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ASME Swiss Section Newsletter #10 Page No 1 January 2015

Swiss Section News

Newsletter Published – 10 January 2014 Inside this Issue 1 Highlights from The Swiss Section

3 ONE ASME and The Swiss Section

7 Celebration of the New Historical Landmark: Giessbach Funicular

8 2014 ASME Swiss Section Young Engineer Award

11 TECH in BRIEF: Innovative system for fatigue strengthening of beams in a 120-year-old bridge using pre-stressed CFRP laminates

14 Call for 2015 ASME Swiss Section Young Engineer Award

15 TECH in BRIEF: Acoustic Handling of Droplets on Microchips

19 Guided Tour Zürich Rail Way Main Station - A Look Behind the Scenes

Highlights from The Swiss Section by Gregory Hespe, News Editor The winter break is over and the ASME Swiss Section is back for 2015 with a full agenda. I am personally looking forward to the confirmation of the Giessbach Funicular as an ASME Historical Landmark due to the diligence of Hans Wettstein, our History & Heritage chair. This year is the 20th anniversary of the Blade Mechanics Seminar which will be held in Winterthur on 8th September. More details will follow in the upcoming newsletters. Nevertheless, please mark it in your dairy. Always of interest is the young engineer’s award that will be held a little earlier this year; please encourage any eligible young engineers to apply and, if applying, make sure that you don’t miss the deadline. A summary of last year’s award ceremony is incorporated in this newsletter and a couple of the very high quality papers, including the winner, are included in the Tech in Brief sections. Also contained within this newsletter is a summary of our tour around the Zurich Main Station and its major upgrades that are currently in progress. We always welcome anyone who wants to get involved with the planning of the events! If you have an idea about something that you would like to see, please contact a member of the executive committee; their email addresses are to the left. To remain informed of upcoming events and activities , please remember to login to ASME.org and join the Swiss Section group (https://community.asme.org/switzerland_section/default.aspx). While on ASME.org, check out the new ASME WorkSmart online reference tool. I would like to personally thank all the contributors for their effort to ensure the production of this interesting newsletter. See you soon at one of our meetings, Gregory Hespe

ASME Swiss Section Executive Committee

• Chair: Jaroslaw SZWEDOWICZ, [email protected]

• Vice-Chair: Wolfgang KAPPIS, [email protected] • Secretary: Said HAVAKECHIAN,

[email protected] • Treasurer: Geoffrey Engelbrecht, [email protected] • News Editor: Gregory HESPE, [email protected] • Communication & Web: Manveer BAHADUR,

[email protected] • Members Interest: Armin ZEMP, [email protected] • Past Chair: Andre BURDET, [email protected] • College Relations: Daniel KEARNEY, [email protected] • Honors & Awards: Daniel KEARNEY, [email protected] • History & Heritage: Hans WETTSTEIN, [email protected]

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Now in its 60th year, ASME Turbo Expo is recognized as the must-attend event for turbomachinery professionals. The technical conference has a well-earned reputation for bringing together the best and brightest experts from around the world to share the latest in turbine technology, research, development, and application in the following topic areas: gas turbines, steam turbines, wind turbines, fans & blowers, Rankine cycle, and supercritical CO2. Turbo Expo offers unrivalled networking opportunities with a dedicated and diverse trade show floor. The 3-day exhibition attracts the industry's leading professionals and key decision makers, whose innovation and expertise are helping to shape the future of the turbomachinery industry and will feature a Student Poster Session.

Plan now to join 3,000 turbine colleagues from around the world at ASME TURBO EXPO, ASME's premier turbine technical conference and exposition, set for June 15-19, 2015 at the Palais de Congrès in Montréal, Canada.


ONE ASME and The Swiss Section by Dr Jaroslaw Szwedowicz

ASME is a voluntary society which enables knowledge sharing, career enrichment and skills development across all engineering disciplines. This Non-Profit-Organization helps the global engineering community to develop solutions for benefiting the whole of society. ASME has flourished through the decades to include more than 140,000 members in 151 countries. Thirty thousand of these members are students. All ASME members collaborate among each other in different geographical sections or/and disciplinarily based units. These groups now exceed 250 and one of them is the ASME Swiss Section which consists of 240 members including 25 students. By organizing regular technical tours, training seminars, workshops, the Blade Mechanics Seminar with exhibition and the Swiss Section Early Career Awards, our section offers opportunities for networking and know-how exchange among all engineers in Switzerland; see the article “Section Roadmap – Looking ahead” in Swiss Section Newsletter No. 2 from May 2012.

