Dislocation nucleation from a penny-shaped crack

We present an analysis of dislocation nucleation from a penny-shaped crack of near-atomic dimensions under a simple shear stress. By using a variational boundary integral method in the Peierls-Nabarro framework, we have determined the saddle-point configurations of embryonic dislocation loops and their associated activation energies under stress levels up to the critical loading of athermal nucleation. The results show that the crack facilitates dislocation nucleation not only by stress concentration but also by supplying elastic strain energy. These new findings broaden the previous understanding of dislocation nucleation in crystalline materials and have significant implications on the development of mechanical models based on dislocation nucleation mechanisms in plastic deformation and fracture. (C) 2001 Elsevier Science B.V. All rights reserved.