Relaxation Properties of Polyester Based on Polyurethane under Small Deformations Superposed on Large Deformations

摘要

An investigation was carried out to determine the extensional mechanical behavior of a viscoelastic material when it is subject to an infinitestimal displacement field superposed on a finite steady deformation. Experiments were conducted on a thin strip of a polyester based polyurethane at a temperature of about 77 F. It is shown that the relaxation modulus of this material can be expressed as a product of two functions, one of which depends only upon the elongation ratio and the other only upon time. This form is applicable for basic state elongation rations 1