Fatigue behavior of electrically resistance welded (ERW) line pipes with a gouge in a dent was experimentally investigated. After denting and machining a gouge, fluctuating internal pressure was applied to line pipes. The fatigue behavior differed above and below the threshold Q(Qth), as a function of defect size and fracture toughness. When Q < Qth, ductile crack growth was observed with a consequent decrease in fatigue life. On the contrary, fatigue crack growth was observed when Q ≧ Qth. Fatigue life was predictable with an experimentally based power law equation incorporating dent depth, gouge depth, and hoop stress amplitude when Q ≧ Qth.

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