Unified mechanics theory based flow stress model for the rate-dependent behavior of bcc metals

A unified mechanics theory-based micromechanical model is developed to investigate the rate-dependent post-yield behavior of body-centered cubic(bcc) metals. The entropy generation mechanisms in bcc metals at a high strain rate are investigated. Thermodynamic State Index(TSI) in the unified mechanics theory is used to model the state of material as a function of entropy generation rate and then a dynamic yield stress function is derived. This work introduces a novel approach to modeling the internal heat generation and vacancy concentration change, at high strain rates. The derived rate-dependent model is validated for a wide range of strain rates, using the test data [1] for mild steel and compared with an irreversible thermodynamics-based model, available in the literature.