin film systems is therefore obtained from the
combination of nanoindentation based experiments and FEM modelling.
3rd Structural Integrity Conference and Exhibition – SICE2020
109
Extracting uniaxial flow stress-strain behavior of metals from cantilever
under bending using Digital Image Correlation
Priya Goel
Priya Goel, Praveen Kumar, Vikram Jayaram
Department of Materials Engineering, Indian Institute of Science Bengaluru
Abstract
The accuracy and reliability of material parameters obtained through small scale testing of
the next generation of materials is a challenge as testing is limited by difficulty in sample
preparation, its mounting and alignment. In a cantilever, the measurement of strain gradient
using digital image correlation (DIC) generates a large volume of data from a single
specimen. The use of a single specimen in bending improves accuracy and reliability as
scatter is reduced. Bending also simulates the behavior of structures in applications more
closely than uniaxial testing. Therefore, in addition to ease of gripping and alignment,
bending also allows optimization of material volume in applications as well as in testing by
knowing the overall distribution of stress and strain in the sample. However, the non-linear
stress-strain law in plasticity leads to redistribution of stress across the cantilever to
maintain section planarity. The stress redistribution is transient and evolves as a function
of elastic to plastic strain ratio before it saturates at large plastic strain. The extraction of
flow parameters using a cantilever relies upon the estimation of stress during the
deformation. In the present work, the methodology to extract flow parameters from a
cantilever under deflection rate-controlled tests using DIC is explored. The studies on Al
show that yield strength and strain hardening exponent can be estimated within an error of
10%. The accuracy and limitations of the proposed methods in terms of extent of hardening
and DIC resolution are discussed using a model which numerically calculates stress
evolution during deformation.
Keywords: Bending, Flow parameters, Digital image correlation, modelling
3rd Structural Integrity Conference and Exhibition – SICE2020
110
TS10
Material Behaviour Characterization Under High
Strain Rate Loading
Organizers: E. P. Korimilli – IIT Indore
K. N. Jonnalagadda – IIT Bombay
G. Tiwari – NIT Nagpur
Dec 11th 5.00 pm to 6 pm
Dec 11th7 pm to 10 pm
12th Dec Time: 6 pm to 10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
111
Invited Speakers
Metal Foams and Their Behaviour at High Strain Rates
Manmohan Dass Goel
Assistant Prof. Department of Applied Mechanics, Visvesvaraya National Institute of
Technology (VNIT), Nagpur, India
[email protected], [email protected]
Metal foams are a new class of materials and can be tailored for their mechanical properties
with particular focus on their end applications. In comparison with dense materials, metallic
foams have very low densities, higher energy absorbing capability, higher specific stiffness,
and improved acoustic damping and mechanical properties. These metallic foams are
smart option for various applications, wherein they are used as sandwich cores in structural
application, packaging along with blast-resistant structures/components. The talk will
discuss about foam in general and metal foam in particular.
Further, deformation of metal foams under high rate of loading is a complex phenomenon
due to the effects of various parameters involved therein. In this talk, primary focus will be
dynamic behaviour on aluminium metal foams at high rate of loading. The talk will focus on
experimental investigation of metal foams using split Hopkinson pressure bar (SHPB).
Dr. Manmohan Dass Goel completed his bachelor of engineering from Yeshwantrao
Chavan College of Engineering at Wanadongri, Nagpur under the then Nagpur
University in 2000. He was awarded three gold medals by Nagpur University for
academic excellence. He pursued master of technology (M. Tech.) in offshore
engineering from Indian Institute of Technology (IIT) Bombay, Mumbai till 2003. He
completed his Ph. D. from Department of Civil Engineering, Indian Institute of
Technology (IIT) Delhi and University of Federal Armed Forces, Munich. Awards :
Surendranath Mukherjee Memorial Medal, Innovative Student Project Award 2013,
CSIR Young Scientist Awards-2014, IGS-HEICO Biennial Award- 2017, Young Engineer
Award. Currently he is serving as Assistant Professor, Department of Applied
Mechanics, Visvesvaraya National Institute of Technology (VNIT),
3rd Structural Integrity Conference and Exhibition – SICE2020
112
Resistance of Masonry Walls under Repeated Impact Loading
Dr. K. Senthil
Assistant Professor
Department of Civil Engineering, NIT Jalandhar
[email protected]; [email protected]
Masonry can be designated as the urban curtains due to their extensive usage in residential
and industrial structures. Further, the outer periphery walls of almost 80% structures are
made up of brick units stick together with mortar. These walls are at times subjected to
accidental impact loads such as large mass of hard objects traveling with low velocities.
Therefore, present study is focused to estimate the multi hit impact response of clay brick
masonry wall under low velocity and large mass loading. The experiment as well as
simulations were performed in order to predict the behvaiour of masonry walls under multi
hit impact. The experiments were performed on pendulum impact testing frame capacity
of 250 kN and the response history was measured using dynamic load cell and high
frequency data logger system. The response of 110 mm thick clay brick masonry wall was
studied against 60 kg mass with hemisphere nose shape. The specimens were tested under
repeated loading of same magnitude and direction until failure. In addition to that, the
influence of aspect ratio of the wall and boundary conditions of the walls were studied. The
numerical simulations were performed using ABAQUS finite element technique and the
results thus predicted were compared with the experimental results. The damage behavior
of masonry wall was incorporated through Drucker-Prager and traction- separation law has
been implemented to model the hardening behaviour and brick-mortar joint interface of clay
bricks respectively.
Dr. Senthil has been actively involved in research since 2010 and he has published
31 refereed International Journal [11 SCI, 13 Scopus and 7 Peer Review Journal]
and 40 refereed international Conferences. He have two International
Collaborative project and first one Sponsored by the Royal Society UK in
collaboration with University of Bath UK – NIT Jalandhar and Second one
sponsored DST-RFBR in collaboration with the Saint Petersberg State University
Russia - IIT Roorkee India – NIT Jalandhar. He has received Seven National as
well as International awards for his academic and research excellence including
Best Teacher Award at NIT Jalandhar for the year 2018- 19. He has organized one
national Conference sponsored by TEQIP, STTP Sponsored by DST-SERB, five
national level workshop’s sponsored by TEQIP and few seminars. He is member
of 10 Civil Engineering Society including ASCE, Indian Concrete Institute and
Indian Geotechnical Society
3rd Structural Integrity Conference and Exhibition – SICE2020
113
Technical talk and Demonstration of Physical simulation in high strain rate
therm-mechanical processes using the Gleeble platform
Dr. Fulvio Siciliano
Metallurgist and Senior Application Consultant, Dynamic Systems Inc., USA
Gleeble systems are powerful tools for high temperature forming, processing and dynamic
mechanical behavior studies that enable world-class researchers to solve real-world challenges. Its unique ability to accurately and easily reproduce the thermal-mechanical history permits simulation
of large scale industrial processes such as rolling, forging, heat treating, welding, casting and others.
This presentation shows a compilation of Gleeble applications in high strain rate metallurgical processes including non-contact measuring techniques such as DIC, Laser Ultrasonics and
Pyrometers.
Dr. Fulvio Siciliano has close to 30 years of international experience in the areas of hot rolling, microstructural evolution, mathematical modeling and steel development for transmission pipelines and other applications. He visits India since 2003 and has accumulated extensive experience with Indian Steel Companies, Universities and R&D Institutes. Fulvio has a Ph.D. degree in Physical Metallurgy of Hot Rolling from McGill University (Canada / 1999) directly supervised by Prof. John J. Jonas; Master in Engineering and Metallurgical Engineer Degrees from University of São Paulo, Brazil. He is also a Professor of Metallurgy, Materials Science and International Relations.
3rd Structural Integrity Conference and Exhibition – SICE2020
114
Complex plastic flows and the machining of metal polycrystals
Narayan K. Sundaram
Associate Professor of Civil Engineering
Indian Institute of Science
The simulation of machining of soft metals in the critically important 100 micron-few mm
length-scale is challenging, requiring one to capture the complex flow physics induced by
the high ductility and polycrystalline aggregate nature of these metals. This talk will provide
an introduction to the phenomenology and engineering importance of these flows, and a
recently developed remeshing and mesh-to-mesh transfer-based FE approach that can
successfully simulate the cutting of polycrystalline aggregates. I will discuss the design of
these simulations including plasticity models, microstructural models, ductile failure, and
meshing / remeshing strategies; the trade-offs required, and outstanding problems that
remain to be addressed.
I am an Associate Professor of Civil Engineering at IISc, Bangalore. My group (the
Interfacial Solid Mechanics Group) explores a range of problems in contact
mechanics, adhesion, indentation, and large strain plasticity in metals processing with
a focus on polycrystalline aggregates. Our goal is often a first-in-class simulation in
these areas. I have a BTech Metallurgical (IIT Roorkee); and an MS in Materials and a
PhD in Aerospace Engineering both from Purdue University. I joined IISc after
postdoctoral work at the Center for Manufacturing Processes and Tribology, Purdue.
3rd Structural Integrity Conference and Exhibition – SICE2020
115
Contributed Speakers
The effect of sabot mass and the interfacial friction between the sabot and
striker on the incident signals of a split-Hopkinson bar
D. Kumar
D. Kumar, S. N. Khaderi
Department of Mechanical and Aerospace Engineering, Indian Institute of Technology
Hyderabad
[email protected], [email protected]
Abstract
The split Hopkinson pressure bar (SHPB) setup is used to characterize the dynamic
mechanical response of material. It consists of a coaxially aligned striker, incident (input),
and transmission (output) bar. Usually, same gas gun barrel is used for different diameters
of the striker. Sabots (plastic, brass) are fitted on the striker to keep striker radially aligned
in the barrel. From literature, it has been established that the sabot mass increases the
magnitude and time duration of the input pulse. These findings are studied through the
hypothesis of equivalent density of striker. The drawback of this hypothesis is that it cannot
explain the variation in the input signal pulse due to change in fabrication or the installation
method of striker (like the sabot length, sabot-striker frictional interfacial conditions, and
sabot location).
In present work, the influence of sabot on the amplitude and shape of input pulse was
experimentally studied. An integral striker with sabot projection was used for experiments.
We observe that the magnitude of strain at the beginning and the end of the incident pulse
is larger than that of the plateau. This enhancement is larger when the length of the integral
sabot is larger. These features of the incident signals have not been reported. It was inferred
that the way strikers are fabricated/fitted on to the striker also determines the nature of the
incident signal. The axisymmetric and 1D finite element simulations were performed for
validation of the input signal. The effect of fabrication/assembling method of sabot on
striker, effect of sabot length, and sabot- striker interface conditions on the input pulse has
been simulated. An analytical solution by 1D wave propagation complements the
experimental observation. Moreover, the integral striker and sabot mounted striker has been
compared.
Keywords: shpb, high strain rate characterization.
3rd Structural Integrity Conference and Exhibition – SICE2020
116
Evolution of deformation modes, microstructure, texture during high strain
rate deformation of Zircaloy-4
G. Bharat Reddy
[G. Bharat Reddy], [Rajeev Kapoor], [Apu Sarkar]
[Mechanical Metallurgy Division], [Bhabha Atomic Research Centre, Mumbai]
Specimens of recrystallized Zircaloy-4 were deformed at room temperature at a strain rate
of ~1000 s-1 using a split Hopkinson pressure bar. The compressive deformations were
carried out in different specimen orientations to study the effect of loading direction (for a
given texture of the material) on the selection of deformation modes, microstructure and
subsequent flow behaviour. The microstructure and texture evolution was studied by
deforming the specimens to intermediate strains. Electron backscatter diffraction was
used to characterize the microstructure and texture of deformed specimens. The applied
strain was found to be accommodated by both slip and twin modes. A crystal plasticity
model was used to determine the evolution of deformation modes in terms of their relative
activities by simulating the observed flow behaviour and texture evolution.
Keywords: Zirconium, split-Hopkinson pressure bar, EBSD, crystal plasticity
3rd Structural Integrity Conference and Exhibition – SICE2020
117
Through-Thickness High Strain-Rate Compressive Response of Glass/Epoxy
Laminated Composites Embedded with Randomly Oriented Discontinuous
Carbon Fibers
Shubham
Shubham*1, Chandra Sekher Yerramalli2, Rajesh Kumar Prusty1, Bankim Chandra Ray1
1FRP Composites Laboratory, Department of Metallurgical and Materials Engineering,
National Institute of Technology, Rourkela, India-769008
2 Department of Aerospace Engineering, Indian Institute of Technology Bombay, Mumbai,
400076, India
The fiber-reinforced polymer (FRP) composites, due to its outstanding mechanical
properties over metallic materials has gained a lot of attention in the last few decades. Many
structures made up of FRP composites are subjected to high strain rate (HSR) loading
conditions. This study presents the HSR compressive behavior of woven E-glass fiber
reinforced epoxy embedded with randomly oriented discontinuous carbon fibers (RODCF).
A compressive split Hopkinson pressure bar (SHPB) apparatus was used for testing the
samples along the through-thickness direction. Cylindrical samples were used for SHPB
testing having a length to diameter ratio (L/D) of 0.75. All the samples were tested at a
constant propelling cylinder pressure of 30 PSI and the strain rate range of 1819-2135/s.
The amount of RODCF dispersion in the sample tested was 0.25% and 0.5% by weight of
epoxy. It was observed that the mean compressive strength of the glass/epoxy (GE) sample
increases up by 10 % and 12.7% with the RODCF addition of 0.25% and 0.5% by weight of
epoxy, respectively. The peak force obtained from the strain gage mounted on the incident
bar was found to be higher as compared to the peak force received from the strain gage
mounted on the transmitter bar, which was explained by the phenomenon of stress wave
attenuation. An increase in the mean ultimate strain was also observed for the samples
containing RODCF. Dynamic plots of true stress–true strain, strain rate versus time, true
strain versus time, true stress versus time, as well as forces versus time were obtained for
each type of sample and discussed.
Keywords: fiber-reinforced polymer, high strain rate, compressive split Hopkinson pressure
bar, glass/epoxy
3rd Structural Integrity Conference and Exhibition – SICE2020
118
Evaluation of J-integral of pre-cracked steel specimen using Split
Hopkinson Pressure Bar Setup
Sonal Chibire
Sonal Chibire1, Nitesh P. Yelve1, and Vivek M. Chavan2
1Department of Mechanical Engineering, Fr. C. Rodrigues Institute of Technology, Vashi,
Navi Mumbai, India
2Bhabha Atomic Research Center, Trombay, Mumbai, India
The mechanical properties of the material respond distinctively at quasi-static as well as
high strain rate conditions. The Split-Hopkinson Pressure Bar (SHPB) is established for high
strain rate testing in the range of 102 to 104 s-1 of strain rates and used to carry out dynamic
three-point bend (TPB) test for measuring J-integral. The mechanical properties of the pre-
cracked steel specimen and the methodology of calculation of J-integral are presented.
