Selection of Slim Hole Core Rods by Vibratory Analysis

[+] Author and Article Information
A. W. Eustes, B. J. Mitchell, M. S. Stoner

Drilling Engineering Research Group, Colorado School of Mines, Golden, CO 80401

J. Energy Resour. Technol 116(4), 251-257 (Dec 01, 1994) (7 pages) doi:10.1115/1.2906450 History: Received December 12, 1992; Revised August 24, 1994; Online April 16, 2008


This paper describes the axial, torsional, and transient buckling vibratory models developed for the selection of optimum core rod size. The axial and torsional vibratory core rod simulator (VCRS) models are coupled by way of a transient buckling wave which propagates over the length of the core rod. This paper reports the frequencies and magnitudes of the stresses in the 101 core rod now in use. In addition, four core bit vibratory forcing functions for thrust and torque were developed. The thrust and torque frequencies and magnitudes for the bit forcing functions were extracted from full-size laboratory core bit tests with fast Fourier transforms. The natural frequencies of the core rod were determined with closed-form solution models and were confirmed with a finite element model. Finally, a selection of core rod sizes were modeled to determine the best size to minimize damaging stress which stems from vibration.

Copyright © 1994 by The American Society of Mechanical Engineers
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