抄録
The statistical fatigue tests were carried out on low carbon steel specimens by using a multi-type rotating bending machine developed by the authors, in which fifty specimens were assigned to each of five stress levels. The fatigue life distributions obtained experimentally at these stress levels were well fitted by either the three parameter Weibull distribution or the log-normal distribution, and, hence, equations were derived to transform three parameters of the Weibull distribution into two parameters of the log-normal distribution. Stress dependency of the distribution parameters was discussed and it was suggested that, at lower stress levels near the endurance limit, the distribution parameters are independent of the stress and only probability of survival at ultra long life region is increased with the decrease of stress. Discussions were also made on the dependency of the estimates of distribution parameters on sample size and on the distribution of fatigue strength at a given life.
