抄録
In the previous paper, the authors revealed that fatigue-induced substructures such as tangled dislocations of high density were responsible for the formation of nonpropagating fatigue cracks in sharp notched-specimens of iron. In stainless steel, such substructures are expected to be developed extensively in the course of fatigue tests. Nevertheless, it is still in dispute whether nonpropagating cracks are formed in this material. To clarify this point and to get more information on nonpropagating crack formation, fatigue tests were made on sharp notched-specimens of stainless steel. Furthermore, the changes in hardness and dislocation structures with an increasing number of stress cycles were investigated, and these were compared with those in the case of iron, respectively. Also, the martensitic transformation due to cyclic strain was examined. It was concluded that, in stainless steel, fatigue-induced substructures were developed at the root of the notch in the very early stage of fatigue tests, so that the stress required for the crack initiation was higher than those in iron and steel. This seemed to be the reason why nonpropagating fatigue cracks were difficult to be formed in this material.
