Alternative General Disciplines for Plastic Flow, New Phenomenological and Crystal-Plasticity Models Applicable from Quasi-Static to Extreme High Strain Rate Loadings

Abstract

Traditional plasticity theories, either time-dependent phenomenological plasticity or crystal plasticity, have been discovered to have some inconsistency problems under dynamic loadings. Such discrepancy is essentially arisen from the fundamental postulation that only internal states of the material determine the additive plastic strain rate tensor. However, in logical, except for internal states, the external loading conditions are also close-relevant factors. In this article, we modified the fundamental postulation, and proposed a set of general disciplines for the determination of material plastic flow, which is based on the view that the plastic flow is determined by both internal states and external loading conditions, and is satisfied with the principle of maximal increment of entropy. Then, we proposed a crystal plasticity model and a phenomenological model based on the new disciplines. A few shock experiments on single-crystal zirconium were conducted to validate the new disciplines and models, including two shots of poly-crystal OFHC copper impacting and one shot of high-energy laser ablation. It was demonstrated that our disciplines and models are well-matched and applicable even up to the strain rate at the order of 109s-1.