APPLICATION OF FRACTURE MECHANICS TO MATERIALS AND STRUCTURES

Application of Fracture Mechanics to Materials and Structures

Proceedings of the International Conference on Application of Fracture Mechanics to Materials and Structures, held at the Hotel Kolpinghaus, Freiburg, FoRoGo, June 20-24, 1983

edited by

G. c. SIH Institute of Fracture and Solid Mechanics, Lehigh University, Bethlehem, Pennsylvania, U.S.A.

E. SOMMER Fraunhofer-Institut fur Werkstoffmechanik, Freiburg, F. R. G.

W.DAHL Institut fur Eisenhuttenkunde, Rheinisch- Westfiilische Technische Hochschule, Aachen, F.R.G.

1984 MARTINUS NIJHOFF PUBLISHERS ..... a member of the KLUWER ACADEMIC PUBLISHERS GROUP lIB THE HAGUE / BOSTON / LANCASTER .~

Distributors

for the United States and Canada: Kluwer Boston, Inc., 190 Old Derby Street, Hingham, MA 02043, USA for 0/1 other countries: Kluwer Academic Publishers Group, Distribution Center, P.O.Box 322, 3300 AH Dordrecht, The Netherlands

Library of Congress Cataloging in Publication Data

International Conference on Application of Fracture Mechanics (1983 : Freiburg im Breisgau, Germany) Application of fracture mechanics to materials ar.d

structures.

1. Fracture mechanics--Congresses. I. Sih, G. C. (George C.) II. Sc~er, E. (Erwin) III. Dahl, Winfried. IV. Title. TA4Q9.143 1983 620.1'126 84-4214

ISBN-13: 978-94-009-6148-7 001: 10.1007/978-94-009-6146-3

Copyright

e-ISBN-13: 978-94-009-6146-3

© 1984 by Martinus Nijhoff Publishers, The Hague. Softcover reprint of the hardcover 1 st edition 1984 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publishers, Martinus Nijhoff Publishers, P.O. Box 566, 2501 CN The Hague, The Netherlands.

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CONTENTS

PREFACE by G. C. Sih, E. Sommer and W. Dahl xi

WELCOME ADDRESS AT IWM by H. Keller xv

HISTORICAL REMARKS AND ACTIVITIES AT IWM by G. W. Becker xvii

OBJECTIVES AND CAPABILITIES OF FRAUNHOFER-INSTITUT fur WERKSTOFFMECHANIK xix

CONFERENCE PHOTOGRAPHS xxi

PLENARY LECTURES

Microstructural aspects of the resistance to crack extension of engineering alloys

by J. F. Knott 3 Numerical analysis in fracture mechanics

by A. S. Kobayashi 27 Macro- and micromechanics of fatigue crack initiation and propagation under constant and variable amplitude loading

by H. Nowack 57 The strength calculation on the basis of nonlinear fracture mechanics

by N. A. Makhutov 103 Time effects and their influences on test procedures for measuring dynamic material strength values

by J. F. Kalthoff 107 Nonlinear and dynamic fracture of cracked structures under electro-magnetic force

by G. Yagawa and S. Yoshimura 137 Residual stresses

by E. Macherauch 157 Effect of environments on fracture of materials and structures

by M. O. Speidel 193 Fracture mechanics in structure design

by A. Pellissier Tanon 213

SECTION I CRACK INITIATION AND GROWTH Continuum aspects of crack initiation

by E. E. Gdoutos 237 Effect of loading history on crack growth

by G. C. Sih 251

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Conditions for hydrostatic rupture in the vicinity of cracks or notches by V. Schmidt 263

The step before the application of fracture mechanics to fatigue by K. Heckel and G. Schweiger 273

Size effects in solid mechanics due to topology transformation during crack growth

