The statistical fatigue tests were carried out on S35C steel specimens by using three multi-type rotating bending machines designed previously. Fifty specimens were assigned to each of eight stress levels having the failure probability from zero to 100 percent. Based on the experimental results, Weibull three parameters were estimated and their stress dependency was investigated.
The results are summarized as follows:
(1) It was observed that some specimens survived 10
8 cycles at the stress levels below σ=31kgf/mm
2 (304MPa), and in this stress region the scatter of lives became very large. An irregularity was observed in the same region that the shortest life of 50 specimens became small with a decrease of stress.
(2) Based on the Weibull three parameters estimated from the correlation coefficient and the saturated failure probability, the experimental fatigue life distribution was well fitted by the Weibull distribution. Regarding the stress dependency of the parameters of Weibull distribution, the shape parametar
A took a value of 0.7-1.0 in the region of σ≤31kgf/mm
2 (304MPa), and it increased gradually with an increase of stress in the region of σ≥32kgf/mm
2 (314MPa), but no acceptable relationship was found between the stress and the scale or location parameter.
(3) Since the normal distribution did not agree well with the experimental results of the endurance limit distribution, at its extreme regions, an attempt was made to apply a beta distribution defined in the finite region. Good agreement was obtained throughout the whole range of experimental data.
抄録全体を表示