ABSTRACT The fatigue properties of carburized steel under axial loading were examined by preparing numerous specimens carburized under the same conditions and analyzing a large dataset. The fatigue strength under axial loading was lower than that under rotating bending because of the difference in the stress gradient of two types of loadings. Even under axial loading without a stress gradient, fatigue cracks initiated at the specimen surface and the surface morphology affected the fatigue life. Carburized steel exhibited a duplex‐N curve comprising surface and subsurface fracture modes. The fatigue lives of the specimen exhibiting subsurface fracture were longer than those of the specimen exhibiting surface fracture and were dominated by the local stress amplitude at the fracture origin.
Takesue et al. (Wed,) studied this question.