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Residual stresses have significant effect on the crack-tip constraint [1, 2], which can further influence the fracture toughness of materials. Understanding how residual stresses influence the fracture behavior becomes more and more important when high strength steels are increasingly utilized in offshore industry.Panontin and Hill [3] investigated the effect of residual stresses on the micromechanics of fracture initiation and found that the residual stress reduced the brittle fracture toughness significantly. They also pointed out that the reduction of the brittle fracture toughness is due to the change of the crack-tip constraint conditions caused by the residual stresses. Hill and Panontin [4] employed the RKR [5] failure theory to predict the brittle fracture for three-point bending samples with and without residual stresses. Their results showed that the residual stress affects both the crack driving force and the crack-tip constraint, and together these effects decrease the fracture toughness.