IUTAM Symposia – serie

Polymer composites were introduced for the aerospace industry as light, strong, stiff materials, and adopted by the construction and automobile industries, among others. Meanwhile, composite materials have been introduced to fulfill the uses that these conventional materials could not, such as in extreme environments. The research for new composites includes not only new polymer systems, but metals, ceramics and intermetallic systems as well. This volume contains a selection of recent work by leading researchers in micromechanics on the topics of prediction of overall properties of elastic, perfectly bonded systems, problems associated with inelastic deformation of the phase, debonding at interfaces and growth of distributed damage. Many familiar aspects of mechanical behavior, such as fatigue, fracture, strength and buckling, etc. have been reexamined and adapted for these new systems.

Der BeschluB des Generalrats der Internationalen Union fill Theo- retische und Angewandte Mechanik (IUTAM), ein Symposium tiber Grenzschichtforschung vorzubereiten, war von dem Wunsch getragen, Wissenschaftlern aus aller Welt, die in eigenen Arbeiten zu den neueren Fortschritten auf diesem wichtigen Gebiet der Stromungsmechanik wesentlich beigetragen haben, zu grtindlichen Diskussionen Gelegenheit zu geben. Die grundsatzlichen Probleme der Grenzschichtforschung soUten bei der Aussprache im V ordergrund stehen, die technischen An- wendungen muBten im Hintergrund bleiben. Da eine echte Diskussion nur in einem relativ kleinen Kreis moglich ist, hat das Wissenschaftliche Komitee den Kreis der Teilnehmer be- schrankt, dabei aber nach Moglichkeit Vertreter aus allen an den Fort- schritten der Grenzschichtforschung beteiligten Nationen zusammenge- fUhrt. Die Teilnehmer wurden in Beratungen des Wissenschaftlichen Komitees ausgewahlt und entweder zur Erstattung eines allgemeinen oder eines speziellen Berichtes eingeladen bzw. zur Teilnahme an den Diskussionsveranstaltungen aufgefordert. Das Ergebnis dieser Tagung legen wir hiermit vor.1m Druck sind aIle jene Fragen und Bemerkungen aus den Diskussionen weggelassen wor- den, die sich durch das V orliegen des voUen V ortragstextes in diesem Buch von selbst erledigen, bzw. die durch nachtragliche Bearbeitung des Manuskriptes von den Autoren beriicksichtigt worden sind. Wir empfinden es mit Dank als eine Ehrung, daB die erste Veranstal- tung der IUTAM in Deutschland die Grenzschichtforschung behandelt und damit das Gedenken an LUDWIG PRANDTL wachhalt, den Begriinder der Grenzschichtforschung und den Forderer der modernen Stromungs- forschung.

The origins of turbulent flow and the transition from laminar to turbulent flow are among the most important unsolved problems of fluid mechanics and aerodynamics. Besides being a fundamental question of fluid mechanics, there are many practical applications for information regarding transition location and the details of the subsequent turbulent flow. This proceedings volume contains the papers of two keynote lectures as well as of 104 technical presentations and posters that were presented at the IUTAM Symposium on Laminar-Turbulent Transition in Sedona, Arizona, September 13-17, 1999. The papers published in the present volume document the state of the art in transition research, and therefore, increased emphasis on the various topics covered in this meeting can be expected in the future.

The origins of turbulent flow and the transition from laminar to turbulent flow are among the most important unsolved problems of fluid mechanics and aerodynamics. Besides being a fundamental question of fluid mechanics, there are many practical applications for information regarding transition location and the details of the subsequent turbulent flow. This proceedings volume contains the papers of two keynote lectures as well as of 104 technical presentations and posters that were presented at the IUTAM Symposium on Laminar-Turbulent Transition in Sedona, Arizona, September 13-17, 1999. The papers published in the present volume document the state of the art in transition research, and therefore, increased emphasis on the various topics covered in this meeting can be expected in the future.

