内压作用下含凹痕管道三维应变计算新方法  

A new three-dimensional strain calculation method for dented pipes under internal pressure

作　　者：伍颖[1] 吴鹏[1] 张媛 鄢小兵[3] WU Ying;WU Peng;ZHANG Yuan;YAN Xiaobing(School of Civil Engineering and Geomatics,Southwest Petroleum University,Chengdu,Sichuan 610500,China;DEC Dongfang Boiler Co.,Ltd.,Chengdu,Sichuan 611731,China;Central Sichuan Oil&Gas Field,PetroChina Southwest Oil&Gas Field Company,Suining,Sichuan 629000,China)

机构地区：[1]西南石油大学土木工程与测绘学院,四川成都610500 [2]东方电气集团东方锅炉股份有限公司 [3]中国石油西南油气田公司川中油气矿

出　　处：《天然气工业》2022年第9期122-134,共13页Natural Gas Industry

基　　金：四川省科技计划项目“基于损伤的凹痕缺陷埋地管道失效判据研究”(编号:2020YJ0153)。

摘　　要：凹痕缺陷是造成长输油气管道失效的一个常见原因,目前大多通过应变评估来判断其严重性,但尚无精确的分析方法确定实际管道凹痕处的应变。为此,在对内压作用下的油气管道凹痕缺陷进行准确应变分析的基础上,建立了含约束型和非约束型凹痕缺陷的有压管道非线性有限元模型,分析了管道内外壁等效塑性应变分布规律,通过对凹痕变形区域进行三维插值生成定义凹痕表面的位移函数,采用以应变张量形式分析凹痕区域应变的解析模型,建立了考虑剪切应变的管道凹痕区域应变计算模型,并利用该解析模型预测的应变分布与非线性有限元法预测的应变分布进行了对比。研究结果表明:(1)凹痕区域最大应变总是处于管道内表面,且约束凹痕的应变大于同等条件下的非约束凹痕;(2)解析模型可用来求解管道凹痕区域的应变,且能很好地预测凹痕管道的最大应变值和峰值位置;(3)通过考虑和不考虑剪切应变的等效塑性应变求解可知,尽管剪切应变对凹痕区域等效塑性应变的峰值影响较小,但剪切应变会影响凹痕区域范围的应变分布。结论认为,考虑剪切应变的计算新方法能够更为准确、全面地反映管道凹痕区域的应变分布,为评估含凹痕缺陷管道的适用性提供重要参考,并有助于现有的基于应变的凹痕评价体系的改进和完善。Dent defect is one common reason for the failure of long-distance oil and gas pipelines, and its severity is currently judged through strain assessment, but there is no accurate analysis method to determine the strain at the actual pipeline dent. In this paper,the strain response of dent defect in oil and gas pipeline subjected to internal pressure is accurately analyzed. Based on this, a nonlinear finite element(FE) model of pressurized pipeline containing unconstrained and constrained dent defects is established, and the distribution laws of the equivalent plastic strain on the inner and outer wall of pipeline are analyzed. Then, the displacement function defining dent surface is generated by the three-dimensional interpolation of dented area, an analytical model of the strain in the dented area is analyzed in the form of strain tensor, and a calculation model of strain in the dented area considering shear strain is established.Finally, the strain distribution predicted by the analytical model is compared with the result predicted by the non-linear finite element method. And the following research results are obtained. First, the maximum strain in the dented area is always located at the pipe inner surface, and the strain of the constrained dent is greater than that of the unconstrained dent under the same condition. Second, the analytical model can be used to calculate the strain in the dented area, and can well predict the maximum strain value and the peak strain location of the dented pipe. Third, it is indicated by the solution of equivalent plastic strain with and without shear strain that the shear strain has less influence on the peak equivalent plastic strain in the dented area, but shear strain can influence the strain distribution in the range of dented area. In conclusion, the new calculation method considering shear strain can reflect the strain distribution in the dented area more accurately and comprehensively, which provides important reference for evaluating the feasibility of dented pipes and i

关 键 词：油气管道 凹痕缺陷 有限元 解析模型 应变分析 应变张量 剪切应变 应变分布 

分 类 号：TE973[石油与天然气工程—石油机械设备]