S45C調質材の二段二重変動荷重下の回転曲げ疲労寿命評価

概要

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Rotating bending fatigue tests were performed using heat-treated 0.45%C steel specimens under the constant amplitude and the two-step loading and then the cumulative fatigue was investigated. Firstly, both the original S-N curve for the virgin specimen and the S-N curves for the specimens damaged by prior fatigue were plotted on the double-logarithmic scale. All curves could be linear approximately. The values of the cumulative fatigue damage defined by modified Miner's rule under two-step loading were less than unity. The fatigue life and fatigue limit for the damaged specimen tended lower, as the degree of prior damage increased. Next, the life prediction method for the damaged specimens was proposed. The estimated results were in good agreement with the experimental ones. Then the lower limit of cumulative fatigue damage was examined based on the proposed method. The minimum value of the estimated lower limit was about 0.6, but it was 0.4 when the scatter of the experimental results was considered.
2009-03-25