DISLOCATION MULTIPLICATION BEHIND THE SHOCK FRONT

A new model of fast operated dislocation source based on multiplication and motion of partial dislocations bounding the stacking fault is suggested, Stress-activated stretching of lateral branches of the partial dislocation bowed-out segment results in collapse of these brandies with subsequent restoration of the ''initial'' dislocation half-loop and generation of a ''fresh'' partial dislocation loop, both capable to produce the next multiplication act. The multiplication results in the exponential increase of both dislocations and stacking faults concentration and is accompanied with the plastic deformation having a strain rate d epsilon/dt similar to 2(t/Delta T). The characteristic time of the process, Delta T, ranges from 10(-9) to 10(-10) s. The model explains the variations of x-ray diffraction pattern for the material undergoing shock compression, the shock-induced formation of twins, and shear bands and pre-fracture voids nucleation in the rarefaction wave. (C) 1995 American Institute of Physics.