Three dimensional dislocation-loop emission criterion for void growth of ductile metals

摘要

Dislocation emission has been regarded as an important mechanism of void growth during the failure process of ductile metals. Existing criteria for dislocation emission on the void surface are based on the elastic plane strain analysis of the 2-D configuration, namely emission of the edge dislocation from the cylindrical void surface. Based on a more realistic 3-D configuration in which the prismatic dislocation loop (PDL) is emitted from the spherical void, we propose a criterion to predict the far-field stress required for PDL emission and the corresponding emission angle from the void surface. The present criterion is further generalized to porous media by the micromechanical analysis. The influence of the stress triaxiality is investigated in our 3-D criterion, it is demonstrated that the stress triaxiality is an important factor for PDL emission while it is quite difficult to be studied in 2-D criteria. Furthermore, the proposed model reveals the dependence of PDL emission on geometric parameters and the porosity, which agrees with the molecular dynamic (MD) simulations.