ON PHYSICAL FOUNDATIONS OF PLASTICITY

Complexity of plastic response is caused by the fact that plastically deformed solids are composites with a changing structure. At the mesos cale (mu m) a pattern of high and low dislocation density regions is s pontaneously formed. The evolution of the composite structures is trea ted as a consequence of the structuralization process governed by four types of mechanisms: (i) the overproduction of dislocations, (ii) the screening of their elastic fields, (iii) the formation of dipolar dis location patterns, (iv) the instability transition leading to the form ation of subgrain boundaries, dislocation grids, microshear bands, or persistent slip bands. The proposed theoretical model consists of the balance law for the dislocation density of stored dislocations, the re lations which determine the average shape of glide dislocations, and t he continuum mechanics equations for stress and strain. To demonstrate the capacity of the model some available solutions simulating the mes oscale structure evolution are briefly reviewed.