String vibrations in hammered dulcimers

An analysis of the longitudinal forces and the resulting longitudinal motions of an idealized drill string is presented. The only external force excitation considered occurs at the bit and is due to the intermittent contact of the teeth with the bottom of the hole. Attention has been restricted to the following two salient possibilities: 1 - Excitation at the bit may develop oscillating forces at the bit with amplitudes of the same order of magnitude as those of the bit load. 2 - Appreciable bit load variation may be detected by instruments which measure the motion of the drill string near its top. The first possibility is important if maximum penetration rate is to be achieved, and the second possibility is important in implementing practical measurement of the phenomenon. From the results of the specific example considered in this report, it is concluded that possibilities 1 and 2 may occur in sufficient magnitude to be influential, but experimental data on the actual bit motion and the damping will be required to evaluate the effect. The analysis is presented in such form that the influence of the various parts of the system can easily be evaluated.

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Coupled Plate-String Vibrations of a Stiff String Against an Obstacle: Application to Musical Instruments Like Sitar

Proceedings of the 5th International Congress on Computational Mechanics and Simulation ◽

10.3850/978-981-09-1139-3_209 ◽

2014 ◽

Author(s):

Ashok K. Mandal ◽

P. Wahi

Keyword(s):

Musical Instruments ◽

String Vibrations

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Optimal boundary control of string vibrations by a force under elastic fixing

Differential Equations ◽

10.1134/s0012266111120081 ◽

2011 ◽

Vol 47 (12) ◽

pp. 1796-1805 ◽

Cited By ~ 4

Author(s):

A. A. Nikitin

Keyword(s):

Boundary Control ◽

Optimal Boundary ◽

Optimal Boundary Control ◽

String Vibrations

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The Study on Harmonic Vibration of Drill String in Horizontal Well

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.139-141.2397 ◽

2010 ◽

Vol 139-141 ◽

pp. 2397-2400

Author(s):

Chun Jie Han ◽

Tie Yan

Keyword(s):

Horizontal Well ◽

Drill String ◽

Harmonic Vibration ◽

Well Drilling ◽

Harmonic Vibrations ◽

String Vibrations ◽

Resonance Frequencies ◽

Set Up ◽

Drill Tool ◽

Modal Vibration

During exploitation of horizontal well drilling engineering, the problem of drill string failure is very serious, there are many reasons, and drill string vibrations are main reasons. In this paper drill string of horizontal well is object being studied. The models about various vibrations are set up. The vibration rule of drill string is obtained under different situation; the axial and lateral frequency of drill string vibration in free state is studied. The analysis of modal vibration of drill string is the basis of the analysis of harmonic vibration of drill string. The harmonic vibrations rules of drill string of horizontal well are studied. All sorts of resonance frequencies are obtained practicability. This study can prove basic method for optimizing drill tool of horizontal well and reducing drill string failure.

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Longitudinal and Angular Drill-String Vibrations With Damping

Journal of Engineering for Industry ◽

10.1115/1.3604707 ◽

1968 ◽

Vol 90 (4) ◽

pp. 671-679 ◽

Cited By ~ 35

Author(s):

D. W. Dareing ◽

B. J. Livesay

Keyword(s):

Viscous Friction ◽

Field Measurements ◽

Computer Programs ◽

Drill String ◽

Recording Instrument ◽

String Vibration ◽

String Vibrations ◽

Different Types ◽

Drilling Operations ◽

Computer Calculations

This paper discusses longitudinal and angular drill-string vibrations and supporting field measurements taken with a special downhole recording instrument. Computer programs based on the theory are used to calculate longitudinal and angular vibrations (caused by periodic bit motions) along the drill string; field measurements made during actual drilling operations are used to check computer calculations. The main difference between this and other theory on the same problem is the inclusion of friction, which acts along the length of a drill string and impedes longitudinal and angular vibrations. For the sake of simplicity, the effect of different types of friction, such as fluid, rubbing, and material, which act along the string, is approximated by the effect produced by viscous friction. This approximation is generally accepted and appears to give adequate results for the drill-string vibration problem.

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