Jan De Pauw

Validating numerically predicted make-up of threaded connections using digital image correlation and infrared monitoring

To ensure a reliable connection between two pipe sections, an initial make-up is applied to the threaded connections to induce a favorable stress state. Using finite element analysis techniques, it is possible to predict the internal strains and stresses of the connection when torque is applied. This article presents the outline of an experimental setup, which allows to directly validate the occurring strains together with the torque versus turn diagram and indirectly the contact pressures. The strains are measured by means of digital image correlation and strain gages. Both methods provide similar results and comply with the predicted finite element analysis strains when taper mismatch is taken into account. In an effort to qualitatively validate the simulated contact pressures, the temperature of the box is measured during make-up by means of infrared monitoring. The maximum temperature increase occurs near the vanishing threads where contact pressures are larger. Despite promising results, no decisive validation for the contact pressures could be obtained.

Fatigue Life Improvement of Threaded Pipe Couplings

In this study it is demonstrated experimentally that the fatigue life of threaded pipe couplings can be improved by providing a more uniform load distribution over the threads of the coupling. The load distribution was changed by applying both global and local stiffness reductions to the coupling. The obtained results were evaluated using finite element simulations of 2D axisymmetric models. To study the validity of these models a critical comparison was made with a full 3D model that accounts for non-linearities in material and contact properties.Copyright

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

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.