The Swiss Section is already 22 years old (see the article in Swiss Section Newsletter No. 7 from January 2014). Indeed, isn’t significant in comparison with ASME which was founded in 1880 by a small group of leading industrialists. Due to the rapid development of steam technology in the late 18th century, the key driver of ASME was to establish Boiler and Pressure Vessel Code (B&PVC) for the safety of the public. At that time, thousands of boilers were being built or operated in the USA and Europe which were manufactured by various companies. A lack of manufacturing standards for pressure vessels led to numerous accidents. An example is the terrible boiler explosion at the Grover Shoe Factory in Brockton, Massachusetts in 1905 where fundamental design failures resulted in the death of 58 people and injuries to another 117. However, the worst incident unfortunately occurred in 1865 when three boilers exploded on the steamship Sultana while sailing on the Mississippi. This caused more than 1’500 fatalities. The public concern that followed these and other catastrophes resulted in the publication of the first ASME Boiler and Pressure Vessel Code (B&PVC) - 1914 Edition in 1915 as a single book with a total of 114 pages. Today’s B&PVC consists of 28 books meeting all engineering needs for different pressurized systems, for instance, the Construction and Inspection of Nuclear Power Plant Components. a) COMMUNICATION MANNER IN THE PAST

b) PRESENT-DAY COMMUNICATION MANNER

Fig. 1 a) Boiler Code Committee at the Biltmore Hotel in Los Angeles in 1947 as the example of the ordinary

communication b) contemporary manner of communication

To establish any engineering practice or guideline, experienced engineers and industrial leaders need to meet each other to build up a common understanding of the issues at hand. In open literature, there is a well-known photo of the Boiler Code Committee, which was taken at the Biltmore Hotel in Los Angeles in 1947 (see Fig. 1a). This picture shows a few rows of engineers sitting in the same hall and formulating the work-instructions for boilers.


Today’s way of communication through the internet simplifies the process as it does not require physical presences of the participants in the same room. This allows for a fast alignment process of different opinions into a common outcome obtained from online meetings attended by stakeholders from different places all over the world (see Fig. 1b). These new means of communication allow much faster transfer of information and thus permit higher rates of technological innovation by engineers participating in meetings through their computers or smart-phones.

Recognising these changes in communication, the ASME leadership team consisting of more than 100 members have reviewed the overall situation with an aim find opportunities for improvement with respect to the organization of our society. Their discussions resulted in “Pathway 2025” as “cultural values and vision for strategic growth, financial sustainability and delivering a positive technical impact on humankind and the world”. This also resulted in the new organization chart is shown in Fig. 2 which does not consider ASME Districts anymore. In other words, ASME District H consisting of European countries, Israel, Turkey and Russia does not operate as the individual unit, and all ASME sections (groups) report directly to GPS (Group Pathways and Support) as illustrated in Fig. 2. The GPS is responsible for collaboration among all sections called now groups.

Fig. 2 New organization chart of ASME in which Swiss Section (Group) is extraordinarily pointed out

In the new strategy called “ONE ASME”, the website asme.org becomes an important tool for communication and organizing new groups with respect to needs of local engineering society. The GSP coordinates all on-going activities and new proposals into one optimal plan for conferences and events in terms of time and locations around the world. The ONE ASME requires more pro-active responsibility from each section whose proposals are finally aligned with the ideas of other sections (groups). The TEC (Technical Events and Content) Council consolidates the overall plan of Technical Conferences, Events, Webinars, Expos, Sponsorships and Speakers with four Segments of “Energy Sources & Processing”, “Energy Conversion & Storage”, “Engineering Science”, and “Design, Material & Manufacturing” (see Figure 2). This alignment process ensures that each ASME member and non-member engineers obtain the best product with respect to content. In the new concept of “ONE ASME”, the role and functions of the ASME Swiss Section remain the same as in the past. This strategy shares with us even more responsibility for identifying local needs of engineers and students that are aligned with the rest of the ASME world representing by 140’000 members in 151 countries.


Fig. 3 A part of the participants of one-day ASME Leadership Orientation Event which was held on October 11, 2014 in Istanbul, Turkey

On October 11th 2014, the top leadership of ASME including Madiha Kotb (past ASME President) and Michael Ireland (Managing Director), Elio Manes, Ty Booker, Marian E. Heller, Murat Dogru and others met all the local ASME Sections Chairs from Africa, Asia, and Europe in Istanbul. This seminar explained the motivation, background and goals of ONE ASME to participants who attended personally (Fig. 3) or through internet connection. We are now experiencing the roll-out phase of the ONE ASME and look forward to collaboration within this new framework which gives new opportunities for local innovations and ideas. Since July 2014 each ASME section (group) follows “Pathway 2025” which meets the present engineers’ needs in this day and age, when private SPACE X spaceships flight in universe and other private companies are testing their spaceships for all tourism.

For details about ONE ASME, please visit the ASME website at: https://community.asme.org/group_pathways__support/w/wiki/10618.documents-guides.aspx

Please register yourself at Swiss Section (Group) on the ASME.org website: https://community.asme.org/switzerland_section/default.aspx


BOOK YOUR CALENDER ON 8TH SEPTEMBER 2015

and

JOIN US FOR

THE 20TH BLADE MECHANICS SEMINAR AND EXHIBITION

IN WINTERTHUR.

Be part of the engineering local event and share with us your tacit knowledge about Rotating Components.


