Elasto-viscoplastic constitutive equations for polycrystalline fcc materials at low homologous temperatures

A kinetic equation for the shearing rates on slip systems based on the thermally activated theory for plastic flow is formulated, and an evolution equation for slip system deformation resistances is developed. These constitutive functions are incorporated in a model for elasto-viscoplasticity of face-centered-cubic (f.c.c.) single crystals. For polycrystalline materials, the classical Taylor assumption is invoked. This constitutive model has been implemented in a finite element program to facilitate simulations of quasi-static as well as dynamic non-homogeneous deformations of polycrystalline f.c.c. materials. The material parameters in the model have been calibrated against existing experimental data for aluminum. The improved physical description for plastic flow and hardening evolution, enables the constitutive model to reproduce the macroscopic stress-strain response in aluminum up to large strains (approximate to 100%), for a wide range of strain-rates (10(-3)-10(2) s(-1)), and a wide range of low homologous temperatures (77-298 K). Important strain-rate-history and temperature-history effects on the strain-hardening behavior of aluminum are shown to be well represented by the constitutive model. (C) 2001 Elsevier Science Ltd. All rights reserved.