Low Cycle Fatigue Evaluation of Duplex Stainless Steel with Material Degradation Effect Under Torsional Load

Abstract

Monotonic torsional and pure torsional low cycle fatigue (LCF) tests with artificial degradation were performed on duplex stainless steel (CF8M). CF8M is used in pipes and valves in a nuclear reactor coolant system. It was aged at 430°C for 3600 hrs. Through the monotonic and LCF tests, it is found that mechanical properties (i.e., yield strength, strain hardening exponent, strength coefficient etc.) are increased and fatigue life (Nf) is decreased with degradation of material. The relationship between shear strain amplitude (γa) and Nf was proposed.