Celebration of the New Historical Landmark: Giessbach Funicular by Hans Wettstein

We have already three Historical Landmarks of Mechanical Engineering in Switzerland out of some 250 worldwide. Please follow the following links to the corresponding descriptions:

− The system Locher cog wheel railway to Mount Pilatus. https://www.asme.org/about-asme/who-we-are/engineering-history/landmarks/220-pilatusbahn

− The steam ship “Uri” with the first fixed steam cylinders allowing a sequential expansion and corresponding higher steam pressure. https://www.asme.org/about-asme/who-we-are/engineering-history/landmarks/200-paddle-steamer-uri

− The gas turbine Neuchatel, the first commercial power generating gas turbine. It was operating 62 years and is now an exhibit in Birr. https://www.asme.org/about-asme/who-we-are/engineering-history/landmarks/135-neuchatel-gas-turbine

We are now approaching the celebration of the new landmark, the Giessbach Funicular. This is the world’s first single track funicular with a half-way turnout. The challenge of this turnout was the requirement of two rail switches with inherent safe function. This was invented 1879 by Carl Roman Abt (1850–1933) and his improved version of 1886 has been in operation to the present day without modification or any reported malfunction in over 1000 installations worldwide. It is called the Abt switch (Abt’sche Weiche) in his honour. The Giessbach Funicular allowed the clientele of the hotel that arrived by steamboat from Interlaken to avoid the 100 meters ascent from the jetty to the hotel. The funicular is still in scheduled operation coordinated with the boat stops. The celebration will take place at Giessbach (near Brienz, BE) on August 27th 11:00 till 13:00 followed by lunch in the nearby Hotel Giessbach. This allows most of the Swiss residents to arrive and depart the same day. All ASME Swiss Section members are invited and you may mark this date in your agenda. More details will follow later.


2014 ASME Swiss Section Young Engineer Award Dr. Daniel KEARNEY; [email protected]

2014 ASME Swiss Section Young Engineer Finalists from left to right: Peter Reichert and Ivo Leibacher demonstrating a video for their novel concept of micro droplet control, Robert Ernest explaining his work on defect detection and Santiago Illucia presenting his experimental work on the evaluation of the local heat transfer coefficient for impinging jets in turbomachinary applications.

The 2nd Edition of the ASME Switzerland Young Engineer award was presented at our AGM meeting last October. This event marked another milestone in the ASME Switzerland calendar where approximately 30 of our local members attended the technical tour at the Zurich Hauptbahnhof. The technical tour followed by technical presentations of our Young Engineer finalists and the announcement of the coveted ASME Switzerland Young Engineer Award 2014.

This annual award is open to young mechanical engineers across Switzerland with no more than two years of engineering experience since graduation from their primary degree. Applicants were required to submit a technical publication on a topic of their choice directly relevant to mechanical engineering. The work is written for the general mechanical engineering community and the 2014 applicants represented various branches of the Swiss Industry and Academia such as micro-fluidics, non-destructive testing, railway engineering and heat transfer for turbine applications. Each of the technical papers presented was reviewed by both technical experts in the specific field as well as engineers not familiar with the specific area. One of the key focuses of the technical paper is for the participants to be able to demonstrate and articulate their complex work to the general engineering audience. The finalists for the grand prize were invited to present their work at the apéro event held after the technical tour.

The top prize went to ETHz students Peter Reichart and Ivo Leibacher, whose research demonstrated a novel concept of micro droplet control using acoustic waves for lab-on-chip applications. Mr Reichart and Mr. Leibacher claimed the top prized of CHF1,000, one year’s ASME membership and subscription to an ASME journal of choice for their technical paper.

First runner up was Mr. Elyas Ghafoori for his excellent research work outlining a novel solution of pre-stressed carbon fibre reinforced polymer plates to strengthen bridge beams. This retrofit solution allows the lifetime of the bridge to be extended without the need for complete overhaul – a pertinent topic considering in Switzerland’s prominent railway infrastructure.

Mr. Santiago Illucia’s received the second runner prize for his experimental work evaluating the heat transfer coefficient for impingement cooling focused on turbomachinery applications. The technical work experimentally assessed the influence of the number of impingement holes on the heat transfer characteristics of narrow impingement channels.

This month’s Tech in Brief includes condensed versions of both Mr. Reichart and Mr. Leibachers winning paper and Mr. Ghafoori runner paper.


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TECH in BRIEF: Innovative system for fatigue strengthening of beams in a 120-year-old bridge using pre-stressed CFRP laminates

Elyas GHAFOORI Dipl. Mech. Eng. PhD candidate ETH Zürich – Masoud Motavalli, Empa, Dübendorf [email protected] Summary There are a large number of aging metallic bridges worldwide that remain operational and require to accommodate ever increasing traffic loadings. Many of these structures are subjected to cyclic loading and are nearing their design fatigue life. To combat this problem, municipalities often recommend that a retrofit option be considered to extend the remaining fatigue lives of deficient elements before a decision is made to replace the entire bridge. This is because the retrofitting costs are often much cheaper than the costs for demolishing and replacement of the entire bridge. The conventional method of repairing aging metallic bridges often involves bulky and heavy steel plates that are difficult to attach and are prone to fatigue and corrosion of their own.

