2020 Volume 76 Issue 2 Pages I_193-I_204
In this study, a novel implicit stress-update algorithm of the extended subloading surface model, a class of unconventional plasticity model, incorporating the nonhardening strain region is developed to improve the predictive capability for cyclic loading property of metallic materials. Ohno (1982; J. Appl. Mech., ASME) proposed a sophisticated plasticity model equipped with nonhardening strain region in order to reproduce the stagnation of isotropic hardening resulting in transient stabilization of hysteresis loop during cyclic loading with a fixed strain amplitude. In the plastic strain space, when the plastic strain moves inside the nonhardening strain region, the region does not expand, and hence, isotropic hardening does not proceed,while only kinematic hardening proceeds. When the plastic strain moves outside of the nonhardening strain region, isotropic hardening proceeds being accompanied by expansion of the region. As a specific prototype model, von Mises plasticity model is reformulated based on the hyperelastic constitutive equations within the framework of infinitesimal deformation theory. A numerical algorithm for stress calculation using return mapping is developed, in which we devise a novel scheme consisting of hardening/nonhardening judgment and nested iteration to update variables associated with the nonhardening strain region. Numerical examples of cyclic loading demonstrate that the developed constitutive model properly reproduces the stabilization of hysteresis loop. The iteration solution process exhibits satisfactory convergent property, which validates the numerical scheme developed in this study.
