Simulation of plastic deformation initiation in crystal materials under dynamic loading

Abstract

In the last decade the scope of experimental and theoretical investigations into the initial stage of plastic deformation in solids has been expanded significantly. Nevertheless its atomistic mechanisms are as yet imperfectly understood. One of the major open questions concerns the existence of proto-defects, i.e. local structural distortions which provide the basis for the formation of conventional structural defects — carriers of plastic deformation. The investigations were applied to crystallines with different boundary types (free surfaces and grain boundaries) and different type of crystal lattice. The influence of loading intensity and deformation scheme was studied. Simulation was performed for various temperatures from 50 K to 500 K. It has been demonstrated that there is a certain threshold value of strain at which zones with local structural changes grow almost abruptly. A detailed analysis of atomic displacements at the stage of nucleation of local structural distortions (protodefects) has revealed that their formation is related with specific rearrangement in the first and second coordination spheres of one of the atoms. It is realized in the conditions of local expansion of the atomic volume.