低炭素鋼の耐久限度近傍における微小き裂進展特性について

抄録

This paper discusses the characteristics of the small crack prpagation behaviour near the stress level of the endurance limit in association with a role of a pearlite structure on the above propagation of small crcaks subjected to rotating bending. The results obtained are as follows : (1) According to the coalescence of cracks, the feature of small crack propagation on the surface of the smooth specimen shows the apparent manner of microstructural sensitive propagation up to a range of a relatively large size of the above crack (2) The transition of the crack propagation mode from a microstructurally sensitive to an insensitive manner in the growth of a single crack without the accompanying coalescence occurs at a relatively short crack length. (3) The length of the critical nonpropagating crack at the stress level of endurance limit corresponds to the transitional crack length from the microstructurally sensitive crack to the insensitive crack.