S45C調質平滑材の二段二重重複応力下における疲労被害

概要

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In order to clarify the fatigue damage of plain specimens under complex loadings, it is important to investigate the effect of stress change through the behavior of a small crack because the fatigue life of the specimens is occupied mainly by the propagation life of a small crack. However, these kinds of studies made in heat-treated carbon steels are few. In this study, the fatigue tests of heat-treated carbon steel plain specimens under two-step loading were carried out and the effect of stress change on the behavior of a small crack is investigated. Results show that the value of cumulative cycle ratio Σ(n/N) is smaller than unity when the first stress level σ_1 is higher than the second oneσ_2, however Σ(n/N) is about unity whenσ_1 is lower than σ_2. This difference in the value of cumulative cycle ratio is explained by the behavior of a small crack after the stress change.
1989-03-25