Stress Relaxation as a Method of Analyzing Stress Growth, Stress Overshoot and Steady‐State Flow of Elastomers

Abstract

Stress relaxation behavior is a manifestation of stored memory which existed just prior to the relaxation. Stress relaxation after instantaneous deformation and stress relaxation after constant rate of deformation have already been treated theoretically for the case of linear viscoelastic behavior. This paper extends the interpretation to the large deformation, where the viscoelastic behavior includes nonlinear cases. Of particular interest is the stress relaxation after cessation of steady‐state flow. We have succeeded in estimating the magnitude of deformation, whereby the relaxing stress was converted to a modulus‐time curve. Consequently, the relaxation after cessation of flow can be interpreted in a consistent manner with other types of relaxation, where the magnitude of deformation is known. The interpretation is based on the storage and dissipation of memory in the preceding deformational process. A quantitative comparison of the gain and loss of memory may be made by comparing relaxation modulus‐time curves to see which part of the time‐distribution of memory was affected.