Numerical Simulation and Experimental Study of Plastic Strain Localization under the Dynamic Loading of Specimens in Conditions Close to a Pure Shear

Mechanisms of plastic strain localization under the dynamic loading of specially shaped specimens made of the AMg6 aluminum alloy and intended for tests under conditions close to a pure shear on a split Hopkinson–Kolsky pressure bar are studied theoretically and experimentally. The mechanisms of plastic flow instability are related to collective effects in the ensemble of microdefects in spatially localized regions visualized in situ using a CEDIP Silver 450M high-speed infrared camera. The calculation corresponding to the experimental loading scheme is implemented using wide range constitutive equations reflecting the dependence of structural relaxation mechanisms—manifestation of the collective behavior of microdefects—on the evolution of the localized flow shear instability. Microstructure analysis of deformed specimens included the study of the spatial relief (porosity) scaling by the data of a NewView-5010 microscope-interferometer in regions of plastic strain localization. An increase in the structural scaling exponent (Hurst exponent) reflected the degree of the multiscale correlated behavior of defects and the porosity induced by them in regions of localized plasticity. Infrared scanning of the strain localization region and numerical simulation followed by an estimate of the defect structure corroborated the hypothesis that effects of thermal softening do not play a decisive role in the process of plastic shear localization in the tested material under the considered loading regimes. A new, one of the possible ones, mechanism of plastic strain localization under dynamic loading is justified. It is caused by the multiscale collective behavior of mesodefects—structure-scaling transitions—and establishes the stadiality of the localized shear evolution.