Fatigue Properties of High Strength Steel under Two-step Stress Amplitude

Abstract

In order to clarify the influence factor on high-cycle fatigue of High strength steel SUJ2,the fatigue test have been carried out up to (10)^8 cycles under rotating bending at room temperature. According to the experimental results, in the case of failure under the conventional stress condition, there is only one crack initiation point. On the other hand, in the case of two-step stress condition there are plural crack initiation points. Furthermore, when the fatigue damage under the two-step stress condition is evaluated by Modified Miner's low, it should be added with S-N curve by surface failure and that by internal one respectively.