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Mathematical Problems in Engineering
Volume 2014, Article ID 287076, 11 pages
http://dx.doi.org/10.1155/2014/287076
Research Article

Loading and Contact Stress Analysis on the Thread Teeth in Tubing and Casing Premium Threaded Connection

1State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, School of Petroleum and Natural Gas Engineering, Southwest Petroleum University, Chengdu 610500, China
2R&D Center of Tianjin Pipe (Group) Corporation, Ltd., Tianjin 300301, China

Received 20 April 2014; Revised 15 August 2014; Accepted 21 August 2014; Published 13 October 2014

Academic Editor: Chunlin Chen

Copyright © 2014 Honglin Xu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Loading and contact stress distribution on the thread teeth in tubing and casing premium threaded connections are of great importance for design optimization, pretightening force control, and thread failure prevention. This paper proposes an analytical method based on the elastic mechanics. This is quite different from other papers, which mainly rely on finite element analysis. The differential equation of load distribution on the thread teeth was established according to equal pitch of the engaged thread after deformation and solved by finite difference method. Furthermore, the relation between load acting on each engaged thread and mean contact stress on its load flank is set up based on the geometric description of thread surface. By comparison, this new analytical method with the finite element analysis for a modified API 177.8 mm premium threaded connection is approved. Comparison of the contact stress on the last engaged thread between analytical model and FEM shows that the accuracy of analytical model will decline with the increase of pretightening force after the material enters into plastic deformation. However, the analytical method can meet the needs of engineering to some extent because its relative error is about 6.2%~18.1% for the in-service level of pretightening force.