Dislocation-based plasticity model by analysis of discrete dislocation dynamics

Abstract

Plasticity accompanied by dislocation motion is the essential property of metals. A large number of crystal plasticity models have been developed to predict the mechanical response in the work hardening regime while little attention is paid to pre-yield behavior. In this work, we propose a novel model both pre-yield and post-yield from a discrete dislocation dynamics (DDD) database of 55 DDD realizations. Dislocation density and Frank-Read source height are chosen as microstructural state variables to represent the material state. Flow rule and dislocation multiplication model are in good agreement with DDD results. Discrepancies result from the onset of micro-plasticity in pre-yield. The axial stress-strain response predicted by the novel model is consistent with current DDD data. The evolution equation of source height fails in capturing the evolution in accordance with DDD data, which originates from the inaccuracy brought by indirect extraction of source shape from DDD dislocation networks. Future research recommendations include enlargement of the database, extraction of source shape in situ, and evolution equations for link-based microstructural variables.