For a long period Soil Mechanics has remained at the semi-empirica stage, and only a few decades ago it has shown a tendency to become a fundamental science. However, this evolution is taking place slowly; in spite of the efforts of numerous research scientists, the very complex rheological laws of soils are still not well known. Even if these laws were elucidated, it would take a long time still to deduce simple rules from them for reliable and convenient use in current practical engineer­ ing. In the pursuit of these distant aims - and of others more imme­ diate - fundamental research and applied research are very active, both in Rheology and Soil Mechanics. The complexity of the problems to be solved should incite the laboratory researchers and the engineers to a continuous collaboration. Everyone acknowledges the advantage of these connections although aware of the difficulty of realizing this wish. However, contacts are being made little by little between the repre­ sentatives of the different branches of Rheology and Soil Mechanics, to the great benefit of science. The bureau of the International Union of Theoretical and Applied Mechanics (IUTAM), aware of the importance of these two associat­ ed fields of mechanics, considered it possible to accelerate the natural and necessary processus of their interpenetration by organizing in Grenoble, from 1st to 8th April 1964 an International Symposium on Rheology and Soil Mechanics.

This volume includes original papers presented at the 4th Symposium on Satellite Dynamics held at the XII Annual Plenary Meeting of COSPAR. At a time where it might be thought that very few problems were left un­ solved in celestial mechanics, we discover that new and more challenging questions must be answered. The pre­ cision of observations reaches the centimeter level and physical phenomena which had been disregarded come into play. We need a better treatment of atmospheric drag, radiation forces, and a better knowledge of the earth's gravitational field. Time has to be precisely defined as well as reference systems, including improved values for precision and nutation. The question of resonances introduced by nonzonal harmonics was to be carefully in­ vestigated. Numerical integration techniques must be optimized and means of controlling their errors improved. Analytical techniques must be made appropriate for com­ puter processing. Presently existing methods of solu­ tions of differential equations of interest to celestial mechanics are getting cumbersome as all these new facts come to light. It is clear that entirely new and more effective methods are necessary. These methods must, among other requirements, take into account the essential nonlinear character of the equations. Finally, the mo­ tion about the center of mass of a satellite is becoming an essential need for the thorough understanding and de­ scription of the orbital motion.

Depuis Ie lancement de SPOUTNIK I par l'Union Sovietique Ie 4 Octobre 1957, des experiences humaines de Mecanique celeste de cette sorte ont ete repetees it de nombreuses reprises en U. R. S. S. et aux U. S. A. En 1961, sur ma proposition, l'Union Internationale de Mecanique tMorique et appliquee retint l'idee de consacrer en 1962 un Symposium special it la confrontation des resultats des experiences sovietiques et americaines en vue d'en tirer Ie maximum d'enseignements sur la question fondamentale suivante concernant la " Dynamique des satellites artificiels) de la Terre: quelles sont la nature et les lois des forces reelles qui agissent sur ces mobiles au voisinage de notre planete, et qui determinent par consequent leur mouvement~ En d'autres termes, il s'agissait de faire Ie point de nos connaissances sur Ie probleme du mouvement des Astres, magistralement resolu par NEWTON il Y a plus de trois siecles pour des astres quasi-ponctuels et assez eloignes. Les moyens d'observation utilises pour connaitre avec la meilleure precision possible Ie mouvement des satellites artificiels lances depuis 1957, et Ie fait de. la proximite relative de ces satellites par rapport it la Terre sont par eux-memes d~ nature it reveler soit des alterations de la loi classique de 1'attraction newtonienne, dont la signification serait it rechercher, soit l'intervention de forces per- turbatrices, dont l'origine et Vexpression seraient it preciser.

Auf einer Sitzung des :Biiros der Internationalen Union fiir Theore- tische und Angewandte Mechanik (IUTAM) in :Briissel am 21. Septem- ber 1953 wurde beschlossen, ein Kolloquium iiber Festkorpermechanik (vorlaufiger Titel) fiir die letzte Septemberwoche 1955 zu pla.nen, und zwa.r in Madrid, entsprechend einer EinIadung, welche die Vertreter der zugehorigen spanischen Organisation Instituto Naciona.l de Tecnica Aeronautica "Esteban Terradas" (INTA) , die Herren A. NUNEz und A. PEREZ-MARiN personIich iiberbrachten. Das vom :Biiro der IUTAM hierfiir eingesetzte Wissenschaftliche Komitee bestand aus R. GRAMMEL als Vorsitzendem und den Herren TH. VON K.ARMiN, M. Roy und G. I. TAYLOR, das spanische Organisa- tions-Komitee aus den Herren A. NUNEz und A. PEREZ-MARiN samt einem Stab technischer und administrativer Mitarbeiter. In drei :Beratungen des Wissenschaftlichen Komitees (:Briissel, 27. Juli 1954; Farnborough, to. September 1954; Paris, 23. Mai 1955) wurde das Programm des Kolloquiums mit dem endgiiltigen Titel "Verformung und FlieBen des Festkorpers" festgelegt und dann in den Tagen vom 26. bis 30. September 1955 gemaB dem Plan von Seite IX verwirklicht.Jedes der drei Themen (Versetzungen und Plastizitat; Nichtlineare Elastizitat; Viskoelastizita.t und Relaxation) und insbesondere jede Sitzung wurde durch einen AIIgemeinen V ortrag eingeleitet. Die Titel aller V ortrage gibt das Inhaltsverzeichnis Seite XI und XII an. Die Vortrage wurden am 26., 27. und 29. September im Consejo Superior de Investigaciones Cientificas in Madrid gehalten, am 28. Sep- tember in Torrej6n de Ardoz, verbunden mit einer :Besichtigung der Laboratorien des INTA daselbst.