This article presents an innovative retrofit system (patent number CH 706 630 B1 [1]) to pre-stress carbon fiber reinforced polymer (CFRP) plates. CFRP materials have high strength-to-weight ratio, high corrosion resistance and excellent fatigue performance. The efficiency of the system was demonstrated by fatigue strengthening of a 120-year-old metallic railway bridge in Switzerland. The system does not require any glue between the CFRP plates and the beams; therefore, surface preparation is not necessary, which reduces the time and cost of retrofitting. The proposed pre-stressed un-bonded reinforcement (PUR) system includes a pair of mechanical clamps that function based on friction. Each clamp can simultaneously hold and attach three CFRP plates to the beam. The PUR system uses CFRP laminates. The principle of the constant life diagram (CLD) was used to determine the magnitude of CFRP pre-stress level. The PUR strengthening system uses an applied pre-stress force to reduce the mean stress level (and stress ratio), and thereby to shift an existing fatigue-susceptible metallic detail from the 'at risk' finite life regime to the 'safe' infinite life regime. The applied CLD method is particularly valuable when the stress history of the detail is not known and it is difficult to assess the remaining fatigue life.

Strengthening Technique Assume an I-beam as shown in Fig. 1.a. First, the mechanical clamps are placed near two ends of the beam, and three parallel CFRP plates are placed and tightened inside the clamps, as shown in Fig. 1.b. The CFRP plates are initially un-stressed and nearly straight; however, because of the self-weight of the CFRP material, they have a small initial deflection. Each CFRP plate has dimensions of 50 mm width and 1.2 mm thickness. Each friction clamp consists of a lower plate, a middle plate and two upper plates. The middle and the lower plates consist of three hard plates, which provide a uniform stress distribution along the CFRP anchorage length. Each CFRP plate is anchored between the lower plate and the middle plate and is subjected to compressive force, which is applied by pre-tensioned bolts. The beam flange is also gripped between the middle plate and the upper plates and subjected to the compressive force of pre-tensioned bolts. A pre-stressing chair is used to increase the eccentricity between CFRP plates and steel beam, as shown in Fig. 1.c. The pre-stressing chair consists of a saddle that can move along two vertical threaded bars. The distance between the saddle and the beam can be manually changed by turning the threaded rods using a wrench. Thus, by turning the threaded rods, the saddle pushes the CFRP plates away from the beam, and the CFRP pre-stress is increased. A larger eccentricity between the CFRP plates and the beam corresponds to a larger CFRP pre-stress level. After the desired pre-stress level is achieved, two plates are placed between the CFRP plates and the beam (see Fig. 1.d). Each plate is positioned between the saddle and a shoe. The two shoes are connected by two steel bars and four nuts, as shown in Fig. 1.e, and then the pre-stressing chair is removed. Figure 1.e shows the final configuration of the strengthened beam. The system has two saddles: one clamp saddle and one column saddle. Both saddles have a smooth surface with low curvature (approximately 200 mm) to accommodate the change in longitudinal direction of the CFRP plates. Note that if the CFRP pre-stress must be changed, the pre-stressing chairs must be placed again, and the columns should be removed. Then, the previously mentioned procedure in Figs. 1.c-e must be performed again.


To install the mechanical clamps, additional holes or welding are not necessary. It is also possible to uninstall the system by following the reverse procedure in Fig. 1 (i.e., beginning from Fig. 1.e and ending at Fig. 1.a). Note that all elements of the trapezoidal PUR system including the mechanical clamps, pre-stressing chairs, and columns, are constructed out of steel.

Saddle

Column shoe

Column plate

Pre-stressing chair

Clamp saddle

Friction clamp

Threaded rods

Saddle

90˚

0.6

Lower plateMiddle plate

Upper plate

(a)

(b)

(c)

(d)

(e)

Hard plate

1.2

Steel barNut

Fig. 1. Different components of the PUR system [2].

Advantages of the PUR system The advantages of using the proposed trapezoidal PUR system are: 1) the CFRP plates must not be glued to the beams, 2) fast on-site installation because surface preparation is not necessary, 3) each clamp simultaneously holds and attaches multiple CFRP plates to a beam, 4) no traffic interruptions for bond curing, 5) easy to pre-stress the CFRP plates because hydraulic actuators are not necessary, 6) no damage to the existing metallic beam in the forms of creating holes, gluing, grinding, etc., 7) if the pre-stress level is reduced (because of relaxation or creep effects), it can be increased again, 8) the system can be easily uninstalled (if necessary) without residual damage to the beam, 9) pre-stressing can be conducted against the beam, and an external frame to pre-stress the CFRP plates is not required. Note that although the proposed trapezoidal PUR system in this article was originally developed to retrofit metallic beams, with slight changes in the mechanical clamps, the system can be used to strengthen concrete beams. The pre-stressing technique will be similar to the method described in this article, however the connection between the clamps and the concrete beams has to be modified.

CLD Fatigue Design Approach The CLD methodology is an approach that predicts the lifetime of materials under high cycles fatigue. The method uses the combined effect of alternating stress, mean stress and material properties to predict the damage due to cyclic loads. The results of the CLD analysis in this study show that strengthening parameters can be chosen such that the alternating and mean stresses cause only negligible fatigue damage, and therefore, the lifetime of the aging metallic detail is increased to infinity. The proposed CLD method is particularly valuable when the stress history of the metallic detail, due prior traffic loadings, is not known exactly. The developed analytical solutions based on the CLD approach can be used to calculate the CFRP properties (e.g., pre-stress level and laminate


dimensions) such that the metallic detail is shifted from a 'at risk' finite-life regime to a 'safe' infinite-life regime [3]. Figure 2 shows a CLD that defines the three main stress regions.

