TORSIONAL AND BENDING VIBRATION MEASUREMENT ON ROTORS USING LASER TECHNOLOGY
✍ Scribed by T.J MILES; M LUCAS; N.A HALLIWELL; S.J ROTHBERG
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 342 KB
- Volume
- 226
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) was developed for non-contact measurement of torsional oscillation of rotating shafts, o!ering signi"cant advantages over conventional techniques. This paper describes comprehensive theory to account for the sensitivity of the LTV's measurements to shaft motion in all degrees of freedom. The optical geometry of the LTV o!ers inherent immunity to translational motion of the target shaft, either axial or radial. However, its measurements are sensitive to angular lateral vibration of the shaft. The signi"cance of this sensitivity is compared with the instrument noise #oor and typical torsional and lateral vibration levels. Optimum alignments of the instrument are then speci"ed to ensure e!ective immunity to all lateral motion in typical applications. To overcome this problem more reliably, a new technique is proposed permitting unambiguous measurement of pure torsional vibration in situations where use of a single LTV demonstrates unacceptable sensitivity to angular lateral vibrations. Practical application of this technology is demonstrated with torsional vibration measurements from a diesel engine crankshaft. Simultaneously, previously unattained measurements of shaft bending vibration measurements are made. The "rst bending mode of the crankshaft was identi"ed and its vibration amplitude and damping estimated. This application of laser vibrometry for non-contact measurements of shaft vibration represents a further step forward in the use of this technology for machinery diagnostics.