OS1532 S45C焼入れ焼戻し材を用いた欠陥形状が疲労き裂の停留挙動に及ぼす影響の検討

A small artificial hole is regarded as a pre-crack and square root area parameter is considered as one of the most important parameter for the fatigue limit of materials which contain small defects. In this study, introducing a sharp notch by using focused ion beam (FIB) or a small artificial hole which have the same area on the quenched and tempered 0.45% carbon steel specimen, we carried out these specimens fatigue tests and we investigated the difference of the two defect shape in the hard material. From the fatigue tests, we obtained two important results. First, the fatigue limit of the specimen with the small artificial hole was higher than the specimen with the FIBed notch. Second, fatigue crack initiation and propagation behavior was different between the two types of the specimens. Usually, there are no differences for annealed steel in the two defect shapes. Therefore, the hardness may affect the fatigue crack behavior of the two defect shapes.