管道含外表面裂纹时的疲劳寿命预测研究

Fatigue Life Prediction of Pipe with Cracks on External Surface

为有效预测含外表面裂纹管道的疲劳裂纹扩展寿命,基于扩展有限元方法,计算了不同管道半径厚度比、裂纹形状参数、裂纹相对深度下的管道外表面裂纹的应力强度因子。研究结果表明:管道外表面裂纹形状因子随裂纹相对深度的增加而增大,且随着裂纹形状参数的增大,其增加趋势更加显著;裂纹相对深度相同时,裂纹形状参数越大,裂纹形状因子越大;管道半径厚度比对管道外表面半椭圆裂纹形状因子的影响较小。在此基础上,建立了管道外表面裂纹应力强度因子的工程计算模型及基于Forman方程的含外表面裂纹管道的疲劳寿命预测模型。同时,开展了0Cr18Ni10Ti材料管道的三点弯曲疲劳试验,试验结果验证了所建含外表面裂纹管道疲劳寿命预测模型的有效性。该疲劳寿命预测模型可为管道结构工程设计提供参考。

To effectively predict the fatigue crack propagation life of pipe with external surface crack,based on the extended finite element method,the stress intensity factor of the crack on the external surface of the pipe was calculated at different pipe radius thickness ratios,crack shape parameters,and relative crack depths.The research shows that the shape factor of the crack on the outer surface of the pipe increases with the relative depth of the crack,and the increasing trend is more significant with the shape parameter of the crack.Given the relative depth of the crack,the crack shape factor increases with the shape parameter of the crack.The ratio of the pipe’s radius to thickness has a smaller effect on the shape factor of the semi-elliptical crack on the external surface of the pipe.Based on the above understanding,the engineering calculation model of the stress intensity factor of the external surface crack of the pipe and the relevant fatigue life prediction model based on the Forman equation are established.Furthermore,a three-point bending fatigue test of the 0Cr18Ni10Ti material pipe is carried out to verify the validity of the fatigue life prediction model of the pipe with external surface crack.The fatigue life prediction model can provide a reference for engineering design of pipeline structure.