Methods and results of studying the Portevin - Le Chatelier effect: physically-oriented continuous and multilevel models

The effects of intermittent plasticity, despite almost 200 years of history since its discovery, are still intensively studied by mechanics, materials scientists, and technologists processing metals and alloys by plastic deformation. With the development of experimental methods and instrumentation, more and more new mechanisms are being discovered that are responsible for the violation of the monotonicity of the response (stresses) under monotonic effects (growth of strains). To describe these effects, constitutive models (constitutive relations) based on various (macrophenomenological, thermodynamic, structural-mechanical, physical) approaches have been proposed and continue to be developed. Despite the variety of reasons for the emergence of discontinuous plasticity, it is generally recognized that in order to build correct constitutive models, it is necessary to analyze the processes that occur during inelastic deformation at the meso- and microlevels, and to describe the evolving structure of materials at various scale levels. Thus the use of physically oriented models is the most promising area of studies for the formulation of constitutive relations. The proposed article provides a brief overview of works constructing physically-oriented constitutive models suitable for studying the effects of discontinuous plasticity. The first part of the review presents models based mainly on the phenomenological approach to the formulation of a set of equations for studying the evolution of the defect structure of single- and polycrystalline alloys, most of which use the continuum description. When creating physically-oriented models, special attention is paid to the consideration of the mutual influence of defects of various natures, including the interaction of impurity atoms with dislocations. The second part of the review considers works based on the introduction of internal variables, a multilevel physically-oriented approach. Unfortunately, second-class models are currently very limited; nevertheless, the authors consider them the most promising for constructing constitutive models that adequately describe the effects of discontinuous plasticity.