Effect of finite crack length and blunting on dislocation nucleation in mode III

Abstract

Continuum models, based upon both the Volterra and the Peierls descriptions of a screw dislocation ahead of a mode III crack, are used to evaluate the critical loading for dislocation nucleation at the tip of a finite pre-blunted crack. Results are presented for various crack tip root radii, for several crack lengths. Moreover, the effect of ledge formation at the crack tip is evaluated. It is found that blunt cracks require a substantially larger load to induce dislocation nucleation, and this effect is amplified by including ledge formation in the analysis. It is also noted that short cracks require a reduced load for dislocation nucleation.