Multiaxial cyclic ratcheting in coiled tubing -- Part 1: Theoretical modeling
Coiled tubing is a long, continuous string of steel tubing that is used in the oil well drilling and servicing industry. Bending strains imposed on coiled tubing as it is deployed and retrieved from a well are considerably into the plastic regime and can be as high as 3%. Progressive growth of tubing diameter occurs when tubing is cyclically bent-straightened under constant internal pressure, regardless of the fact that the hoop stress imposed by typical pressure levels is well below the material's yield strength. A new incremental plasticity model is proposed in this study that can predict multiaxial cyclic ratcheting in coiled tubing more accurately than the conventional plasticity models. A new hardening rule is presented based on published experimental observations. The model also implements a new plastic modulus function. The predictions based on the new theory correlate well with experimental results presented in Part 2 of this paper. Some previously unexpected trends in coiled tubing deformation behavior were observed and correctly predicted using the proposed model.
- Research Organization:
- Univ. of Tulsa, OK (US)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 20075669
- Journal Information:
- Journal of Engineering Materials and Technology, Vol. 122, Issue 2; Other Information: PBD: Apr 2000; ISSN 0094-4289
- Country of Publication:
- United States
- Language:
- English
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