Molecular dynamics simulations of edge cracks in copper and aluminum single crystals

Edge cracks in Cu and Al single crystals under mode I loading conditions are investigated using molecular dynamics simulations. Calculations are carried out at 0 K and the embedded atom method potentials are adopted for (100)[011] edge crack systems. Five different crack lengths are employed to examine the effects of crack length on the fracture behavior of each material. The results show that Cu and Al exhibit different fracture mechanisms. The overall failure feature of Cu is brittle except for the shortest crack, for which the emission of dislocations preceded crack propagation. All the edge cracks in Al are extended through void nucleation and coalescence, and a zigzag fracture pattern is observed for each crack. Detailed analysis shows that the strikingly different fracture behavior of the two materials is the result of their different vacancy-formation energies and surface energies.