Abstract: Due to the effects of service environment, corrosion defects inevitably appear on pipeline surface, which will cause stress concentration and promote crack nucleation. In this study, a coupled stress and electrochemical multi⁃physical field model for predicting the morphological development of corrosion defects was established based on the finite element method. The time dependence of stress corrosion behavior and corrosion morphology of X70 pipeline steel in sea mud simulated solution were studied by using the established model via deformation geometry and dynamic mesh technology. The results showed that the mechanical⁃electrochemical effect played an important role in the nucleation of stress corrosion cracks. The smaller the width of corrosion defects, the greater the stress concentration, the negative shift of the electrode potential and the higher the corrosion rate. With the increase of the operating pressure, there was a large area of high stress concentration area in the bottom of the corrosion defect, and the area of metal loss caused by corrosion increased.

Key words: Pipeline steel, Corrosion defect, Stress corrosion, Finite element model

摘要： 由于服役环境的影响，管线钢表面不可避免的会出现腐蚀缺陷，腐蚀处会产生应力集中，促进裂纹形核。基于有限元方法建立了用于预测腐蚀缺陷形貌发展的应力和电化学多物理场耦合模型。在模型中采用了变形几何和动态网格技术，用以研究X70管线钢在海泥模拟溶液中的应力腐蚀行为和腐蚀形貌随时间发展情况。结果表明，机械⁃电化学效应对应力腐蚀裂纹的形核具有重要作用；较小的腐蚀缺陷宽度使应力集中程度加大，电极电位负移，腐蚀速率增大；随着操作压力增大，腐蚀缺陷底部的管壁出现大面积的高应力集中区域，因腐蚀导致的金属损失面积增大。

关键词: 管线钢, 　腐蚀缺陷, 　应力腐蚀, 　有限元模型