DISLOCATION MULTIPLICATION IN FCC METALS AT PRESENCE OF HIGH-SHEAR STRESS

A new model of shock-induced stress relaxation based on multiplication and motion of partial dislocations bounding the stacking fault is suggested. Shock-generated high shear stress leads to stretching of lateral branches of a bowed out dislocation segment (half-loop) followed by collapse of those branches. The result of the collapse is the forming of the ''fresh'' partial dislocation loop bounding the stacking fault area and ''initial'' dislocation half-loop, both being capable of the next multiplication act. After every collapse time interval Delta T the process leads to the doubling of both the dislocation concentration and stacking faults total area. The energy dissipation rate behind the shock front increases exponentially, dW/dt approximate to 2(t/Delta T), but it should be limited as soon as the cross-slip of the ''fresh'' loops will be impeded and the loops doubling will be stopped. An explanation of twinning and shear bands formation in shocked material is proposed.