Effect of Pre-Deformation on Fatigue Crack Propagation Life of X60 Pipeline Steel

It is impossible to keep oil and gas pipeline free from defects in fabrication, installation and serving processes. Mechanical damage is one of import causes of pipeline failure accidents. Mechanical damage might endanger the safety of pipelines and even shorten their service life. Pre-tensile deformation of X60 steel is employed to experimentally simulate the influence of dents on the fatigue crack initiation life. The investigation indicates that the fatigue crack propagation life of pre-deformed X60 pipeline steel can be predicted using a previously proposed equation, i.e., da/dN = B(ΔK − ΔK_th)². The threshold ΔK_th for fatigue crack propagation decreases with the pre-deformation. The fatigue crack propagation coefficient B increases with the pre-deformation. So pre-deformation accelerates fatigue crack propagation and shortens fatigue life. The result is expected to be beneficial to the understanding of the effect of dents on the safety of pipelines and fatigue life prediction.