Cohesive Zone Modeling of Crack Propagation in FCC Single Crystals via Atomistic Simulations

This paper presents a cohesive zone model of fracture in Cu and Ni single crystals under tension, based on an atomistic analysis. The molecular-statics approach based on the conjugate-gradient method was used to investigate the crack-growth behavior at the atomic level. The fracture toughness was evaluated on the basis of energy considerations, and the cohesive traction was calculated using the J integral and the atomic-scale separation in the cohesive zone. The cohesive traction and separation curves obtained using computational data from atomistic simulations were compared with the exponential form of continuum mechanics. The results showed that the exponential form satisfactorily represented the cohesive zone properties of Cu. However, the cohesive traction and separation curves for Ni were found to deviate from the exponential form in the softening stage, owing to small-scale nonlinear features near the cohesive zone.