Monitoring of Lubricant Film Failure in a Ball Bearing Using Ultrasound

[+] Author and Article Information
Jie Zhang

Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, United Kingdom

Bruce W. Drinkwater1

Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, United Kingdomb.drinkwater@bristol.ac.uk

Rob S. Dwyer-Joyce

Department of Mechanical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom


Corresponding author.

J. Tribol 128(3), 612-618 (Mar 20, 2006) (7 pages) doi:10.1115/1.2197848 History: Received December 12, 2005; Revised March 20, 2006

A lubricant-film monitoring system for a conventional deep groove ball bearing (type 6016, shaft diameter 80 mm, ball diameter 12.7 mm) is described. A high-frequency (50 MHz) ultrasonic transducer is mounted on the static outer raceway of the bearing. The transducer is focused on the ball-raceway interface and used to measure the reflection coefficient of the lubricant in the “contact” ellipse between bearing components. The reflection coefficient characterizes the lubricant film and can be used to calculate its thickness. An accurate triggering system enables multiple reflection measurements to be made as each lubricated contact moves past the measurement location. Experiments are described in which bearings were deliberately caused to fail by the addition of acetone, water, and sand to the lubricant. The ultrasonic reflection coefficient was monitored as a function of time as the failure occurred. Also monitored were the more standard parameters, temperature and vibration. The results indicate that the ultrasonic measurements are able to detect the failures before seizure. It is also observed that, when used in parallel, these monitoring techniques offer the potential to diagnose the failure mechanism and hence improve predictions of remaining life.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Geometry of the lubricated “contact” region of the ball bearing and the region of focus of the 50MHz ultrasonic transducer

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Figure 2

Schematic diagram of the experimental apparatus made up of four 6016 ball bearings

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Figure 3

Transducer attachment and bearing geometry

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Figure 4

Shaft speed of 506rpm and a radial load of 15kN. (a) Measured reflection compared with a theoretical prediction based on a predicted oil film thickness. (b) Measured lubricant thickness compared with a theoretical thickness.

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Figure 5

Reflection coefficient versus time for failure by the addition of (a) acetone, (b) water, and (c) sand

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Figure 6

Photograph for a small contacting area at outer-raceway surface for different ball bearings (2.5×1.9mm2 of the surface is shown). (a) Undamaged surface, (b) after contamination by acetone, (c) after contamination by water, and (d) after contamination by sand.

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Figure 7

Temperature versus time for a ball bearing under normal operation (labelled “normal”) and various failure cases

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Figure 8

Vibration signals before and after failure for sand case

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Figure 9

Vibration signals versus time for various failure cases: (a) maximum amplitude and (b) standard derivation




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