【摘要】 完成了一组X70管道钢预制裂纹试件在碳酸盐/碳酸氢盐溶液中阴极保护条件和3种载荷频率(0.1、1.0、5.0 Hz)下的疲劳裂纹扩展试验。结果表明,在较高的载荷频率下,裂纹的扩展以机械作用为主,高pH值的腐蚀环境的影响不明显;如果载荷频率较低,高pH值环境则会促进裂纹的加速扩展。出乎意料的是,其中有2个试件的裂纹在预裂后停止了扩展,而在裂尖表面出现了蚀坑和开裂,这一现象进一步说明循环载荷可以破坏钝化膜的形成,从而导致表面裂纹萌生。更多还原

【Abstract】 Fatigue crack growth experiments were performed on a set of precracked specimens of X70 line pipe steel in a carbonate-bicarbonate solution,under condition of cathodic protection and at a loading frequency of 0.1Hz、1Hz、5Hz.These experiments show that the mechanical factors dominate crack growth at a high frequency,whereas high pH environment accelerates crack growth at a low frequency.Unexpectedly,crack stop growing in two of these specimens.Pitting and cracking occur on the surface at tip of pre-crack in the two specimens.The phenomenon further show that cyclic loading damages the passivation film on the surface at tip of pre-crack and then surface cracks initiate.更多还原