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Pre-Project Presentation Measurement of Residual Stress Distribution & Fatigue Life Assessment of Butt Welded Joint
Pankaj Kumar : (1BG11ME034)
Shailendra Kumar :(1BG11ME048)
Dinesh Sah :(1BG11ME014)
Shree Kaustub :(1BG11ME053)
Internal Guides:
Mr .Vasudev.U Mr. Harish Mr.Karthik
Asst. Prof. Asst. Prof. Asst. Prof.
Mechanical Dept. Mechanical Dept. Mechanical Dept.
B.N.M.I.T B.N.M.I.T B.N.M.I.T
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Aim of the Project
Measurement of Residual Stress Distribution and Estimation of Fatigue life of a Butt Welded Joint before and after surface treatment.
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Project Objectives1] To review the literature on fatigue life of welded joint and on
surface enhancement treatment.
2] Experimental investigation of induced residual stress in butt welded joint before and after surface modification process by shot peening method.
3] Estimation of fatigue life in butt welded joint before and after surface modification process.
4] Analyzing the Effect of residual stress modification on fatigue life of the welded component.
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Methods and Methodology Objective 1:
To review the literature on fatigue life of welded joint and on surface enhancement treatment.
Literature Review: Sylvain Chataingner et al: Steel structures are mainly prone to two types of
degradation: corrosion and fatigue particularly in the case of welded structures. The presented work aims at investigating two treatment methods to increase the fatigue life expectancy of welded steel joints. It includes both numerical and experimental investigations and is interested in the use of shot peening. As far as experimental investigations are concerned, for both treatment methods and for untreated samples, the stress concentration coefficients are determined, surface residual stresses are measured using X-ray diffraction and fatigue tests are conducted. The results allow explaining for both methods the observed improvements in fatigue behaviour.Numerical investigations are concerned and this allows the determination of residual stresses due to welding operation and their comparison with the former experimental measures.
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M Hasegawa et al: The shot peening method, which requires simple equipment and treatment, is extensively employed as a method to improve fatigue strength. However, conventional steel ball shot material has a low specific gravity, so high speed projection is required in order to improve fatigue strength; thus, the accompanying noise and high air flow are problems. Accordingly, in order to improve these aspects, high hardness and high specific gravity shot material has been developed with 1.7 times the hardness (HV1400) and approximately 1.9 times the specific gravity (approximately 14) compared with a conventional steel ball.
Mark S. Molzen et al: The welding process induces residual tensile stress that is detrimental to fatigue life. Tensile stresses act to stretch or pull apart the surface of the material. With enough load cycles at a high enough tensile stress, a metal surface will initiate a crack. Significant improvements in fatigue life can be obtained by modifying the residual stress levels in the material. Two methods of performing this are through heat treating and shot peening. Both will be thoroughly analyzed in this paper through the use of x-ray diffraction. X-ray diffraction is the most accurate and best-developed method to characterize the residual stress in polycrystalline material.
Methods and Methodology
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Manoj Saini et al: Dissimilar metal joints between austenitic stainless steels and carbon steels containing low amounts of carbon are being extensively utilized in many high-temperature applications in energy conversion systems. In steam generating power stations, the parts of boilers that are subjected to lower temperatures as in the primary boiler tubes and heat exchangers are made of ferritic steel(mild steel) for economic reasons. Other parts, such as the final stages of the super heaters and repeaters operating at higher temperatures where increased creep strength and resistance to oxidation are required, are constructed with austenitic stainless steels. Therefore, transition welds are needed between the two classes of materials.Dissimilar metal weld is also used to anlysis of strength of joint.Beacause due to residual stress induces in the weld.We can find the amount of residual stress in two different metal.
Methods and Methodology
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Literature Summary : Residual stresses are a consequence of the welding process and are an important consideration in structural assessment . The welding process induces residual tensile stress that is detrimental to fatigue life. Tensile stress act to stretch or pull apart the surface of the material . With the enough load cycles at a high enough tensile stress a metal surface will initiate the crack .
It is commonly observed that complex fabricated structures subject to fatigue loading fail at the welded connections. Some problems can be corrected by improved detail design but fatigue performance can also be improved using post-weld improvement methods.
Methods and Methodology
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Method and Methodology RESIDUAL STRESS MODIFICATION:Residual stress can significantly affect engineering properties of materials and structural components, notably fatigue life, distortion, dimensional stability, corrosion resistance etc.
The residual stress analysis is a compulsory stage in the design of structural elements and in the estimation of their reliability under real service conditions Significant improvement in the fatigue life can be obtained by modifying the residual stress levels in the material.
