A two surface plasticity model for uniaxial ratchetting of cyclically stabilized material

Most cyclic plasticity models used in ratcheting simulations employ the rate-independent elastoplastic stress- strain relation of Chaboche-type nonlinear kinematic hardening models, which have a dynamic recovery term that takes into consideration the back stress tensor. For improved ratcheting response simulations of metals, this paper describes the use of a two surface plasticity model based on yield theory, following both the isotropic hardening rule (the yield surface expands uniformly as a bounding surface) and the kinematic hardening rule (the yield surface translates as an inner surface) in stress space. The two surface plasticity model was used to simulate the uniaxial ratcheting response of CS 1020 steel and the results were compared with those from the bilinear model and the nonlinear kinematic hardening model. Parameters used for the two surface plasticity model were optimized by a numerical algorithm on the basis of the characteristics of the initial range and stabilized range of CS 1020 steel. Finally, the results obtained with the two surface plasticity model were validated against experimentally measured maximum axial strain per cycle. It was found that the ratcheting response calculated with the two surface model had similar behavior to that seen in the experimental results and were much more accurate than the bilinear model and kinematic hardening model.