2017 年 4 巻 4 号 p. 17-00035
The fatigue life of austenitic stainless steel is significantly reduced in the environment of a pressurized water reactor (PWR). One of the methods for evaluating the environmental effect involves the use of the environmental correction factor (Fen) determined from the fatigue lives of the material in air and the PWR environment. It has been reported that the environmental correction factor increases with decreasing strain rate, eventually saturating at a low strain rate. However, the exact behavior of the parameter remains unclear considering evidences of a relationship between environmentally assisted fatigue and stress corrosion cracking. It is therefore of importance to examine the possibility of continuity between environmentally assisted fatigue and stress corrosion cracking at very low strain rates. In the present study, time domain analyses of short fatigue cracks initiated in 316 stainless steel in air and simulated PWR water were used to ascertain the existence of such continuity by investigating the relationship between the environmentally assisted fatigue and stress corrosion cracking. The acquired environmentally assisted fatigue life data were uniquely interpreted, and superposition of the plots of the stress corrosion cracking data obtained by slow-strain-rate tensile tests over the time domain analyses and environmentally assisted fatigue data suggested continuity among the parameters. This was clearly substantiated by further time domain analyses.
