The Peierls stress for coupled dislocation partials near a free surface

Abstract

The effect of a free surface on the Peierls stress of a perfect dislocation, as well as on one of two dislocation partials under a free surface, has been accounted for by considering the Lubarda–Markenscoff variable-core dislocation model (VCM). The VCM dislocation smears the Burgers vector, while producing on the slip plane the Peierls–Nabarro sinusoidal relation between the stress and the slip discontinuity with a variable width. Here the core radius is allowed to depend on the distance to the free surface and the other partial. The Peierls stress is computed as a configurational force by accounting for all the energies and the image stresses to satisfy the traction-free boundary conditions. The results are applied to aluminum and copper and comparisons are made with atomistic calculations in the literature that show that the partials merge as they approach the free surface.

Keywords:

• Peierls stress
• free surface
• dislocation partials

Acknowledgments

Discussions with Dr. Vassilis Pontikis of the Atomic Energy Commission, Sacklay, France, throughout this research are gratefully acknowledged. This research was partially supported by the National Science Foundation grant CMS 0555280.