2018 年 63 巻 9 号 p. 618-628
In this paper, the progress of peeling was quantitatively examined by the estimation of repetitive stress acting below the rolling contact fatigue (RCF) surface. The repetitive stress was calculated as the sum of the residual stress and the contact stress generated below the real contact area. The residual stress was obtained from X-ray stress measurement. The contact stress was calculated by the boundary element method (BEM). The effect of a black oxide treatment on the suppression of peeling was also investigated by the same stress estimation. Estimated repetitive stress (von Mises stress) indicated that continuous plastic deformations occurred on the RCF surface, and brought about initial cracks of peeling. It was also considered that the principal shearing stresses which act along the direction oblique to the rolling direction contributed to the initial crack propagation. With regard to the black oxide treatment, the repetitive von Mises stress was reduced as compared with the untreated case, since the black oxide treatment reduces the surface roughness of base metal and promotes the running-in. This reduction of von Mises stress resulted in the suppression of the initial cracks and hence the peeling was prevented.
