应力比对D36钢腐蚀疲劳裂纹扩展的影响

he effect of stress ratio R on the fatigue crack propagation rate (FCPR) of D36 steel was investigated in air and sea water with different applied potentials. The results reveal that by a given applied cyclic stress intensity K in air, the da/dN-K curve exhibits a slight change in fatigue crack propagation rate with the increase of stress ratio. However, by intermediate K values, the increase of the fatigue crack propagation rate is obvious in sea water, which may be ascribed to the hydrogen embrittlement. With applied potentials with in a range from -400 to -1200 mV onto the test steels at f=1 Hz, R=0.1, it follows that with the potential corresponding toeither the over-cathodic protection (-1200 mV) or the anodic dissolution (-400 mV) conditions the corrosion fatigue crack propagation rate (CFCPR) will be accelerated within a certain K range, and therewiththe optimal protection potential of -800 mV is identified. But the protection effect by the applied potential -800 mV was weakened with the increase of the stress ratio from 0.3 to 0.5.