Prior to this, stress intensity factor is evaluated experimentally and analysed using Finite
Element Method (FEM). The relevant ASTM fracture toughness test standards considered
in this paper are E399 for KIC testing, E1820 for J-integral. The J- integral obtained
experimentally are compared with the values obtained by using Finite Element Method
(FEM).
Keywords: Fracture mechanics, Split Hopkinson Pressure Bar, J-integral, Fracture
toughness.
3rd Structural Integrity Conference and Exhibition – SICE2020
119
High strain rate deformation behavior of dual phase high entropy alloy
Al0.65CoCrFe2Ni
Samrat Tamuly
Samrat Tamulya, Saurabh Dixitb, V. Parmeswaranc, Prasenjit Khanikara
a Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Assam
781039, India
b Mishra Dhatu Nigam Limited, Hyderabad , Telangana 500058,India
c Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Uttar
Pradesh 208016, India
A novel high entropy alloy Al0.65CoCrFe2Ni is designed, and fabricated at industrial scale
through induction arc melting at a solidification rate of ~10 K/s. The XRD analysis confirms
the presence of both FCC and BCC phases in the alloy sample. The presence of both phases
improves the balance of strength and ductility of the material. Split Hopkinson pressure bar
test is carried out under compressive loading over a range of high strain rates of the order
of 103 s-1. The effect of dynamic deformation on the microstructure of the alloy is
investigated using orientation image microscopy. The work hardening behavior of the alloy
is studied, and the strain rate sensitivity is evaluated. The predictability of high strain rate
behavior of the high entropy alloy is also examined using Johnson-Cook (J-C) modeling.
3rd Structural Integrity Conference and Exhibition – SICE2020
120
Modified Cowper-Symonds model for predicting the stress-strain behaviour
of SA516 Gr. 70 carbon steel
S Sharma
S Sharma1, M K Samal2,3, V M Chavan4
1HomiBhabha National Institute, Mumbai 400 084, India
2Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
3Division of Engineering Sciences, Homi Bhabha National Institute, Mumbai 400 084, India
4Refueling Technology Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
Abstract. The flow behaviour of SA516 Gr.70 carbon steel under dynamic loading condition
was studied experimentally using the split-Hopkinson pressure bar (SHPB). These tests
were performed at room temperature at strain rates ranging from 450/s to 3500/s. Quasi-
static tensile tests were performed for comparison with high strain rate test results. The
strain rate sensitivity at these dynamic rates was found to be positive. The experimental
data was fit to the Cowper Symonds (CS) model. As the CS model did not fit the high strain
rate data satisfactorily, the Cowper Symonds model was modified. This modified Cowper
Symonds model gave the best fit to the experimental data.
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Strain path effects on martensitic transformation in medium Mn steels.
Poornachandra
Poornachandra1, Saurabh Kundu2 and Prita Pant1
1Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai,
India.
2Research and Development division, TATA steel, Jamshedpur, India.
Email: [email protected]
Most of the industrial metals forming processes are characterized by a complex strain path.
To make effective use of medium Mn steels in automotive parts, the formability analysis
along with the proper understanding of deformation mechanisms and their effect on
delayed fracture phenomenon at different strain and strain paths are important areas to be
investigated. In the present work, we carried out formability analysis of Fe-5Mn-0.2C-0.73Si-
0.34Al medium Mn steels at different strain paths. We observed that the samples failed at
low effective strain in case of plane strain conditions as compared to uniaxial and biaxial
loading conditions. We observed more martensitic transformation during deformation (TRIP
effect) in case of plane strain loading condition as compared to uniaxial and biaxial loading
conditions. Favored texture development to austenite to martensite transformation could
be the reason behind more martensitic transformation in plane strain loading condition.
Key words: Strain path, martensitic transformation, texture.
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Enhancing dynamic fracture behaviour of laminated composite by short
fiber reinforcement
Manoj. K. Singh
Manoj. K. Singh1, R. Kitey2
1Ph.D Student, 2Associate Professor, Department of Aerospace Engineering, IIT Kanpur-
208016, India
Email of corresponding author: [email protected]
Abstract: Continuous fiber reinforced laminated composites are mostly preferred in
engineering applications where in-plane strength and modulus are key requirements.
Although the composites’ in-plane mechanical and failure behavior can be tailored to meet
the end user requirements, their weaker out-of-plane characteristics often remain a cause
of concern. Failure in such materials initiate either at fiber/matrix interfaces or from matrix
rich regions within the laminae or at the interlaminar regions. Stiffening matrix rich zones
by using reinforcements is one of the methods which can be employed to reduce the
probability of failure. In this investigation short fiber reinforced matrix is used to enhance
the failure characteristics of laminated composites under impact loading conditions. Plain
weave bidirectional Glass Fiber Reinforced Polymer (GFRP) composites are fabricated by
employing hand layup technique. Laminae are prepared by coating fiber clothes with
chopped fiber (of 6 mm length and 16 m diameter) reinforced epoxy systems. Fillers are
embedded into the epoxy at 4% volume fraction. Sixteen plies are stacked together and
cured in a vacuum assisted hot press. Test specimens are prepared by following ASTM
D7136M standards and the experiments are conducted at 5 J and 20 J impact energies by
employing INSTRON CEAST 9340 drop weight impactor. The fracture energy is calculated
from the force history recorded by an instrumented tup with hemispherical end. The visible
damage areas at the front and back surfaces and the depth of the dent are measured to
assess the degree of damage in the laminates. Failure mechanisms are identified through
optical micrographs of the damaged area and by imaging the cross section of the laminates
under scanning electron microscope (SEM) at the failure sites. Experimental data show that
the chopped fiber reinforcements increase the resistance to deformation as well the energy
required to induce fracture in the laminates. Energy dissipation during fracture is observed
to decrease for reinforced case. Optical micrographs show that the visible damage area and
the indentation depth increase with increasing impact energy. SEM images reveal
transverse matrix cracking at lower impact energy in both unreinforced and reinforced
laminate cases with a few interlaminar failure in the prior. On the contrary when the
laminates are subjected to higher impact energy, significant matrix cracking along with the
delamination at several interfaces is observed. Keywords: GFRP; Impact energy; chopped
fiber reinforcement; damage mechanisms; energy dissipation
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TS12 + TS16
Multiscale Modeling of Plasticity, Creep, Fracture,
and Fatigue and Role in Material and Structural
Integrity
Organizers:
A. Alankar, IIT Bombay
P. Chakraborty, IIT Kanpur
13th Dec 4-6 pm
19th Dec 5-9 pm
20th Dec 4-7.30 pm
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Invited Speakers
Hydrogen assisted crack initiation in metals: Insights using novel
experimental analysis and multiphysics simulations
Prof. Dhiraj Mahajan
Associate Professor
Ropar Mechanics of Materials Laboratory, Department of Mechanical Engineering, Indian
Institute of Technology Ropar
Hydrogen is associated with the embrittlement phenomenon in metals that causes
substantial damage to the infrastructure due to reduction in the ductility, fracture strength
and fatigue life of metallic components. Thus, understanding hydrogen-assisted crack
initiation in metals is of prime importance. In this work, hydrogen-assisted crack initiation is
studied on the surface of uncharged and hydrogen charged specimens of pure nickel during
in-situ tensile experiments under SEM. A novel experimental analysis combines high-
resolution digital image correlation (HR-DIC) and EBSD measurement to provide
microstructural stress maps, through strain and stiffness tensor extracted at each point in
the region of interest (RoI). Maximum Schmid factor as well as elastic modulus maps in the
loading direction, hydrostatic stress, von Mises stress and triaxiality factor maps are
correlated with the crack initiation sites in the hydrogen charged specimens. This novel
analysis highlighted two independent factors responsible for hydrogen enhanced
decohesion (HEDE) based intergranular failure observed at the random grain boundaries of
hydrogen charged specimens, (i) strain localization due to hydrogen enhanced localized
plasticity (HELP) mechanism of hydrogen embrittlement, and (ii) hydrostatic stress-based
hydrogen diffusion to the crack initiation sites. These insights are then used to design a
fracture indicator parameter (FIP) which is implemented within the coupled framework of
dislocation density-based crystal plasticity model and slip rate dependent hydrogen
transport model showing high degree of correlation in the crack initiation sites observed
during experiments and simulations using similar microstructure of RoI. The work highlights
the role of metallic microstructure on hydrogen-assisted crack initiation and thus will help
design metallic microstructures that are resistant to hydrogen embrittlement.
Dr. Dhiraj K. Mahajan is an Associate Professor in the Department of Mechanical Engineering, IIT Ropar,
Punjab, India. At IIT Ropar, he is coordinating a research laboratory naming “Ropar Mechanics of Materials
Laboratory” that is focused on mechanics of materials and advanced manufacturing. His immediate focus is
on the manufacturing of critical biomedical devices (like bioresorbable polymeric stents) and hydrogen energy
technology development (including the development of high-pressure hydrogen storage Type IV tanks, proton
exchange membrane fuel cells) towards zero-emission future for the country. He has recently filed two patents
and has more than INR 40 million worth of sponsored and consultancy projects running in his lab. He has (co)-
authored more than 18 refereed journal publications (h-index: 8, total citations > 222) and 10 refereed
conference publications. He is also the winner of several awards from the Hydrogen Association of India.
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Life Management of Aeroengine Components: A Damage Mechanics Approach
Dr. Jalaj Kumar
Defence Metallurgical Research Laboratory (DMRL), DRDO, Hyderabad-500058
Contact: [email protected]
Current life management of turbine engine fracture critical components is based on design limits, which requires replacement of all components at pre-determined flight intervals as specified by manufacturers irrespective of actual usage. This approach is based on nominal fleet-wide usage and ignores the actual capability of each component. These fatigue design limits are derived from extensive testing and statistical assessment of data assuming uniform material microstructure in all specimens and components, resulting in very conservative replacement intervals and high sustainment costs. There is a growing need to improve the current life managements practice and significantly reduce the sustainment costs of legacy and future systems. Next generation life management can be achieved by integrating life prediction that incorporates variations in microstructure with material state awareness based on nondestructive material and damage characterization techniques. Characterizing each component’s microstructure at critical locations will enable prediction of remaining life for each component based on actual usage. This analysis based performance assessment, when coupled with nondestructive damage characterization will facilitate replacement of components only as needed, thus increasing readiness and decreasing sustainment costs significantly.
As a result of the in-house research efforts as well as interaction with other academic institutes/ research agencies, a multi-disciplinary expertise in the area of Damage Mechanics has been established in DMRL. This includes finite element analysis (FEA) based simulation expertise and damage assessments using NDT technologies. In the present talk, the expertise / technology thus developed in the area of damage mechanics would be discussed with few case studies related to life managements of aeroengine components.
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Spall Characterization via Laser Spallation: A New Optical Technique
Prof. R. Kitey, IIT Kanpur
Associate Professor
Department of Aerospace Engineering, IIT Kanpur
The strength of materials under extreme dynamic loading conditions is assessed from their
spall characteristics. The spall strength is often evaluated by employing flyer plate impact,
or sometimes by using laser-induced stress waves, in combination with velocity
interferometer system for any reflector (VISAR). Although the VISAR can record the velocity
of extremely fast-moving surfaces, it requires a complex optical setup and a specialized
data reduction technique. In this presentation, a newly developed approach for determining
the spall strength of polymers is discussed. The epoxy layers with different thicknesses are
deposited onto glass substrate. Laser spallation method is extended to instigate spall in the
(thick) epoxy films, while in situ interferometric measurements are directly performed on
their aluminium coated top surface. Laser-induced stress waves transmit across the
substrate/film interface and induce subsurface failure in the epoxy at sufficiently high
incident laser energy. The interferometric data reveal the development of two (temporally)
well-separated stress waves: an ablation-induced high-amplitude short-duration
longitudinal pulse, which is referred to as the primary wave, and a secondary wave, which
travels at a comparatively slower speed. The complex constructive interaction of the two
waves develops a high-magnitude tensile stress region in the epoxy layer. The spall strength
is quantified by superimposing the two stress wave histories associated with the critical
energy fluence. The spall depths predicted from spatiotemporal wave travel analyses are in
excellent agreement with the experimental observations.
Dr Rajesh Kitey is Associate Professor in the Department of Aerospace Engineering, Indian Institute of
Technology Kanpur (IITK) India. He received his doctorate from Auburn University, Auburn AL USA. He was
Postdoctoral Research Associate at the University of Illinois at Urbana-Champaign. Prior to joining IITK, he has
worked at Penn State, Dubois PA USA, as Assistant Professor. His area of specialization is Fracture Mechanics
and Experimental Stress Analysis. His research interests involve quasi-static and dynamic fracture in
heterogeneous materials, mechanics of thin films, novel material development and testing, and optical
methods and measurements. Dr Kitey has 50+ articles in international journals and conference proceedings.
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A Novel Cohesive Constitutive Law for Simulating Fatigue Delamination in
Composites
Prof. S. Mukhopadhyay, IIT Kanpur
Assistant Professor
Indian Institute of Technology Kanpur
Fibre reinforced composites are gradually replacing metals for manufacturing load-bearing
primary structures in aircraft and automobile industries due to the many structural and
functional advantages that they provide. However, failure behaviour of composites is
inherently more complex than metals. In particular, failure under fatigue loading is more
concerning to designers. Under high-cycle fatigue, small ply delaminations can initiate and
grow in a stable manner at a load amplitude that can remain much below than the static
failure load, and yet, can bring in unexpected failure, curtailing its designated operational
lifetime significantly.
In this work, the development of a novel cohesive constitutive law to simulate fatigue
delamination in composites will be discussed. This is implemented in a 3D cohesive finite
element framework using a user-defined interface in a commercial solver. A set of novel
physically based onset and propagation criterion is used that is shown to provide very
accurate predictions for delamination onset and growth in large composite structures.
