MODELING OF VISCOPLASTIC CONSTITUTIVE EQUATION FOR INELASTIC DEFORMATION OF POLYMER WITH UNLOADING

摘要

A viscoplastic constitutive equation for inelastic deformation of polymers was formulated by combining the kinematic hardening creep theory of Malinin and Khadjinsky with the nonlinear kinematic hardening rule of Armstrong and Frederick. The nonlinear kinematic hardening rule was modified in order to describe peculiar inelastic deformation of polymers during unloading in particular. Experimental results for polyethylene were simulated by the constitutive equation and the validity of the modification was verified.