The motion of a dislocation in Aluminum is considered at room temperature with allowance for the Peierls relief. This study has been accomplished using the methods of mathematical modeling. It was shown by means of numerical experiment that the free path length of dislocation depends on the frequency of applied external elastic field. Here a hardening of crystal took place due to the dynamical losses. In the presence of resonant frequency external alternating elastic field the gradient of hardening curve growth, and therefore, the yield strength, is reduced. It was shown that the regularities of large-scale processes occurring in deformable body may be clarified by means of analyzing the micro processes.