Studies of crack growth and propagation of single-crystal nickel by molecular dynamics

Abstract

Abstract The crack growth and propagation of pre-cracked single-crystal nickel under mode I loading conditions are investigated by molecular dynamics simulation based on the many-body tight-binding potential. The effects of temperature, loading rate, and orientations are evaluated in terms of atomic trajectories, von Mises stress, and a centrosymmetry parameter. Simulation results clearly show that partial dislocations begin to slip at the crack tip and propagate along the close-packed (1 1 1) plane until fracture. There are different modes of crack propagation between finite or infinite length in y direction. A brittle-to-ductile transition occurs between temperatures of 50 and 700 K, with the brittle fracture response more obvious at lower temperature. The critical stress increases with increasing strain rate and decreasing temperature. The magnitude of critical stress is σc〈111〉 > σc〈100〉 > σc〈110〉 for difference direction Ni nanoribbons, indicating that the critical stress is strongly dependent on the crystallographic direction.