両振平面曲げ疲労過程における構造用鋼板の残留応力ならびに半価幅の変化について

抄録

In the first place, several statical tension and bending tests were carried out ranging from the elastic to the plastic with annealed specimens, and the surface stress and the half-value breadth were measured by X-rays at several steps of strain during and after the loading.
Then, completely reversed bending fatigue tests ranging from high to low load were performed with annealed, pre-pulled and shot peened specimens. The residual stress and the half-value breadth were measured by X-rays at intervals during the fatigue process together with hardness measurement.
The results obtained are as follows.
1. In the statical tension tests, the residual stress was observed immediately after the nominal stress exceeded the tensile yield point, and the increase of half-value breadth or hardness started at the same time. In the case of bending tests, although the residual stress began to increase at the stress level near the tensile yield point, the increase of half-value breadth or hardness was not observed till the yield in bending took place.
2. During the reversed bending tests under high loads, the initial residual stresses varied intensely in the first few cycles, and faded away prior to fracture in the case of pre-pulled as well as shot peened specimens.
3. By the action of reversed bending under low loads, the initial residual stresses of pre-pulled specimens diminished with ease and faded away, but those of shot peened specimens decreased gradually according to the stress levels, and remained almost constant under the stress level of the endurance limit.
4. The half-value breadth and hardness measured at intervals during fatigue process were found to keep a fairly good linear relation.