. by A. Carpinteri 281 Ductile fracture propagation studies by a kinematic approach

by G. Buzziche11i, G. Demofonti, E. Monti, S. Venzi and A. DeVito 295

SECTION II MIXED MODE FRACTURE AND MULTIAXIAL STRESS STATE Examination of brittle fracture criteria for overlapping Mode I and Mode II loading applied to cracks

by H. A. Richard 309 Safe-life analysis of structures subjected to general in-plane loadings

by N. N. Au 317 Mode II fracture toughness testing with application to PMMA

by L. Banks-Sills and M. Arcan 337 The influence of mu1tiaxial stress states on characteristic parameters for cleavage fracture in the elastic-plastic range

by D. Aurich, W. Brocks, R. Jordan, J. Olschewski, H. Veith and J. Ziebs 345

SECTION III MATERIAL CHARACTERIZATION AND TESTING Comparison of J-integral estimating methods and techniques

by I. Havas and E. Czoboly 359 The strain hardening of structural steels with different yield strengths and its influence on the materials properties during plastic deformation

by W. Hesse and W. Dahl 369 The application of a direct approach in the study of the initiation mechanisms of cleavage fracture in a 26 Cr - 1 Mo ferritic stainless steel

by M. K. Veistinen and V. K. Lindroos 377 On the influence of specimen orientation on the ductile fracture behaviour of the steel FeE 350

by D. Dormagen and W. Dahl 393 Failure assessment diagrams and J estimates: validation for an austenitic steel

by K. N. Akhurst and 1. Milne 401 Perspective on J-T plots

by H. A. Ernst, D. E. McCabe and J. D. Landes 415 Recategorisation of embedded defects as a single embedded or surface defect

by Y. Phang and C. Ruiz 429

SECTION IV DYNAMIC FRACTURE Towards the development of a dynamic fracture initiation test

by R. S. J. Corran, F. G. Benitez, J. Harding, C. Ruiz and T. Nojima 443 Dynamic analysis of impact test specimens

by T. Peuser 455 Failure behaviour of an aluminium plate under impact loading

by G. Bretz, J. Kinscher, A. Poth, F. Scharpf, L. W. Meyer, H. Rothenhaus1er and H. Senf 467

An application of fracture mechanics to presplitting blasting by X. F. Wang, Z. Q. Wang and T. Y. Fan 485

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Stress intensity factor distributions by optical methods by C. W. Smith 709

Convergence - aspects of K-determination procedures by H. P. Rossmanith 725

Detection of defects in an austenitic strain-hardened steel using acoustic emission analysis

by H. Bretfeld and G. Stein 739

SECTION VIII FATIGUE Fatigue life assessment in welded rectangular hollow sections using fracture mechanics

by J. A. Ferreira, C. M. Branco and J. C. Radon 749 A local inelastic strain-stress analysis of fatigue crack growth

by G. Glinka, C. Robin and G. Pluvinage 763 A contribution to the evaluation of sequence effects under variable amplitude loading by applying defined predeformations

by K. Schulte, R. Marissen, K.-H. Trautmann and H. Nowack 777 Variable amplitude fatigue damage analyses: postulate and critical experiments

by B. N. Leis and T. P. Forte 787 Spectrum loading effects on crack growth in major components of com-mercial transport aircraft

by C. K. Gunther and U. G. Goranson 811 Ferrite selection ratio of fatigue crack path in dual phase steel

by T. Ishihara and Y. Kowata 829 The behaviour of fatigue cracks in shot-peened components

by R. B. Scarlin and A. StUcheli 837 Stress intensity factors for surface cracks under thermal fatigue conditions

by H. Stamm, C. Mattheck and D. Munz 855 An elastic-plastic fracture mechanics approach to notch sensitivity in low-cycle fatigue

by D. Rhodes 867

SECTION IX ENVIRONMENTAL EFFECTS Moisture and temperature effects on the transient stresses around crack-like defects

by S. C. Chou, G. C. Sih and M. T. Shih 877 Effects of residual stresses on the fatigue of aluminum alloy 7017 in moist air

by R. Hermann and C. N. Reid 889 The improvement of fatigue strength of steel by thermomechanical surface treatment

by R. PrUmmer and R. Zeller 899 Stress corrosion cracking behavior in gaseous oxygen of a U-7.5 Nb-2.5 Zr alloy

by D. Lepoutre, A. M. Nomine and D. Miannay 907 Effect of corrosive environment on the fatigue life of cyclic loaded specimen and structures

by W. J. Oberparleiter 919 Micromechanism of environmental fatigue crack growth in A533B steel

by G. Airoldi, C. A. Be and T. Bruno 931 The effect of temperature, orientation and constraint on the toughness of A533B class I steel

by S. J. Garwood 939

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SECTION X STRUCTURAL AND COMPONENT DESIGN Surface cracks in welds of 7020 T6 aluminium alloy

