渤海石油平台用钢A537疲劳裂纹的扩展特征

FATIGUE CRACK PROPAGATION OF A531 STEEL USED FOR BOHAI OFFSHORE PLATFORM

对渤海石油平台管节点用钢A537在238K,237K和303K三个温度下的疲劳裂纹扩展情况进行了试验研究.试验结果表明.这种钢材在每一个测试温度下的疲劳裂纹扩展均遵循Paris规律.不同温度下的疲劳裂纹扩展曲线随应力强度因子幅值的增加而有汇合趋势,并在某一高扩展速率处相交.试验还表明,温度降低,A537钢的裂纹扩展速率下降,而Paris指数n则大为增加.在裂纹扩展后期,低温下裂纹扩展速率的增长速度远大于室温,因此,低温时的扩展速率反而高于室温时的扩展速率.

This paper investigates the fatigue crack propagation of steel A537 used for tubular joints of offshore structures in Bohai Oil Company. The fatigue crack propagation of A537 steel at the temperatures of 238K, 273K, 303K was tested. It was found that the fatigue crack propagation of steel A537 was in accordance with Paris law at each testing temperature.The propagation diagram showed that the curves of fatigue crack. growth rates tended toconverge with the increase of stress intensity factor range at different temperatures andintersected at a high crack growth rate. The test results showed that as the temperature decreased the fatigue crack growth rate was reduced, and the Paris exponent was increased which caused a much greater increase of growth rate at low temperatures. Therefore, the crack growth rate during the later period of fatigue crack propagation at low temperatures was higher than that at normal temperature.