The authors have developed a new model of multi-type fatigue testing machine in axial loading, in which fatigue tests for four specimens can be performed simultaneously. Setting up the fatigue testing machines at different organizations and preparing a lot of specimens of high carbon chromium bearing steel (JIS: SUJ2), fatigue tests in the ultra-long life regime were performed as a common research project. Thus, the fundamental S-N characteristics were first clarified at the respective organizations, after which all the fatigue test data were pooled altogether and the statistical fatigue property of this steel was analyzed from a viewpoint of the reliability engineering. It was finally found that the P-S-N characteristics in the long life regime were well evaluated by applying the mixed mode of Weibull distribution consisting of fatigue life distributions for surface-induced fracture and interior inclusion-induced fracture.