by Z. Milosevic, C. Bathias and A. Pellissier Tanon 953 The comparative analysis of crack propagation in the gear tooth

by J. Flasker and A. Jezernik 971 Fracture resistance of fatigue cracked wp.lded details

by H. Hausammann 983 Leak areas in cracked pipes

by C. WUthrich 993 Influence of cracks on structural design criteria

by J. Lereim 999 Creep crack growth on actual and simulated heat affected zones of CrMoV steampipe welds

by M. Bain and D. D'Angelo 1013 Effects of residual stress on fatigue crack propagation properties of rail heads

by S. Nishida, C. Urashima and H. Masumoto 1025

SECTION XI NON-METALLIC MATERIALS Role of cracks during the annealing of residually stressed brittle structural ceramics

by D. P. H. Hasselman, Y. Tree and A. Venkateswaran 1043 Crack resistance curves of an alumina material at elevated temperatures

by H. Wieninger, A. Bornhauser and R. F. Pabst 1059 Fracture of ice under compression with constant speed

by N. C. Huang 1067 On penny-shaped crack at an ice-substrate interface

by L. H. N. Lee 1085 A simple method for the experimental K-value evaluation of the cracked body using brittle fracture characteristic of epoxY resin

by S. Harada, T. Endo, Y. Harada and Y. Murakami 1095

LIST OF PARTICIPANTS 1109

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PREFACE

An International Conference on the Application of Fracture Mechanics to Ma­terials and Structures was held at the Hotel Kolpinghaus in Freiburg, West Ger­many, June 20-24, 1983. It was attended by more than 250 participants from different countries which include Austria, Canada, Czechoslovakia, Democratic Republic of Germany, Denmark, Federal Republic of Germany, Finland, France, Greece, Hungary, Israel, Italy, Japan, Netherlands, Norway, People's Republic of China, Portugal, Sweden, Switzerland, United Kingdom, United States of America, USSR and Yugoslavia.

Conference Co-Chairmen were Professor G. C. Sih, Lehigh University, Bethle­hem, Pennsylvania, U.S.A., Dr. E. Sommer, Fraunhofer-Institut fur Werkstoff­mechanik, Freiburg, FRG and Professor W. Dahl, Rheinisch-Westfalische Technische Hochschule, Aachen, FRG.

Dr. Wenrich, as the representative of the Land Baden-WUrttemberg, delivered the opening address with the remarks that International Conferences can serve the means to further enhance the technology development of a country. He empha­sized that the Federal Republic of Germany is presently in need of strengthening the engineering manpower in order to keep her in a competitive position. The Conference was officially cast off with the leading plenary lectures that under­lined the theme of the technical lectures for the first day. This pattern was observed for the five-day meeting. The interplay between material and design re­quirements was the theme and emphasized in many of the technical presentations that amounted to approximately ninety (90) papers. A panel discussion was held to further clarify the objectives of fracture mechanics as a discipline and tool that can be applied to guard structural and machine components against premature failure. This is accomplished by focusing attention on the initiation of small flaws in the material until they grow into sizable cracks that can be detected by nondestructive testing. The conditions under which these cracks become unstable must be supplied by the researchers and practitioners who are knowledgeable in performing failure analyses. To this end, numerical and experimental techniques are essential so that useful laboratory data on fracture can reliably simulate the service conditions. Emphasized were the need for developing rational pro­cedures to guide the design of modern structures ensuing safety and reliability requirements.

A highlight of the Conference was the visit to the Fraunhofer-Institut fur Werkstoffmechanik (IWM) which is situated in the industrial section of Freiburg. A brief write-up on the objectives and capabilities of the Institut can be found in this Proceedings. Dr. H. Keller, President of the Fraunhofer-Gesellschaft, addressed the visitors and gave an account of the organization. He praised IWM being an active research group that plays an important role in the evaluation of material behavior in engineering applications. The history of IWM was also viv­idly presented by Professor Dr. G. W. Becker, President of the Bundesanstalt fUr

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Materialprufung. Many of the past and current activities involving individuals from IWM and Lehigh University provided the impetus for organizing this Confer­ence. The modern facilities and highly-qualified personnel at IWM were most im­pressive to the visitors.