Dr Supratik Mukhopadhyay obtained his B.E in Production Engineering from Jadavpur University, Kolkata in
2009 and an M.Tech in Manufacturing Science and Engineering from IIT Kharagpur in 2011. Subsequently, he
went to the UK on a Dorothy Hodgkin Postgraduate Scholarship to pursue a PhD in Aerospace Engineering in
the University of Bristol on a Rolls-Royce sponsored project. His research was on experimental and
computational investigation of failure from manufacturing induced defects in composite laminates used for
aircraft engine applications. As part of that, he developed several novel predictive tools for damage analysis
of composite structures subjected to static and cyclic loads. After finishing his PhD in 2016, he joined the
Rolls-Royce University Technology Centre at the Bristol Composites Institute, University of Bristol, as a Post-
Doctoral Research Associate where he continued to work for nearly two years on several projects involving
efficient design of composite structures guided by high-fidelity computational simulations. Since late 2018, Dr
Mukhopadhyay is based in IIT Kanpur, as an Assistant Professor in the Department of Mechanical Engineering.
His present research interests include simplified modelling methods for large scale structural simulation of
composites, virtual structural health monitoring and damage prognosis, fatigue failure, multiscale modelling
techniques, machining of composites.
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Thermal stability of nanocrystalline materials: Alloy and Microstructural
design and Implications for creep
Prof. Srikant Gollapudi
Assistant Professor
Indian Institute of Technology Bhubaneswar
The focus of the presentation will be on understanding the thermal stability of
nanocrystalline materials and how grain growth tendencies of nanocrystalline materials has
prevented systematic investigations on creep deformation of these materials. Work in the
last decade has demonstrated that in addition to Zener drag approach, the grain size of
nanocrystalline materials can also be stabilized through solute additions, wherein the solute
element chosen is one that has a tendency to segregate at the grain boundary of the parent
element. This in turn can reduce the grain boundary energy of the parent element and can
introduce higher thermal stability to the nanostructure. A thermally stable nanostructure
would allow the determination of the stress exponent, activation energy and grain size
exponent, key creep parameters which will reveal the mechanism of creep operating in these
materials. The alloy and microstructural design approaches to making thermally stable
nanocrystalline materials will be discussed in this context.
Dr. Srikant Gollapudi obtained his Bachelors in Metallurgical Engineering from NIT Rourkela, Masters in
Metallurgy from Indian Institute of Science, Bangalore and PhD in Materials Science and Engineering from NC
State University. He pursued his post doctoral research at Massachusetts Institute of Technology and gained
industrial experience from his stints at Defence Metallurgical Research Laboratory, Hyderabad and Saint
Gobain Research India, Chennai. His research interests are in the area of Nanocrystalline materials, Corrosion
and Creep of a variety of materials. He has more than 25 publications in national and international peer
reviewed journals and 6 patent applications to his name.
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Post-Critical Instability in Nonlocal Strain Gradient Arches
Prof. S. Mishra
Associate Professor
Department of Civil Engineering,
Indian Institute of Technology Kanpur
The buckling and post-critical behavior of classical arch is an important benchmark problem in nonlinear mechanics. This study investigate the same for nano-arch subjected to external
pressure using nonlocal (NL) and Strain Gradient (SG) theory, assuming the arch to be
shallow and is restrained in its out-of-plane. The governing equations are derived as a sixth
order nonlinear integro-differential equation, in contrast to the fourth order for classical
arch. The equation is then solved numerically using Differential Quadrature (DQ) with a set
of boundary conditions. An arc-length continuation is employed for the solution of the
resulting system of equations. The equilibrium paths are obtained for the possible instability
modes; e.g. symmetric/anti-symmetric bifurcations, snap through and limit point instability.
Each mode is triggered at certain range of the slenderness ratio for the arch and are
significantly influenced by the NL and SG interactions, which not only cause quantitative
changes but may also lead to qualitative changes (cessation, shift and conversion of
modes). The pre-buckling nonlinearity is significant and cannot be linearized meaningfully.
Sudib K. Mishra is an Associate Professor in the Department of civil engineering at the IIT Kanpur. He
completed his bachelor's in Civil Engineering from Bengal Engineering College (Now IIEST), Shibpur in 2003,
followed by his masters from IIT Bombay in 2005 and doctoral studies from the University of Arizona, Tucson.
Thereafter, he served as a post-doctoral associate in the Mechanical and Aerospace Engineering Department
in the University of California, Irvine. Prof. Mishra has varying research interests from Vibration and structural
dynamics, Vibration based structural health monitoring to instability in structures and Solid Mechanics. He
has authored around forty journal publications across various international journals of repute. He also
presented his work in various National and International conferences and delivered a number of invited
presentation on various topics. Prof. Mishra was awarded the Young engineer award in the year of 2016 by
the Indian national Academy of Engineering, the Young Engineer Award in the year of 2013 by the Institute of
Engineers and the Young Faculty Research Fellowship by IIT Kanpur in the year of 2020.
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A Diffused Interface Crystal Plasticity Model to Investigate the Effect of
Corrosion Pit Geometries on Microscale Deformation
Prof. Pritam Chakraborty, IIT Kanpur
Assistant Professor
Indian Institute of Technology Kanpur
Pitting corrosion significantly reduces the fatigue life of Aluminium alloys, which are widely
used in aircraft industry. This results in loss of useful life, and increases maintenance
schedules of aircrafts. Thus, development of mechanistic models incorporating the
influence of pits on fatigue life reduction can aid life extension and optimal planning for
maintenance. Experimental studies reveal that pits interact with the microstructure and
have a significant effect on crack nucleation. The extent of this influence depends on the pit
geometry and surrounding microstructure. To understand this interaction, a diffused
interface crystal plasticity finite element method model has been developed in this work.
The framework helps in ensuring a structured mesh while discretizing polycrystalline
representative volume elements; incorporating interface behaviour as constitutive models,
and natural coupling with phase-field or electron-microscopic image based microstructures.
The method has been applied on microstructures containing a narrow deep pit and a
subsurface pit with similar geometric parameters to compare their influence on localization.
The comparisons show that the interaction of the pit geometry with the surrounding
microstructure can have a strong influence on microcrack nucleation.
Dr. Pritam Chakraborty has done in Ph.D. from The Ohio State University and worked as a Scientist at Idaho
National Lab., US, before joining his current position. His interests are in solid mechanics, multi-scale modeling,
fatigue, fracture, plasticity and large scale computing.
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Contributed Speakers
Effect of strain localisation on constitutive model for porous metal plasticity
under combined shear and tensile loading
Suranjit Kumar, BARC
Suranjit Kumar1,2∗, M. K. Samal1,2, P. K. Singh2, J. Chattopadhyay1,2
1Homi Bhabha National Institute, Mumbai 400 094, India
2Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
Abstract
The micro-mechanism of ductile fracture involves processes of void nucleation, growth, and
coalescence. The evolution of void with loading in porous metals affects their stress
carrying capability. Most of the existing material constitutive models for the porous ductile
solids were derived through limit-analysis of hollow representative volume element (RVE)
under influence of homogeneous boundary strain rate. First, widely accepted material model
was presented by Gurson (1977). This model captures the spherical growth of voids only
and disregarded void shape effects. Gologanu et al. (1993, 1994, 1997) account for the
effects of void shape on the derivation of yield function considering the axisymmetric
ellipsoidal void geometry. Madou and Leblond (say, M&L) (2012) extend the Gologanu work
for more general ellipsoidal void geometry. All these constitutive models are developed for
a randomly distributed void in infinite space. It does not account for the effect of the
interaction of voids. The ductile failure under the low-stress triaxiality occurs by a void
sheeting mechanism, where voids rotate and form a shear band. It contains a localized
strain in a very thin band. The onset of strain localisation may also contribute to the yielding
of a particular representative volume.
In view of the above, the numerical determination of the yield surfaces of an RVE having an
elliptical cylindrical void has been carried out under the combined shear and tensile loading
to capture the effect of strain localisation on yielding behaviour. Performance of the M&L
constitutive material model was also checked against the numerical results. It has been
found that strain localisation takes place in a narrow band under the shear dominated
loading which leads to early yielding of RVE. This effect decreases with an increase in the
contribution of tensile load. It has also been found that the ML model doesn’t reproduce the
yield surface accurately under low-stress triaxiality loading, however, it works well for
relatively higher stress triaxiality.
Keywords: Ductile material, Shear loading, Void fraction, Stress triaxiality
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CDM Model for Creep life prediction of Alloy 625M nickel base superalloy
for high temperature power plant applications
Somnath Nandi, BHEL
*Somnath Nandi and Kulvir Singh
Metallurgy Department, Corporate R&D Division, BHEL, Hyderabad 500093, India
*Email: [email protected] FAX: 0091-40-23776320
Creep life prediction of critical components in thermal power plants has become an
important metallurgical area to study over the last few years. Prediction of Creep strain
trajectories and rupture strains is of generic importance for ensuring stable operation of
existing power plants and for developing current procedures to extend design lifetimes
safely. It is very important to understand how various degradation mechanisms affect the
creep strength of the components and to incorporate these in constitutive laws to ensure
effective extrapolation. Nowadays, with the advancements in new technologies heat
resistant steels are being replaced by nickel base superalloys which can withstand high
temperature and pressure. Alloy 625M is one of the probable alloy to be used in steam
turbine. Traditional parametric methods for estimating the long-term creep rupture lifetimes
of alloys from short term data are employed. Larson Miller parameter methods and
Robinson’s Rule are generally employed for prediction but these methods never incorporate
the microstructural degradation of the alloys at high temperatures. In the present paper,
preliminary idea of the creep curve using constitutive laws, Continuum Damage Mechanics
(CDM) model based on microstructure/ property relationships and relevant aspects of
microstructure are discussed to have a realistic prediction of the creep life of the Alloy 625M
for power plant applications.
Keywords: Creep, CDM Model, Alloy 625M, Creep life predictions, Creep Curves.
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Phase field modeling of crack propagation in crystalline microstructures
under hydrogen atmosphere
Vishal SIngh
Vishal Singh*, Rakesh Kumar, Dhiraj K. Mahajan Ropar
Mechanics of Materials Laboratory, Department of Mechanical Engineering,Indian Institute
of Technology Ropar, Rupnagar, Punjab, 140001, India
Insight to the damage behavior of metallic materials is of great significance to understand
the overall mechanical performance even in not so favorable environmental conditions.
Present work intent to simulate the hydrogen-induced damage in crystalline metallic
materials. Crystal plasticity coupled with phase-field for fracture and hydrogen transport
model is used to simulate crack propagation under the hydrogen atmosphere. The proposed
model istested on simple geometry with face-centered cubic single crystal and image-based
multi-grain RVE. Crystallographic orientation and hydrogen content are shown to affect the
test results in terms of failure pattern and corresponding global and local response.
Keywords: Phase field modelling, crystal plasticity, hydrogen embrittlement, damage
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Coupled Thermomechanical Analysis of SMA Structures
Animesh Kundu
Chenna Sai Krishna Chaithanya, Animesh Kundu, Atanu Banerjee
Department of Mechanical Engineering, Indian Institute of Technology, Guwahati
Email of corresponding author: [email protected]
Abstract
Of late, Shape Memory Alloys (SMA) are found in wide variety of applications in the field of
aerospace, robotics, biomedical, etc., due to their well-known behaviors called, Shape
Memory Effect and Super-elasticity. To simulate the behavior of these alloys several
constitutive models are proposed over the past four decades. In one of them, the phase
evolution was derived based on fundamental laws of thermodynamics and maximization of
dissipation potential. This approach has been reported to be more suitable for the analyses
of structural problems in 2D and 3D, under practical thermomechanical loading conditions.
In literature, temperature is considered as an input variable, whereas, in practice, it evolves
as a state variable, depending on applied thermal and mechanical loads and material
properties. The martensitic transformation processes exhibit endothermic and exothermic
effects, significantly affecting temperature and the response. Hence, a fully coupled
thermomechanical finite element-based analysis tool is required simulate the behavior of
these materials.
The objective is to develop a coupled thermomechanical analysis tool to predict the
response of SMA structures under practical thermomechanical loading conditions in
ABAQUS. The constitutive model proposed by Qidwai and Lagoudas (2000) is implemented
in UMAT, a user material subroutine of ABAQUS, to analyze the response of SMA actuators,
beams etc., considering the effect of material level coupling terms, i.e., the latent heat of
transformation and thermoelastic heating effects. The results emphasize a significant
difference in the transient response of SMA structures while thermal coupling terms are
considered; illustrating the importance of the coupled analysis of these materials. Finally,
the response of a SMA biomedical staple, used for idiopathic scoliosis treatment of
vertebral body, is simulated using the developed FE tool, considering the practical
thermomechanical loading conditions.
Keywords: Shape Memory Alloy, Coupled Thermomechanical Analysis, Material Non-
linearity, Latent heat.
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Phenomenological Constitutive Modeling of Magnetic Shape Memory Alloys
Avinash Kumar, IIT Bombay
Avinash Kumar, Krishnendu Haldar
Department of Aerospace Engineering, Indian Institute of Technology Bombay, [email protected], [email protected]
Abstract
Increasing demand for a lighter and more durable material with sensing and actuation functionality, Magnetic Shape Memory Alloys (MSMA) are one of the promising members, among many other smart materials. This study investigates the magneto-thermal-mechanical (MTM) the behavior of MSMA through a 3D phenomenological constitutive modeling in a thermodynamically consistent way. A specific Helmholtz free energy function is postulated after identifying the external and internal state variables. The evolution equations of the internal state variables are defined by proposing a transformation function. The model parameters are calibrated through different MTM loading conditions. Selective loading conditions demonstrate the magnetic field coupling with the actuation strain.
Keywords: Magnetic shape memory alloy (MSMA), magneto-thermal-mechanical (MTM), magnetic field induced strain.
