Kinetics of Lüders deformation as an autowave process

Abstract

The authors investigated the nature and kinetics of the moving fronts of localized deformation, which are formed at the elastoplastic transition in materials with dislocation and martensitic micromechanisms of plastic deformation under active tension at different velocity. Digital image correlation was used for registration and quantitative specification of front movement. Attained results were discussed under synergistic approach. A deformed subject is considered as open and far-from-equilibrium system (active medium) containing distributed potential energy source stress, which are microconcentrators. In process of external influence these concentrators relax through microslip and cause a form change of the object itself. Each microconcentrator can be considered as an active element, it has two states: metastable elastically stressed and stable relaxed. In external influence, transition is possible only from the first state to the second. Such elements are characterized as trigger elements and active medium is characterized as a bistable medium. In bistable media, switching autowaves propagate. They represent moving boundaries, which separate metastable and stable states. Within this concept considered fronts of localized deformation can be interpreted as switching autowaves. The study showed that shape and kinetic parameters of fronts of localized deformation do not depend on chemical composition, structure and micromechanisms of deformation, it confirms their autowave nature. On the other hand, the kinetics of switching autowaves should be determined by characteristics of the external influence. Genuinely, velocity of localized deformation fronts increases with deformation velocity. It is found that dependence of these fronts on deformation velocity is non-linear parabolic with index less than one and equally for all examining materials.