On the sweeping mechanism of dipolar dislocation loops under fatigue conditions

Dislocation dynamics simulations of the interaction between prismatic dipolar loops and a glide screw dislocation are presented. As a result of stress gradients generated by the glide dislocation, dipolar loops execute drift motion along their glide cylinders. Simulations of the combined motion of two dipolar loops in the stress field of a glide dislocation clearly show that inter-loop forces are essential in determining their spatial trajectories. Under cyclic stress conditions, it is shown that same-type dipolar loops drift monotonically in the same direction, and that their spatial clustering is largely determined by strong inter-dipolar binding forces. The investigated sweeping mechanism is discussed in terms of the prerequisites for the formation of persistent slip bands under fatigue loading conditions.