Cyclic deformation of 316L stainless steel and constitutive modeling under non-proportional variable loading path

In order to investigate the effect of non-proportional loading history on cyclic deformation of 316L stainless steel, a series of multiaxial cyclic experiments with variable loading path are conducted at room temperature. It is found that the materials exhibit cyclic hardening at initial stage, followed by a long period of cyclic softening. Significant cyclic softening is observed when non-proportional loading path changes into proportional loading path and the rate of cyclic softening is related to non-proportional loading history. A visco-plasticity constitutive model based on Ohno-Wang kinematic hardening rule and Marquis isotropic hardening rule is used to characterize non-proportional cyclic behavior. Simulation results agree with experiments very well in terms of cyclic hardening effects. However, this model is found to be less effective in simulating cyclic softening effect, especially considering the influence of non-proportional loading history. A modified isotropic hardening model is thus proposed to simulate the cyclic softening behavior of 316L stainless steel by introducing a memory non-proportionality and qualifying a partial recoverable softening term of isotropic hardening rule. Simulation results of the proposed model agree much better with experimental values.