The reception by the Lord Mayor of Freiburg, Dr. R. Bohme, at the Historisches Kaufhaus was most delightful. It was his marvelous and dynamic personality that charmed the audience with laughter and many pleasant hours. A superb view of Freiburg was unfolded at the Schlo8bergrestaurant Dattler which was the site of the Conference Banquet. It overlooks the city from the top of the mountain. These social events together with the detailed arrangements of the Conference could not have been made possible without the many hours of laboring from three individuals who should be highly acknowledged. They are the members of the Local Organizing Committee: S. Lecointre, Dr. T. Hollstein and Dr. W. Schmitt. Mrs. Barbara Sommer organized the ladies program that was well attended everyday. She provided not only the leadership at many of the social events but also per­formed those unnoticed tasks behind-the-scene.

The Co-Chairmen of this Conference are particularly grateful to those or­ganizations that have provided financial support. They include:

Deutsche Forschungsgemeinschaft DFG (German Research Foundation), Bonn

Deutscher Akademischer Austauschdienst DAAD (German Academic Exchange Service), Bonn

European Research Office, United States Army, London

Aesculap-Werke, Tuttlingen

Carl Schenck AG, Darmstadt

Dr. Otto Rohm Gedachtnisstiftung, Darmstadt

Hewlett Packard GmbH, Frankfurt

Hottinger Baldwin Me8technik, Darmstadt

Instron International Ltd., Karlstein

Kraftwerk Union AG, Erlangen

MFL PrUf-und Me8systeme GmbH, Schifferstadt

MTS-Systems GmbH, Berlin

Niefert GmbH, Rodermark

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Finally, the publication of this volume involved many hours of editorial as well as secretarial work. Special thanks are due to Mrs. Barbara DeLazaro and Mrs. Constance Weaver who were patient enough to retype the manuscripts.

Freiburg, FRG June, 1983

G. C. Sih E. Sommer W. Dahl Conference Co-Chairmen

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WELCOME ADDRESS AT IWM

Let me first offer a hearty welcome to all of you at the inauguration of the new facilities of the Fraunhofer-Institute for Material Mechanics. My special greetings go first of all to our foreign guests. A lovely welcome to the speakers at this event: The Lord Mayor of Freiburg, Dr. Bohem. He has al­ways been in his political career a member of our parliament, as parliamentary Secretary of State and in his new position as Lord Mayor of this beautifully lo­cated town of Freiburg, a great supporter of science, specially of applied re­search. I welcome as well the representatives of the federal government, Dr. Rembser, and of the Land of Baden-WUrttemberg, Dr. Weidenbach. Last, but not least, I greet the personnel, its staff and the head of the institute, Dr. Sommer.

Sommer is translated summer and today it is summertime in the double meaning of the word. Summertime, because of the season and for the institute. Because after a long time of working under rather rough research conditions, they finally have got these new facilities, which are certainly an important step forward to conditions on which applied research can flourish. And this is an obligation too.

As president, I bring the kindest congratulations of our society and all of its members to the collaborators of the institute and its head. I express my sincerest thanks for the fine research work being carried out on the unfavour­able conditions.

We are a research organization mainly eating the hard bread of contract re­search. Despite of that, or in favour of that, we had the aim to reach the fol­lowing situation: As I love the number 3,

we were shooting for three executives at the board; for 30 Fraunhofer-Institutes; for a research volume not less than 300 Mio German Marks; and a personnel staff not less than 3000 in our organization.

And we have been successful due to the many efforts of our collaborators. The main fields of our research work have been focused to the following 6 items:

1. micro electronics and sensor technology

2. information technology and production automation

3. production technology and behaviour of materials and components

4. process engineering, energy technology and construction engineering

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5. environmental research and technology

6. technical economic studies, special technical information.

To focus our research to that extent we had to close during the last 7 years 5 institutes, to change the research topics in 3 institutes and to found 8 new ones.

Let me go back from these general remarks to a more specific one, referring again to the Fraunhofer-Institute of Material Mechanics: As president, I have to be from time to time a little bit schizophrenic. I have to advise some in­stitutes to do more for basic applied research. To others, like this institute here at Freiburg, would you please look for some more application! And the ques­tion was: can they aim a yielded fracture at some useful production technologies. And their answer was: of course, yes. And they did very well, for instance in the production technology and manufacturing of bifocal spectacle glasses.

