Abstract
Elastoplastic constitutive theory with tangential plasticity, which is able to describe the inelastic strain rate due to the stress rate tangential to the plastic potential surface, has been proposed for prediction accuracy enhancement of the inelastic material behavior under non-proportional loading. This tangential plastic theory, however, is not able to apply to the prediction of cyclic softening behavior of metal subjected to the non-proportional cyclic stress histories with the stress amplitude less than the yield stress such as high cyclic fatigue problem. In this article, the proposed formulation of tangential plasticity theory is enhaced to more accurately describe the cyclic softening behavior of metal under non-proportional cyclic loading which has stress amplitude less than the yield stress. The numerical simulations with this enhanced tangential plasticity theory for the material behavior prediction under the non-proportional circular shaped stress path is conducted. The response characteristics of the enhanced tangential plasticity theory is revealed in detail according to comparing the simulation results with ones by the traditional plasticity theory and the conventional tangential plasticity theory.
