Dislocation-density mechanisms for void interactions in crystalline materials

Dislocation-density based evolution formulations that are related to a heterogeneous microstructure and is representative of different crystalline interactions, have been developed and used to investigate the dominant dislocation density mechanisms for void interactions, localized plastic strains, failure paths and ligament damage in face centered cubic (f.c.c.) and body centered cubic (b.c.c.) crystalline materials. The balance between the generation and annihilation of dislocation-densities, through glissile and forest interactions at the slip system level is taken as the basis for the evolution of mobile and immobile dislocation densities. The evolution equations are coupled to a multiple-slip crystal plasticity formulation, and a framework is established that relates it to a general class of crystallographies and deformation modes. Specialized finite-element (FE) methodologies have then been used to characterize void interactions in f.c.c. and b.c.c. crystals at different orientations, to obtain a detailed understanding of the interrelated physical mechanisms that can result in ductile material failure. The results indicate that dislocation-density interaction mechanisms, such as dislocation-density junction formation and annihilation, can have significant effects on shear strain localization and void interaction behavior.