High-cycle fatigue behavior of type 316 stainless steel at 288 °C including mean stress effect

Establishment of a life evaluation method for structural components is essential for the rational operation and maintenance of light water reactor plants. High-cycle fatigue induced by mechanical vibration or temperature fluctuation is still a major cause of troubles of plants. In this study, high-cycle fatigue tests for austenitic stainless steel SUS316NG were conducted at 288 °C with/without mean stress. Fatigue tests with constant stress amplitude less than a certain level ran out over 108 cycles, which suggested SUS316NG has a fatigue limit at 288 °C. The effect of mean stress on fatigue life was investigated through the correlation with the variation of mean strain and strain amplitude. Methods to predict fatigue life under mean stress condition was newly developed based on the concept of ductility exhaustion. The stress-based approach such as the modified Goodman constituting the basis of the current design rule predicted excessively conservative fatigue life, while the developed methods gave more accurate prediction.