Fatigue of Clip connectors for offshore drilling risers under biaxial tension

Abstract

Drilling riser connectors designed by IFPEN undergo cyclic in-phase biaxial tension in their critical area. This type of loading was reproduced on steel tubular specimens loaded in cyclic tension and internal pressure. The fatigue lives were substantially reduced when the load biaxiality was increased from 0 to 0.4 and then further to 1, which was not captured by existing fatigue criteria. A deeper investigation is thus in progress. Emphasis is laid on the separate evaluation of mean stress and biaxiality effects, often treated in the same way in existing criteria. The influence of load biaxiality on the resistance of the steel to fatigue-corrosion in seawater will also be investigated.