Some of the different methods of residual stress modification methods area.) Shot peening b.) Hammer peening c.)Ultrasonic method d.) Heat treatment.
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Shot peening: Shot peening is a cold work process used to finish metal parts to prevent fatigue and stress corrosion failures and increase product life for the part. In shot peening, small spherical shot bombards the surface of the part to be finished. The shot acts like a peen hammer, dimpling the surface and causing compression stresses under the dimple.
Methods and Methodology
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Objective 2: Experimental investigation of induced residual stress in butt welded joint before and after surface modification process.
Experimental details :a. Material: Stainless steel 304L and Mild steel.
b. Specification of material: 25×12×5 (all dimension in mm).
c. Type of joint : Butt welded joint.
d. NDE technique for residual stress measurement.
Methods and Methodology
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Methods and MethodologyX-Ray Diffraction Method:
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Methods and Methodology
XRD is a non destructive method which is used to measure stress in the material without damaging it. XRD uses x-ray beam which is made to incident on the material surface for which we need to find stress. XRD uses Bragg’s law to determine the stress on the surface of material.
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Objective 3: Estimation of fatigue life in butt welded joint before and after surface modification process.
Estimation of fatigue life of the butt welded component is carried out with the help of MTS uni axial testing machine.
Specimen prepared for fatigue Testing
Methods and Methodology
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Objective 4: Analyzing the Effect of residual stress modification on fatigue life of the welded component.
Stress modification process such as Shot peening reduces the residual tensile stress and induces the residual compressive stress in the specimen.
Due to Shot peening the fatigue life and hardness of the component increases.
Methods and Methodology
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Work Done Till Now
After completing literature survey the ASTM standard specimen specification is prepared.
Selection of material(MS,SS 304L).
Purchase of material Welding Shot peening Measurement of Residual stress
Type of material C Mn P S Si Cr Ni N I
Mild Steel 0.16-0.18%
0.7-0.9%
0.04max
0.04max
0.40max
- - - -
Stainless Steel (304L)
0.03max
2max
0.045max
0.030max
0.75max
18-20% 8-12% 0.1max
Balance
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Remaining Work
Fatigue Test Hardness test
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Project Schedule
Total duration of project is 16 weeks
Activity/ Week W-0 W-12/3/15 to8/3/15
W-29/3/15 to15/3/15
W-316/3/15 to 22/3/15
W-423/3/15 to29/3/15
W-530/4/15 to5/4/15
W-620/4/15 to25/4/15
W-725/4/15 to2/5/15
Pre-Project Presentation
1st Presentation
Literature Survey
Selection of material
Purchase and Machining of Material
Butt Welding
Residual stress measurement
Shot peening
Residual stress measurement
Fatigue Test
Result and verification
Final Presentation
Submission of Technical Paper, Poster, Final Report
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Place of Work
B.N.M. Institute of Technology C.M.T.I, Bangalore Hi-Tech Enterprises, Pune Acharya Institute of Technology, Bangalore
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Resources• Software Resources:
1] Solid edge
2] FEM software, ANSYS-15(advanced)
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References
1] R. Snoeys, Thermal Damage in Grinding, Proc. Milton C. Shaw Grinding Symp., R. Komanduri and D.Maas, Ed. (Miami Beach, FL), The American Society of Mechanical Engineers, 1985, p 425-434
2] J. Peters, R. Snoeys, and M. Maris, Residual Stress in Grinding, Advanced Fabrication Processes, Conference Proceedings No. 256, Advisory Group for Aerospace Research and Development.
3] J.S. Eckersley and T.J. Meister, Intelligent Design Takes Advantage of Residual Stresses, Practical Applications of Residual Stress Technology, Clayton Ruud, Ed., ASM International, 1991, p 175-181
4] Control of Residual stresses, Material Selection and Design, ASM Hand Book, 20, ASM International , USA
5] Haagensen, P. J., Alnes O., 2005. Progress report on IIW WG2 round robin fatigue testing program on 700 MPa and 350 MPa YS steels.
International Institute of Welding Doc. XIII-2081-05. 6] Hobbacher, A., 2009. IIW Recommendations for Fatigue Design of
Welded Joints and Components. WRC Bulletin 520, Welding Research Council, New York, pp. 144
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Benefits of the work
• Will it result into a publication? yes
• Will it result into a product? yes
• Will it be a solution to an existing problem of an industry? yes
• Is it pursued for academic interest? Yes
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Thank You