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Dynamic creep response of MWCNT-COOH filled PP nanocomposites
Vivek Khare
Vivek Khare* , Sudhir Kamle#
*Ph.D. Scholar, #Professor
Department of Aerospace Engineering, IIT Kanpur
Corresponding author: [email protected]
Polypropylene (PP) is a widely used thermoplastic polymer in aerospace applications due
to, its strength, low cost, low weight, ease of formability and fatigue resistant properties. It’s
semi crystalline state provides both strength and flexibility. Nano fillers such as multi walled
Carbon nanotubes (MWCNT) significantly enhance mechanical properties of PP
nanocomposites. However, at higher MWCNT concentrations, MWCNTs are self-assembled
in form of agglomeration due to high van-der-waal attraction which hinders matrix to fiber
stress transfer efficiency. Present investigation elucidates the effect of functionalized
carbon nanotubes (MWCNT-COOH) and temperature on dynamic creep and recovery strain
in nanocomposites through experiments and nonlinear viscoelastic modeling. The strain
response is studied to address stress dependent nonlinear parameters that characterize
nonlinearity. Solution casting method is used for development of thin nanocomposite films
using PP in pellet form and –COOH functionalized multi walled carbon nanotubes with
varying MWCNT concentrations. Temperature controlled dynamic creep and recovery
experiments were performed at constant 10 MPa creep stress in dynamic mechanical
analyzer (DMA). Prior to creep measurements, the dynamic properties of nanocomposites
were obtained from a temperature ramp test at constant frequency of 1 Hz for storage
modulus, loss modulus and loss factor. Experiments reveals that temperature activated
deformation is controlled by incorporating MWCNTs up to 1% fraction. High temperature
and stress loading pertain to the development of recoverable viscoelastic strain and
unrecoverable viscoplastic strains. Schapery nonlinear viscoelastic model coupled with
Zapas-Crissmann viscoplastic model is incorporated to characterize the creep response,
stress induced nonlinearity in material and viscoplastic strain predicted in experiments. The
model prediction agrees with experimental findings.
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A meso-mechanical simulation of the effects of Stress Concentration
around a counter sunk hole in a Hybrid Fibre Metal Laminate
Chandrashekhar Telkar
Shashidhar Naik H.G.1, Shubha Javagal 2, Prem Kumar B.1 , Chandrashekhar Telkar2*
1Compressors Global Department, QuEST Global Pvt. Ltd., Bangalore, Karnataka, India.
2Dept. of Mechanical Engineering, Dayananda Sagar University, Bangalore, Karnataka,
India
Fibre metal laminates (FML) are one of the novel engineering materials developed for
applications in the Aerospace industry. They are composed of several layers of very thin
metal (often aluminium), along with layers of uni-directional Glass Fibre pre-pregs, bonded
to each other with the use of matrix such as epoxy-resin system. The major advantage of
this material is that it can be tailored to fit the stress condition by varying the orientation of
the Glass Fibre layers. They possess all the expedient characteristics of both the materials
and have several advantages like better damage tolerance, corrosion resistance, fire
resistance, low specific weight and improved impact resistance.
Usage of FMLs in structural components of aircrafts has various challenges. One such
challenge is joining FML plates to the airframe. The most widely used method of joining
various structural components is riveting. This method of joining introduces stress
concentration due to rivet holes, varied load paths, added secondary loads etc. Accurate
prediction of these local stresses will lead to better prediction of fatigue life as well as the
joint strength of the structures.
In the current paper, stresses around a centrally located countersunk hole is investigated in
a plate specimen. The major aim of this work is to determine the Stresses around the hole
for a commercially available GLARE configuration. Various lengths of the countersunk hole
in the specimen are considered and the effect of the hole is studied without altering the
countersunk angle. The GLARE plate is modelled using ABAQUS Standard platform to
appropriately simulate the stress concentration developed in each layer for a particular load.
The detailed layer wise behavioral study is presented by plotting the stress and force values
obtained across time and displacements. Furthermore, a parametric study is carried out to
formulate a holistic understanding of the effect of tensile load in a plate with a countersunk
hole.
Keywords: Fibre metal laminates, Counter sunk holes, GLARE, Stress Concentration
3rd Structural Integrity Conference and Exhibition – SICE2020
138
Homogenisation of Transformed β Colony of a Titanium Alloy using CPFEM
S. Mustafa Kazim
S. Mustafa Kazim1*, Kartik Prasad2, Pritam Chakraborty1*
1Department of Aerospace Engineering, Indian Institute of Technology Kanpur, India 2Defence Metallurgical Research Laboratory, DRDO, Hyderabad, India
[email protected], [email protected]
Abstract
The microstructure of Timetal 834 (Titanium alloy) consists of primary α grains and
transformed β colonies. The colonies contain consecutive lamellae of alpha (HCP) and beta
(BCC) phases. Depending on the Burger’s Orientation Relation (BOR) the common slip
systems between the two phases govern the transmission or hindrance of the mobile
dislocations across the phase boundaries. These interactions dictate the elasto-plastic,
fracture and fatigue response of the alloy and needs consideration in the Crys tal Plasticity
Finite Element Method (CPFEM) models of the alloy. Though crucial, it is computation ally
not viable to include both the lath structure and the primary-alpha grains in the CPFEM Repre
sentative Volume Element (RVE) owing to the disparate length-scales of these
microstructural features. Thus, homogenised models of the lath structure have been
proposed in the literature to incorporate their effect in RVE simulations. In one class of
model a virtual homogenised crystal with both the BCC and HCP slip systems has been
proposed. The other class of model considers both the phases separately at a material point
with the assumption that they experience the same deformation gradient but has sepa rate
evolution of state. The stress at the material point is obtained from a mixture rule. In this
work, a RVE of the lath structure (alternate alpha and beta lamella) has been developed and
simulated using CPFEM. The size effect due to dislocation pileup at the lath interfaces has
been captured using the Hall Petch relation. Strain controlled Periodic Boundary Condition
has been applied to the RVE to capture the homogenized stress-strain behaviour of the
lamellae microstructure. The results from the RVE anal yses have been compared with the
homogenized models to identify their adequacy for Timetal 834.
Keywords: Homogenization; Crystal Plasticity Finite Element Method; Titanium alloys; RVE
analysis
3rd Structural Integrity Conference and Exhibition – SICE2020
139
An atomistic study of activation parameters for plasticity evolution from a
pristine and damaged grain boundary in Ni
Sagar Chandra
S. Chandra1, M. K. Samal2,3, V. M. Chavan4
1Homi Bhabha National Institute, Mumbai 400 084, India
2Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
3Division of Engineering Sciences, Homi Bhabha National Institute, Mumbai 400 084, India
4Refueling Technology Division, Bhabha Atomic Research Centre, Mumbai - 400 085, India
Abstract
Grain boundaries are important microstructural features in polycrystalline materials that
impact their deformation and failure behavior at the macroscopic scale. Thus, we perform
atomistic simulations at the nanoscale along with nudged elastic band calculations to
quantify activation parameters for dislocation nucleation from a grain boundary. Since ∑3
grain boundaries are most common in polycrystalline metals and alloys of face-cantered
cubic structure, we choose ∑3 twin boundary in bicrystal Ni as a model system for this
purpose. We also introduce a pre-existing defect (a void) at the grain boundary and contrast
the activation parameters for partial dislocation nucleation from pristine as well as
damaged grain boundary in the material. We find that the activation energy as well as kinetic
parameters for dislocation nucleation are different for pristine and damaged grain
boundary. This highlights a change in the underlying kinetics of deformation process when
a damaged grain boundary is present in the material. Consequently, this approach can be
generalized to determine kinetic parameters for other thermally activated grain boundary
dominated deformation or failure processes in metallic crystals like grain boundary sliding
at higher temperature, intergranular crack growth etc. It can, therefore, provide direct
numerical inputs to the flow rules of phenomenological crystal plasticity based finite
element models that explicitly take into account the grain boundary effects on plasticity and
damage behavior of the material at the continuum scale.
Keywords: Molecular dynamics, plasticity, grain boundary, damage.
3rd Structural Integrity Conference and Exhibition – SICE2020
140
Effect of tungsten addition on shock loading behavior in Ta-W system: A
molecular dynamics study
Kedharnath A
A. Kedharnatha,b, Rajeev Kapoora,b, Apu Sarkara,b
aMechanical Metallurgy Division, Bhabha Atomic Research Centre, Mumbai 400085, India bDivision of
Engineering Sciences, Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
Tantalum-tungsten (Ta-W) alloys are used for applications in various fields such as defense,
nuclear, electronics, furnace, and medical due to their enhanced corrosion resistance, high
temperature strength, and biocompatibility properties. Ta-W alloys are proposed alloys for
high temperature reactors and are already been used in containing molten plutonium and in
ballistic missile parts. They also have potential space applications as a coating on base
materials and intricate parts to withstand micrometeroids and debris. However, the effect
of tungsten addition on mechanical behavior during shock loading and dynamic high-
pressure conditions in Ta-W alloys is not explored atomistically. In this article, the effect of
tungsten addition to tantalum on spall strength is studied using molecular dynamics
technique. The single crystal configurations with piston lying on different planes are
modeled. The atoms within piston region are frozen and do not deform. The configurations
with various tungsten contents (0, 5, and 10 atomic percent tungsten) is added as solvent
and equilibrated. The piston velocity is fixed and initial temperature is 0 K. The piston is
displaced till 1 nm and stopped which produces a square shock wave. The configurations
are allowed to evolve dynamically using microcanonical ensemble. The elastic and plastic
wave is analyzed at different time period for various crystallographic orientations of the
single crystal with various tungsten contents. The spall strength increases as tungsten
content is increased. The spallation event is visualized and analyzed using stress-time
response.
Keywords: Molecular dynamics, Tantalum-tungsten, Shock loading, Spall strength
3rd Structural Integrity Conference and Exhibition – SICE2020
141
TS13
Non-destructive Testing and Evaluation for Structural
Integrity Assessment
Organizer: K. Jonnalagada, IIT Bombay
12th Dec 5.30-6 pm, 9-10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
142
Contributed Speakers
Optimal Location of Single Sensor for Structural Health Monitoring of a
Steel Truss using Acoustic Emission Technique: An Experimental
Investigation
Sheersha Karmakar
Sheersha Karmakar, Dr. Pijush Topdar, Dr. Aloke Kumar Dutta
Department of Civil Engineering
National Instittute of Technology, Durgapur, Durgapur, India.
Continuous monitoring of any engineering structure involves use of sensors. However, from
the economic and computational viewpoint, only a limited number of sensors can be used.
Hence finding out the optimal location of sensors is very important. In light of this, the
current study makes an effort to achieve the mentioned work. Structural Health Monitoring
refers to the continuous monitoring and maintenance of the strategic engineering
structures. The research primarily focuses on steel bridge structures owing to the Acoustic
Emission (AE) Testing. The study involves placing of one R15D sensor on the different
nodes of the laboratory scale model of the steel bridge and executing Pencil Lead Break
(PLB) at other nodes. Based on statistical analysis of the obtained waveform components,
a series of nodular positions were inferred which implicated the optimal position for the
sensor on the steel bridge to track the best quality waveforms in decreasing order. This
study also showed that the acoustic waveforms follow a pattern religiously when travelling
across similar sections. More research work and study can help detect the exact location
of the crack in real time for better structural health monitoring and also to prevent the
catastrophe of engineering structure failure.
3rd Structural Integrity Conference and Exhibition – SICE2020
143
Influence of elastic follow-up and residual stress on structural integrity
assessment of an engineering component
Anilkumar Shirahatti
Anilkumar Shirahatti1 , Y. Wang2
1 Jain College of Engineering, Visvesvaraya Technological University, Belagavi, India
2United Kingdom Atomic Energy Authority, Culham Science Centre, Abingdon, United
Kingdom
Email of corresponding author : [email protected]
Abstract
One of the many challenges in the behavior of structures is to understand if the presence of
residual stress plays an important role in contributing to the failure of a structure. The
presence of residual stresses in safety-critical engineering components can lead to an
increased tendency for degradation and premature failure, thereby compromising structural
integrity and necessitating costly servicing overheads. Residual stresses are generally
induced during the manufacturing of engineering components, and the magnitude of the
residual stresses can be comparable to the yield strength of the material, for instance in
welds, and the effect of the residual stresses can be either beneficial or detrimental for the
static and fatigue strength of the component. Residual stresses arise because of
incompatibility of strains and therefore are usually treated as secondary stresses. However,
when residual stresses are seen as sufficiently long range and do not balance across a
cracked section, these stresses are classed as primary. In practice, the boundary conditions
on a structure can be any combination of primary and secondary stresses and
understanding their interaction is difficult. Whether the residual stresses contribute to the
primary stresses depends on two things: how plastic deformation or crack growth
accommodates the original misfit and how the structure responds or elastic follow-up (EFU)
when changes in relative stiffness occur as a consequence of plastic deformation or crack
growth. In this paper, the concept of EFU as per R5 structural integrity assessment
standards is discussed. Further, the experimental results obtained from long term creep
tests (316H SS) performed on low and high EFU test rigs is presented. It is concluded from
the test results that EFU will affect the rate of residual stress distribution in the components
& will intern influences the creep crack initiation time.
Keywords: Residual stress, elastic follow-up, 316H stainless steel, Crack
3rd Structural Integrity Conference and Exhibition – SICE2020
144
TS14
Nuclear Reactor Safety, Radiation and other Extreme
Conditions
Organizer: A. Alankar, IIT Bombay
12th Dec 4-8 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
145
Contributed Speakers
Modelling of hardening and loss in ductility due to neutron irradiation in
Zircaloy-4
Nevil Martin Jose
Nevil Martin Josea, M K Samala, P. V. Durgaprasada, A. Alankarb, B. K. Duttac
aReactor Safety Division, Bhabha Atomic Research Centre,Trombay, Mumbai-400085
bIIT-Bombay, Powai, Mumbai-400076
cHomi Bhabha National Institute, Anushaktinagar, Mumbai-400094
Corresponding author email: [email protected]
Abstract
Zircalloy-4 is a material used to make the cladding of nuclear fuels. The fuel cladding
is subjected to neutron irradiation during its service inside the nuclear reactor, which leads
to degradation of its mechanical properties. In this work, the irradiation hardening and
softening of the polycrystal Zircalloy-4 material subjected to various doses of neutron
irradiation is simulated using crystal plasticity finite element model. The crystal plasticity
model is based on dislocation density and defect (produced during irradiation) density
based kinetics of plastic deformation in crystals. Increase in yield stress due to irradiation
is modelled via interaction of dislocations and irradiation defects. The defect density
evolution accounts for the loss in ductility occurring to the irradiated material due to the
formation of defect free channels with plastic straining. The model parameters are obtained
by fitting the model against experimental data reported in the literature. The calibrated
model is then used to predict the irradiation hardening behaviour of Zr-4 subjected to
different levels of irradiation dose.
