DISLOCATION MULTIPLICATION BEHIND THE SHOCK FRONT

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