低合金鋼SNCM439の極低速き裂進展に及ぼす最大応力の影響

抄録

High strength steel shows the unique fatigue fracture called Fish eye failure, that's internal originated fatigue failure, in very long cycle region with the stress below a fatigue limit. Therefore, in order to build the lifetime method evaluation in a very high cycle region, an elucidation of the mechanism of internal fatigue failure is desired. It's reported internal fatigue crack in high strength steel is propagating extremely slowly. However, it is not clear whether this extremely slow fatigue propagation is a phenomenon peculiar to high strength steel. In this study, the materials which were changed hardness of high strength steel SNCM439 were used, and the crack propagation by ΔK decrease fatigue test in vacuum were observed. And it was inquired whether the extremely slow crack propagation would be very peculiar to high strength steel.