The middle region bounded by R=0 and R=±∞ is for tension-compression (T-C) stresses, the right region bounded by R=1 and R=0 is for tension-tension (T-T) stresses, and the left region bounded by R=±∞ and the horizontal axis is for compression-compression (C-C) stresses. The level of the fatigue failure probability has also been schematically illustrated by different markers. The green triangle marker shows the safe zone, in which no macrocracks form. The yellow square marker indicates the risky zone, where macrocracks may form with approximately a 50% probability. The red circular marker shows the unsafe region, where macrocracks will form with a probability of more than 50%. Laboratory test results have shown that by pre-stressed CFRP laminates, it is possible to shift the metallic detail from unsafe or risky ‘finite-life’ zones to ‘infinite-life’ safe zone.

Sy

Se

-Sy Sy Sut0

Safe Zone

Compression TensionMean stress,

Alternating stress,

T-T zone: 0<R<1t

s

R=1

R=-1C-C Zone: R>1

t

s

t

s

t

sT-C zone: R<0T-C zone: R<0

R=±∞R=0

Safe: No fatigue crack initiatesRisky: Fatigue crack may initiateUnsafe: Fatigue crack initiates

45°45°

Fig. 2. Definition of the safe, risky and unsafe zones. Each CLD can be partitioned into three stress regions of tension–

tension (T-T) when 0 < R < 1, tension–compression (T-C) when R <0 and compression–compression (C-C) when R > 1.

Strengthening of the Münchenstein Railway Bridge The Münchenstein Bridge was constructed in 1875 by G. Eiffel, who later built the Eiffel Tower in Paris. The bridge is located near Basel City over the river Birs in Switzerland.

Fig. 3. Münchenstein Railway Bridge, Basel, Switzerland [4].

-35

-25

-15

-5

5

15

25

35

0 250 500 750 1000 1250 1500 1750 2000

Mea

sure

men

ts

Time (S)

Stress in Metal (Mpa)CFRP Pre-stress Level (%)

Fig. 4. As the eccentricity between the CFRP plates and beam increased, the CFRP pre-stress and the

compressive stress at the rivet holes increased too [4].


In 1891, after 15 years of service, the bridge suddenly collapsed and took the lives of 73 passengers that is historically the worst railway accident ever in Switzerland. A single-span riveted bridge was then constructed in 1892, as a replacement for the collapsed one. The bridge, as shown in Fig. 3, consists of 10 frames and was constructed approximately 5 m above the water level. The total length of the bridge is approximately 45.2 m and it is subjected daily to both passenger and freight trains. Finite element (FE) analysis has shown that the cross-beams of the bridge are the most fatigue prone details [4]. Thus, in order to demonstrate the efficiency of the PUR system for old metallic bridge, the system was used for strengthening of two bridge cross-girders. During the on-site strengthening, the CFRP pre-stress level and the magnitude of the compressive stress at the rivet holes increase, as shown in Fig. 4. Figure 5 shows a view of one bridge cross-beam after strengthening. More details on measurements before and after strengthening as well as FE modelling of the bridge can be found in [4-5]. To ensure no slip occurs between the CFRP plates and the clamps and also between the friction clamps and the metallic beams, one strain gauge was glued on each CFRP plate, as shown in Fig. 5. All of the strain gauges as well as the humidity and temperature sensors were connected to the wireless sensor network (WSN) node. The housing of the WSN node and those of the temperature and humidity sensors, shown in Fig. 6, were equipped with four magnetic footings, which allows for a simple and fast mounting. The WSN system reads the strains, temperature and relative humidity at intervals of 5 min and sends the data to a base station, which then sends the data online. The results of long-term measurements have proved the superior performance of the strengthening system in the coldest and warmest days of a year.

3 CFRP plates

Adjustable column

Saddle

3 bonded strain gauges

Fig. 5. Cross-girders retrofitted by the PUR system [4].

Humidity and temperature sensors

Wireless sensor node

Fig. 6. Use of WSN system for long-term monitoring [4].

References [1] Ghafoori, E. and M. Motavalli, Verfahren zum Vorspannen eines Stahlbauwerkes sowie damit vorgespanntes

Stahbauwerk. Swiss Patent, CH 706 630 B1, 14th May 2013.

[2] Ghafoori E., Motavalli M. Innovative CFRP Pre-stressing System for Strengthening of Metallic Structures. ASCE Journal of Composites for Construction, 2015. accepted. doi: 10.1061/(ASCE)CC.1943-5614.0000559.

[3] Ghafoori E., Motavalli M., Nussbaumer A., Herwig A., Prinz G., Fontana M. Determination of minimum CFRP pre-stress levels for fatigue crack prevention in retrofitted metallic beams. Engineering Structures, 2015. 84: p. 29–41.

