油气管道上凹痕应变计算方法

Calculation method for dent strain in oil and gas pipeline

针对管道上的凹痕缺陷,深度准则已不能满足油气工业的需要,因此提出了基于应变的凹痕评价体系.在经典的板壳理论中,弯曲应变能够通过凹痕深度值计算得到,但膜应变无法直接计算得到.为获得所需的膜应变值,分别采用弧长法、多项式、能量法以及根据弯曲应变计算膜应变的方法来模拟和计算凹痕管道的真实膜应变,并与有限元结果进行对比.通过分析和比较可知,根据弯曲应变计算得到的膜应变更加贴近真实值,对于运用应变准则评价凹痕管道完整性具有很重要的意义.

Since the depth criterion cannot meet the demands of oil and gas industry for detecting dent defects in pipeline,a dent evaluation system based on strain was proposed in this paper. In classical shell theory,bending strain can be calculated by the values of dent depth,but the membrane strain can not be calculated by the geometric relationship between displacement and strain. In order to obtain the desired membrane strain values,arc-length method,polynomial,energy method and calculation method of membrane strain according to the bending strain were used respectively to simulate and calculate the actual membrane strain values,and compared with results from finite element calculation. It was found from the analysis and comparison that the calculated membrane strain according to bending strain was closer to actual membrane strain values,which is instructive for the use of strain criterion in evaluating integrity of dented pipeline.