Keywords: Zircaloy-4, Irradiation, Crystal Plasticity
3rd Structural Integrity Conference and Exhibition – SICE2020
146
Design of shock absorber for radioactive coolant tube transportation cask
and impact analysis of cask with shock absorber
J.V. Mane
J.V. Mane1, Ravindra Pal2, Lokendra Kumar1,V.M. Chavan1
1Refuelling Technology Division, Bhabha Atomic Research Centre, Mumbai, INDIA - 400085
2 Remote Tooling Systems, Nuclear Power Corporation of India Ltd., Mumbai, INDIA – 400094.
Abstract
Radioactive coolant tube transportation cask has been designed for in-house storing of full
length pressure tube of 220 MWe IPHWR. It is 8200 kg, Lead shielded, cylindrical cask of OD
435mm and length of 5735mm. It is required to transport full length pressure tube from
reactor site for post-irradiation examination and will require Type B(M) cask qualification.
The existing configuration of cask is not Type approved and will not qualify regulatory
accident condition tests. In order to meet compliance to the regulatory requirements such
as 9m drop on unyielding target and 800°C thermal test, an external shock absorber along
with thermal shield should be designed and used. Therefore a suitable shock absorber is
conceptualized and designed without modifications in the cask which will meets the
regulatory requirements of accident condition drop. Thermal shield in the form of
sandwiched ceramic board is mounted inside shock absorber cage which will meet in
qualifying requirement under thermal tests. Through number of FE simulations,
configuration of shock absorber is finalized. The performance of cask with shock absorber
is evaluated in all possible most damaging orientations under 9m drop on rigid target. It is
observed that cask components meet the structural integrity requirements. Also delicate
thermal shield is protected without any damage. Thermal analysis of cask with thermal
shield for regulatory accident condition is also carried out. Two different thermal
environments of equivalent to average flame temperature of 800°C and fully engulfing pool
fire condition are considered. It is found in CFD analysis that temperature of outer Lead
surface reaches upto 139°C under sever condition and there is sufficient margin for Lead
melting. The detailed shock absorber design along with thermal shield and compliance to
regulatory requirement using FE and CFD simulations are presented in the paper.
Keywords: cask, impact, shock absorber, FE and CFD simulations
3rd Structural Integrity Conference and Exhibition – SICE2020
147
Design, impact and thermo-mechanical analysis of radioactive surveillance
specimen transportation cask
J.V. Mane
J.V. Mane, S. Sharma, H. Ali, V.M. chavan
Refuelling Technology Division, Bhabha Atomic Research Centre, Mumbai, INDIA - 400085
Abstract
Transportation of radioactive material through public domain is carried in Type qualified
casks. One of the important issues in designing of cask is shielding material. The widely
available and used shielding material is Lead due to its ease of manufacturing and better
radiation shielding property. However Lead is having low melting point and upon melting, it
expands. Melting and subsequent solidification will generate void in shielding which will
lead to direct streaming of radiation. Also it is difficult to meet structural integrity
requirement under molten Lead conditions. Therefore surveillance specimen transportation
cask without Lead is conceptualized, designed as Type B(M) package and its compliance
to regulatory requirement is demonstrated using FE simulations. Considering availability of
material and its form, present cask is designed as welded plates structure to form a cylinder
with removable and bolted end closure on both sides. Steel plates are used effectively both
for shielding as well as structural material. Type B(M) cask should demonstrate compliance
to regulatory 9m drop test on rigid target in most damaging orientations and 800°C thermal
tests. As welded steel plate cask will act as monolithic solid piece, shock absorber is needed
to meet the structural integrity criteria under regulatory 9m drop on rigid target. Therefore
shock absorber is conceptualized and designed in such way that it will reduce number of
worst orientation drops. FE simulations under 9m drop on unyielding target are carried out
with shock absorber and finalized cask configuration so as to meet the structural integrity
requirement. Coupled transient thermo-mechanical FE simulation of cask has been carried
out to evaluate performance and assess structural integrity of cask design under regulatory
thermal test. The detailed cask design with shock absorber and demonstration of
compliance to regulatory requirement using FE simulations are presented in the paper.
Keywords: cask, impact, shock absorber, FE simulation
3rd Structural Integrity Conference and Exhibition – SICE2020
148
Structural Integrity Assessment of Calandria End-Shield Assembly for In-
Vessel Corium retention under Severe Accident Condition
V.Chaudhry
V.Chaudhry*, Nirmal Kumar, Varun Mishra, D. Faisal, R.K.Chaudhary, S.M.Ingole
Nuclear Power corporation of India limited, Mumbai-400094, India
*Corresponding author email: [email protected]
Abstract
Safety demonstration of nuclear power plant for Beyond Design Basis Accident (BDBA)
conditions, called as design extension conditions, has become an important requirement in
Indian Pressurized Heavy Water Reactors (IPHWRs). The BDBA condition resulting in severe
core damage has been postulated due to loss of coolant accident along with failure of
emergency core cooling system and loss of moderator circulation. Under such condition,
the reactor core geometry progressively degrades and results in core collapse. Calandria
End-Shield assembly of standardised IPHWRs acts as an important barrier in limiting the
accident progression. Structural integrity assessment of calandria end-shield assembly has
been carried out for in-vessel retention of collapsed core/corium due to a postulated BDBA
scenario by maintaining the calandria vault cooling water level surrounding the calandria
vessel as a heat sink, as per the Severe Accident Management Guidelines (SAMG) provision.
Coupled thermo-mechanical analysis of the assembly has been carried out to simulate the
accident scenario with SAMG provision. The thermal analysis accounts for the variation of
decay heat, melt solidification, and also corium latent heat. The analysis gives spatial
distribution of temperature at various locations of the assembly in time domain. Using this
temperature distribution, structural analysis of the assembly has been carried out
accounting for temperature dependent material properties. Sensitivity analysis has also
been carried out to account for the uncertainties associated with input parameters,
specifically, heat transfer coefficient. The failure modes provided in IAEA TECDOC-1549 viz.,
failure due to creep, failure due to molten metal, and failure of drain lines have been
analyzed. Based on analytical evaluation, structural integrity of calandria end shield
assembly for in-vessel corium retention for IPHWRs has been demonstrated.
Keywords: safety, structural integrity, in-vessel retention, thermo-mechanical analysis
3rd Structural Integrity Conference and Exhibition – SICE2020
149
Numerical modeling of clad tube ballooning phenomenon under transients
conditions
Ashwini Kumar Yadav
Motilal Nehru National Institute of Technology Allahabad, Uttar-Pradesh 211002, India
Abstract. The high temperature deformation of clad tube plays a vital role in design of
emergency core cooling system (ECCS). Accordingly several investigations regarding effect
of internal pressure, heating rate and temperature on ballooning deformation of Zircaloy-4
cladding has been widely carried out in the past. The recent experiments conducted at
Halden-IFA-650 [1] with high burn-up fuel seeking attention of research community. In
addition to that, the revised ECCS acceptance criterion is compelling precise prediction of
fuel rod behavior by the safety analysis codes. In this context, a one-dimensional code is
developed to simulate the thermo-mechanical behavior of Zircaloy-4 cladding under
transient conditions. The radial deformation of the clad tube in α-phase was predicted by
time integration of plastic equation of state [2] and steady state creep equation [3]. The
predicted results were compared with the experimental results conducted by in the past [4].
Due to time-independent behavior, the plastic model was not able to predict the rupture
precisely. The gradual increment in hoop stress with ballooning until burst by the creep
model led to better prediction of the hoop-strain, burst time, and burst temperature.
Keywords: Loss of coolant accident, Clad tube ballooning, LOCA, Nuclear Fuel.
3rd Structural Integrity Conference and Exhibition – SICE2020
150
TS15+TS23
Reliability of coatings-Keshri+TS23-Thin Film
Deformation and Failure
Organizer: K. Jonnalagadda, IIT Bombay
18th Dec 4-8 pm, 9-10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
151
Invited Speakers
Fe-based Amorphous Metallic Coatings –A Cost Effective Way to Design and Synthesis
for Tribological Application
Kaushal Kishore1, Pavan Bijalwan2, Abhishek Pathak2, Kuntal Sarkar2, Mohd Shaberoz
Uddin3, Amit Bikram Sengupta3, P K Tripathy4, Atanu Banerjee2*
1Scientific Services, Tata Steel; 2Research & Development, Tata Steel; 3Iron Making Area
Mechanical Maintenance, Tata Steel; 4Product Technology Group, Tata Steel
*Corresponding Author (Email: [email protected])
Abstract:
Corrosion and wear are the two most important challenges in tribology that limit the service
lives of engineering components. The current work is aimed to design and synthesis of
amorphous metallic coating (metallic glass) from blast furnace pig iron which can
potentially replace costly metal grades used for these tribological applications. Good glass
forming ability of the blast furnace hot metal (with inherent impurities) as determined by
thermodynamic calculation has been experimentally validated by making its glassyribbons
by melt spinning in air. Subsequently, the pig iron ingots were converted to metallic powder
using water atomization technology. These predominantly amorphous powders were used
as feed stock to synthesize metallic glass coating using thermal spray technology. The
effect of powder feed rates, plasma energy etc. during thermal spray process on the
microstructure, corrosion and wear behaviour of the coating was studied in detail at
laboratory using x-ray diffraction, scanning electron microscopy, potentiodynamic
polarization tests, electrochemical impedance spectroscopy, sliding wear and dry sand
abrasion tests. The optimised coating showed an amorphous structure with porosity less
than 2 %, corrosion resistance comparable to that of austenitic stainless steel, hardness
value greater than 800 HV and specific wear rates lower than conventional wear resistance
steel grades. Subsequently, successful field trials were taken on corrosion and wear prone
components used in iron ore fine conveyor circuitat sinter plant area of Tata Steel.
Keywords:Pig iron, thermal spray, metallic glass coating, corrosion, wear
Acknowledgement:
Authors sincerely acknowledge the contribution from the collaborative partners – Prof. Kallol
Mondal, IIT Kanpur; Prof. Anup K. Keshri, IIT Patna and Dr. Ashis K. Panda, NML Jamshedpur;
M/s Padmashree Ent., Hyderabad; M/s MEC Pvt. Ltd., Jodhpur
3rd Structural Integrity Conference and Exhibition – SICE2020
152
Plasma Spraying of Yttria Stabilized Zirconia Based Thermal Barrier
Coating
Kantesh Balani
AriharanS1, Pratyasha Mohapatra2, Alok Bhadauria3, Ashutosh Tiwari4,S.T. Aruna5, Anup
Keshri6, KanteshBalani3,*
1Department of Metallurgical and Materials Engineering, IIT-Madras, Chennai-600036
2Department of Materials Science & Engineering, Iowa State University of Science and
Technology, Ames, IA 50011, USA.
3Department of Materials Science and Engineering, IIT Kanpur, Kanpur-208016
4Department of Applied Sciences and Humanities, Rajkiya Engineering College Banda-
210201
5Surface Engineering Division,CSIR-National Aerospace Laboratories, Bangalore -560 017
6Metallurgical and Materials Engineering, IIT Patna, Bihta, Patna-801106.
* Corresponding author e-mail id: [email protected]
Thermal barrier coatings (TBC) provide thermal insulation due its low thermal
conductivity (1.8-2.2W/mK) and comparable thermal expansion coefficient (~7x10-6K-1)
compared to that of nickel-based turbine blades. It may be pointed out that the coating
failure occurs owing to the poor fracture toughnessof coatings and development of residual
stresses during coating deposition and also during service. Herein, Al2O3is deposited as TBC
material on Inconel 718 alloy with incorporation of 20 wt.% of 0, 3 and 8 mol.%Y2O3doped
zirconia(YSZ). Further, 4vol.%multiwall-carbon nanotubes (CNTs)are reinforced to enhance
the fracture toughness ofplasma sprayedcoatings. Complimentary spark plasma sintering
technique is also utilized to produce bulk YSZ-CNT composites. Phase retention has been
analyzed using x-ray diffraction, transmission electron microscopy and Raman
spectroscopy. The retentionof ~26% transformable tetragonal ZrO2phase is believed to play
a major role in imparting enhanced fracture toughness (by 28%, from ~4.3MPa.m1/2 to
~5.4MPa.m1/2), whereas, CNTs have shown to provide synergistic toughening (from ~5.2to
~5.9MPa.m1/2).The orientation of CNTs may also provide anisotropic thermal conduction
(lower transverse conductivity) to suit the needs of application as coatings of turbine
blades. Thus, synergistic toughening can render enhanced damage resistance and provide
prolonged life to thermal barrier coatings.
Keywords: Thermal barrier coating, plasma sprayed coatings, spark plasma sintering, yttria
stabilized zirconia (YSZ), Al2O3, carbon nanotubes (CNTs).
3rd Structural Integrity Conference and Exhibition – SICE2020
153
Wetting Phenomena in Plasma Sprayed Rare Earth Oxide Coating
Anup Kumar Keshri
O.S. Asiq Rahman, Biswajyoti Mukherjee, Anup Kumar Keshri
Plasma spray Coating Laboratory, Metallurgical and Materials Engineering
Indian Institute of Technology Patna
We have fabricated the novel parahydrophobic cerium oxide (CeO2) coating using a
industrially viable plasma spray technique, which has prospective applications in
microfluidic chips, no loss microdroplet transportation and chemical microreactors. Our
coating displays significantly high water contact angle (∼159.02˚) along with high contact
angle hysteresis (CAH≥90˚), very much similar to a ‘Rose petal’. This is supported by by the
fact that the coating displayed remarkable adhesion even with large inverted water droplets
of 70 μL, which is significantly higher than the reported values of 18 μL for polymer and 20
μL for drop casted CeO2 nanotubes. A systematic characterization results have been
displayed to clarify the ongoing confusion regarding the hydrophobicity of CeO2 coatings
often reported in literature. Meanwhile, our parahydrophobic coating also showed
remarkable thermal and mechanical stability even at a significantly high temperature of 200
°C for 14 h and with 50 g abrasive paper.
