A Description of History Dependent Plastic Flow Behavior of Anisotropic Metals

An analytical model that describes the loading-history-dependent hardening behavior of anisotropic metals is presented. The proposed hardening model assumes that the rate of change of primary material variables is dependent upon their limiting values, similar to the use of saturation back stress proposed by Rice. The primary material variables are defined by an anisotropic yield function characterizing “distortion,” “translation,” and “size” of the current yield surface. All the material parameters in the model have been obtained from experiments made with hourglass-type specimens loaded in tension and compression along different principal directions of anisotropy and under monotonic and load reversing conditions. Depending on the details of strain hardening characteristics, a set of secondary material variables was defined to describe the behavior at large plastic strains. Results of numerical analysis indicated that the simplified model based on the measured material parameters is capable of simulating the loading-history-dependent hardening behavior of anisotropic metals under uniaxial loading conditions. Sample simulations with Zircaloy-2 were compared with experimental data, and isotropic behavior was demonstrated with 304 stainless steel.