力-电化学耦合下埋地管道点蚀演化的毗域动力学模型与寿命预测方法

Pipeline is the main way to transmitting oil and natural gas resource around the world. Because the influence of soil environment and operating pressure, pitting corrosion is more likely to occur on the buried pipeline, which will reduce pressure bearing capacity and shorten remaining lifetime of pipeline. The evolution process of pitting corrosion is considered to be collective, stochastic and nonlinear. How to accurately describe pitting evolution behaviors is a difficult and critical issue for predicting the service lifetime of equipment. For this purpose, this research project is applied for. In this project, the evolution rule of collective pitting corrosion of pipeline considering mechano-electrochemical coupling effect are firstly studied by means of electrochemical tests, laser scanning confocal microscopy and stochastic process theory. Secondly, a peridynamics model for pitting corrosion considering mechano-electrochemical coupling effect, which combines mechano-chemical theory, kinetics of electrode reaction and ion transport equation. This model is used to explore the evolution mechanism of pitting corrosion. On this basis, numerical simulation technology is employed to investigate the quantitative relationship between the key factors (i.e. electrochemical parameters, operating pressure, pipe geometry and mechanics properties of materials) and local stress and strain distributions around the pitting defects. Finally, a remaining lifetime prediction model for gas transmission pipeline containing pitting corrosion is proposed, which couples the electrochemical parameters and mechanical parameter. This research project can provide the theoretical basis for improving the accuracy of lifetime prediction of pipeline, and it has important theoretical significance and engineering application value.

管道运输是当今世界油气资源输送的最主要方式。埋地天然气管道受土壤介质和工作载荷耦合作用极易发生点蚀，导致管道承载能力降低，服役寿命缩短。由于管道点蚀演化具有群体性、随机性和非线性的特点，如何准确掌握其在载荷（力）和环境（电化学）耦合作用下的演化规律，是预测管道剩余寿命的难点和关键。为此，本项目采用电化学测试、激光扫描共聚焦显微技术和随机过程理论，研究力-电化学耦合作用下管道点蚀群的时空演化规律；综合机械力化学、电化学反应动力学和离子输运过程，采用非局部作用的毗域动力学方法，建立力-电化学耦合下的点蚀演化动力学模型，揭示其内在驱动机制；在此基础之上，运用数值模拟方法，考察电化学参量、工作压力、管道尺寸、材料力学性能等关键因素与管道点蚀群缺陷处力学场之间的关联关系，提出一种耦合力学与电化学参量的管道剩余寿命预测方法。本项目的实施对提高埋地天然气管道安全运行具有重要的理论研究意义和工程应用价值。

管道运输是当今世界油气资源输送的最主要方式。埋地天然气管道承受多种腐蚀介质和外加载荷耦合作用极易发生点蚀等腐蚀问题，导致管道承载能力降低，服役寿命缩短。如何准确掌握其管道在环境和载荷作用下的演化行为与规律，是预测管道剩余寿命的难点和关键。为此，本项目开展了相关研究工作，主要结论和进展如下：（1）外加拉伸应力对埋地管道腐蚀有一定程度的促进作用，特别是当外加应力超过材料屈服强度时，管道钢的腐蚀速率较明显高于应力未超过材料屈服强度的情况；（2）综合机械化学、电化学反应动力学和离子输运过程，构建了基于多物理场耦合的埋地管道腐蚀动力学模型，并分析了管道点蚀缺陷处的应力应变分布和腐蚀电流密度分布规律。结果表明，点蚀缺陷底部的应力应变最大，且腐蚀电流方向由坑底中心指向两端，蚀坑中心处腐蚀电位较低，而两端电位较高。同时，管道表面塑性变形对管线钢腐蚀有着明显的促进作用；（3）提出运用自适应神经模糊推理技术，构建了预测埋地管道腐蚀速率与寿命的模型，模型将腐蚀介质含量和管道应力水平作为关键因素，腐蚀速率作为预测参数，预测值与实验值误差不超过18%，表明预测模型具有较高的准确性。