[4] Ghafoori E., Motavalli M., Nussbaumer A., Herwig A., Prinz G.S., Fontana M. Design criterion for fatigue strengthening of riveted beams in a 120-year-old railway metallic bridge using pre-stressed CFRP plates. Composites Part B, 2015. 68: p. 1-13.

[5] Ghafoori E., Prinz G.S., Mayor E., Nussbaumer A., Motavalli M., Herwig A., Fontana M. Finite element analysis for fatigue damage reduction in metallic riveted bridges using pre-stressed CFRP plates. Polymers, 2014. 6(4): p. 1096-1118 (open-access).


Call for 2015 ASME Swiss Section Young Engineer Award

The Swiss Section of the American Society of Mechanical Engineers (ASME Swiss Section) serves the Swiss engineering community by advancing, disseminating and applying engineering knowledge for improving the quality of life; and communicating the excitement of engineering to its members. The aim of the ASME Swiss Section Young Engineer Award is to recognize and promote excellence in engineering across Switzerland and reward young engineers on the merit of their work.

The Award is open to young engineers who have at least a Bachelor degree in Mechanical Engineering and have no more than two years’ engineering experience since the date of Bachelor or Master graduation, provided the Masters was obtained within two years from the Bachelor graduation.

Applicants are required to submit a technical publication (3 pages max. of about 1500 words including 2-3 diagrams or pictures) on a topic of their choice directly relevant to mechanical engineering. The work must be written for the general mechanical engineering community, which may be understood by engineers and researchers representing various branches of the Swiss Industry and Academia. The template of the paper is available from the ASME Swiss Section website space on ASME.org

Evaluation of the Award will be conducted by ASME Swiss Section members with technical expertise in the field and a shortlist of finalists will be selected based on an established grading criteria.

The winner will be finalized by the ASME Swiss Section committee and will be presented with their award at an ASME Swiss Section function held in June 2015. All shortlisted entrants will have their article published in the October edition of the ASME Swiss Section newsletter.

The prizes will be distributed as follows:

• 1st CHF1,000 Certificate and one year’s ASME membership and a one-year subscription to an ASME journal of choice.

• 2nd Certificate and one year’s ASME membership

• 3rd Certificate

Application

To apply for the award, interested persons shall, before the deadline of April 15th 2015, send by email a .pdf file containing the following:

1. a copy of the technical paper

2. a brief application letter with picture explaining the nature of their work

3. a copy of their graduation certificate or proof of graduation from university.

4. a short biography of the author,

Submissions to Dr. Daniel Kearney: [email protected]

Key dates

• Submission open February 1st 2015 • Closing date April 15th 2015 • Award announcement – May newsletter 2015 • Presentation of award – June 2015


TECH in BRIEF: Acoustic Handling of Droplets on Microchips

Ivo LEIBACHER and Peter REICHERT (MSc. Mech. Eng., PhD candidates), Prof. Jürg DUAL

Institute of Mechanical Systems (IMES), ETH Zurich

Licensing opportunity: contact [email protected] and [email protected]

Introduction Miniaturization is a major technological trend across many engineering disciplines. Its benefits were impressively demonstrated in electrical engineering, where room-filling computers shrunk to the size of smartphones over the last decades. Similarly, current research aims at miniaturization also in mechanical engineering. The miniaturization of fluid handling methods has evolved into the field of “microfluidics” over the last decade, mainly to shrink the fluid handling of biological-chemical laboratories. The name and vision of this field is called “lab on a chip”, where biotechnological sample processing will be performed on a cheap and portable microchip. A main goal of this field is the handling of discrete fluid droplets, i.e. reagents, on microfluidic chips [1]. For these droplets, a set of unit operations (moving, sorting, merging) is necessary to handle them. For such unit operations, mechanical engineering is required to develop fluid handling methods. An ideal method would be a contact-free external force field which acts selectively on certain fluid droplets. Acoustic methods fulfill these criteria. Therefore, here we present a novel method for droplet handling with bulk acoustic waves (BAW) [2], whereas earlier droplet handling methods were based on surface acoustic waves (SAW). Bulk wave methods have formerly been known for particle handling [3], yet here we demonstrate their ability for novel droplet handlings.

Setup and operating principle The proposed fluid handling method operates on a silicon/glass chip as photographed in Figure 1a with a centimeter ruler. This device was fabricated with similar fabrication tools as they are used for the fabrication of electronic microchips, namely photolithography, etching and bonding steps on silicon wafer substrates. Such devices are sometimes also referred to as “micro-electro-mechanical systems” (MEMS). The huge technological advantage of this microfabrication technique is called “batch fabrication”: it takes the same amount of time to fabricate one wafer, regardless whether 1, 10 or 1’000 devices are structured on this wafer at the same time. Both the droplet generation and their subsequent manipulation by acoustic forces can be conducted on this chip. Water-in-oil droplets (silicone oil) with diameters ranging from 50 μm to 250 μm were generated with T-junctions as illustrated in Figure 1b. Hereby, the water droplets are the substrate to be handled, which may be seen as a “vessel” or “carrier” for an aqueous, biological sample or any other fluid of e.g. pharmaceutical or diagnostic interest. The water droplets are like a microfluidic equivalent to the conventional test tubes in laboratories. The oil is an immiscible carrier layer, which can carry the droplets within the microfluidic channels on the chip by its flow, which is generated by syringe pumps.

