Torsion of a viscoelastic cylinder

Finite torsional deformations of an incompressible viscoelastic circular cy linder are studied with its material modeled by two constitutive relations. One of these is a linear relation between the determinate part of the seco nd Piola-Kirchhoff stress tensor and the time history of the Green-St. Vena nt strain tensor, and the other a linear relation between the deviatoric Ca uchy stress tensor and the left Cauchy-Green tensor, its inverse, and the t ime history of the Green-St. Venant strain tensor. It is shown that the res ponse predicted by the latter constitutive relation is in better agreement with the test data, and this constitutive relation is used to compare energ y dissipated during torsional oscillations of the cylinder.