In recent years there has been an unmistakable tendency for research in the fields of hydraulics and fluid mechanics to involve ever more sophisticated study of increasingly detailed aspects of problems, while in the process becoming further and further detached from the reali­ ties faced by practising engineers. At the same time, too many hy­ draulic engineers have continued to conduct model studies with the goal of obtaining ad-hoc solutions for specific problems, while direct­ ing little if any of their attention toward elucidation of the underlying mechanics and toward generalization of their results for future appli­ cation. It was against this background that the International Union of Theoretical and Applied Mechanics (IUTAM) and the International As­ sociation for Hydraulic Research (IAHR) were approached and asked to cosponsor the Symposium on Flow-Induced Structural Vibrations, which would have as its objective the promotion of interaction between the active researchers and the practitioners, and of communication between the different disciplines concerned. To this end, invitations were extended to individuals who together represented the full range of the investigation-application spectrum, and contributions were so­ licited from scientists and engineers who, in general, approach vi­ bration problems along different avenues. In soliciting contributions to the Symposium it was emphasized that priority would be given to IV Preface papers which shed light on the constituent phenomena involved in vi­ bration problems and thereby enhance our understanding of the basic vibration-inducing mechanisms.

The Symposium on the Photoelastic Effect and its Applications sponsored by IUTAM with the cooperation of the Permanent Committee for Stress Analy- sis and the Society for Experimental Stress Analysis was convened at IBM Ed- ucational Center, Ottignies, Belgium, September 9-14, 1973. The subject of the Symposium was the study of the interaction of matter with light in a broad sense. More specifically three main subjects were proposed: (1) Classical and advanced photoelasticity (2) Rheooptics and (3) Theoretical mechanics of a continuum in interaction with the electro-mag- netic field. For a better understanding of the problems at hand, three general conferences presented these three subjects and three others treated (4) the available ex- perimental methods for measuring the optical properties, (5) streaming dou- ble refraction and (6) magneto-and electro-photoelasticity, making a total of six general conferences. The scientific program included also 21 papers. Plen- ty of time was provided for discussions after the conferences and after the pa- pers. The symposium ended with two concluding conferences followed by a gen- eral discussion. In an introductory conference, Professor R.Van Geen (Brussels) has put the study of the Photoelastic Effect in its right place, and given further com- ments on the aims of this Syposium.

Requirements on high efficiency of rotating machinery forces engineers to deal with problems of self-induced vi­ brations and balancing of rotors in a serious and scientific manner. The last decade has shown a leap towards the solution of advanced problems of this kind as indicated by the large amount of scientific and engineering papers on rotor dynamics published in international journals. In appreciation of this situation the General Assembly of the International Union of Theoretical and Applied Mecha­ nics (IUTAM) at its meeting in Moscow in 1972, acting on a proposal by the Danish Adhering Organization, decided to sponsor an international symposium on the "Dynamics of Rotors" . The scientific planning of the symposium was handed by a scientific committee, consisting of Prof. R.E.D. BISHOP, UK, Prof. S.H. CRANDALL, USA, Prof. F.M. DIMENTBERG, USSR, Dr. A. TONDL, CSSR, Prof. H. ZIEGLER, Switzerland and Prof. F.I. NIORDSON, Denmark, (Chairman). This committee was charged with the selection and invitation of a small number of outstanding scientists in the field, whose contributions to the symposium are presented in this volume. Participation was restricted to invited scientists and there were 87 active participants from 18 countries. Apart from a financial contribution from IUTAM to sup­ port travel and subsistence of invited participants, generous contributions were received from the following Danish Companies: Burmeister & Wain, Danfoss, The Danish Sugar­ corporation, DISA, Elsinore Shipbuilding Engineer, Kyndby­ v~rket, Niro Atomizer, and the Swedish Company STAL-LAVAL. The contributions are gratefully acknowledged.

