- A new model of stress relaxation based on multiplication and motion of partial dislocations bounding the stacking fault is suggested. High shear stress values leads to stretching of lateral branches of 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 ΔT the process leads to the doubling of both the dislocation concentration and stacking faults total area. The time dependence of strain rate has the form de/dt∼2t/ΔT. An explanation of twinning, shear bands formation in shocked material and voids nucleation in rarefaction wave is proposed.