Abstract

Poynting showed that steel wires and rubber rods become longer on twisting, by an amount proportional to the square of the torsion. This was explained by Rivlin as a direct consequence of the theory of large elastic deformations. Rivlin also showed that the ratio of the torsional stiffness of a stretched rod to the tensile load is a universal quantity. This feature can be used to test whether proposed models for the elastic behavior of rubber are feasible. (Some don’t pass the test.)

The corollary of the Poynting effect is that a compressive load must be applied to hold a twisted rod at constant length. It can be concluded that large torsional deformations of rods held at fixed length will become unstable. This phenomenon has now been analyzed. It can also be inferred from Rivlin’s analysis that unexpectedly-large internal stresses will be set up by simple shear of rubber blocks or tubes, as in engine mounts. Again, this appears to be true.

A general conclusion is that simple elastic deformations of rubber exhibit a number of surprising features that call for more detailed study.

Biography

Alan N. Gent is Research Professor and Professor Emeritus of Polymer Physics and Polymer Engineering at The University of Akron, where he has been since 1961. He also served as Consultant and Scientific Advisor to the Research Division of The Goodyear Tire & Rubber Company (1964 – 2002). He has published over 200 papers and book chapters on the mechanical properties of rubber and plastics, and presided over three national scientific societies: The High-Polymer Physics Division of the American Physical Society, The Society of Rheology, and The Adhesion Society. He has chaired four Gordon Research Conferences, dealing with Elastomers, Cellular Materials, Adhesion, and Composites. In 1991, he was elected to the National Academy of Engineering.

He has received many awards including the Bingham Medal of the Society of Rheology, the Colwyn Medal of the U.K. Plastics and Rubber Institute, the International Research Award of the Society of Plastics Engineers, the 3M Award and the President's Award of the Adhesion Society, the Charles Goodyear Medal of the A.C.S. Rubber Division, the High Polymer Physics Prize of the American Physical Society, and N.A.S.A.'s Public Service Medal for services rendered after the Challenger disaster. He has also been awarded honorary doctoral degrees by the Universite de Haute-Alsace, France, and De Montfort University, U.K.