抄録
Giga-cycle fatigue properties were investigated for high-strength spheroidal graphite cast iron. Fatigue tests were carried out using ultrasonic fatigue testing at 20 kHz and conventional fatigue testing at 30 Hz used specimens with 3 and 6 mm diameters under stress ratio of R=-1. As the results, frequency effects were very small in the both of the 3 and 6mm specimens. Accordingly, ultrasonic fatigue testing could be applicable to spheroidal graphite cast iron. Decrease in fatigue strength in the giga-cycle region were a little independent of specimen size. Moreover, effect of specimen size on fatigue strength was not remarkable. However, the furacture sites were graphite and microshrinkage in 3mm specinens, while all of them were rnicroshrinkage in 6mm specimens.
