Ductile Crack Extension Resistance of Carbon Steel STS 42

Fracture toughness tests were conducted on 2 CT plane size specimens (thickness t = 20 mm), prepared from carbon steel pipe STS 42 with circumferential TIG weldment (20 B, sch. 100), in ambient air. Some approximate expressions for J-Δa data are discussed from the view point of applicability to fracture analysis. The following conclusions are obtained. (1) Weld metal possesses higher resistance to stable crack growth and to unstable transition than base metal does. (2) The transition condition, from stable to unstable ductile crack growth, depends on the type of approximate expression of the J-R curve.