As can be seen from the Figs. 7 and 8, the fatigue life of the specimensis relatively scattered at the same stress range, but all test datahave a good fit with a correlation coefficient r = 0.95, and conformedto the trend that the lower stress range, the longer the fatigue life. Inaddition, by calculating the standard deviation of fatigue test data, wecan derive the S-N curve equation under 97.72% survival probability, asshown in Eq. (5).