Effects of Prestrain on Fracture Toughness and Fatigue-Crack Growth of Line Pipe Steels

Crack-tip-opening displacement (CTOD) and fatigue-crack growth tests were conducted for several line pipe steels with uniaxial tensile or compressive prestrain, e pr . Critical CTOD decreased with increasing |e pr |. The reduction of critical CTOD due to prestrain was dependent on the ductile-brittle transition temperature of the steels without prestrain. A few percent of e pr induced the ductile-brittle transition for the steels with a higher transition temperature. The compressive e pr had larger effects on both reduction of critical CTOD and strain induced ductile-brittle transition than the tensile e pr . Only the high compressive e pr accelerated both fatigue crack initiation and growth, and no obvious effect of the tensile e pr on the fatigue properties was observed.