Plastic distortion as a fundamental mechanism in the nonlinear mesomechanics of plastic deformation and fracture of solids
It is proposed to consider a deformed solid as consisting of two self-consistent functional subsystems, namely, a 3D crystalline subsystem and a 2D planar subsystem (surface layers and all internal interfaces). Primary plastic flow in the form of nonlinear waves of structural transformations occurs in the planar subsystem that is not translationally invariant and is in thermodynamic nonequilibrium. Planar nonlinear flows of nanoscale structural transformations lead to crystal structure curvature in the 3D subsystem where bifurcational interstitial structural states appear. They give rise to a fundamentally new effect, namely, plastic distortion under plastic deformation and fracture of solids which is not taken into account in both continuum and fracture mechanics. The paper substantiates the leading role of plastic distortion in the generation and crystallographic slip of dislocations, in plasticity, superplastic flow and plastic strain localization, and in the evolution of fracture mechanisms in solids.