Ultrasonic oil-film thickness measurement: An angular spectrum approach to assess performance limits

J Zhang*, BW Drinkwater, RS Dwyer-Joyce

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

7 Citations (Scopus)


The performance of ultrasonic oil-film thickness measurement in a ball bearing is quantified. A range of different viscosity oils (Shell T68, VG15, and VG5) are used to explore the lowest reflection coefficient and hence the thinnest oil-film thickness that the system can measure. The results show a minimum reflection coefficient of 0.07 for both oil VG15 and VG5 and 0.09 for oil T68 at 50 MHz. This corresponds to an oil-film thickness of 0.4 μm for T68 oil. An angular spectrum (or Fourier decomposition) approach is used to analyze the performance of this configuration. This models the interaction of component plane waves with the measurement system and quantifies the effect of the key parameters (transducer aperture, focal length, and center frequency). The simulation shows that for a focused transducer the reflection coefficient tends to a limiting value at small oil-film thickness. For the transducer used in this paper it is shown that the limiting reflection coefficient is 0.05 and the oil-film measurement errors increase as the reflection coefficient approaches this value. The implications for improved measurement systems are then discussed. © 2007 Acoustical Society of America.

Translated title of the contributionUltrasonic oil-film thickness measurement: an angular spectrum approach to assess performance limits
Original languageEnglish
Pages (from-to)2612 - 2620
Number of pages9
JournalJournal of the Acoustical Society of America
Issue number5
Publication statusPublished - 10 May 2007

Bibliographical note

Publisher: American Institute of Physics

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