Abstract
In order to examine the fatigue limit in interior induced fracture mode for bearing steel, rotating bending fatigue tests were carried out at the stress amplitude 1100MPa below the fatigue limit in surface induced fracture mode. The tests were interrupted at arbitrary number of cycles to charge hydrogen. And then the fatigue tests were continuously carried out. Based on SEM observations of the fracture surfaces, FGA was not formed in all specimens. Fracture mechanics study was performed for FGA formed fracture surfaces. As a result, the relation between the stress intensity factor range of FGA, AKFGA, and number of cycles before hydrogen-charging did not show good correlation. However, AKFGA tended to increase with an increase in the ratio of prediction FGA size to real FGA size. From this relation, AKFGA in which FGA is not formed in very high cycle fatigue regime was estimated.