Fig. 1: a) Photograph of a microfabricated chip with fluidic channels on the front side. b) Sketch of the microchip and its electrical and fluidic interconnections.


The goal of this article is to demonstrate acoustic forces on droplets within the shown main channel of 1 mm width and 200 µm height. Therefore, a piezoelectric transducer for the excitation of ultrasonic waves was glued on the back side of the device. Similar to a loudspeaker, it transforms a sinusoidal electrical signal into mechanical vibration. The transducer was excited by an electric function generator and amplifier at a channel resonance frequency with about 30-50 Volt amplitude. The transducer requires only low power. Therefore it is suitable to be integrated on portable devices, as desired in the lab-on-a-chip concept. The experiments were monitored by a high speed camera on a microscope. This setup can exert an acoustic field within the main channel, which then induces so-called radiation forces on the water droplets. For small spherical droplets of radius r, this acoustic force F can be calculated by a simple equation . For a droplet in a 1D standing wave field, the analytic calculation yields

F=4πΦkr3Eac sin(2ky) with the material-dependent acoustic contrast factor Φ, the acoustic energy density Eac, the wave number k and the spatial coordinate y. This equation expresses that droplets will be attracted to the pressure nodes of the acoustic waves within the microfluidic channel.

Experimental Results Droplet fusion: For acoustic droplet fusion experiments on this chip, two water-in-oil droplets

were generated in a temporally synchronized manner. Droplet fusion is a key unit operation to enable the mixing of two fluids. As illustrated earlier in Figure 1b and know shown experimentally in Figure 2a, droplets were generated at microfluidic T-junctions. Further downwards in the channel, the one-to-one fusion of droplets in a continuous flow is induced by focusing them on the channel centerline with acoustic waves (illustrated with the red wave pattern). A resonance mode with a standing pressure wave of λ/2 across the channel width was found by tuning the transducer frequency to 464 kHz. With the speed of sound coil≈1000 m/s of silicone oil, this frequency value approximately matches the expectation of the first resonance frequency f =coil/λ= 1000 m/s / 2 mm= 500 kHz, where a λ/2 mode will be generated between the two channel walls. In Figure 3, the fusion of two droplets was analyzed in more detail to study their mixing. In this experiment, one of the two droplets was marked with a fluorescent dye. As the time series of the high-speed fluorescence microscopy photographs show, a well-mixed droplet resulted in less than one second. Compared to other droplet fusion methods, acoustic methods show several benefits: they allow active on/off control (unlike passive hydrodynamic fusion), they are simple to fabricate (simpler than electrodes for fusion by electric fields), they can easily be integrated on chip-level (unlike laser-assisted methods), and they work for many combinations of dispersed and continuous phase liquid as long as they are acoustically contrasting (no

Fig. 2: a) Generation and subsequent fusion of light and dark droplets (~200 µm) by acoustic forces. b) Droplet sorting between the two outlet channels: acoustic forces can deflect the droplet to outlet 1 or 2. c) A droplet in dyed oil is deflected into a different oil phase by an acoustic resonance mode with one wavelength λ across the channel.


dependency on magnetic/dielectric properties). As a disadvantage of this acoustic method, it is less suited for fusion of strongly surfactant-stabilized droplets. The shown active droplet fusion method allows fluid sample mixing operations on the micro scale. It allows e.g. reaction initiation, droplet dilution and cell-in-droplet handling, which are of interest for biochemical applications of droplet microfluidics.

Fig. 3: Droplet fusion in a time series, stitched together from 10 frames of high-speed fluorescent imaging. A thorough mixing of the fluorescein-dyed droplet with the undyed water droplet is observed. Droplet sorting: Acoustic forces are also suitable for droplet sorting tasks . As shown in Figure 2b, by turning the ultrasound transducer on/off, droplet paths can actively be switched between upper/lower outlet by the same method as for the droplet fusion of the last section. This valve-like operation might allow controlled droplet sorting, when a further upstream sensor is installed to characterize the inflowing droplets. Depending on the measured droplet characteristics, they can then be guided through the upper or lower outlet and collected further downstream. Sorting of droplets is an important task for many biotechnological laboratory workflows, e.g. to extract and collect certain droplets of interest for their further analysis. Droplet medium exchange: As a third droplet handling unit operation, it is often desired to transfer droplets to another continuous phase, in other words to move them from the oil to another suspending fluid. In Figure 2c, droplets experience an exchange of their initially dyed suspending oil (center) to the undyed oil in the lower third of the channel. This is feasible because the acoustic radiation force acts selectively on the dispersed water since it is acoustically contrasting to the continuous phase, namely the oil. This method enables e.g. to stabilize droplets by moving them from a surfactant-free oil to a surfactant-blended oil.

