The dynamics and energetics of intergranular crack growth along a flat grain boundary in Al was studied by a molecular-dynamics simulation model for crack propagation under steady-state conditions. Using the ability of the molecular-dynamics simulation to identify atoms involved in different atomistic mechanisms, it was possible to identify the energy contribution of different processes taking place during crack growth. The energy contributions were divided as: elastic energy—defined as the potential energy of the atoms in face-centered cubic crystallographic state; and plastically stored energy—the energy of stacking faults and twin boundaries; grain-boundary and surface energy. In addition, monitoring the amount of heat exchange with the molecular-dynamics thermostat gave the energy dissipated as heat in the system. The energetic analysis indicated that the majority of energy in a fast growing crack was dissipated as heat. This dissipation increased linearly at low speed, and faster than linear at speeds approaching 1/3 the Rayleigh wave speed when the crack tip became dynamically unstable producing periodic dislocation bursts until the crack was blunted.

Dynamics of Nanoscale Grain-Boundary Decohesion in Aluminum by Molecular-Dynamics Simulation. V.Yamakov, E.Saether, D.R.Phillips, E.H.Glaessgen: Journal of Materials Science, 2007, 42[5], 1466-76