液中で鋼の腐食疲労き裂進展に及ぼす荷重繰返し速度の影響 き裂先端で発生するキャビテーションの影響について

Abstract

It was already reported that many bubbles were observed gushing from the tip of cracks in fatigue tests in liquid environments. These bubbles occur due to the cavitation accompaning with the opening and closing action of the crack. In this study, the influence of cavitation bubbles on the crack growth behavior was investigated at various load frequencies in synthetic seawater and in ion exchanged water. The following conclusions were drawn.(1) The ratio of crack growth rate in a liquid environment to that in laboratory air at a constant ΔKeff was obtained as a function of load frequency. This curve showed a constant in low frequency range (<0.2Hz) and in high frequency range (>5Hz), respectively, and a transition range was observed between these constant ranges.(2) It may be considered that the corrosion fatigue crack growth at high frequencies in liquid environments was reduced to the almost same value as in the laboratory air, because the cavitation bubbles were gushing at the tip of the crack.