On the theory of plasticity of amorphous and polycrystalline media

The study is devoted mainly to amorphous materials (including polycrystals) of different nature. It is shown that in the Marchenko - Misbach plasticity model, in the case of stretching or compression in the material volume, there appears an additional condition concerning the positive definiteness of the dissipative part of the full Lagrangian. As a result of such an effect, inelastic density changes can be observed in the continuum, which in turn can be related to the displacement of vacancy-like defects and their redistribution in the material structure during its deformation. Changes in the equations of the model arising as a result of possible healing of existing structural imperfections in the investigated volume or microscopic accumulation of point defects in local regions of the material are noted. A correction to the Maxwell equation for viscoelastic bodies is obtained. The question of calculating internal friction on the basis of a quadratic form modelling the plastic behavior of the material is touched upon. The nature of the rheological coefficient h of the model is revealed for the mechanism of micro creep in polycrystals. On this basis, a formula for the high-temperature background of internal friction controlled by the diffusion of impurity atoms is derived. The influence of grain size on the background of internal friction is established on the example of the study of Koble creep.

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