Measurement of Lubricant Film Thickness in Soft EHL

Dedison Gasni
M. Kamel Wan Ibrahim
Prof. Rob Dywer-Joyce

In lubricated contacts between low modulus materials, the pressure is relatively low so that lubricant viscosity remains constant.  This is known as the elastic isoviscous regime, or soft EHL. Engineering applications using low elastic modulus (soft EHL) materials include rubber seals, human tissue, and tires.

The ultrasonic method involves bouncing a sound wave off oil films. In this work, we have been using such a method to measure soft EHL film thickness in an Elastomer and Perspex contact. A transducer is mounted on the surface of the Perspex and emits an ultrasonic pulse directly onto the lubricated interface. The reflected signal is then recorded and digitally processed to obtain the lubricant film thickness. The digital signal processing method is tailored to the lubrication regime under measurement.


The aim of this research is to measure the film thickness behaviour of soft EHL materials such as Fluoroelastomer, Nitrile and Polyurethane, which are usually used as seal on bearings.