Wedge indentation of single crystalline monazite: A numerical investigation

Abstract

A numerical investigation of wedge indentation, with a nearly flat indenter, into a monazite (LaPO4) single crystal is carried out to obtain the asymptotic field solution associated with the moving contact point singularities. The crystal orientation is such that plane strain conditions prevail, under the assumption of small scale yielding, as out-of-plane deformations are eliminated due to out-of-plane mirror symmetry of the crystal, specimen and loading state. The plastic deformation in such a 2D study can be described in terms of effective in-plane slip systems comprised of crystallographic slip systems with equal and opposite out-of-plane deformation and rotation. The numerical simulations are conducted within a framework specialized for self-similar problems and adopts a visco-plastic single crystal material model. The detailed numerical investigation of the monazite single crystal reveals that the effective slip systems lead to a non-symmetric in-plane deformation field, which is consistent with the absence of in-plane mirror symmetries of the crystal. Interestingly, the non-symmetric deformation field results in one contact point singularity travelling at a greater speed than the other. The deformation near the moving contact point singularities are found to be divided into two angular sectors separated by a boundary of glide shear type. The slip rates on the individual systems reveal that one slip system dominates at both contact points, whereas the other slip system shows negligible activity. Thus, only one slip system gives rise to a discontinuity in the slip rate field.