Karl Weissenberg - The 80th Birthday
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It is a fitting tribute to the extent of Karl Weissenberg’s influence that this work to celebrate his eightieth birthday, which falls on the eleventh of June, nineteen hundred and seventy three, should emanate from a Department of Mechanical Engineering in a University in Africa, which is at once physically remote from his own working environment and scientifically removed from his academic training.
Karl Weissenberg has had two distinct lives in the scientific world and in each he has made far-reaching contributions to different branches of science as the various authors in this volume make clear.
The idea of celebrating his birthday in this way came to me whilst working in Britain, and it was born out of the realisation that some of those who had been intimately connected with him in professional life and understood at least in part the extent and nature of his contributions were passing into retirement. It seemed an opportune moment in time to obtain their first-hand impressions, and indeed if a record of them was to be compiled at all, then no time should be lost in drawing suitable work from the pens of these authors. The majority of the authors have been selected on the principle that they have worked at first hand with Weissenberg and are therefore in a special privileged position to comment on the extent and nature of his work. The remaining authors have a particular interest in his work.
A peculiar problem associated with obtaining a comprehensive survey for this volume has been that even those who have worked with Karl Weissenberg, or who have a particular interest in his work are, for the most part, unaware of the full extent of his contributions in science. A particular example may be quoted; in good faith an acquaintance of Weissenberg’s of many years standing and who is especially interested in his work in Rheology wrote offering a list of his publications with the message that it might well constitute a complete list of his publications in this field: there were seventeen items in it altogether. This number may be compared with the list contained in this volume, which is authoritative. No doubt many will learn for the first time the range of work covered and it may well come as a surprise that the list in Crystallography is longer than that in Rheology.
Weissenberg, the last person who would show an imposing or inaccessible front to the world, has often been completely underestimated both in the range and importance of his work. It is unfortunately true at the present time that to present a moderate attitude is to ask to be brushed aside in the struggle for plaudits even in the supposed impartial world of science. Therefore, it is not possible to record that the support which a subject merits, such as the present, is always forthcoming. Weissenberg has always had time and patience to answer with courtesy and at length, the letter on a scientific subject from an unknown and insignificant person. There is no doubt that his high standards in science are matched by equally high moral standards. Perhaps that list of publications would be even longer were this not the case. He is notable in scientific achievements and noble in personal qualities.
During the last three decades the name of Weissenberg has become familiar in Rheology, although like an iceberg only a part of the presence is explicit, the remainder is not visible to the casual observer's unaided eye. There are fundamental ideas, of which he is the source, that are pervasive and implicit in most of the published work on visco-elastic liquids. For example, the occurrence of finite elastic strain in flowing liquids and the corresponding tensile stress in simple shear flow for which the present author found unmistakable and direct evidence (Nature, Lond., 1961, 190, 993).
In his paper entitled "Abnormal Substances and Abnormal Phenomena of Flow" presented to the International Congress on Rheology in Holland, 1948, Weissenberg explicitly introduced the concept of a coordinate system embedded in the deforming material, a theme taken up at a later date by J. G. Oldroyd and termed a convected coordinate system. In the same. paper Weissenberg showed experiments in which sheet rubber material samples were subjected to an initial deformation (and therefore boundary stress), fixed in space, whilst the rubber sheet was subsequently rotated inside the fixed boundary. This was an experimental demonstration ;of the rotational part of the motion undergone by the convected coordinate system.
The authors of papers on Rheology who have contributed to this volume wish to record other facts than those mentioned above which verify that Weissenberg has a deep and sensitive appreciation of the essence of a range of natural phenomena. Certainly, in the field of Rheology his contributions have been of a pioneering nature and are more influential than many might suppose.
Prior to his work in Rheology, Weissenberg had made contributions in a distinctly different field of science. In Crystallography the Weissenberg Goniometer is known and used throughout the world and in itself would have been sufficient to secure fame for the originator. So distinct at the present time are the subjects of Rheology and Crystallography that I believe few Rheologists have even a remote idea of Weissenberg's contributions in Crystallography. No doubt the same applies to Crystallographers in relation to Rheology. This work is intended to elucidate and confirm his place in the founding era of both these branches of science. His dual role has indeed been exceptional.
A debt is due to all the authors represented in this volume for their generous and esteemed contributions. Also to the East African Literature Bureau, especially in the person of Mrs. R. Mwangi, for the kind help given in publishing and distributing this work. For my own part, nothing could have given greater pleasure than to assist in paying tribute to a man who will no doubt be remembered long after many of us have been forgotten.
John Harris, University of Nairobi, April, 1973.
Preface / Acknowledgements / Biographical Notes
Weissenberg’s Influence on Crystallography
Karl Weissenberg and the Development of X-Ray Crystallography
The Isolation of, and the Initial Measurements of the Weissenberg Effect
The Role of Similitude in Continuum Mechanics
The Effect of Molecular Weight and Concentration of Polymers in Solutions on the Normal Stress Coefficient
Elasticity in Incompressible Liquids
The Physical Meaning of Weissenberg's Hypothesis with Regard to the Second Normal-Stress Difference
A Study of Weissenberg's Holistic Approach to Biorheology
The Weissenberg Rheogoniometer Adapted for Biorheological Studies
Dr. Karl Weissenberg, 1922-28
Weissenberg’s Contributions to Rheology
The Early Development of the Rheogoniometer
Some of Weissenberg's More Important Contributions to Rheology: An Appreciation
Publications of Karl Weissenberg and Collaborators / List of Contributors
© Copyright John Harris