A HYBRID NONLINEAR CONSTITUTIVE MODEL: COMPARISONS WITH MULTIPLE STEP DATA FOR A POLYURETHANE RUBBER

摘要

A nonlinear constitutive equation based on the model of Bernstein, Kearsley and Zapas (BKZ) is developed by noting that the BKZ model has a structure that looks like a time-dependent finite elasticity. By postulating, as did Valanis and Landel (VL) for rubber, that the strain potential function can be represented by a separable function in the stretches we develop a hybrid VL-BKZ viscoelastic model. Results of model predictions for multiple step deformation and stress histories are compared with experiments using a polyurethane elastomer.