Fatigue crack growth in magnesium single crystals under cyclic loading: Molecular dynamics simulation

The fatigue crack propagation behavior of magnesium single crystal was analyzed using molecular dynamics simulation. The inter-atomic potential used in this investigation is Embedded Atom Method (EAM) potentials. The studies of the mechanism of fatigue crack growth in different crystal orientation were performed using Center Crack (CC) specimens while Edge Crack (EC) specimens were employed to investigate the effects of strain rate and temperature. For CC specimen, the periodic boundary conditions were assigned in the x and z direction, while for EC specimen, only z direction was allowed periodic boundary conditions. In order to study the orientation dependence of fatigue crack growth mechanism, 10 crystal orientations of initial crack were analyzed and the simulation results reveal that the fatigue crack growth rate and the crack path vary significantly with the crystallographic orientations of initial crack. The growth rate of orientation D is the highest and the resistance of fatigue crack growth of orientation B is the highest. The analysis of the influences of strain rate was carried out on the orientation F and the results revealed that the growth rate of fatigue crack decreasing with increasing strain rate. The fatigue crack growth rates of different orientation decrease with increasing temperature.