YIELDING, ANISOTROPY, AND DEFORMATION PROCESSING OF POLYMERS

Constitutive equations that characterize the deformation induced anisotropy in polymers at large strains are developed for both flow and deformation (nonlinear elastic) theories of plasticity. These equations are used first to predict the evolution of yield surfaces for anisotropies that develop under simple plane strain deformations. Then, non‐uniform deformations are considered including neck propagation and extrusion. Finite element solutions are based on the flow theory version of the constitutive models. Neck propagation loads and draw ratios are found to be sensitive to the degree of anisotropy and pressure sensitivity, while extrusion forces are less so. The results are compared to solutions for an isotropic material with the same effective stress‐strain behavior. Copyright © 1990 Society of Plastics Engineers