Theoretical and Experimental Investigation of Coiled-Tubing Deformation Under Multiaxial Cyclic Loading

Abstract

Summary Coiled tubing is continuous thin-walled steel tubing several thousands of meters in length without screwed connections. Cyclic plastic-bending deformation occurs during tubing spooling on the reel and when passing through the gooseneck arc guide. The coupling effect of cyclic plastic bending and internal pressure causes coiled-tubing diametral growth and wall thinning (referred to as ratcheting). This paper presents a numerical algorithm to calculate the deformations of the diameter and wall thickness on the basis of the incremental plasticity theory and the principle of virtual work. It is shown that predictions with the algorithm correlate well with experimental results.