The Symposium originated in a proposal made in 1969 by Professor A. A. Ilyushin, Moscow. A study group (chairman J. Hult) , appointed by the General Assembly of IUTAM in 1971, suggested in areport to the Bureau of IUTAM in 1972 that the following topics should form the basis of the scientific program: 1) Limits of linearized theories and effective versions of the non-linear theory of viscoelasticity 2) Theory of experimental studies in linear and non-linear viscoelasticity aiming at the determination of consti­ tutive equations and conditions of strength and failure under an arbitrary deformation process 3) Experimental and theoretical studies of thermal effects in viscoelasticity taking into ac count thermo-mechanical coupling 4) Novel analytical and numerical techniques for the solution of problems in viscoelasticity and thermo-viscoelasticity. This proposal was accepted by the Bureau, and the following Scientific Committee was appointed: J. HULT, Chalmers University of Technology, Fack, S-402 20 GÖTEBORG, Sweden (Chairman) J. F. BESSELING, Technische Hogeschool Delft, Mekelweg 2, DELFT, The Netherlands P. CHADWICK, School of Mathematics and Physics, University of East Anglia, Wilberforce Road, NORWICH NOR 880, England A. A. ILYUSHIN, Dept. of Mechanics and Mathematics, University of Moscow, MOSCOW B-234, USSR E. H. LEE, Dept. of Applied Mechanics, Stanford University, STANFORD, California 94305, USA W. OLSZAK, Int.

The advent of the digital computer has given great impetus to the development of modern discretization methods in structural mechanics. The young history of the finite element method (FEM) reflects the dramatic increase of computing speed and storage capacity within a relatively short period of time. The history of the boundary element method (BEM) is still younger. Presently, intense scientific efforts aimed at extending the range of application of the BEM can be observed. More than 10 years ago, O.C. Zienkiewicz and his co-workers published the first papers on the coupling of FE and BE discretizations of subregions of solids for the purpose of exploiting the complementary advantages of the two discretization methods and reducing their disadvantages. The FEM has revolutionized structural analysis in industry as well as academia. The BEM has a fair share in the continuation of this revolution. Both discretization methods have become a domain of vigorous, world-wide research activities. The rapid increase of the number of specialized journals and scientific meetings indicates the remarkable increase of research efforts in this important subdolll.ain of computational ulechanics. Several discussions of this situation in the Committee for Discretization Methods ill Solid Mechanics of the Society for Applied Mathematics and Mechanics (GAMM) resulted in the plan to submit a proposal to the General Assembly of the International Union of Theoretical and Applied Mechanics (IUTAM) to sponsor a pertinent IUTAM Symposium.

Substantial progress has been made in the field of fluid mechanics under compensated gravity effects (microgravity). The main task of this disciplinehas evolved tremendously. Starting out with the aim of providing assistance in describing flow problems in other microgravity sciences, microgravityfluid mechanics has itself now become acknowledge as a powerful means of research. The IUTAM Symposium on Microgravity Fluid Mechanics has pro- vided the long-awaited forum for scientists from 15 coun- tries to discuss and concretize the "state-of-the-art" in this discipline. The main themes treated are: Interface Phe- nomena, Convective Processes; Marangoni effects, Solidifica- tion, Combustion, Physico-Chemical Processes, Multiphase Phenomena, Residual Acceleration effects, Fluid Handling and Non-Newtonian Flows.

In 1976 a similar titled IUTAM Symposium (Structure of Turbulence and Drag Reduction) was held in Washington . However, the progress made during the last thirteen years as weil as the much promising current research desired a second one this year. In Washington drag reduction by additives and by direct manipulation of the walls (compliant walls and heated surfaces) were discussed. In the meantime it became evident that drag reduction also occurs when turbulence is influenced by geometrical means, e.g. by influencing the pressure distribution by the shape of the body (airfoils) or by the introduction of streamwise perturbances on a body (riblets). In the recent years turbulence research has seen increasing attention being focused on the investigation of coherent structures, mainly in Newtonian fluids. We all know that these structures are a significant feature of turbulent flows, playing an important role in the energy balance in such flows. However their place in turbulence theories as weil as the factors influencing their development are still poorly understood. Consequently, the investigation of phenomena in which the properties of coherent structures are alte red provides a promising means of improving our understanding of turbulent flows in general.

