Molecular dynamics simulation of microcrack healing in aluminium

The molecular dynamics method is used to simulate microcrack healing during heating or under compressive stress. A center microcrack in an iii crystal could be sealed under a critical compressive stress or by heating it over a critical temperature. During microcrack healing, dislocation and vacancy are generated and moved, and sometimes twin appears. The critical temperatu re necessary for microcrack healing depends upon the orientation of the cra ck plane. For example, thp critical temperature of the crack along the (111 ) plane is the lowest. When there are pre-existing dislocations around the microcrack, the critical temperature necessary for microcrack healing will decrease. The energy condition for crack healing is sigma (2)pia(1 - nu (2) )/E + partial derivativeU(T)/partial derivativeA greater than or equal to2 gamma + gamma (p), where sigma is the applied compressive stress, a the len gth uf the crack, nu the Poisson's ratio, E the Young's modulus, U-T heat e nergy driving crack healing, A the area of the crack, gamma the surface ene rgy, and gamma (p) the plastic deformation work. Pre-existing dislocations can reduce gamma (p).