Modelling screw dislocation mobility in the bulk and in the vicinity of crack tips using a Peierls-Nabarro approach

Abstract

Double kink generation in three-fold screw dislocations in bcc crystals is studied within the framework of the generalised Peierls-Nabarro (P-N) model in which the partial dislocations are described by non-singular displacement fields. The kink geometry is modelled by dividing the dislocation into elemental slabs, each of which is assumed to have its own 2-D displacement field calculated using the P-N model. The apparent activation energy is predicted to vary with stress in an approximately parabolic manner, and is found to be in good agreement with experimental findings for a wide range of BCC metals. The interaction between a three-fold screw dislocation core and a mode III crack tip is also investigated. The results suggest that the dislocation mobility is sufficiently eased off in front of a crack tip. © 2000 Trans Tech Publications.