Nonlinear Contact Analysis of Different API Line Pipe Coupling Modifications

Abstract

Threaded pipe couplings are used to join pipelines when they have to be uncoupled frequently or as an easy to assemble alternative to welding. A large variety of patented coupling modifications are available, but little is known about their influence on the connection’s behavior. In this study, the finite element model of an API line pipe threaded pipe connection is presented and its nonlinearities in material properties and contact behavior are discussed. Test results obtained from a four-point bending fatigue experiment are in good agreement with the results of the numerical simulations. A series of modifications of the standard connection are simulated to gain a better understanding in the influence of geometrical and material parameters on the connection’s performance. It was found that not all existing coupling modifications are improving the connection’s performance. It can be concluded that critical evaluation of the performance of existing coupling modifications is necessary and finite element analyses are proven to be a useful tool for this.