Product Form of Kernel Functions for Nonlinear Viscoelasticity of PVC Under Constant Rate Stressing

Abstract

Determination of all the kernel functions for multiple integral representation of creep is very involved. In this paper the kernel functions were assumed to have a product form, such as f2(t−τ1,t−τ2)=f2(t−τ1)f2(t−τ2). The validity of this assumption was tested by experiments on a poly(vinyl chloride) plastic tube subjected to constant rates of stressing in combinations of tension and torsion. Some experiments also included abrupt changes in stress. Application of the theory to several complex experiments is illustrated. Agreement between theory and experiment is generally satisfactory, so the assumption seems adequate for the type stress histories investigated.