Continuum models which were based upon the Volterra and Peierls descriptions of a screw dislocation ahead of a mode-III crack were used to evaluate the critical loading condition for dislocation nucleation at the tip of a finite pre-blunted crack. Results were presented for various crack-tip root-radii, and for several crack-lengths. The effect of ledge formation at the crack tip was also evaluated. It was found that blunt cracks required a substantially higher load in order to induce dislocation nucleation, and this effect was augmented by including ledge formation in the analysis. It was also noted that short cracks required a reduced load for dislocation nucleation.

Effect of Finite Crack Length and Blunting on Dislocation Nucleation in Mode III. G.E.Beltz, L.L.Fischer: Philosophical Magazine A, 1999, 79[6], 1367-78