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A method for the measurement of hydrodynamic oil films using ultrasonic reflection

Dwyer-Joyce, R.S., Harper, P. and Drinkwater, B.W. (2004) A method for the measurement of hydrodynamic oil films using ultrasonic reflection. Tribology Letters, 17 (2). pp. 337-348. ISSN 1573-2711

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Abstract

The measurement of the thickness of an oil film in a lubricated component is essential information for performance monitoring and control. In this work, a new method for oil film thickness measurement, based on the reflection of ultrasound, is evaluated for use in fluid film journal bearing applications. An ultrasonic wave will be partially reflected when it strikes a thin layer between two solid media. The proportion of the wave reflected depends on the thickness of the layer and its acoustic properties. A simple quasi-static spring model shows how the reflection depends on the stiffness of the layer alone. This method has been first evaluated using flat plates separated by a film of oil, and then used in the measurement of oil films in a hydrodynamic journal bearing. A transducer is mounted on the outside of the journal and a pulse propagated through the shell. The pulse is reflected back at the oil film and received by the same transducer. The amplitude of the reflected wave is processed in the frequency domain. The spring model is then used to determine the oil film stiffness that can be readily converted to film thickness. Whilst the reflected amplitude of the wave is dependent on the frequency component, the measured film thickness is not; this indicates that the quasi-static assumption holds. Measurements of the lubricant film generated in a simple journal bearing have been taken over a range of loads and speeds. The results are compared with predictions from classical hydrodynamic lubrication theory. The technique has also been used to measure oil film thickness during transient loading events. The response time is rapid and film thickness variation due to step changes in load and oil feed pressure can be clearly observed.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright (c) 2004 Springer Science + Business Media. This is an author produced version of a paper published in ' Tribology letters '. Uploaded in accordance with the publisher's self-archiving policy.
Keywords: Lubrication Oil film measurement Ultrasound bearing hydrodynamic lubrication measurement method oil film ultrasonic technique
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield)
Depositing User: Mr Christopher Hardwick
Date Deposited: 20 Aug 2009 13:15
Last Modified: 08 Feb 2013 16:58
Published Version: http://dx.doi.org/10.1023/B:TRIL.0000032472.64419....
Status: Published
Publisher: Springer Science + Business Media
Refereed: Yes
Identification Number: 10.1023/B:TRIL.0000032472.64419.1f
URI: http://eprints.whiterose.ac.uk/id/eprint/9189

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