Lubricant Film Thickness Analysis and Measurement

Most moving parts are lubricated; an oil film separates the sliding surfaces. These oil films can be very thin (ranging from 0.01 – 100 microns) and are hard to measure. We, at the Leonardo Centre, have developed a unique way of measuring them using ultrasound. An ultrasonic pulse is bounced of the oil film and the magnitude of the reflected signal can be used to deduce the oil film thickness.

Ultrasonic Reflection Equipment

Our set up consists of an ultrasonic pulser, a digitiser, and a PC. A transducer is coupled (either with glue or in a fluid bath) to the back face of a bearing and functions as both a transmitter and receiver of the ultrasonic signals (see the sensors research pages for more details). It is possible to measure films in numerous situations; from dedicated test rigs looking at EHL in soft bearings and combustion engines, to in-situ measurements of machinery and testing equipment.

Machine specifications:

  • Measuring range: three ranges depending on frequency and signal processing >100 µm, 10 µm – 100 µm, 0.05 µm – 20 µm
  • Mapping resolution: in the range 100 – 500 µm.
  • Sensor Dimensions: depends on application typically ~diameter 10 mm.
  • Measurement Response Time: >0.1ms

Some Previous Applications: