The Influence of Connection Geometry on the Fatigue Life of National Pipe Thread Threaded Pipe Couplings

Abstract

In this paper, four-point bending experiments are performed to determine the fatigue life of several threaded pipe couplings. It is shown that fatigue life of these couplings can be improved by designing them with more uniform load distribution in the threads, achieved through reducing the global and local stiffness of the coupling. Finite element simulations of a 2D axisymmetric model show consistence between experimental observation and analytical modeling. A 3D finite element simulation, which includes nonlinear material behavior, elaborate contact properties and represents the coupling geometry more accurately, is also performed to evaluate the 2D axisymmetric finite element model.