Safe Operation of Welded Structure with Cracks at Elevated Temperature

Abstract

The fatigue crack growth rate parameters and conditions for abrupt fracture of thick joint in steel at room and operating temperature were analysed. Fatigue cracks generated from sharp weld defects are initial cracks that grow through either the weld joint region or the base metal in accordance with Paris law. Service life of a welded structure depends on position and orientation of the existing sharp weld defect. Different pre-cracked specimens were used in this experimental investigation. They were cut from the base and weld metals and heat-affected zone. In comparison with the base metal, weld joint region showed higher crack growth rate at operating and room temperatures. Fatigue crack growth rate was higher at operating temperature irrespective of the position. Reliability of structure with initial longitudinal cracks positioned in the heat-affected zone was lower than with initial transversal cracks located in the weld metal.