This volume contains the written texts of the papers presented at a Symposium on Buckling of Structures held at Harvard University in June 1974. This symposium, one of several on various topics sponsored annually by the International Union of Theoretical and Applied Me­ chanics (IUTAM), was organized by a Scientific Committee consisting of B. Budiansky (Chairman), A. H. Chilver, W. T. Koiter, and A. S. Vol'­ mir. Participation was by invitation of the Scientific Committee, and specific lecturers were invited to speak in the areas of experimental research, buckling and post-buckling calculations, post-buckling mode interaction, plasticity and creep effects, dynamic buckling, stochastic problems, and design. A total of 29 lectures were delivered, including a general opening lecture by Professor Koiter, and there were 93 reg­ istered participants from 16 different countries. Financial support for the symposium was provided by IUTAM, in the form of partial travel support for a number of participants, and also by the National Science Foundation, the National Aeronautics and Space Administration, and the Air Force Office of Scientific Re­ search, for additional travel support and administrative expenses. Meeting facilities and services were efficiently provided by the Science Center of Harvard University, and administrative support was gen­ erously provided by the Division of Engineering and Applied Physics of Harvard University. The scientific chairman enjoyed the invaluable assistance of his colleagues Professors J. W. Hutchinson and J. L.

Inverse problems occur in a wide variey of fields. Ingeneral, the inverse problem can be defined as one where oneshould estimate the cause from the result, while the directproblem is concerned with how to obtain the result from thecause. The aim of this symposium was to gather scientistsand researchers in engineering mechanics concerned withinverse problems in order to exchange research result anddevelop computational and experimentalapproaches to solveinverse problems.The contributions in this volume cover the followingsubjects: mathematical and computational aspects of inverseproblems, parameter or system identification, shapedetermination, sensitivity analysis, optimization, materialproperty characterization, ultrasonic nondestructivetesting, elastodynamic inverse problems, thermal inverseproblems, and other miscellaneous engineering applications.

The management of vortices and separation behind the bodiesat high angles of attack is important for highmaneuvrability of airplanes and other fluid dynamicapparatus. The recent international developments in thefundamental sciences and the application to the control offluid behaviours were presented at the IUTAM Symposium onFluid Dynamics of High Angle of Attack in September 1992 inTokyo and documented in this volume.

Until recently there was no uniform stability theory. Different approaches to stability problems had been developed in the different branches of mechanics. In the field of elasticity, it was mainly the so­ called static method and energy method which were used, while in the field of dynamics it was the kinetic method, which found its perfect expression in the theory of Liapunov. During the last few decades there has been a rapid development in the general theory of stability, stimulated, for example, by the investigations of H. ZIEGLER on elastic systems subject to non-conservative loads, and by the problems arising in aeroelasticity which are closely related to those introduced by ZIEGLER. The need was felt for kinetic methods which could also be used in investigating the stability of deformable systems. Efforts were made to adapt such methods, already known and developed in the stability theory of rigid systems, for application in the stability theory of continuous systems. During the last ten years interest was focused mainly on the application of a generalized Liapunov method to stability problems of continuous systems. All this was done in attempts to unify the various approaches to stability theory. It was with the idea of encouraging such a tendency, establishing to what extent a uniform physical and mathematical foundation already existed for stability theory in all branches of mechanics, and stimulating the further deve­ lopment of a common stability theory, that a IUTAM-Symposium was devoted to this topic.

