抄録
In order to investigate the scatter characteristic of growth rate for small cracks, rotating bending fatigue tests of smooth specimens were carried out using a normalized 0.21% carbon steel. Fifteen specimens were fatigued at each stress range, and the growth rate of major cracks was calculated from the smoothed growth curve for all the specimens. The growth rate obtained was analyzed statistically. The results show that the growth rate for each crack length can be expressed by three- or two-parameter Weibull distribution. The CV, coefficient of variance, for crack growth rate distribution was calculated, and by using the CV the scatter characteristic of growth rate was investigated. Furthermore, the relation between the average growth rate calculated from the smoothed growth curve and the real growth rate determined from the raw growth data was studied, and the applicability of small crack growth law to the microstructurally small crack was discussed.
