抄録
In order to investigate the scatter characteristics of growth rate for small cracks, rotating-bending fatigue tests of smooth specimens were carried out using 0.21% carbon steels with different ferrite grain sizes. Fifteen to eighteen specimens were fatigued at each stress amplitude, and the growth rate of a crack which led to the fracture was measured for all the specimens. The growth data were analyzed statistically. The results show that the growth rate for each crack length can be expressed by a three- or two-parameter Weibull distribution. The CV, coefficient of variance, for crack growth rate distribution was calculated, and using the CV the relations between the scatter in growth rate and the ferrite grain size were investigated.
