Localized deformation and fracture of polycrystals at mesolevel

Abstract

Recent experiments have shown that shear band formation and rotation of structural elements at the mesolevel are fundamental to the development of plastic deformation and fracture of solids. Attention should be focused on a mesovolume of deformed material because the local stress and strain differ from those averaged at the macroscale. The discrete nature of the microshears and restricted deformation of the mesofragments should be accounted for. Rotation of the different mesofragments being parts of a grain, grains, grain conglomerates, etc., plays an important role in plasticity. Moreover, knowledge of the local parameters is needed for developing plasticity theories and fracture criteria. Models have been proposed within the framework of the physical mesomechanics. They take into account structural elements of different scales for simulating shear band nucleation and propagation in addition to mesofragment rotations. Calculations have been made for different mesovolumes under dynamic loading. In this work, a new criterion of plasticity is considered at the mesolevel. It accounts for the nucleation of plastic shears at the surfaces and interaction of structural elements. The numerical technique combines both the continuum mechanics approach and discrete cellular automata method.