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

Abstract

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

Evaluation of a numerical model for tapered threaded connections subjected to combined loading using enhanced experimental measurement techniques

“…This difference in powerturns can be explained by the varying frictional forces and therefore, numerical simulations cannot be linked to experimental results using only the torque value and assessment of the hoop strains is required. 2 For the specimen used, the measured values of flank angles and flank lengths fell within the allowable tolerances. A slight, local taper mismatch of 0.07° was observed for the set used to conduct the TLE test, resulting in a fast box and slow pin.…”

“…14 Therefore, the temperature of the connection is considered an additional variable which is able to validate the numerical model and has proven to be effective when making-up the connection. 2…”

“…Additional details can be found in Galle et al. 1,2 The main objective of the article is to investigate the applicability of new, enhanced techniques to validate the adopted models. These techniques consist of digital image correlation (DIC) and infrared (IR) monitoring.…”

“…These techniques consist of digital image correlation (DIC) and infrared (IR) monitoring. While these techniques in combination with initial make-up have been investigated before Galle et al, 2 this article focuses on the effects of applying load combinations consisting of internal pressure and axial tension in addition to the initial make-up. In addition to the advanced optical strain measurements using DIC, conventional strain gages are applied.…”

Optimal Make-Up Torque for Trapezoidal Threaded Connections Subjected to Combined Axial Tension and Internal Pressure Loading

“…From this figure, it can be observed that the location of the maximum temperature coincides with the location of the maximum average contact pressure in the contact area. The assumption that the temperature increase is mainly caused by frictional heat and not by deformation energy [7] can be backed up by the fact that the location of maximum strains (see Figure 4) and the maximum temperature are not situated at the same position at the box.…”