Abstract
Based on the stress fields of screw dislocation and cracks emanating from an elliptic hole, the elastic interaction of screw dislocations and a sharp crack emanating from a surface semi-elliptic hole is investigated. The stress field, stress intensity factor at the crack tip, strain energy, and image force on the dislocation are derived. When the crack is blunt, the stress intensity factor at the crack tip and strain energy arising from the lattice dislocation are reduced. In addition, the distance between the zero-force position of dislocation and the crack tip increases as crack blunts, so the plastic zone for crack blunting will be larger than that without crack blunting. The stress intensity factor for dislocation emission decreases when the crack is blunt. Therefore, a material with a blunt crack is more ductile than that with a sharp crack.