大口径含椭球型凹坑缺陷弯管极限承载能力研究

发布时间：2018-05-31 01:39

本文选题：椭球凹坑 + 大口径弯管　；参考：《西南石油大学》2017年硕士论文

【摘要】：腐蚀凹坑是石油天然气长输管道中常见缺陷之一。存在腐蚀凹坑的管道并未完全失去承载能力,此时对管道进行维修或更换,在一定程度上增加了经济成本。为充分利用管材性能,减低管道维修和更换频率,有必要对含腐蚀凹坑缺陷的管道进行精细的力学分析,以此得出管道的极限承载力。而弯管作为管道运输中必不可少的部分,在服役时受力更为复杂,作为为长输管道中的应力集中部位,出现凹坑缺陷会对管道安全增加风险。对弯管部分进行极限承载能力分析对于保障管道安全和减少经济损耗具有重要意义。论文以外径为1016mm和1219mm的两种管弯管,曲率半径为6D,材料为X80的90°弯管为研究对象,根据内压作用下管道的应力相关理论,与有限元模拟软件ABAQUS相结合,研究了含不同凹坑缺陷弯管的极限承载能力。论文对内压作用下管道的环向和轴向应力进行理论分析,选择了塑性失效准则和二倍弹性斜率法作为本文的极限载荷确定方法。运用ABAQUS软件对无缺陷弯管进行建模分析,与理论计算值对比分析,确定边界条件可靠性。采用相同边界条件对二十五个缺陷位置、六种缺陷深度、五种缺陷长度、四种缺陷宽度和三种管道壁厚进行建模分析,共得到134个不同缺陷参数的极限载荷值,并研究了各项参数变化下的弯管极限载荷变化规律,对各项缺陷参数进行数值拟合。使用MATLAB软件对各项拟合公式与极限载荷数据进行非线性回归,得到了含缺陷弯管的极限载荷求解公式,并验证了其合理性。最后使用Visual Basic语言将整合公式编制成含缺陷及无缺陷弯管极限载荷计算软件,给实际工况的大口径弯管安全评定参考的作用,为管道的及时维修和更换提出建议。论文研究成果可以为同等工况下的管道运营决策和处理提供科学的指导意见,在保障安全的前提下,进一步发挥了管道材料的潜能,减少了不必要的经济损耗,同时也可以为大口径含缺陷弯管的完整性评价及剩余强度评价提供指导和借鉴意义。
[Abstract]:Corrosion pit is one of the common defects in oil and gas pipeline. The pipeline with corrosion pit does not lose its carrying capacity completely, so the maintenance or replacement of the pipeline will increase the economic cost to some extent. In order to make full use of the performance of pipe and reduce the frequency of pipeline maintenance and replacement, it is necessary to carry out fine mechanical analysis on the pipeline containing corrosion pit defect, so as to obtain the ultimate bearing capacity of pipeline. As an indispensable part of pipeline transportation, the bending pipe is more complicated in service. As the stress concentration in long distance pipeline, the defect of pit will increase the risk of pipeline safety. It is of great significance to analyze the ultimate bearing capacity of the bend pipe to ensure the safety of the pipe and to reduce the economic loss. In this paper, two kinds of pipe bends with outer diameter of 1016mm and 1219mm, with curvature radius of 6D and material of X80, are studied. According to the stress correlation theory of pipeline under internal pressure, it is combined with the finite element simulation software ABAQUS. The ultimate bearing capacity of curved pipes with different pitches was studied. In this paper, the circumferential and axial stresses of pipelines under internal pressure are theoretically analyzed, and the plastic failure criterion and the double elastic slope method are chosen as the limit load determination methods in this paper. ABAQUS software is used to model and analyze the non-defect bend, and the reliability of boundary condition is determined by comparing with the theoretical calculation value. Using the same boundary conditions, 25 defect positions, six defect depths, five defect lengths, four defect widths and three pipe wall thicknesses are modeled and analyzed, and the limit load values of 134 different defect parameters are obtained. The variation law of ultimate load of bent pipe under various parameters is studied, and the defect parameters are fitted numerically. By using MATLAB software, the nonlinear regression between the fitting formula and the limit load data is carried out, and the formula for solving the limit load of the pipe with defects is obtained, and the rationality of the formula is verified. Finally, Visual Basic language is used to compile the integrated formula into the limit load calculation software of the pipe with and without defects, which can be used as a reference for the safety assessment of large-caliber bends under actual working conditions, and some suggestions are put forward for the timely maintenance and replacement of pipes. The research results of this paper can provide scientific guidance for pipeline operation decision and treatment under the same operating conditions. Under the premise of ensuring safety, the potential of pipeline materials is further brought into play, and unnecessary economic losses are reduced. At the same time, it can also provide guidance and reference for the integrity evaluation and residual strength evaluation of large diameter curved pipes with defects.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE973

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