抄録
There are several investigations on the behavior of residual stress during fatigue process. It is, however, difficult to detect the crack initiation from the change in residual stress because of no significant change in residual stress through the fatigue process. The purpose of this investigation is to detect the fatigue damage from the change in actual stress measured by X-ray diffraction technique during fatigue test. In this paper, a cantilever type rotary bending test machine was developed for an X-ray stress analysis based on Single Exposure Technique. The actual stress at the maximum tensile applied stress was measured to failure during cyclic loading.
The actual stress was keeping stable with increasing number of cycles until crack initiation, and this behaivior was independent of stress amplitude. After the crack initiation, it decreased suddenly with crack propagation because of stress relaxation at the crack. These results show that the change in actual stress at the maximum tensile applied stress has much higher sensitivity to detect crack initiation than one in residual stress. In-situ X-ray observation of actual stress during fatigue test is useful to detect fatigue damage.
