Interaction between cracks and dislocations in body-centered cubic crystals under mixed loads

Abstract

A dislocation emission model for body-centered cubic (BCC) crystals with micro-scale grain size is described. When the critical condition of dislocation emission is reached, dislocations will be emitted from the crack tips and move along the slip planes at the crack tip. If the stress concentration at the crack tip is large enough or the distance between the crack tip and the grain boundary is small, the dislocation will move along the slip plane and accumulate at the grain boundary. Three BCC metals have been used to calculate the dislocation emission in this article. The results show the lattice friction has a significant effect on dislocation emission and distribution. Dislocations that emitted from crack tip have a shielding effect on stress concentration near the crack tip. The shielding effect of the dislocations on plane (110) is larger than that of the dislocations on plane (100), resulting in a more easy propagation of the crack in plane (100).