Fig. 5

Activation of a Frank-Read source: A dislocation segment (black) pinned at both ends bows out under applied stress and creates a metastable half-loop. If the shear stress acting on the source is higher than a critical value, this semi-loop expands further and rotates around the pinned ends. The recombination of loop segments (red) then generates a new complete loop (blue) and restores the original configuration