Anup Kumar Keshri is currently an Assistant Professor in Dept. of Metallurgical and
Materials Engineering at Indian Institute of Technology (IIT), Patna, India since
October 2013. Before joining IIT Patna, Dr. Keshri worked with Centre for
Nanotechnology Group, Bharat Heavy Electricals Limited (BHEL), Corporate R&D,
Hyderabad between April 2012-September 2013. He worked as an Associate
Professor in School of Mechanical and Building Sciences at Vellore Institute of
Technology (VIT), Vellore, India since April 2011. Anup Kumar Keshri, received his
Ph.D. degree in Materials Science and Engineering from Florida International
University (FIU), Miami, USA in July, 2010 and worked as Postdoctoral fellow in FIU
until March 2011. He has a B.E. degree in Metallurgical Engineering from Bihar Institute of Technology (BIT),
Sindri, India in 2002 and a M.S. degree in Metallurgical and Materials Engineering from Indian Institute of
Technology (IIT), Madras, India in 2004. He worked as Asst. Manager in Ispat Industries Limited, Mumbai
(2004–2006). During his Ph.D., he has worked on Process Map Development of Plasma Spraying, Splat
Formation, Liquid Precursor Plasma Spray and High Temperature Tribology. He has published 73 papers in
peer reviewed journals, delivered 30 talks in international conferences and 14 invited talks in academics and
industries. He is a recipient of many awards and honors such as, Research stay grant by Humboldt Foundation,
Dissertation Year Fellowship (2009–2010) from FIU, Arthur E. Focke leadership award by ASM Foundation
delegate of “President’s Council of Student Advisors (PCSA)” formed by The American Ceramic Society
(ACerS). Dr. Keshri also serves as reviewers for several journals in the area of coatings and thermal spray. His
h-index of 26 (total citations close to ~2000) strongly endorses his research productivity.
3rd Structural Integrity Conference and Exhibition – SICE2020
154
Delamination and cracking in Ni-HVOF coating
Deepesh Yadav
Deepesh Yadav1, Sanjay Sampath, Balila Nagamani Jaya1
1Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai,
Maharashtra, India
Abstract
Thermal spray coatings are widely used to enhance the surface properties of materials like wear resistance, hardness, corrosion resistance, and thermal insulation. The substrate is
the primary load-bearing material but since the coating is intimately attached to the
substrate, load transfer can take place from substrate to coating when substrate is loaded
in tension. Load transfer from substrate to coating leads to cracking and delamination in
coatings. This study investigates the adhesive and cohesive strength of Ni coating,
manufactured by a high-velocity oxy-fuel technique, on a steel substrate, under tensile
loading. To understand the load transfer mechanism shear lag tests on coatings of different
thicknesses have been done and numerical simulations have also been carried out. Tensile
properties obtained from testing of free-standing coatings are input into the simulations.
Delamination or cracking in coatings starts from edges or terminated surfaces. Decrease
in coating thickness from 2 mm to 0.1 mm improves the resistance for delamination but
cracking cannot be avoided. This establishes a methodology to determine interface
dominated properties in such coatings.
Keywords:- Delamination, Cracking, Shear lag, Load transfer mechanism and FEA
3rd Structural Integrity Conference and Exhibition – SICE2020
155
Phase transformations on aging of air plasma sprayed commercial purity
and high purity 7YSZ thermal barrier coatings
Vikram Hastak
Vikram Hastak1, Sanjay Sampath2and A. S. Gandhi1
1Department of Metallurgical Engineering and Materials Science, Indian Institute of
Technology Bombay, 400076, India
2Center for Thermal Spray Research, Stony Brook University, Stony Brook, NY, USA
E-mail: [email protected]
ABSTRACT
Air plasma sprayed (APS) 7 wt% Y2O3 stabilized ZrO2 (7YSZ) thermal barrier coatings (TBCs)
are widely used in gas turbine engine components for increasing thermal stability. However,
thermal exposure induced phase changes in yttria-stabilized zirconia (YSZ) are still a subject
of concern as it might lead to TBC failure. The present work is mainly focused on examining
the evolution of multiple phases on aging of 7YSZ APS-TBCs. The topcoats were first
removed from the substrate through acid etching. Both, commercial purity 7YSZ (CP7YSZ)
and high purity 7YSZ (HP7YSZ) free-standing coatings were heat treated at 1200˚C, 1250˚C
and 1300˚C for various aging periods (from 0.5 to 512 h). Characterization by X-ray
diffraction reveals that the initial non-transformable t’ phase gradually transformed into
yttria-lean tetragonal (t) and yttria-rich cubic (c) phases in both CP7YSZ and HP7YSZ free-
standing coatings. However, cubic phase precipitation started sooner in CP7YSZ as
compared to HP7YSZ. Some amount of t’ phase was also retained even after aging for
considerably higher
aging periods. The variation in tetragonality (of t and t’) and phase fractions (t, t’ and c)
with increasing thermal exposure were investigated and further correlated with changes in
Raman spectra.
Keywords: Yttria Stabilized Zirconia, APS-TBCs, CP7YSZ, HP7YSZ, Phase transformations
3rd Structural Integrity Conference and Exhibition – SICE2020
156
Hot Corrosion Kinetics of Alumina plus 8% Yttria-Stabilized Zirconia Applied
on Cast Iron Substrate”
Abhinav
Assistant Professor, Department of Mechanical Engineering, Alliance University,
Bangalore.
.Email id: [email protected]
Abstract:
The hot corrosion test was conducted as per ASTM G111-97 standards on the plasma
coated specimens. Three cast iron specimens of size 30 mm x 30 mm were prepared and
act as a substrate. A mixture of pure alumina and 8% yttria-stabilized zirconia in 50:50
proportion was used as a topcoat. The topcoat thickness was varied in 100,200 & 300 μm.
Blended mixture of vanadium pentoxide (V2O5) plus 45 wt.% of sodium sulphate (Na2SO4)
powders were prepared and used as a corrosive medium. The test was conducted at 850±2
°C in a muffle furnace. Results obtained from the SEM & EDX analysis found that that
microcracks and micropores facilitated the corrosive elements diffuse into the bond coat.
It has been understood that as the thickness increases, the rate of diffusion of corrosive
elements decreases. A detailed discussion is made on the mechanism of corrosion and on
corrosion prevention of functionally graded composite coatings.
Keywords: Hot corrosion, Al2O3+ ZrO2ꞏ8Y2O3, Muffle furnace.
3rd Structural Integrity Conference and Exhibition – SICE2020
157
Contributed Speakers
The study of adhesion and viscoelasticity on hardness and elastic modulus measurement in different cross-linked SU-8 thermoset
polymer
Prakash Sarkar, IIT Bombay
Prakash Sarkar1, Prita Pant1and Hemant Nanavati2
1Department of Metallurgical Engineering and Materials Science,
2Department of Chemical Engineering,
Indian Institute of Technology Bombay, Mumbai- 400076, India
E-mail: [email protected]
Abstract
SU-8 is a cross-linked thermoset amorphous polymer, which is involved to design ultra-thick and high aspect ratio micro-electrical mechanical system (MEMs) components. We are interested to measure elastic modulus (Er) and hardness (H) of different extent of cross-linked SU-8 samples. To study this, we have fabricated samples by following standard photolithography process where the duration of post-exposure baking and hard baking are varied to achieve different extent of cross-linking. The amount of cross-linking is estimated by Fourier-transform infrared spectroscopy (FTIR). Nanoindentation is carried out to measure Er and H values at constant 0.01 strain rate (1/s) by applying 800 μN maximum load. By following conventional method, we have obtained high Er and H values for less (~ 82 %) cross-linked samples and less values for high (~ 95 %) cross-linked samples. The main reasons for these inverse values of Er and H are adhesion between the tip surface and contact sample surface, the influence of viscoelastic behavior and wrong measurement of contact area (Ac). After minimization of adhesion effect and viscoelasticity, we have considered Ac as residual indent impression projected area, which is obtained from scanning probe microscopy (SPM). Thereafter, obtained values of Er is 4.61 ± 0.13 GPa and 5.02 ± 0.18 GPa, and H is 256.97 ± 1.42 MPa and 285.48 ± 1.17 MPa for less and high cross-linked samples respectively.
Keywords: SU-8; Lithography process; FTIR; Nanoindentation; SPM
3rd Structural Integrity Conference and Exhibition – SICE2020
158
Synthesis and comparative characterization of electroless Ni-P, Ni-P-nano Al2O3 and duplex Ni-P/ Ni-P-nanoAl2O3 coatings on aerospace graded Al2024
alloy
Rajsekhar Chakrabarti, Techno India University
Rajsekhar Chakrabarti, Souvik Brahma Hota, Pradipta Basu Mandal
Department of Mechanical Engineering, Techno India University
Abstract
The essence of electroless coatings is realized by the scientists since last decade which makes them a vital player in material coating industry. Incorporation of a second phase micro or nano element into the Ni-P matrix widens the area of applications for these types of coatings. Researchers are showing their interest to develop more innovative electroless coatings where they are deploying different types of second phase material to enhance their physical, mechanical and chemical properties. Duplex coatings have shown promising capabilities by providing excess hardness, wear and corrosion resistance which can be attributed to the resultant effect of two consecutive layers of coating. In our research, three different types of electroless nickel phosphorous (EN) coatings were applied on the aerospace graded Al2O24 alloy substrate. The first type was plain Ni-P coating, the second one was a composite coating where nano alumina incorporated into the electroless Ni-P matrix and the third coating was a duplex coating with the inner layer having Ni-P and the outer layer consisting of a Ni-P layer incorporated with nano alumina particles. Characterization of the deposits by Scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDS) confirms the production of flawless, adherent coatings onto the substrate. Maintaining the surface roughness at acceptable level, a great increase in nano hardness was observed that was further enhanced by incorporation of nano Al2O3 particles and inclusion of one additional external layer in duplex coating. Excellent wear resistance also evaluated by the Nano-scratch test and cost effective Ferroxyl test supports the evidentiary fact of producing non porous electroless duplex coating which provides an excellent corrosion resistance to the inner Al2024 alloy. This study further provides a scope for analysis of heat treated electroless duplex coating onto various substrates especially used in Aerospace and defence industries.
Keywords: Duplex coatings, Nano-scratch test, Ferroxyl test, Aerospace and defence industries.
3rd Structural Integrity Conference and Exhibition – SICE2020
159
TS17
Reliability Aspects in Medical Devices and Implants
+
TS25
Biomechanics
Organizer:
A. M. Kuthe, NIT Nagpur
20th Dec 6-8 pm
20th Dec 9-10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
160
Invited Speakers
Class III medical devices development - challenges and opportunities for
India
Dr. A.M.Kuthe, VNIT A. M. Kuthe
Professor Mechanical engineering Department Visvesvaraya National Institute of Technology (VNIT) Nagpur
Email: [email protected] The Class III medical devices are more critical as the devices are either implanted in the patient body or their function directly affect the metabolism of the patient body and hence, they are classified under high risk category. Unfortunately, in India, most of the class III devices are imported and Indian manufacturer are not willing to enter in the market of class III medical devices as quality plays important role which needs high technical know-how. This has boomeranged in developing confidence of medical fraternity on the imported class III devices and the import bill for such devices are increasing every year. Despite having premier educational & research institutes in India, the scenario in the design and manufacturing of class III medical devices is poor. This is mainly because of lack of team effort in R & D activity on national level. There is a tremendous opportunity to develop in house class III medical devices like metallic implant. The confidence of the medical fraternity can be built if the human resources from premier educational and research institutes play role in design and manufacturing of the Class III medical devices. The perfect coordination of premier institutes and research-oriented company will bring down drastically the import bill of such devices. The customised medical class III devices developed at VNIT and implanted in the patient body and tissue engineering research can prove as important steppingstone. .
Prof. Kuthe earned his PhD in 2001. His research work is focussed in the area of rapidprototyping(RP). The capabilities of RP equipment were extensively exploited by him to make custom build metallic implant that were implanted in human bodies by surgeons in several complicated medical cases including some cases of cancer. His contribution to international and national journals, demonstrates his deep study as well as authority on the subject. Creation of well-equipped CAD-CAM centre at VNIT speaks volumes of his passion for raising the bar of academic standard.
3rd Structural Integrity Conference and Exhibition – SICE2020
161
The Challenges of Additive Manufacturing in Medical Devices
Gaffar Gailani
Professor, New York City College of Technology of the City University of New York [email protected]
In the last few years, the market of Additive Manufacturing (AM) of medical devices has been growing very fast. Financial forecasts estimate that this market will reach $10.8 billion by 2021. AM is playing a big role because it offers shorter supply chains, shorter lead time, optimised design, and precise customisation. However there are still some challenges needs to be addressed. These challenges include price of machines, sustainability of materials, reliability, high-volume production, lack of standards and many others.
Gaffar Gailani is a professor in the Mechanical Engineering Technology Dept at New York City College of Technology and the founder and director of the Centre of Medical Devices and Additive Manufacturing. He received his Master and PhD degrees from the City College of New York. His research areas include poroelasticity, design and manufacturing of medical devices and bone biomechanics.
3rd Structural Integrity Conference and Exhibition – SICE2020
162
Contributed Speakers
An in-depth look into mechanical testing of biomechanics & orthopedics
Jochen Niederberger, Industry Manager for Biomechanics &
Orthopedics, Dental and Biomaterial
ZwickRoell in ULM, Germany
The medical devices industry in India consists of large multinationals as well as small and
medium enterprises (SMEs) growing at an unprecedented scale with estimated current
market size of $11 bn.
The Government of India has taken several steps to ensure the growth of medical devices
manufacturing in India. Few amendments like implementation of the new Medical
Device Regulation will make tests of each medical device legally mandatory. This evolved
needs to assure quality standards and perform testing of the medical devices.
We would be focusing on the mechanical testing of spinal, hip, knee,
osteosynthesis implants, medical bone screws and other biomedical devices which
needs testing to assure the quality of the devices abiding the stringent medical devices
regulation. We will also highlight the requirements of different global standards (like ISO
and ASTM) and the importance of their existence in the testing world.
3rd Structural Integrity Conference and Exhibition – SICE2020
163
Non-invasive, anesthesia free Glaucoma screening device for early
detection and monitoring of glaucoma: A fully automated approach
Neha Lande
Neha Lande*1, Mahesh Mawale2, Abhaykumar Kuthe3, Nitesh Raul, Ashwini Lande
Production department, Okoicaresolutions private limited, Nagpur1
Mechanical engineering department, Kavikulguru Institute of Technology and Science Ramtek, Nagpur2
Mechanical engineering department, Visveswaraya National Institute of Technology, Nagpur3
Glaucoma is a progressive optic neuropathy caused by high intraocular pressure (IOP)
results in permanent vision loss within a few years. About 120 Lakhs Indians are affected
by Glaucoma with 10% of them permanently losing their vision. This can be prevented by
suitable care and treatment, if the condition is diagnosed early enough. Currently available
devices are invasive need anesthesia drops for taking IOP also not enough for large scale
screening. Considering all these aspects we have developed a novel glaucoma screening
device overcoming all mentioned problems which will greatly reduce the skill level, time and
cost involved in glaucoma screening. This device is robust, portable, non-invasive which is
placed over the eyelid and takes only few seconds to detect the level of IOP. We have used
a novel approached combining two different principles applanation and fixed indentation.