Conclusion The presented acoustic droplet handling enables a range of fluid handling operations for droplet microfluidics. This is feasible because the acoustic radiation force acts selectively on dispersed water droplets due to their acoustically contrasting fluid. The method is ideally suited for active droplet handling tasks in portable, low-power lab-on-a-chip systems. Compared to the earlier surface acoustic wave (SAW) methods , our proposed bulk acoustic wave (BAW) method has a more flexible, versatile and simple setup, and it allows the handling of larger droplets up to ~500 μm size. In view of applications, the shown contactless fluid sample handling by ultrasonic waves offers significant benefits for fluid handling e.g. in laboratory diagnostics/analytics and biochemical research.

References: [1] Casadevall i Solvas, X. and de Mello, A., 2011, “Droplet microfluidics: recent developments and future

applications,” Chemical communications, 47(7), pp. 1936–1942. [2] Leibacher, I., Reichert, P. and Dual, J., 2015, „Acoustophoretic droplet handling in bulk acoustic wave devices,“

patent application PCT/EP2015/050388. [3] Bruus, H., Dual, J., Hawkes, J., Hill, M., Laurell, T., Nilsson, J., Radel, S., Sadhal, S. and Wiklund, M., 2011,

“Forthcoming Lab on a Chip tutorial series on acoustofluidics: Acoustofluidics - exploiting ultrasonic standing wave forces and acoustic streaming in microfluidic systems for cell and particle manipulation,” Lab on a Chip, 11(21), pp. 3579-3580.


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Guided Tour Zürich Railway Main Station - A Look behind the Scenes Said HAVAKECHIAN, [email protected] Transport is one of the greatest areas of interest for the ASME and is of utmost importance to the Swiss economy. Recently, the Zurich Main Station (ZHB) has been undergoing a major transformation. Therefore, the committee members of the Swiss section have decided to visit the Zurich Main Station for the 2014 Technical Tour. The visit to Zürich Main Station was guided by Mr. Guido von Arx and comprised of an introduction given by Mr. von Arx followed by a projection of two short films showing the various phases of the Cross-City Link project and describing the technical challenges of the projects as well as the very unique engineering solutions introduced to tackle them. The second half of the visit comprised of a tour of various sites in the Zürich Main Station normally hidden to ordinary passengers. A brief historical review and the highlights of this visit are given below. The ZHB was inaugurated on 7th of August 1847 with the first train operated from Zürich main station in the direction of Baden with 140 guests on board. The inaugural trip to Baden took 45 minutes. Today, Zürich is known as Switzerland’s business power house and the ZHB is considered to be the throbbing heart of the city. Due to its strategic location as the station where Switzerland’s major rail connections intersect and customer’s growing needs for mobility, it was realised that the ZHB would no longer meet passenger demand without appropriate expansion. In addition, any disturbance in rail traffic flow in the Zürich Main Station triggers a knock-on effect over the regional and national rail network throughout Switzerland. It is noteworthy that during the last few years the number of passengers using the ZHB has doubled. Over 420,000 passengers and 2915 trains pass through the station daily, making the ZHB one of the world’s busiest train stations. In order to alleviate the threat of a bottle neck at the ZHB for the entire Swiss rail network, the people of Zürich passed a referendum in 2001 approving the extension of the station and the Cross City Link project. The initial projected cost for the project was CHF600 million.

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Fig.1: Photos Related the Visit of Zürich Main Station a) Presentation of Mr. von Arx, Exhibition room of Zürich main station b) Surrounding of Zürich Main Station, a view from the roof of the Zürich Main Station


The Cross-City-Link project is claimed to be one of the largest urban construction projects ever realized in Switzerland, with the 9.6 km long double track rail, the so called Durchmesserlinie, connecting Altstetten, ZHB and Oerlikon forming the very central part of the project. The Durchmesserlinie crosses city quarter Altstetten and Zürich city center, leading to the city quarter of Oerlikon through a long, arc-shaped path. There are a number of significant highlights specific to these connections as described in the following:

- Erection of the underground rail station at Löwenstrasse located 16 meters below the Sihl River and under the current platforms 4 to 9.

- Erection of the 5km long Weinbergtunnel connecting the ZHB – Bahhof Löwenstrasse to the city quarter of Oerlikon.

- Letzigrabenbrücke (approx. 1160 meter long) and Kohlendreieckebrücke (approx. 400 meter long) sky bridges connecting Altsetten to the Löwenstrasse Bahnhof.

- Expansion of Oerlikon Bahnhof to accommodate two additional tracks.

The remaining construction works of the ZHB extension project, the Durchmesserlinie, is anticipated to be completed by the end of 2015. However, new offers for both regional S-Trains as well as the long distance network have already been rendered possible midway through 2014. The route that benefits most from the resulting improved connections and shorter travel duration is the connection: Geneva – Bern – Zürich Airport – St. Gallen. Following the presentation of the above mentioned two films and the question and answer round, Mr. von Arx offered a guided excursion throughout the various locations (new retail space, ventilation and heating facilities, etc.) of the ZHB. The visit was ended at around 20:00 when Dr. Armin Zemp thanked Mr. von Arx for the exciting guided tour and presented him with a specially prepared gift.

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Fig.2: Photos Related the Visit of Zürich Main Station a) Zürich Exhibition room b) Attendees of the Swiss Section members in the Technical Tour c) Map of works related to the Cross City Link

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