A Viscoplastic Constitutive Model Describing Cyclic Hardening/Softening Behavior Under Proportional and Nonproportional Loading Conditions

Abstract

The present paper is concerned with the formulation of a viscoplastic constitutive model describing both cyclic hardening and cyclic softening under proportional and nonproportional loading conditions. The history effects of cyclic hardening and softening are also incorporated into the model. We first formulate a parameter and the relevant evolutional equation describing the amplitude dependence of cyclic hardening. Then by using the parameter together with the nonproportionality parameter proposed by Tanaka et al., the evolutional equations of the isotropic hardening variable are examined in detail. The proposed model is established by incorporating these equations into a Chaboche model. To evaluate the adequacy and the accuracy of the model, the experimental results by Bennallal et al. and those by Tanaka et al. are simulated. The predicted results show that the proposed model can describe the cyclic hardening/softening behavior of various complex proportional and nonproportional cycles with amplitude variations and path changes.