Abstract
The notions of plastic flow localization are outlined in the paper. It is shown that each type of localized plasticity pattern corresponds to a definite stage of deformation hardening. In the course of plastic flow development, a changeover in the types of localization patterns occurs. The types of localization patterns are limited in number: four pattern types are all that can be expected. A correspondence was set up between the emergent localization pattern and the respective flow stage. It is found that the localization patterns are manifestations of the autowave nature of plastic flow localization process, with each pattern type corresponding to a definite mode of autowave. In the course of plastic flow development, the following modes of autowaves will form in the following sequence: switching autowave → phase autowave → stationary dissipative structure → collapse of the autowave. Of particular interest are the phase autowave and the respective pattern observed. Propagation velocity, dispersion, and grain size dependence of wavelength were determined experimentally for the phase autowave. An elastic-plastic strain invariant was also introduced to relate the elastic and plastic properties of the deforming medium. It is found that the autowave characteristics follow directly from this invariant.
Highlights
Almost 200-year-old history of scientific research of the nature of plastic deformation in solids has not yet led to a complete understanding of this problem, but has elucidated limitations of mechanical and physical approaches to it
It is reasonable to assume that plastic flow at intermediate stages is macroscopically localized, and the lack of data is caused by disadvantages of experimental procedures used to record a plastic flow. These considerations have allowed us to hypothesize in [23] that macroscopic localization is a general distinguishing characteristic of plastic deformation process accompanying it from elastoplastic transition to failure
We will take into account that the presence of minimal size lmin that allows the implementation of such a process is characteristic for the autowaves in active media [9]
Summary
Almost 200-year-old history of scientific research of the nature of plastic deformation in solids has not yet led to a complete understanding of this problem, but has elucidated limitations of mechanical and physical approaches to it. In 1987 Seeger and Frank [8] proposed to consider plastic deformation as a process of structurization stating that “the use of thermodynamics of irreversible processes in open systems to a description of structurization during plastic deformation of crystal materials is quite promising on qualitative level.” This idea opened the way to application of synergetic methods in physics of plasticity [9,10,11,12]. Authors of [10] pointed out that “it is impossible to investigate so important and widespread mechanical phenomena as plasticity and fluidity on purely mechanical basis; instead, they should be considered as a part of the general subject area of nonlinear dynamic systems operating far from resonance” This explains current interest to the study of the plasticity problem within the framework of a more general problem of the behavior of a substance far from the equilibrium state. It is important that the microscopic aspect of the problem has been studied much better than the macroscopic one (for example, see [4,5,6,7,19,20,21])
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