焼きなまし材と調質材の疲労寿命のばらつき特性(<小特集>強度設計・安全性評価小特集)

概要

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In order to investigate the physical basis of scatter in fatigue life, rotating bending fatigue tests of smooth specimens were carried out using two steels with different microstructures. 16 or 18 specimens were fatigued at each stress range, and the initiation and propagation behaviors of a crack which led to the fracture were examined for all the specimens. The fatigue data exhibited a large scatter in fatigue life N_f at a stress near the fatigue limit. The scatter in N_f is controlled by the behavior of a micro-crack, namely it is controlled by the scatter in N_<0.3> for an annealed steel and N_<0.1> for a heat-treated steel, where N_<0.3> and N_<0.1> are the number of cycles to attain a crack length of 0.3 and 0.1 mm, respectively. On the other hand, after the crack became 0.3 or 0.1 mm, the propagation life exhibited small scatter, and its scatter was hardly affected by the stress range. To estimate the scatter characteristics quantitatively, the statistical treatment of fatigue data was performed by assuming a Weibull distribution.
1992-10-15