抄録
In order to clarify the influence factor on high-cycle fatigue of high strength steel SUJ2, the rotating bending fatigue tests have been carried out up to 10^8 cycles at room temperature. According to the experimental results, in the constant stress condition, the fatigue crack is initiated from a specimen's surface. On the other hand, in the case of two-step stress amplitude condition the fatigue crack is initiated in the specimen's surface parts. Furthermore, when the fatigue damage under the two-step stress condition is evaluated by a modified Miner's low, it will be better way to evaluate the fatigue life with S-N curve by surface failure and that by internal one respectively.