Therefore, each Fraunhofer-Institute acts like a Janus-head. Looking with one side for future research and looking with the other side to the transfer of obtained results. Thus I am looking to the future of this institute as one act­ing both ways. And I wish them every success.

We are already in the mid of your international conference. I hope it shall be a successful and an amusing one. I thank you for your audience.

Freiburg, Germany June 22, 1983

H. Keller President Fraunhofer-Gesellschaft

HISTORICAL REMARKS AND ACTIVITIES AT IWM

It is indeed a great honour and a pleasure for me to give an introduction on the work of the Fraunhofer-Institute for Materials and Mechanics (IWM) on behalf of the Board of Trustees, the "Kuratorium", of this institute. Since

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Dr. Sommer later will give a survey about the various activities, I would like to make some remarks on the history of the institute, on the role which it plays in the fracture research in Germany, and on one example for applicability of the institute's work in practice.

At first to the -very short- history of the IWM: The institute was founded on January 1st, 1971. The first director was Professor Dr. Frank Kerkhof, whom we may welcome here in the audience. Before this time, the institute was a sec­tion of the Ernst-Mach-Institute which was engaged in the application of optical matters and high-speed photography. The former chief of the Ernst-Mach-Institute was Professor Hubert Schardin. The section head of the later IWM was Professor Kerkhof, who worked in brittle fracture, fractography, strength of glasses, fast fracture and terminal velocities of glasses.

Besides these fields, the scientific background of the institute is based on another important root: the fracture mechanics. The first contact between Pro­fessor George R. Irwin and Professor Kerkhof took place at the "DVM-Tag" (the annual meeting of the German Association for Materials Testing) in 1961 at Wurz­burg/Germany, where Irwin presented a lecture on fracture mechanics. In 1965, Professor Irwin spent three months at the Ernst-Mach-Institute working very ef­fectively in his own research field on the topic of moisture assisted crack growth in glasses. In addition, there were at that time very stimulating dis­cussions with him.

In 1967 and 1968, Dr. Erwin Sommer was a post doctoral fellow at Lehigh Uni­versity, Bethlehem, Pa., USA. Afterwards, frequent visits of professors of this university followed in Freiburg: George Sih, Paul Paris, Fazi1 Erdogan as well as George Irwin. .

At the end of November 1977, Frank Kerkhof retired and Erwin Sommer became the new director of IWM. Finally, in February of this year, the IWM moved into this new building at WohlerstraSe 11. So far, this is the end of the history of IWM.

What could be said to the work of IWM in fracture research? As a matter of fact: the institute became one of the main promoters of fracture research and application of fracture mechanics in Germany. The first short course in fracture mechanics was held in 1969 by the institute. Furthermore, the German working group "Fracture Processes" was founded under the roof of DVM, and Professor Kerkhof became the first head of this group, followed by Dr. Sommer. Up to 150

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scientists regularly participate in the annual meetings of the group. And last but not least: the field of fracture mechanics was extended to various working areas of the institute. Emphasis was put on the analysis and avoidance of failures and the assessment of safety and reliability.

The work of the institute is sponsored by various institutions. In the field of fracture research, there are research programmes of the government of the Fed­eral Republic of Germany, for instance, the programme for the safety of reactor components. Other sponsors are the Deutsche Forschungsgemeinschaft - DFG (the German Research Association), the Arbeitsgemeinschaft industrieller Forschungs­vereinigungen - AIF (the Association of German Industrial Research Societies), the EuropHische Gemeinschaft - EG (the European Community), the Stiftung Volks­wagenwerk as well as industrial firms. Sometimes the members of the Board of Trustees of IWM are also actively engaged in the support of this institute.

Of course, there is a close cooperation with other research institutes in Germany. For instance, the work of the analysis and development of fracture con­cepts in the frame work of reactor safety is done together with the Bundesanstalt fUr MaterialprUfung - BAM, Berlin, and the Institut fUr EisenhUttenkunde - IEhk, Aachen.

In respect to the theme of this international conference, the "Application of Fracture Mechanics to Materials and Structures", I may finally give an out­standing example of the work of IWM.