The first IUTAM Symposium on Creep in Structures was held in Stanford, Cal. 1960 (Proceedings, ed. N. J. HOFF, Springer-Verlag 1962). That meeting reflected an intense research activity in the field of structural creep, and many important results were pre­ sented. In spite of this progress design rules for high temperature equipment are still often inadequate. Design against creep deformation and creep rupture is all too often based only oli experience and intuition. With technological processes moving into ever higher temperature regions the effects of creep must be given steadily increasing attention. The IUTAM Bureau in 1967 decided to arrange a Second Symposium on Creep in Structures, to be held in Gothenburg under the chairmanship of F. K. G. ODQVIST. This meeting was to take stock of the progress made in the ten years since the first symposium. Notable advances in the establishment of a sound phenomenological theory, refined experimental techniques and several new methods of structural analysis of shells in the creep range gave impetus to this second symposium. Problems of rupture and stability under complex loads had been studied and many new results in these fields were presented and discussed. Attendance was strictly limited to persons active in the field covered by the symposium. Financial support was generously provided by IUTAM, Chalmers University, the Swedish Board for Technical Develonment and four Swedish industrial companies (ASEA, Sand­ mens Jernverk, Saab-Scania, Volvo).

The Thirteenth International Congress of Theoretical and Applied Mechanics was held in Moscow from Monday, 21 August, to Saturday, 26 August 1972. About 2500 participants from 37 countries all over the world attended the congress that was convened by the Congress Committee of the International Union of Theoretical and Applied Mechanics. The local or­ ganization lay in the hands of the Organizing Committee, established by the USSR National Committee on Theoretical and Applied Mechanics. The USSR Academy of Sciences rendered partial financial help to the organization of th8 congress. The Organizing Committee was assisted by the Institute of Problems of Mechanics of the USSR Academy of Sciences, by the Research Institute for Mechanics of Moscow University, and by the Computing Center and the Institute of Applied Mathematics of the USSR Academy of Sciences. The Bureau of IUTAM had allocated a considerable sum for partial financial support of young scientists attending the congress. The Thirteenth Congress was officially opened on Monday morning at the Kremlin Palace of Congresses by Academician N. 1. Muskhelishvili, President of the Congress, and Professor W. T. Koiter, President of IUTAM. Greeting addresses were offered by: Mr. K. N. Rudnev, Minister, member of the Council of Ministers of the USSR, Academician M. V. Keldysh, President of the USSR Academy of Sciences, Mr. L. N.

The International Union of Theoretical and Applied Mechanics (IUTAM) decided in 1992 to sponsor the fourth Symposium on Laminar-Turbulent Transition, Sendai/Japan, 1994. The objectives of the present Symposium were to deepen the fundamental knowledge of stability and laminar­ turbulent transition in three-dimensional and compressible flows and to contribute to recent developing technologies in the field. This Symposium followed the three previous IUTAM-Symposia (Stuttgart 1979, Novosibirsk 1984 and Toulouse 1989). The Scientific Committee selected two keynote lectures and 62 technical papers. The Symposium was held on the 5th to 9th of September, 1994, at the Sendai International Center in Sendai. The participants were 82 scientists from 10 countries. The keynote lectures have critically reviewed recent development of researches concerning the laminar-to-turbulent transition phenomena from the fundamental and the application aspects. Many papers presented were concerned about the detailed mechanism of the boundary layer transition (receptivity, secondary instability, turbulent spot and bypass transition). Particular emphasis was further placed on the transition of three-dimensional boundary layers on rotation systems and on swept wings. Attention was also given to compressible hypersonic flows.

Structural optimization, a broad interdisciplinary field, requires skillful combining of mathematical and mechanical knowledge with engineering. It is both intellectually attractive and technologically rewarding. The Symposium on Optimization in Structural Design was the second IUTAM Symposium in Poland. Fifteen years have elapsed since the Symposium on Nonhomogeneity in Elasticity and Plasticity, presided by Professor Olszak, was held in Warsaw. These fifteen years mean a lot for mechanics in Poland. Continuing the tradition of Professor Maksymilian Tytus Huber's research, considerable development of the mechanical sciences has been achieved in this country mostly due to the knowledge, vision and persistence of Professors Wit old Nowacki and Waclaw Olszak, eminent Members of our Academy. The Institute of Fundamental Technological Research was established, competent research groups grew, matured and contri­ buted to thermo-elasticity, plasticity, general theory of constitutive equations, and to structural mechanics-just to mention a few do­ mains. Mechanics is now penetrating into the technology of this country at an accelerating pace. The optimization in mechanics has a tradition in Poland. In 1936 Professor Zbigniew Wasiutynski formulated the optimality criterion for mean stiffness design using an elastic energy concept. Further work in this field has been done since, mostly in the last ten years. On behalf of the Committee for Mechanics of the Polish Academy of Sciences I wish to thank the IUTA1V[ Bureau for the decision to hold in Warsaw the Symposium the present volume contains the contribu­ tions to.

