An energy approach to account for crack initiation in nanocrystalline materials

An energy balance method to calculate the initiation of crack at triple junctions in nanocrystalline materials with the finest grains is developed. In the steady state of crack initiation, work done by an applied stress is considered to be dissipated as heat by specific rotational deformation, grain boundary sliding and diffusion. The stress field at crack tips, the energies of rotational deformation, grain boundary sliding and grain boundary diffusion are calculated. The analysis demonstrates that the existence of finest grains will lead to enhanced local fracture toughness.