The dynamics of dislocation loops that were emitted at, or close to, crack tips in body-centered cubic metals were simulated. The 3-dimensional nature of the model permitted a first study to be made of the differences between dislocations of blunting and non-blunting type, in configurations where the emitted dislocation glide plane did not contain the crack lip. It was found that the blunting configuration introduced a localized shielding of the crack close to the dislocation sources. However, it was insufficient to yield large toughness increases. On the other hand, non-blunting geometries produced more efficient shielding of the crack, and were characterized by a slower extension of the plastic zone far from the crack tip. The model demonstrated the importance of the density of dislocation sources, along the crack tip, in determining the form of the brittle-to-ductile transition.

Three-Dimensional Simulation of Dislocation-Crack Interactions in Body-Centered Cubic Metals at the Mesoscopic Scale. B.Devincre, S.G.Roberts: Acta Materialia, 1996, 44[7], 2891-900