A theoretical procedure for friction behaviour evaluation in threaded connections

Threaded connections are used in many industrial, mechanical, aerospace and naval applications. The make-up torque applied to such connections induces an axial load in the threaded joints, making it possible to tighten and keep together different components and structural elements. Despite the widespread use of threaded joints, their friction behaviour is not well known. Moreover, it is not unusual to find broken threaded connections or unscrewed joints as a result of either unfavourable friction between the mating surfaces or geometrical modification of the threads. The aim of this paper is to propose an analytical procedure, validated by means of full-scale experimental tests, that makes it possible to determine whether to reject a used or new threaded connection. The effectiveness of the procedure was assessed by means of experimental tests carried out on conical threaded connections used in the oil and gas field, taking into consideration different materials, geometries and compounds.