High Temperature Fretting Fatigue of Turbine Steels Under Variable Loading Simulating Practical Operation

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The reduction of fatigue life by fretting was significant at both room and elevated temperatures. The improvement of fretting fatigue strength due to formation of glaze oxide film at elevated temperatures was not found in steam turbine steels used here. The S/N curves, where fretting fatigue life under block loading simulating practical load was arrauged using the wquivalent stress based on the modified miner's rule, were identical with those under constant amplitude loading at both room and elevated temperatures. This results indicate the effectiveness of the modified miner's rule to fretting fatigue under variable amplitude lading at elevated temperatures. the S-N curves, where fretting fatigue life under random loading was arranged using the rms-value of stress amplitudes, were almost identical with those under constant amplitude loading.