The mean elastic interaction between randomly distributed transient sub-critical shear loops of the same sign, formed in the presence of an applied shear stress, was the so-

called image stress. This stress was proportional to the volume density of loops and has the same sign as the applied stress. The image stress promotes the cooperative nucleation of shear loops, and led to an instability in which the number of loops and the image stress increased rapidly, leading to the generation of stable expanding loops. The critical stress at which the instability was predicted was relatively high.

Cooperative Nucleation of Shear Dislocation Loops. Y.Q.Sun, P.M.Hazzledine, P.B.Hirsch: Physical Review Letters, 2002, 88[6], 065503 (4pp)