Numerical aspects associated with the implementation of a finite strain, elasto-viscoelastic–viscoplastic constitutive theory in principal stretches

Abstract

This paper treats the numerical implementation of a finite strain, elasto-viscoelastic–viscoplastic constitutive model for semi-crystalline polymers, written in principal stretches. A parallel configuration of the three model elements is used that enables the decoupled algorithmic treatment of each response within a stress update numerical scheme. The numerical aspects associated with the use of principal stretch constitutive expressions in a tensor space numerical environment are initially developed for the general cases of any elastic or inelastic constitutive element. Included is the formulation of the closed-form, consistent tangential modulus tensor. The principal space algorithmic treatments of the elastic, viscoelastic and viscoplastic elements are then used as specific examples. Of particular importance is the development of a principal space, closest point projection return mapping algorithm for viscoplasticity including isotropic strain hardening. Preliminary numerical examples are presented to illustrate the versatility of the model.