The first Symposium Transsonicum took pl.ace in Aachen thirteen years ago during a period of decreasing governmental. and industrial. support for transonic flow research. Since then, there has been a strong revival. in interest in transonic flow research so that the number of partici­ pants at the second symposium remained about the same as at the first even in spite of tight financial. means and Limited governmental. support. During both meetings the number of participants reached the upper Limit of the number desirabl.e for such a symposium. Participants came from aU over the worl.d and there was a weU bal.anced distribution of participants from aU countries interested in transonic flow research. The discussions - mostLy conducted in EngLish - were stimul.ating and there was a great deal. of interest in the l.ectures as was shown by the good attendance even during the l.ast session on Saturday morning.

The International Union of Theoretical and Applied Mechanics (IUTAM) which is the head organisation of most of the existing national and international societies of mechanics, decided to sponsor a Symposium on METAL FORMING PLASTICITY. It was held near Munich (Federal Republic of Germany) between August 28 and September 3, 1978, in the "Evange- lische Academy" in the Castle of Tutzing which is situ- ated in a park at Lake Starnberg overlooking the Alps. The subjects of the Symposium were basic aspects of the theoretical and experimental mechanics of metal form- ing processes rather than technological details, or plas- ticity as such. Thus the spectrum of the Conference extended from necessary physical background, through ex- perimental, analytical, or numerical methods, to appli- cations to specific technological deformation processes such as rolling, deep drawing, extrusion, etc. The following persons were by the IUTAM-bureau ap- pointed to membership of the "Scientific Committee" which was responsible for the nomination of participants as well as for the form of the scientific program: w. Johnson (U.K.), H. Kudo (Japan), H. Lippmann (F.R.G, chairman), G.S. Pisarenko (USSR), anc W.Szczepinski (Poland) . The technical organisation was in the hands of a "Local Organizing Committee" formed by VI F. Fischer, K. Heckel, G. Kuhn, H. Lippmann (chairman), K. Magnus, V. Mannl, G. Sonntag, all of them from Munich and K. Lange (Stuttgart), O. Pa'Nelski (DUsseldorf) . This committee was supported by two secretaries, i.e.

The Symposium on "The Mechanics of Sound Generation in FLows" th st was held in Gottingen, Germany, 28 - 31 August 1979, at the joint initiative of the International Union of Theoretical and Applied Mechanics (IUTAM), the International Commission on Acoustics (ICA) and the American Institute of Aeronautics and Astronautics (AIAA). From the whole field of flow-acoustics the Symposium concen­ trated on prob lems of sound generation, while sound propagation and the creation of flows by sound were left in the ba- ground. 82 delegates from 12 countries attended the Symposium. 38 papers were given 5 of which were invited general lectures. Emphasis was placed on discussion, a plenary discussion closing the sym- sium. A s care had been taken to invite as many active workers in the field as possible with their most recent results the Symposium provided a momentary overview of the current state of the ra­ pidly developing field of flow-acoustics. Participants appreciated the meeting as a possibility to inform themselves, to discuss their own results and to obtain incentives for future efforts.

In the programme of the symposium was written: "The International Union of Theoretical and Applied Me- chanics has taken the initiative to organize the sympo- sium. As the name of IUTAM implies, the organization brings forward achievements within the field of theore- tical mechanics for application in science and engineer- ing. According to the rules of IUTAM that only invited persons can attend, all lecturers and participants have been ap- pOinted by the members of the scientific committee. To facilitate contact among the attending persons, it has been decided to restrict the total number to 85 persons including the lecturers. Only one session is planned, making it possible for everybody to attend all lectures. Most scientists and engineers have realized that the knowledge attained by extensive basic research is essen- tial in order to solve technological problems.In the process of acquiring this knowledge we often fail to un- derstand that scientific progress is only achieved by two main principles: (1) By studying the scientific litera- ture and applying or improving the theories in order to predict behaviour and forces correctly, or (2) by re- jecting existing theories and developing new ways to cope with the problem, resulting in a more differenti- ated and, hopefully, more exact theory. Ice seems to be a simple material, but it is in fact so complex and strange that it is only in the latest dec- ades that we have come to know some of the natural laws governing its behaviour.