Abstract In this work, a 3-dimensional finite element (FE) model was developed to investigate the effect of cyclic loading, which is induced by vibration during operation of in-line inspection (ILI) tools, on local stress and strain distributions and failure pressure of an X80 steel natural gas pipeline containing a corrosion defect. Modelling was also conducted on a low-grade X60 steel pipe for comparison. Parametric effects, including internal pressure, R-ratio, cyclic frequency and dimension of the corrosion defect (primarily the defect depth), were determined. The cyclic loading greatly increases the von Mises stress and strain at the corrosion defect and reduces the threshold internal pressure to cause plastic deformation at the defect. As the internal pressure increases, both the von Mises stress and the strain increase and the high stress/strain zones expand along the defect length direction. The local stress and strain at the corrosion defect increase with decreased R-ratio and cyclic frequency, resulting in a reduction of failure pressure of the pipeline. An increased defect depth enhances local stress and strain concentrations, reducing failure pressure of the pipeline. A novel method is developed to assess corrosion defect during ILI tool operation and predict the failure pressure of pipelines under cyclic loading for the first time of its kind.

中文翻译：

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循环载荷作用下天然气管道缺陷评估和有限元建模的失效压力预测

摘要 在这项工作中，开发了一个 3 维有限元 (FE) 模型，以研究在线检测 (ILI) 工具运行期间由振动引起的循环载荷对局部应力应变分布和失效的影响。含有腐蚀缺陷的 X80 钢天然气管道的压力。还对低等级 X60 钢管进行了建模以进行比较。确定了参数效应，包括内部压力、R 比、循环频率和腐蚀缺陷的尺寸（主要是缺陷深度）。循环加载大大增加了腐蚀缺陷处的 von Mises 应力和应变，并降低了阈值内压，导致缺陷处发生塑性变形。随着内部压力的增加，von Mises 应力和应变都增加，高应力/应变区沿缺陷长度方向扩展。随着R比和循环频率的降低，腐蚀缺陷处的局部应力和应变增加，导致管道破坏压力降低。增加的缺陷深度会增强局部应力和应变集中，从而降低管道的失效压力。开发了一种新方法来评估 ILI 工具操作期间的腐蚀缺陷，并首次预测循环加载下管道的失效压力。增加的缺陷深度会增强局部应力和应变集中，从而降低管道的失效压力。开发了一种新方法来评估 ILI 工具操作期间的腐蚀缺陷并预测循环加载下管道的失效压力，这是同类方法中的首次。增加的缺陷深度会增强局部应力和应变集中，从而降低管道的失效压力。开发了一种新方法来评估 ILI 工具操作期间的腐蚀缺陷，并首次预测循环加载下管道的失效压力。