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Shock and Vibration
Volume 2016, Article ID 9168747, 7 pages
http://dx.doi.org/10.1155/2016/9168747
Research Article

Stick-Slip Analysis of a Drill String Subjected to Deterministic Excitation and Stochastic Excitation

Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St John’s, NL, Canada A1B 3X5

Received 13 January 2016; Accepted 27 April 2016

Academic Editor: Evgeny Petrov

Copyright © 2016 Hongyuan Qiu 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

Using a finite element model, this paper investigates the torsional vibration of a drill string under combined deterministic excitation and random excitation. The random excitation is caused by the random friction coefficients between the drill bit and the bottom of the hole and assumed as white noise. Simulation shows that the responses under random excitation become random too, and the probabilistic distribution of the responses at each discretized time instant is obtained. The two points, entering and leaving the stick stage, are examined with special attention. The results indicate that the two points become random under random excitation, and the distributions are not normal even when the excitation is assumed as Gaussian white noise.