Cutting of glass is in general a well-known process. Even the separation of glass blocks for eye lens production provides not difficulties in principle: A diamond saw separates the block, the surface may be grinded and polished before further handling can take place. That a proper and clever application of frac­ture mechanics methods could help to reduce the costs of this time-consuming proc­ess has been shown by Dr. Doll and his co-workers at IWM: Thermally induced stresses can guide a crack in such a manner that the two resulting fracture sur­faces of the separated glass block show an excellent quality - sufficient for further handling by the manufacturer. Since in addition the fracture process could be automated the reduction of costs is remarkable. You will see this pro­cedure as well as others during the following visit to the laboratories.

Ladies and gentlemen, at the end of these short remarks let me give my con­gratulations to Dr. Sommer and his staff for this beautiful new building combined with the best wishes for further successful work! And let me close with many thanks to the sponsors for realizing the establishment of this building: the governments of the Federal Republic of Germany and of the State of Baden-WUrttem­berg and of course the Fraunhofer-Gesellschaft to which the IWM is linked to.

Freiburg, Germany June 22, 1983

G. W. Becker President Bundesanstalt fur Materialprufung and Head, Advisory Board of IWM

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OBJECTIVES AND CAPABILITIES OF FRAUNHOFER-INSTITUT fur WERKSTOFFMECHANIK

The Fraunhofer-Institut 'fur Werkstoffmechanik, situated in the northern section of Freiburg, is headed by Dr. E. Sommer, the Director of the Institute. It is supported by industry and government through research contracts that con­cern mainly with the assessment of the mechanical behavior of materials and structural components.

The Fraunhofer-Institut fur Werkstoffmechanik Laboratory in Freiburg

The Institut is well equipped with modern laboratory facilities and highly qualified personnel, particularly in the application of fracture mechanics to the safe and economic design of structures; the appropriate selection of mate­rials; the prevention of failure by defect assessment; the prediction of life­time of components; and the development and optimization of methods for processing materials. There are sixty (60) co-workers in the Institut divided into five (5) groups. They are headed by Drs. J. G. Blauel, W. Doll, J. F. Kathoff, W. Schmitt and R. Prummer as follows:

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(1) Metallic Materials (J. G. Blauel)

- Elastic-Plastic Fracture Criteria - Assessment of Components

(2) Nonmetallic Materials (W. Doll)

- Glasses: Handling and Severing Processes - Polymers: Lifetime Prediction - Ceramics: High Temperature and Fatigue Resistance and Biomechanics

(3) Experimental Stress-Strain Analysis (J. F. Kalthoff)

- Impact Testing - Fast Running Cracks

(4) Numerical Stress-Strain Analysis (W. Schmitt)

- Simulation of Experiments - Analysis of Components under Static and Dynamic Loading

(5) Surface Strength (R. Prummer)

- Improvement of Surface Properties: Microstructure, Residual Stresses

Professor G. C. Sih, Co-Chairman remarked on the Conference objectives and need for more international cooperation in research

Professor W. Dahl, Co-Chairman, emphasized the application of fracture mechanics to materials and structures

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Dr . E. Sommer, Co-Chairman, opened the technical portion of the Conference : First Plenary lecture

The members of the local organizing' committee from left to right: T. Hollstein, S. Lecointre and W. Schmitt

Co-Chairmen gathered at the Lord Mayor Reception in the Historisches Kaufhaus

Exchanging views with the Lord Mayor Dr. R. Bohme

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A toast to the success of the Conference

Making new friends at the reception of Lord Mayor, June 20, 1983

Cocktails on the terrace of the Schlosbergrestaurant Datter on June 21, 1983

Conference attendees at the Banquet Cocktail

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Presentation of plaques from G. C. Sih to E. Sommer and W. Dahl

Banquet dinner overlooking Freiburg

Smiling faces revealing the happy hours at Schlo8begrestaurant Dattler

Enjoying the food and wine at the banquet dinner

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Dr . H. Keller, President of Fraunhofer-Gesellschaft from Munich addresses the visitors to the IWM-Laboratories

Prof. Dr. G, W. Becker, President der Bundesantalt fur Materialprufung from Berlin informed on the history and research act i vities of IWM

A plaque presented from Dr . E. Sommer, Director of IWM to Professor G. C. Sih, Director of Institute of Fracture and Solid Mechanics at Lehigh University

Dr . E. Sommer on the platform to brief on the visits of the laboratories

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Relaxing at the house-warming party hosted by IWM

Members of the panel discussion concluding the conference with some brief remarks from left to right: W. Dahl. H. C. van Elst, J. Schijve, G. C. Sih and E. Sommer

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