The goal to screen large number of patients especially from rural areas where glaucoma
awareness is poor. Such patients can be referred to ophthalmologists for confirmation and
further treatment. 50 patients were screened with new device they have found the new
device is more comfortable than conventional devices. The project has been granted by
BIRAC start-up grant for product development.
Keywords: Intraocular pressure, applanation, indentation, vision, robust
3rd Structural Integrity Conference and Exhibition – SICE2020
164
Integration of nanotechnology and 3D printing technology for organ printing
Arun Bharali
In today’s world the applications of Biomedical Nanotechnology is growing day by day.
Integrating this technology with the current 3D printing techniques and their applications
towards bone, cartilage and Osteochondral regeneration leads to vast scope in this field. In
this paper, with the help of a computer software a solution to repair, restore or replace
skeletal elements and associated tissues that are affected by acute injury, chronic
degeneration or cancer related defects is discussed with an overview to future research in
the related areas.
3rd Structural Integrity Conference and Exhibition – SICE2020
165
Coupling of Mechanical Deformation and Electrophysiology of Brain Neuron
Cell
Rahul Jangid
Rahul Jangid and Krishnendu Haldar
Aerospace Engineering Indian Institute of Technology, Bombay
[email protected]] [[email protected]
Traumatic Brain Injury (TBI) due to a vicious head impact in motor or space vehicle accidents, falls, and sports injuries, causes severe tissue damage. The impact forces make the brain tissue distorted, twisted, and injured. The stress inhomogeneity, due to the impact, creates highly nonuniform strains and damages the axons in the white matter. For more than half a century, electrophysiology of brain neurons was considered pure electrical phenomena. However, recent experimental studies show that mechanical deformation plays a vital role in the electrophysiology of brain neurons. In this work, we model the coupling of mechanical deformation with the Hodgkin-Huxley (H-H) model of electrophysiology of neurons. The sensitivity of pressure on the neuron cell due to the generated electrical field and mechanical stretching is demonstrated.
Keywords: Traumatic Brain Injury, Electrophysiology, Hodgkin-Huxley (H-H) Model.
3rd Structural Integrity Conference and Exhibition – SICE2020
166
TS20-Structural Integrity of Weldments and Welded
Structures
Organizer: A. Shrivastava, IIT Bombay
11th Dec 4:30-6 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
167
Invited Speakers
Cracks and Failures in Space Transportation Systems
Dr. SGK Manikandan, IPRC ISRO Deputy General Manager
ISRO Propulsion Complex, ISRO, Mahendragiri [email protected]
Space systems need defect free components for the intended performance. Space systems are experiencing different loading conditions such as pressure, temperature and other external loads. Same system will behave in a different manner for every condition. Even a micro defect can lead to a catastrophic failure of the mission. All the space systems are qualified at ground prior to flight. This talk addresses the failures encountered in both flight and ground systems and root cause findings through metallographic analysis.
Graduated in mechanical engineering (1997) and joined in ISRO (1998). Completed PhD in Metallurgical and Materials engineering from IIT Madras.
RESEARCH INTERESTS :Metal Joining; Friction stir welding / processing/ surfacing; Electron beam welding; Metallurgical and Mechanical property evaluation of welds; Solidification in superalloy systems Process development for Thermal barrier and wear resistance coating for aerospace components. Development of metamaterials, super strong materials for temperatures exceeding 2000°C, High entropy alloy wear and thermal resistance coatings, thermally assisted friction stir welding of superalloys, Superalloy filler metal with inoculants, Self reacting friction stir welding and Self healing thermal barrier coatings. Publications in international journals (15), books(2) and international conferences (9)
3rd Structural Integrity Conference and Exhibition – SICE2020
168
Material Joining – Aero Engine Perspective
Dr. Vijay Petley, GTRE ISRO Scientist
Gas Turbine Research Establishment (GTRE), DRDO [email protected]
Aero engines have led to the development of advanced materials and processes over the last few decades. Materials with high temperature capability, high specific strength are developed for usage under harsh environments of aero engines. The advancement of processes to develop these materials is the necessity and natural outcome due to the rigorous quality requirement of these materials used for critical application. Further, the fabrication processes are inevitable during part realization and assembly of components. Of the many special processes, metal joining is one of the crucial processes that need to be employed on these advanced materials. Superalloys are the materials used in the hot zone of the aero engine. The combustor and turbine casings, nozzle guide vanes, rotor shafts, turbine blades, core burner ring are few of the components where metal joining is required to be performed. These components operate under the harshest environment of engine and so are the material joints on these components. While both fusion and solid state welding have seen application in aero engines, high temperature high vacuum brazing is a technology in itself for joining of hard-to-access locations of cast superalloys. The characterization of these weld joints and its qualification is utmost important for functional assessment of these parts. Mechanical evaluation and metallurgical characterization of these joints are complimentary techniques to understand the structural integrity of such joints. Additive manufacturing process itself is a micro-arc welding of powder particles with a highly precise mechanism to control the heat input and path travel. Laser cladding, surface crack repair by brazing, IPTIG welding are few of the material joining technologies towards repair and reclamation of aero engine parts. Conventional usage of composites for aero engines requires metal-composite interfaces that are realized by riveting, active brazing, etc. With advancement of material technologies meant for specific product development like BLING has multitude of process specific technologies of which diffusion bonding, linear friction welding are few of the material joining technologies. Even for sensor application like lead wire routing, micro welding techniques are developed for the specific type of sensor material and design. The present talk illustrates and provides a brief about the work performed on material joining for aero engine application and the challenges required to be met with advancement of technologies. With emerging material technologies on several fronts like superalloys, composites, sensors, the advances in material joining technologies has to go hand-in-hand for part and assembly realization. The field of material joining is very expansive and there is a necessity for the collaborative work amongst researches, academicians and institutes to propel these technologies for aero engine application.
Dr. Vijay Petley did his graduation in year 2001 from Department of Metallurgical Engineering & Materials Science of Visvesvaraya Regional College of Engineering, presently, VNIT Nagpur. He joined GTRE DRDO in year 2001. He pursued his doctoral work at Indian Institute of Science. Presently, he works as Scientist at Materials Group of GTRE and is responsible to address the metal joining related issues on the various programs at GTRE.
3rd Structural Integrity Conference and Exhibition – SICE2020
169
Contributed Speakers
Finite element simulation of residual stresses in friction stirs welding of
AA2219 plates
Krishnajith Jayamani Krishnajith Jayamani, K. Abhishekaran, Vasudevan R. , H. M. Umer & A. K. Asraff
Mechanical Design and Analysis Entity, Indian Space Research Organization (ISRO), India,], [Institute]
Friction Stir Welding (FSW) is a solid state welding process in which the temperatures never
exceed the melting point of the work-piece material. The process is widely used in
aerospace industry for welding of aluminium alloys and aluminium-lithium alloys used in the
fabrication of propellant tanks. Knowledge of the residual stresses developed due do the
welding process is an important parameter used in the design of propellant tanks.
The present work details the finite element simulation of friction stir welding of two flat
plates made of AA2219 material, a material used for fabrication of the propellant tanks used
in the launch vehicles of ISRO. The simulation is performed using a non-linear, fully coupled
thermal-structural finite element analysis using ANSYS (Version 18.1) code. The
computational model involves two work-plates and the FSW tool modelled using three
dimensional solid elements and the effect of the fixtures supporting the work-piece is
brought in using appropriate structural and thermal boundary conditions. The constitutive
models used for the analysis are capable of simulating the frictional heat generation and
the associated temperature-dependent mechanical response of the material. The entire
sequence of operations involved in the welding process from initial plunge of the tool to the
final removal of clamps after cooling is simulated.
It is seen that the predicted temperatures on the work-piece falls with 70% to 90% of the
melting temperature of this particular alloy. The predicted residual stress pattern shows a
characteristic M-shaped distribution along the width of the work-piece which agrees fairly
well with results reported in literature.
Keywords: Friction Stir Welding, Residual stress, Finite element simulation
3rd Structural Integrity Conference and Exhibition – SICE2020
170
TS21
TS21-Structural integrity of Gas Turbine Engine
Materials
Organizer: A. Patra, IIT Bombay
13th Dec 4-5.30 pm
20th Dec 4-6 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
171
Invited Speakers
Deformation in thermal barrier coating (TBC) ensemble
Md. Zafir Alam, DMRL
(Other authors: Chandrakant Parlikar, Rajdeep Sarkar and Dipak Das) Scientist & Head
High Temperature Coatings Group [email protected]
The Ni-base superalloy components operating in the hot sections of advanced gas turbine engines are applied with thermal barrier coatings (TBCs). The TBC is a multi-layered ensemble providing thermal insulation, oxidation resistance and enhanced high temperature durability to the components. The advanced TBC system contains: (i) an outer layer of columnar textured 8 wt.% yttria stabilized zirconia (YSZ) which is 150 µm in thickness and provides thermal insulation, (ii) an intermediate layer of thermally grown oxide (TGO) which comprises polycrystalline alumina and is 2-6 µm in thickness, (iii) a subsequent inner layer of diffusion Pt-aluminide (PtAl) bond coat which is about 100 µm thick, exhibits randomly oriented B2-NiAl phase with graded stoichiometry and provides oxidation resistance, and (iv) the directionally solidified (DS)/single crystal (SX) Ni-superalloy substrate containing the γ-Ni/γ´-Ni3Al phases which bears the mechanical loads. Therefore, the constituents transition from ceramic (YSZ, TGO) to brittle intermetallic (PtAl bond coat) and metallic (superalloy) across the TBC coated superalloy. Considering the inherently different slip characteristics in metallic, intermetallic and ceramic systems, scientific understanding of the deformation behavior within the multi-layered and multi-phase TBC ensemble is crucial. The present study evaluates the micro-mechanisms of tensile deformation at various temperatures until 1000°C for a directionally solidified (DS) CM247 LC superalloy applied with TBC. The representative properties of the TBC constituents, i.e. that of freestanding diffusion PtAl bond coat, TGO and EB-PVD columnar YSZ coating are ascertained using micro-tensile testing and nano-indentation techniques. The large B2-NiAl grains (size > 10 µm) oriented for high Schmid factor with respect to the neighboring grains in the PtAl bond coat experience high shear stress on {100}<001>, {110}<001> slip systems and exhibit profuse dislocation activity at room temperature, which is otherwise unusual for the brittle NiAl intermetallic. The outward propagation of cracks from the bond coat along the PtAl/TGO/YSZ interface causes delamination of the YSZ coating layer, whereas the inward propagation of cracks causes lowering of strain tolerance in the superalloy and tensile failure is marked by negligible post-necking strain for temperatures below 800°C. At higher temperatures, the ductile deformation in the PtAl bond coat, aided by its low strength and concomitant dynamic recrystallization, causes shear displacements of the YSZ/TGO/PtAl interface and buckling delamination of the YSZ coating.
Dr. Zafir Alam works as a Scientist in Defence Metallurgical Research Laboratory (DMRL), Hyderabad, India and leads the High Temperature Coatings Group. He obtained Ph.D. from The Department of Materials Engineering, Indian Institute of Science (IISc), Bangalore and purused post-doctoral research at Johns Hopkins University, USA. His research interests are in the processing and micro-mechanical characterization of coatings for advanced high temperature applications. He is recepient of ACTA Student Award-2013, IISc Best-PhD Thesis Award-2013, IIM-Young Metallurgist Award-2011, and DRDO Young Scientist Award-2010. He has about 50 publications in peer-reviewed journals.
3rd Structural Integrity Conference and Exhibition – SICE2020
172
Dheepa Srinivasan, Pratt & Whitney
Chief Engineer Pratt & Whitney R&D Center
Materials and Manufacturing technologies have enabled Gas Turbine engine advancements and played a critical role in various aspects of the engine performance metrics of, thrust, efficiency, firing temperature and weight, since the last 7-8 decades. The temperature capability at the turbine inlet temperature (is higher than the melting point of the metal), the compressor by pass ratio, compressor outlet temperature, have all more than doubled in the last several decades,and owe their advancements to materials capability enhancements,which has gone up by leaps and bounds with each new successive product generation. Today, all these have been possible because of the availability of high temperature alloys and coatings, for rotating turbo machinery. A glimpse of the materials capability from flange to flange will be shared. Directionally solidified and single crystal blades, light weight carbon fiber composite blades and hybrid metallic airfoils, hollow Ti and γ-TiAl blades, Ceramic matrix composites and low K thermal barrier coatings (TBC’s) have all played an everlasting role in the development of new material architectures and enabled propulsion innovation. Several 1000’s of parts receive coatings to address erosion, corrosion, abradable, fretting, oxidation, hot corrosion and thermal protection coatings that optimize the application performance.The talk will address the evolution of Nickel based superalloys in the gas turbine development, and share a couple of examples of the time and effort involved in development of high temperature capability alloys and coatings. Future engine capabilities require lightweight structures and higher temperature capability with greater durability. While evolutionary progress will help, new high temperature materials and manufacturing systems are needed with improved development speed and cost to enable new system architectures.
Dr. Dheepa Srinivasan is the Chief Engineer, at Pratt and Whitney, R&D Center, Bangalore. She is leading research activities at academic and industrial research sites in India for Pratt and Whitney. Dheepa has more than 20 years of total work experience in the area of gas turbine materials and manufacturing technologies.
3rd Structural Integrity Conference and Exhibition – SICE2020
173
Contributed Speakers
Tensile properties and statistical analysis of freestanding YSZ thin films
with circular holes
Supriya Patibanda, IIT Bombay
Supriya Patibanda1, Ralph Abrahams2 and Krishna N Jonnalagadda3
1Department of Mechanical Engineering, IITB-Monash Research Academy, 2Department of Mechanical and Aerospace Engineering, Monash University,
3Department of Mechanical Engineering, Indian Institute of Technology Bombay.
