Fatigue Crack Propagation Analysis of X60 Pipeline Steel Pipelines with Defects

It is impossible to keep pipelines free from defects in the manufacturing, installation and servicing processes. In this paper, pre-tension deformation is used to imitate the defects of the part of material and the electric method is used to measure the distance of the fatigue crack. Experimental investigations were carried out on the fatigue crack propagation characteristics of X60 pipeline steel after different degrees of pre-tension deformation Test results show that the fatigue crack propagation was augmented with the pre-tension deformation increase, especially the crack propagation at the near threshold section. The results of quantitative analysis show, the pre-tension deformation reduced the fatigue crack propagation threshold and increased the crack propagation coefficient; consequently the fatigue performance of the part of mechanical damnification was degenerate.