A new approach to the description of the plastic deformation processes has been developed. The doslocation ensemble is examined as a certain population, an evolution of which is defined by a multiplication of dislocations as well as their transformations, such processes occurring on the background of elastic stress fields created by the dislocaton ensemble itself. The non-linear equation for the change of dislocation density with time due to the operation of sources is proposed. It is analogous to the well-known equation for the population growth, but it contains specific values, such as critical stress and characteristic time required to switch-on the dislocation sources. It is with this last value that is connected the possibility of a fast or slow mutual adjustment of the dislocation density and external stress. On this basis, an explanation was proposed for the non-monotonous stress-strain dependence observed in certain cases at the transition from elastic to plastic deformation. An analysis of the deformation curves at various values of the system parameters was performed with an account of the dislocation transformations in titanium aluminides.
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