Email of corresponding author: [email protected]
Abstract
Yttria stabilized zirconia (YSZ) is used as a top coat in the thermal barrier coating system on
superalloy components of aircraft engines, for its low thermal conductivity and superior thermal
insulation properties. To avoid the premature failure due to excessive operating temperatures,
turbine blades and some engine components are provided with holes for cooling purpose. As TBCs
are coated on to these blades, it is important to understand the effect of these holes on the fracture
behaviour of TBC. Therefore, in this study, the effect of stress concentrations on the tensile
properties of free standing YSZ thin films of ~300 μm was studied using samples with inherent
circular hole of Ø1 mm at the centre of the tensile sample, devoid of any machining. The effect of
the presence of a circular hole on the tensile strength was studied and compared to that of
continuous YSZ films using a custom built uniaxial microtensile setup in conjunction with digital
image correlation. A drop in fracture strength from 16±4 MPa in continuous samples to ~11±3 MPa
in samples with a circular hole was observed. The cracks initiated at the circumference of the hole
and perpendicular to the loading direction. To address the basic problem of data scatter in fracture
strength in these materials, designers have proposed a probabilistic approach in ceramic materials
based on Weibull’s weakest link theory. Hence, Weibull statistical analysis was performed on tensile
strength of continuous and hole containing samples. It was observed that the three-parameter
method is more accurate for YSZ films than two-parameter analysis. The properties reported in this
current study could contribute to the design database for modelling the mechanical behaviour of
YSZ.
Keywords: Freestanding YSZ films; tensile properties; digital image correlation; Weibull analysis,
stress concentration
3rd Structural Integrity Conference and Exhibition – SICE2020
174
Numerical slosh studies of multiple ring baffles in a semi-cryogenic fuel
tank
Aleena Seban, Mar Baselios College of Engineering and Technology
Aleena Seban1, Kodati Srinivas2,M. Satyakumar3, Sarath Chandran Nair S.4
1 Graduate student, Mar Baselios College of Engineering and Technology, Thiruvananthapuram-695015,
[email protected] 2 Head, Structural Dynamics Division, Mechanical Design & Analysis Entity, LPSC/ISRO, Valiamala, Thiru
vananthapuram, 695547
3 Head, Department of Civil Engineering, Mar Baselios College of Engineering and Technology, Thiruvanan
thapuram-695015
4 Engineer, Structural Dynamics Division, Mechanical Design & Analysis Entity, LPSC/ISRO, Valiamala, Thir
uvananthapuram, 695547
Abstract
One of the heavy lift launch vehicles being developed by ISRO uses semi-cryogenic stage.
Semi cryogenic stage uses Isrosene as a fuel and liquid oxygen (LOX) as the oxidizer. These
propellants will be supplied at a specific flow rates to the rocket engine to develop the
required thrust. Sloshing is an important phenomenon to be considered for
liquid/cryogenic/semi-cryo genic stages in order to design control system for the launch
vehicle. For modelling slosh for control system studies, mathematical parameters such as
slosh frequency, slosh mass and its location are required to be evaluated. In addition to
these parameters, damping also play a major role in containing the vehicle response due to
slosh. In the present study the parameters required for mathematical modelling of slosh for
control stability analysis are evaluated using two different FE codes. The requirement of
damping and duration envisaged from control sta bility analysis is met by designing multiple
ring baffles using semi-empirical relations. In ad dition to the above, the achievable damping
values for the designed baffle and its effect on slosh parameters are also studied.
Keywords: Semi-Cryogenic Stage; Sloshing; Slosh Frequency; Slosh Mass.
3rd Structural Integrity Conference and Exhibition – SICE2020
175
TS22-Damage and Failure modeling in Composite
Materials
Organizer: C. Yerramalli, IIT Bombay
19th Dec 6-10 pm
3rd Structural Integrity Conference and Exhibition – SICE2020
176
Invited Speakers
Process optimization in manufactring of composite structures
Amit Salvi, TRDDC, TCS
Fiber reinforced Polymer matrix composites are increasingly used in large Aerospace and Wind Energy Blades. These structures pose unique challenges due to their size, life under fatigue loads and long term reliability. The durability of these structures depend on the damage accumulated over its operational life which in turn depend on the residual stresses developed in the manufacturing stage itself. Thermoset epoxy resin used in the structures acquire their mechanical as well as physical and chemical properties during its cure in which cross-linking of polymers take place. In presence of reinforcing fibers, the elastic as well as inealstic properties of the in-situ resin differs from virgin resin and create lot process induced residual stresses. In this study, a time dependent, multiscale analysis framework is developed to compute process dependent residual stresses in large structures. A n optimisation framework is also developed to control desired quality of these components to reduce the distortion and residual stresses to increase the reliability of these structures.
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177
TBD
Contributed Speakers
Laminate and Sub-laminate Buckling on Delamination Mechanics in Hybrid
Composites
Savitha N Nambisan and B. Dattaguru School of Aerospace Engineering, Jain (deemed to be University)
Bengaluru Laminated composites have become preferred material system in a variety of industrial applications and particularly in Aerospace Engineering. Laminates made of single fibre type and resin are extensively used in aerospace primary structural components with weight saving and in these cases further benefits can be achieved by fibre hybridization. It is the purpose of this paper to demonstrate that combining layers of lamina of different fibres is a promising strategy to enhance tolerance to delamination type of defects in laminates. Also by combining two or more fibre types, the hybrid composites offer a better balance in mechanical properties than non-hybrid composites.For instance, replacing carbon fibres in the middle of a laminate by cheaper glass fibres can significantly reduce the cost,while the flexural properties remain almost unaffected. A 24-layer all carbon layer composite of (+45/-45/0/90)3s lay-up is considered for analysis. The laminate dimensions are 92 X 74 mm with 3mm thickness is analyzed with and without hybridization. This laminate was considered earlier in literature [1] for delamination tolerance analysis. Low velocity impact could result in delamination/s in top or bottom few layers. Parametric study of delamination and its tolerance depending on its size, shape and depth are analyzed.This composite will be converted into a hybrid composite demonstrating the benefits of hybridization. Both the top and bottom 4 layers are replaced by (+45/-45/0/90) layup glass fiber composite laminates maintaining symmetry about the centerline. 3-dimensional finite element analysis is conducted using PATRAN for modeling and NASTRAN software package for structural analysis. Static displacements such as delamination opening and Strain Energy Release Rates (SERR) are compared for all carbon and hybridized composites. The shape of delamination considered is primarily of circular shape. Finite element analysis is conducted using 20-node brick elements and layered composite elements used with 2 or 4 layers in elements. The laminate (in x-y plane) is subjected to compression strain along the edges in x-direction and all edges are simply supported in z-direction. The delamination opening is measured and the SERR are estimated along the delamination front by using Modified Virtual Crack Closure Integral (MVCCI)technique [2]. There is a primary aspect to be considered in the analysis.Buckling of the entire panel and the sub-laminate affects delamination and its growth. So the entire panel and also the delaminated sub-laminate are checked for buckling failure. It is observed that the delamination growth is accentuated as sub-laminate bubbles before buckling failure. On the other hand buckling failure will make the delamination to close. At much higher load levels the total laminate failure could occur and the laminate ceases to take any further load. The buckling failure loads are evaluated with various parameters of the laminate. The hybridization leads to much earlier delamination closure and zero strain energy release rates. Delamination tolerance is much better in hybridized composite due to less stiffness layers at the top and bottom of the layup. This is shown for one typical case. The paper demonstrates these results with variation of some of the geometric parameters.
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Al/GFRP interface strength under quasi-static and dynamic loading
conditions
Madhusudhanan U, Sooriyan S, R Kitey aStudent, Department of Aerospace engineering, IIT Kanpur, India
b Reseracher, TCS Research (TRDDC), Pune, India cAssociate Professor, Department of Aerospace engineering, IIT Kanpur, India
Email of corresponding author: [email protected]
With continual increase of composites in aerospace applications, metal/composite bonded joints have become quite common because several aircraft components cannot be riveted, bolted or welded due to their miniature sizes and/or complex shapes. Apparently, the reliability of such components highly depends upon their interfacial properties. Often pull tests are suggested to evaluate the interface strength of bonded joints. Unless the effect of stress concentration is taken into account, reliable interface strength data cannot be obtained from the experiments. In this investigation the interface strength between Al 6063-T6 alloy and glass fiber reinforced polymer (GFRP) composite is evaluated under quasi-static and extreme dynamic loading conditions. A modified axisymmetric butt joint sample is designed to negate the effect of stress concentration.
Al/GFRP bonded joint specimens to conduct pull tests are prepared by co-bonding.
Laser spallation technique is adopted to measure the interface strength of Al/GFRP
bonded joint at a strain rate of ~ 107/s. Failure initiation is identified through optical
microscopy and interface strength is evaluated by employing experimental/numerical
approach. The dynamic adhesion strength of Al/GFRP joints is measured to be 330.8
MPa.
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A FEA based study on the behaviour of multiple-micro bolted hybrid CFRP
joint under tensile loading
Isha Paliwal and Ramji M. Engineering Optics Lab, Department of Mechanical and Aerospace Engineering,
IIT Hyderabad, India
*Email: [email protected]
Abstract
The extensive use of composite materials in aircraft primary structures led to the increasing
interest of many researchers to improve the joint efficiency of existing joints techniques as
well as develop new joining techniques for composite material. The conventional joints use
in composite structures are bolted, bonded, and hybrid (bonded/bolted) joint. The hybrid
joint exhibits the advantages of both adhesively bonded and bolted. Hence, have the
potential to be employed in primary aircraft structures joint requirement.
To understand, the mode of failure of hybrid joint and the effect of various parameters on
joint strength, many studies have carried out in the previous two decades. From the
literature, we can conclude that the percentage load sharing through the bolt has a
significant effect on hybrid joint strength. In this study, multiple micro bolts are used instead
of a single bolt to fasten the hybrid joint. Multiple micro holes laminate takes a higher
ultimate tensile load than the single hole laminate while keeping the area of cutout constant.
The use of micro bolts also leads to reducing the weight of the joint assembly.
To investigate the effect of multiple-micro bolts in the hybrid joint scenario, a finite element
analysis (FEA) has been performed using a three-dimensional finite element model. A 3-D
progressive damage model is used to assess the damage evolution and prediction of the
ultimate strength of the hybrid composite joint under in-plane tensile loading. The results
show that joint strength is higher for the multiple-micro bolted hybrid model than the single
bolt hybrid model. The percentage of load transfer through-bolt is increased significantly
due to multiple bolts.
Keywords: Hybrid joint; FEA; Micro-bolt; Progressive damage.
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Hot-wet environmental effects on in-plane shear strength of IMA/M21E
aircraft grade CFRP composites
Kishora Shetty* Kishora Shettya, Shylaja Sriharia,b, C M Manjunathaa,b, Suhasini Gururajac
aAcademy of Scientific and Innovative Research (AcSIR), Ghaziabad - 201002, India bCSIR-National Aerospace Laboratoires, Bangalore - 560017, India
cIndian Institute of Science, Bangalore - 560017, India
Abstract
Application of Carbon Fibre Reinforced Plastic (CFRP) composites in aerospace structures
are increasing due to their high specific strength and stiffness. During their service, aircraft
composite structures are usually exposed to a variety of environmental conditions including
hot – wet or hygrothermal, ultraviolet (UV) radiation, chemical environments, biological
conditions etc. These conditions make the composite structures to deteriorate mainly by
making changes to polymer matrix and to matrix/ reinforcement interface. Effect of hot –
wet environments by moisture absorption on properties of CFRP structures is a valuable
factor to designers and application engineers in assessing the structural integrity of the
parts. In this present study, UD-CFRP composite laminates were manufactured from
HexPly® M21E/34%/UD/194/IMA prepreg by standard autoclave process. In-plane shear
strength (IPS) being the matrix dominated property of the CFRP, it is important to evaluate
the effect of moisture absorption in this. In-plane shear (IPS) strength test specimens were
obtained from theses laminates. Specimens were subjected to three hot – wet
environmental conditions: 45 oC/85% RH (relative humidity), 75 oC/85% RH and 55 oC/100%
RH until achieving complete moisture absorption saturation. IPS tests were carried out as
per ASTM test standard ASTM D3518 specifications using a 25 KN servo-hydraulic test
machine. The in-plane shear strength properties were determined for both conditioned and
un-conditioned (control) laminate specimens. Corresponding hot-wet conditions were
maintained during the IPS tests. Tests results show that moisture absorption rate increases
gradually and attains saturation at about 1.2 wt. % under these three conditions. IPS
strength reduced by about 8% due to presence of moisture. Tensile strengths were also
measured while carrying out IPS tests. This paper describes the details of hot – wet
conditioning, moisture absorption and IPS test results.
Keywords: Structures, Composite, Hot-wet, IPS
3rd Structural Integrity Conference and Exhibition – SICE2020
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Performance driven fan case design for durability evaluation in a blade
impact event
Ashutosh Bhat, Lavya Sharma and Sandeep Sharma
Ashutosh Bhata, Lavya Sharmab , Sandeep Sharmac
a,b Research Associate, Aerosphere Technologies, Chandigarh, India c Technical Head,
Aerosphere Technologies, Chandigarh, India
Abstract: The objective of present work focuses on identifying containment capability of a hybrid fan case which uses an impact absorbing (periodic) corrugated lattice structure core (LSC), sandwiched between the inner ring and outer shell having distinct impact resistance followed by perforation, buckling and crushing as a result of excellent strength to stiffness ratio at low relative density. Three different configurations comprising of general (a), twill (b) and triaxial (c) patterns are built for this study and by varying cell parameters such as inclination angle (θ), thickness and face width similar relative densities are derived for numerical investigation. In order to maintain structural integrity during blade penetration at first contact, estimation of maximum allowable thickness for inner ring is critical and best suitable value of 0.9 mm was found deterministically by sub-scale impact tests. Further, to determine design reliability; contact force history, energy locus, triaxial stresses, plastic strain and large deformations that occurs during blade-case interaction in cases a, b and c are studied for effective comparison using finite element solver LS-DYNA. Results reveal that number of unit cells have relevant effect on containment capability within the same spatial envelop. For one-third number of relative cells in 2-d (x-y) plane, significant local buckling causes sudden collapse of corrugated cells circumferentially which is undesirable as it loses interferential strength to counter (shear). However, marginally higher energy is absorbed for case (c) when compared to cases (a, b) and additionally crushing response is also delayed resulting is lesser plastic strain during damage. Effect of multi-blade interaction on blade breakage at is not a part of current study. Lastly, it is concluded that to exploit maximum energy absorbing capacity of a corrugated lattice structure, factors such as topology, cell parameters and unit repetition must be carefully identified.
KEYWORDS: Fan Blade out, Containment, Corrugated lattice core, Hybrid casing
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