Localization in stainless steel using microstructural based viscoplastic model

The plastic deformation behavior of AL-6XN stainless steel over a wide range of strain rates and temperatures is modeled using a combination of recently developed constitutive models VA-BCC [3,52] and VA-FCC [4,53]. In this regard, a general consistent thermodynamic framework for thermo-viscoplastic deformations of steel alloys is presented here along with an appropriate definition of the dissipation potentials and free energy, after considering the strain rate effect imbedded through the flow stress and hardening definition. Moreover, the additive combination of thermal and athermal yield function definitions are utilized in this framework for dynamic deformations of AL-6XN stainless steel. Finite element simulations are performed by implementing the proposed viscoplasticity constitutive models in the commercial finite element program ABAQUS. Numerical implementation for a simple tensile problem is used for validating the material parameters of the AL-6XN under low and high strain rates and temperatures. The numerical results of the adiabatic true stress-true strain curves compare very well with the experimental data. The effectiveness of the present approach is also tested by studying strain localization in plane strain problems. Results indicate excellent performance of the present framework in describing the strain localization problem and in obtaining mesh-independent results.