High frequency cantilever beam rotating fatigue test was carried out with 0.44% carbon steel at a temperature of 500°C with a frequency of 10000rpm, and the effect of periodically applied intermittent loading upon the specimen was investigated at two stress levels that were chosen from the basic S-N curve obtained from the ordinary test without rest periods.
From the obtained results, it was concluded that the existence of rest periods which were given with definite periods in the loading cycles, rather reduced the fatigue life of steel at elevated temperature, compared with that of the continuous loading test, especially in the case when loading frequency is as high as 10000rpm.
Such tendency does not agree with that of the previous investigations by several authors. The cause and the meaning of these different tendencies seem to be caused by many factors, such as testing frequency, method of inserting rest period, kind of stress, but it is not easy to clarify these points at the present stage of study.