Single void morphological and grain-boundary effects on overall failure in F.C.C. polycrystalline systems

An investigation of how dislocation-density interactions, such as impedance, transmission, and absorption, with grain-boundaries (GBs) affect and control void growth and porosity evolution in F.C.C. aggregates has been conducted. A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolution of mobile and immobile dislocation-densities, a new internal porosity formulation for microvoid nucleation and growth, and specialized computational schemes have been developed to understand and quantify the interrelated effects of GB orientation, mobile and immobile dislocation-density evolution, and dislocation-density transmission and blockage on microvoid nucleation and growth. The effects of GB structure and orientation on ductile failure have been accounted for by the development of GB interfacial kinematic conditions that account for dislocation-density interactions with GBs, such as full and partial transmission, impedance, blockage, and absorption. Pile-ups and transmission regions are identified and monitored as the deformation and failure evolves. It is shown that mobile dislocation-density saturation, void size and shape, and dislocation-density interactions within the grains and the GBs are the interrelated triggering mechanisms that lead to porosity nucleation, growth, and localization.