X80管线钢氢损伤失效行为与完整性评价模型研究

Oil and gas pipelines are the "lifeblood" of national energy. China's pipeline has reached 125,000 kilometers and X80 pipeline steel has been used in China's west-east gas transmission line, west-east gas transmission lines, Shaanxi-Beijing Four line and so on, nearly 18,000 kilometers, pressure up to 12Mpa. In recent years, there are lots of pipe leakage accidents, especially in pipeline welding or conveying medium contains a large number of hydrogen atoms, hydrogen molecules. The differences of crack toughness and hardening parameters between high-strength steel and low strength steel are obvious. Under the multi factor coupling of environment, materials and mechanics, The quantitative characterization model of hydrogen damage failure is still not established, and the key problems of X80 pipeline steel integrity evaluation and life prediction in complex environment are still unsolved. This project is to study the failure behavior of hydrogen damage behavior in X80 pipeline steel and to reveal the essential characteristics of its failure. Analyzing the failure behavior difference between X80 steel pipe and traditional low grade steel pipeline, the kinetics model of X80 material damage induced micro-crack initiation and propagation in hydrogen environment is proposed, and the prediction model of crack fatigue growth is established. Finally, through reconstructing the FAD failure assessment chart, the integrity evaluation model of X80 hydrogen damage containing defects is formed. This project relies on the national important project to carry on the basic research, and the result may further expand the basic theory of pipeline safety evaluation in China, which is of great significance in ensuring the safety of pipeline.

油气管道是国家能源的“命脉”，我国管道已达12.5万公里，X80高强度管线钢在我国西气东输二线、西气东输三线、陕京四线等近1.8万公里大量使用，压力达到12Mpa。近年来泄漏事故频发，特别是管道焊接或输送介质中含有大量氢原子、氢分子，高强钢止裂韧性、硬化参数与低强钢明显差异，管线钢在材料、力学、环境等多因素耦合作用下，氢损伤失效的量化表征模型仍未建立，复杂环境下X80管线钢完整性评价、寿命预测等关键问题仍未解决。本项目拟研究X80管线钢氢损伤的失效行为，揭示其失效的本质特征，分析X80钢管道同传统低等级钢管道失效行为差异，提出氢环境下X80材料损伤导致微裂纹萌生、扩展的动力学的模型，建立裂纹疲劳扩展预测模型，重构FAD失效评定图，最终形成含缺陷X80氢损伤的完整性评价模型和方法。本项目依托国家重大工程开展基础研究，研究成果可进一步拓展我国管道安全评价基础理论，对保障管道安全具有重要意义。

本项目开展了X80钢的力学性能测试试验、充氢慢应变速率拉伸试验、氢渗透试验、应力诱导氢致开裂分形试验和X80管道的全尺寸爆破试验，研究了X80管线钢的氢致开裂行为，建立了X80钢氢致开裂裂纹尖端应力应变位移场的弹粘塑性分布模型，提出了X80管道完整性评价和剩余强度计算的有限元模型，在Fatigue and Fracture of Engineering Materials and Structures（1篇），Journal of Pipeline Systems Engineering and Practice（1篇），Reliability Engineering & System Safety（2篇），Journal of Pipeline Science and Engineering（1篇）和中文核心期刊等共发表文章21篇。获得下列研究成果：.1) 通过应力诱导氢致开裂分形试验得到氢致开裂的临界应力强度因子和分形扩展速率，并发现应力强度因子和分形维数具有对数正比趋势，验证了氢致开裂模型的正确性。发表在油气储运 38 (2019) 870~876；.2）基于HRR理论建立了管道不稳定裂纹扩展的速度模型-弹塑性应力应变场和位移场，解决了X80管道裂纹扩展速度的量化问题。该研究结果发表在Fatigue and Fracture of Engineering Materials and Structures 42 (2019) 805-817；.3）建立了X80钢裂纹尖端应力应变位移场的渐近多项式弹粘塑性分布模型，通过X80钢全尺寸爆裂试验验证了弹粘塑性模型的准确性。该研究结果发表在Journal of Pipeline Science and Engineering 2 (2022) 2667-1433；.4）基于管道大数据，使用相关性分析和层次分析法，对安全系数进行修正，为管道安全评价提供新方法。研究成果发表在 Journal of Pipeline Systems Engineering and Practice (2020) 0402002；.5）基于云模型理论，开发了一种考虑了自由度、模糊性和随机性的事故风险定量评估算法。结果发表在Reliability Engineering & System Safety 215 (2021) 0951-8320；