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

Abstract

Threaded connections used in the oil and gas industry have to withstand ever-increasing axial and pressure loads. The structural behavior of these joints can be predicted using numerical models, provided these are soundly validated. Within this article, a finite element model of tapered, shoulderless connections containing a trapezoidal thread type is experimentally validated conducting a test load envelope experiment and a tensile failure test. The evaluation is performed using both conventional and advanced measurement techniques. Surface strains are validated by comparing digital image correlation and strain gage results with the numerical output. An almost perfect quantitative match between the numerically predicted axial strains and the experimentally measured strain gage data is obtained. In addition, a qualitative match can also be observed when considering the axial strains obtained by digital image correlation. Furthermore, infrared thermography measurements are compared to the numerical deformation energy, assuming that temperature is an additional, but indirect parameter to evaluate the validity of the model. From the results, the proposed model has proven to be reliable when a combination of axial tension and internal pressure is applied. While the model is originally designed to predict the connection’s structural behavior for loads up to the yield strength, it is possible to estimate this behavior for higher loads by modifying the contact area.