S. Baragetti et A. Baryshnikov, Rotary shouldered thread connections: Working limits under combined staticloading, J MEC DESIG, 123(3), 2001, pp. 456-463
Rotary shouldered connections (RSC), used in the oil and gas industries, ar
e probably the most stressed components of the drill string because they ar
e subjected both to make-zip torque and to axial and bending loads. Since l
oads can vary and can result in fatigue crack initiation and propagation, t
here is often severe damage to the first threads engaged. Such damage leads
to shoulder load reduction and discontinuity in the drill string. Once we
know the geometric dimensions and the materials of the pin and box elements
composing the RSCs, AN standards make it possible to evaluate the working
limits of RSCs when they are subjected to make-up torque, torsion and tensi
on. It is not, however, possible to establish the stress state of the conne
ction for extreme working limits. The aim of this paper is to propose a num
erical procedure, confirmed by full-scale experimental tests, which enables
the evaluation both of the working limits, combined make-lip and axial ten
sile loads, and of the stress state of RSCs for any load condition and, in
particular, when RSCs are subjected to extreme combinations of make-up, tor
sion and axial tensile loads.