Abstract
The fatigue fracture consists on the crack initiation region and crack growth region. The life in the crack initiation region depends on the stress amplitude. On the other hand, the life in the crack growth region depends on the effective stress range. Under the two-step loading, a crack closure points of high and low stress levels changes to the closure levels under constant loading. Therefore, the fatigue mechanism must be considered in order to precisely predict the fatigue life. Moreover, transition criteria from crack initiation region to crack growth region is different between high and low stress amplitudes. Therefore, there is the transition region between transition points of high and low stress levels under two-step loading. In this study, this region was discussed in the detail.
