Recent advancements in investigations of elbow pipe fatigue under various loading conditions

The elbow pipe is a critical pipe component that is broadly used in petroleum and power plant industries. Due to its asymmetrical shape, this component has a more complex mechanical behavior and critical stress and strain locations compared to a straight pipe. The elbow of the pipe subjected to cyclic loading will undergo plastic failure, which leads to collapse, ratcheting, and fatigue, in the end causing failure to the component. Because of this situation, this article presents recent advancements in analytical analysis, numerical analysis, and experimental investigations of the ratcheting behavior of elbow pipes. In the analytical analysis section, several common equations for estimating elbow fatigue life are listed and elaborated together with their results. Common equations include Paris' law, Neuber's law, and the Manson- Coffin equation. In the numerical analysis section, recent studies employing Finite Element Analysis are reported with details on the constitutive model, software, and results. In the experimental analysis section, the most recent elbow fatigue studies are thoroughly discussed and experimental details listed. Finally, some suggestions for elbow pipe fatigue studies are also proposed