Motion of two screw dislocations in a lattice

Abstract

In a simple model of a cubic lattice with piecewise linear and nearest-neighbor interactions a solution is obtained for the motion of two parallel screw dislocations of the same sign, under the action of a constant applied stress. The only damping mechanism considered is the emission of sound waves. The important parameters are the external strain s and the dislocation separation α. They are determined by energy balance and the boundary conditions imposed by the force law. The main result is the existence of multiple branches in the strain versus velocity curve, the lowest of which corresponds to an external strain less than that of a single dislocation. However, in the snapping bond model, two dislocations, as well as a single dislocation, cannot move at supersonic velocities without causing a breakdown of the crystal.