中高温下低炭素鋼の疲労き裂進展下限界に及ぼす酸化物・破面あらさの影響

抄録

Fatigue crack growth threshold and closure behavior of a low carbon steel with two different grain sizes were investigated both at room temperature and 300°C. Emphasis was placed on examining the effect of fracture surface roughness and oxide products on crack closure. Crack closure was strongly affected near the threshold by the amount of oxide products on the fracture surface. The fracture surface roughness, however, had little effect on the crack closure, even when many oxide products formed on the fracture surface at 300°C. The value of the effective stress intensity factor range at threshold, ΔK_{eff, th}, was found to increase with increasing material structural size and also with test temperature.