Influence of residual stress on apparent fracture toughness of pipeline under different constraints

Taking the cracked pipeline as the research object, different preloads were applied on the cross section of the pipeline to produce different stresses at the crack tip, and these stresses were introduced into the pipeline as the residual stresses by restart method. And then, the apparent fracture toughness of pipeline under different constraints considering residual stress, and the interaction between residual stress and constraint were systematically studied. The results showed that the residual stress had a certain promoting effect on the improvement of the apparent fracture toughness of the pipeline. Compared with the pipeline with low constraint, the apparent fracture toughness of the pipeline with a high constraint was more sensitive to the change of residual stress, it was mainly related to the Mises stress at the crack tip and the triaxle principal stress.