Constitutive modelling of nonproportional cyclic plasticity

A multiplicative hardening function and a unified evolution rule of the hardening factors are proposed. The hardening factorf ₁ is introduced to describe cyclic hardening with respect to the plastic strain range, whilef ₂ andf ₃ describe, respectively, instantaneous and hereditary additional hardening with respect to the nonproportionality of the plastic strain path. Two material dependent memory parametersa ₁ anda ₃ are introduced to keep the memory of the largest cyclic and additional hardening in the previous plastic deformation history. Different hardening mechanisms are then embedded into a thermomechanically consistent constitutive equation through the hardening function. The constitutive response of 304 and 316 stainless steels subjected to biaxial nonproportional cyclic loading is analyzed and the proposed model is critically verified by comparing the results with experimental results obtained by Tanaka et al., and Ohashi et al. The project supported by National Natural Science Foundation of China