Ductile fracture strength of nickel-based alloy plates with a surface flaw

Abstract

Limit-load analysis is applied to fracture analyses of flawed components made of materials with high ductility in the JSME code for inservice inspection for nuclear power plant. However, the applicability of limit-load analysis to Ni-based alloys has not yet been clarified. Furthermore, flow-stress level for Ni-based alloy has not been verified by experiments. To clarify applicability of limit-load analysis and actual flow-stress level for Ni-based alloys, the ductile fracture tests were conducted. The specimens were made from both base metal and welded joint plates with a surface flaw or a through-wall flaw. In specimens with a shallow flaw, the tensile load increased with the tip of flaw blunting, and the load dropped down at the penetration of ductile crack initiated at the blunted flaw tip. In the specimens with a deep flaw, the tensile load increased due to the blunting of the flaw tip at the width direction after penetration of ductile crack. The load dropped down at the beginning of ductile crack growth in the width direction. In all cases, the net stress at the maximum tensile load was higher than 2.7 Sm and the average of yield stress and ultimate strength.