Pipe elbows (bends) are considered critical pressurized components in the piping systems and pipelines due to their stress intensification and the effect of bend curvature. They are prone and hence more exposed to different corrosion failure modes than straight pipes. Late detection of such elbow damages can lead to different dangerous and emergency situations which cause environmental disasters, pollution, substantial consumer losses and a serious threat to human life. A comprehensive safety and reliability assessment of pipe elbows, including usage of prediction models, can provide significant increases in the service life of pipelines. It is well known that the limit pressure is an important parameter to assess the piping integrity. In this paper, the integrity assessment of damaged pipeline elbows made of API 5L X52 steel was done within the framework of numerical modeling using the finite element method (FEM) and finite element analysis (FEA). The evaluation of numerically FEM modeled limit pressure in the corroded elbow containing a rectangular parallelepiped-shaped corrosion defect with rounded corners at the intrados section was done and compared to different codes for calculating limit pressure. Moreover, the area with the corrosion defects with different relative defect depth to wall thickness ratios was FEM modeled at the intrados section of the pipe elbow where the highest hoop stress exists. The results showed that the codes for straight pipes could not be applied for the pipe elbows due to the significantly higher error in the obtained limit pressure value compared with numerically FEM obtained results. However, the results for modified codes, adapted for the pipe elbow case using the Goodall formula for calculation of the hoop stress in pipe elbows with defects are pretty consistent with the numerical FEA results. The notch failure assessment diagram (NFAD) was also used for the straight pipe and pipe bends with different corrosion defect depth ratios, while the obtained critical defect depth ratios further highlighted the criticality of pipe elbows as an essential pipeline component.

弯头（弯头）由于其应力增强和弯曲曲率的影响，被认为是管道系统和管道中的关键加压部件。与直管相比，它们容易发生腐蚀，因此更容易遭受不同的腐蚀破坏模式的影响。此类肘部损伤的较早发现可能导致不同的危险和紧急情况，从而导致环境灾难，污染，巨大的消费者损失以及对人类生命的严重威胁。对管道弯头进行全面的安全性和可靠性评估，包括使用预测模型，可以大大提高管道的使用寿命。众所周知，极限压力是评估管道完整性的重要参数。在本文中，API 5L X52钢制成的受损弯管的完整性评估是在有限元方法（FEM）和有限元分析（FEA）的数值建模框架内进行的。进行了有限元数值模拟，对腐蚀后的弯头的极限压力进行了评估，该弯头的内部有矩形的平行六面体腐蚀缺陷，且在圆弧形截面处有圆角，并与计算极限压力的不同代码进行了比较。而且，在存在最高环向应力的管弯头内段，对具有相对缺陷深度与壁厚比不同的腐蚀缺陷区域进行了有限元建模。结果表明，与有限元数值计算结果相比，所获得的极限压力值误差明显更高，因此无法将直管代码应用于管弯头。但是，修改后的代码的结果适用于管道弯头情况，使用Goodall公式来计算有缺陷的管道弯头的环向应力，与数值有限元分析结果非常一致。缺口破坏评估图（NFAD）也用于具有不同腐蚀缺陷深度比的直管和弯管，而获得的临界缺陷深度比则进一步突出了弯头作为必不可少的管道组件的重要性。使用Goodall公式对管弯头情况进行了调整，以计算有缺陷的管弯头的环向应力，与数值有限元分析结果非常一致。缺口破坏评估图（NFAD）也用于具有不同腐蚀缺陷深度比的直管和弯管，而获得的临界缺陷深度比则进一步突出了弯头作为必不可少的管道组件的重要性。使用Goodall公式对管弯头情况进行了调整，以计算有缺陷的管弯头的环向应力，与数值有限元分析结果非常一致。缺口破坏评估图（NFAD）也用于具有不同腐蚀缺陷深度比的直管和弯管，而获得的临界缺陷深度比则进一步突出了弯头作为必不可少的管道组件的重要性。