Anisotropic Creep Behaviour Induced by Plastic Deformation

Abstract

A rate-dependent constitutive model which describes deformation induced anisotropy is proposed. The model falls in the category of the unified models. In the first place, we describe an inelastic strain-rate in terms of an isotropic tensor function of the deviatoric stress tensor and a second rank internal variable tensor. Based on its polynomial representation, an effective stress characterized by the internal variable is defined. Then, a simple expression of the internal state is postulated which accounts for a combined state of isotropic and anisotropic hardenings. The evolutional rate of the internal state is prescribed in terms of the effective inelastic strain rate which is defined analogous to the effective stress. Finally, the model behavior is demonstrated in the case of combined creep and plasticity.