抄録
In the present study, fatigue fracture behavior of commercially pure iron thin wires with the grain size of 23 μm and the diameter of 700μm was investigated by bending fatigue test. At bending moment ratio M_<min>/M_<max>=-1 and -0.8, microscopic observation of fracture surface shows striations. Therefore fatigue cracks initiated at both the upper and lower surfaces and propagated toward the neutral axis of the specimen. On the other hand for tension-tension fatigue (stress ratio R=0.1), ratcheting failure and necking were occurred and the initiation and propagation of fatigue crack were not observed.
