THE FRACTURE OF PERFECT CRYSTALS UNDER UNIAXIAL TENSION AT HIGH-TEMPERATURES

The fracture of a perfect crystal at a number of temperatures was investigated using molecular dynamics computer simulations in which a crystal was pulled apart at a constant strain rate. At low temperatures the overall stress increased to a maximum after which a series of distinct structural rearrangements each accompanied by a sharp reduction in stress were observed. The material maintained a high degree of crystallinity. At higher temperatures structural rearrangement was more continuous and the material in the region of fracture was more disordered and somewhat liquid-like. At all temperatures failure occurred through the formation of voids which subsequently fused to leave bridges between the nascent surfaces. These bridges stretched and finally broke. In another series of experiments the failure of a bridge which had formed spontaneously between two nearby surfaces was investigated under similar conditions of steadily increasing strain.