Fatigue Behaviour of Threaded Pipe Connections

− Threaded pipe connections are used in different applications in the oil and gas industry. These tubular structural elements are often subjected to fatigue loads. Due to stress concentrations, resulting from the thread geometry, the connections are the weakest points in the pipeline. The stress concentrations depend on pipe dimensions, thread type and friction between the threads. To quantify these stress concentrations, finite element analyses are carried out for different connection types using the software ABAQUS. Based on calculated stress concentration factors the fatigue lives of the connections can be estimated. To validate the models, smalland full-scale experiments will be carried out. A torque machine has been refurbished to assemble the connections with a certain make-up torque. These tests will be performed to study the coefficient of friction between the threads. Fatigue tests will be performed using a universal tensile test machine. Final objective is an optimized fatigue model considering the different connection parameters. Keywords− threaded connection, pipeline, fatigue, FEA