Micromechanical crystal plasticity back stress evolution within FCC dislocation substructure

Abstract

Experiments and theories have suggested the evolution of intragranular back stress is primarily dependent on the characteristics and development of dislocation substructure in face-centered cubic (FCC) metals and alloys. Despite this, continuum modeling of complex cyclic loading phenomena such as inelastic ratchet strain accumulation typically appeals to one of several phenomenological back stress forms with weak connections to physical mechanisms. In the current work, a micromechanically-based back stress evolution law is derived and implemented in a crystal plasticity framework for FCC metals that directly considers the evolution of dislocation substructure. The model is used in a case study of stainless steel 316L (SS316L), and good agreement is found with experiments on single- and poly-crystalline specimens subjected to monotonic, fully-reversed cyclic loading, and stress-controlled cyclic loading with mean stress. Ratcheting is attributed to dislocation substructure formation, dissolution, and stabilization within this physically-based framework.