Analysis of Nucleation of Dislocation Loops from Stressed Surfaces Based on the Peierls-Nabarro Dislocation Model

Abstract

ABSTRACTNucleation of dislocation loops from stressed crystal surfaces is analyzed based on a variational boundary integral method in the Peierls-Nabarro framework. The stress dependent activation energies required to activate dislocation loops from their stable to unstable saddle point configurations are determined. Compared to previous analyses of this problem based on continuum elastic dislocation theory, the presented analysis provides more definitive solutions because it eliminates the uncertain core cutoff parameter by allowing for the existence of an extended dislocation core as the embryonic dislocation evolves. Moreover, the shape of the dislocation loop is solved by the variational principle instead of assumed to be semicircular as in previous analyses based on continuum elastic dislocation theory. It is noteworthy that the presented methodology can be readily used to study effects of surface inhomogeneities such as cracks and steps on dislocation nucleation.