Strain-controlled fatigue tests were conducted for low-carbon nitrogen-added type 316 stainless steel at 550°C. At lower strain range, fatigue life started to change with a larger slope than medium strain range region in log-log plot between the strain range and number of cycles to failure. Simple extrapolation of a best-fit curve was found to be inappropriate because of this characteristic. Application of shot-peening improved fatigue strength but its effect was maxumam at medium strain range and tended to disappear as the strain range was decreased.
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