抄録
The primary aim of present study is to clarify the fatigue fracture mechanism of high strength steel at the high cycle region. Oil-tempered high strength steel wire (SWOSC-V) is prepared for fatigue test by using Nakamura rotating-bending fatigue testing machine. The S-N diagram had a knee point at about 10^5cycle. From scanning electron microscopy (SEM) observation of the fracture surface at the long cycle fatigue range, nonmetallic inclusion was identified at the origin of fracture and it formed "fish-eye" failure. On the other hand, a constitution of the nonmetallic inclusion is measured by using electron probe micro analyzer (EPMA). As a result, Aluminum, calcium and oxygen were detected mainly at the inclusion. Based on these results, finite element analysis (FEA) was conducted for analyzing the stress field around the neighborhood of the nonmetallic inclusion. Then, the effect of mechanical property of inclusion on fatigue failure behavior was discussed.
