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采用三点弯曲实验研究应力比R对处于不同环境下的D36钢稳定裂纹扩展区疲劳裂纹扩展速率的影响。结果表明,空气中应力比对pairs区的疲劳裂纹扩展速率影响不大,然而海水环境中,在中等△K值范围内,应力比对裂纹扩展速率影响较空气中明显,且其裂纹扩展速率随着应力比的增加而增大。这种现象产生的原因是氢脆作用随着应力比的增大显著增强。通过三电极体系在f=1 Hz,R=0.1条件下分别对试件施加-400,-600,-800,-1000和-1200 m V的电极电位。结果表明,强阴极极化(-1200 m V)和阳极极化(-400 m V)在一定△K范围内会加速裂纹扩展,综合得出该条件下腐蚀疲劳的阴极保护电位为-800 m V。而应力比为0.3和0.5时施加-800 m V的电极电位对材料的保护作用减弱。
The three-point bending experiment was used to study the effect of stress ratio R on the fatigue crack growth rate of D36 steel in steady crack propagation zone under different environments. The results show that the stress in the air is less affected than the fatigue crack growth rate in the two plots. However, in the seawater environment, the stress ratio is more obvious than the air in the medium △ K value range and the crack growth rate Increasing the stress ratio increases. The reason for this phenomenon is that hydrogen embrittlement increases significantly with increasing stress ratio. The electrode potentials of -400, -600, -800, -1000 and -1200 mV were respectively applied to the test piece under the conditions of f = 1 Hz and R = 0.1 by a three-electrode system. The results show that the maximum cathodic polarization (-1200 mV) and the anodic polarization (-400 mV) accelerate the crack propagation within a certain range of △ K. The cathodic protection potential of corrosion fatigue under this condition is -800 m V. When the stress ratio is 0.3 and 0.5, the electrode potential of -800 mV impairs the material’s protection.