ON THE PREDICTION OF STRESS-RELAXATION FROM KNOWN CREEP OF NONLINEAR MATERIALS

A method to predict the nonlinear relaxation behavior from creep exper iments of nonlinear viscoelastic materials is presented. It is shown t hat for given nonlinear creep properties, and creep compliance represe nted by the Prony series, the Schapery creep model can be transformed into a set of first, order nonlinear equations. The solution of these equations enables the obtaining of the nonlinear stress relaxation cur ves. The strain-dependent constitutive equation can then be constructe d for a given nonlinear viscoelastic model, as needed for engineering applications. A comparison example of the calculated stress relaxation curves, with test data for polyurethane demonstrates the very good ac curacy of the proposed method.