Formation of Lubricant Film in Rotary Sealing Contacts: Part II—A New Measuring Principle for Lubricant Film Thickness

Abstract

The development of models for the elastohydrodynamic lubrication of rotary lip seals requires the measurement of the film thickness under a real seal. A new method has been developed for this purpose which is based on the use of lubricant oils in which magnetite particles are suspended (so-called magnetic fluids). A change in the fluid film thickness will create a change in the impedance of the coil of the measuring circuit, the magnetic flux of which is directed through the oil film of the contact area. The advantage of this technique is that minimal modifications have to be applied to the tribological system under examination. Initial measurements carried out with a model rubber lip seal provided new insight into the build-up of a lubricant film as a function of the rotary speed and allowed comparison with the results of a theoretical model for the analysis of lip seal lubrication developed in parallel.

Laser-induced fluorescence for film thickness mapping in pure sliding lubricated, compliant, contacts

“…In this regime, the contact pressure is large enough to cause significant elastic deformation of one or both of the interacting solids, but the pressure within the contact is low and insufficient to cause any substantial change in the fluid viscosity [1]. Typical example applications are windscreen wipers [2], rubber o-ring seals [3][4][5][6], synovial joints [7] and tongue-palate contact during oral processing of foodstuffs and beverages [8][9][10][11][12][13],…”

“…Far fewer are suited to measure film thickness in contacts where one or both surfaces are an elastomer or tissue material. However, optical interferometry [25][26][27][28], magnetic resistance [5] and Raman spectroscopy [29] have been used successfully to measure lubricant film thickness within such contacts.…”

“…A small, lateral, sinusoidal motion was introduced by Roberts [26] and film thickness results were reported over a small entrainment speed range. More recently Kaneta et al [3,4] In an attempt to measure film thicknesses up to a hundred microns within compliant, engineering seal contacts, Poll et al [5] used an approach involving magnetic flux measurement. Magnetite particles were dispersed within the lubricant, using surfactant molecules to protect against oxidation and coagulation.…”

A study of lubricant film thickness in compliant contacts of elastomeric seal materials using a laser induced fluorescence technique

“…Optical interferometry [13,18,3], magnetic resistance [28], laser induced fluorescence (LIF) [29][30][31][32][33][34], Raman spectroscopy [35] and ultrasonic reflection [36] techniques have all been applied to measurement of thin films present in compliant lubricated tribological contacts with varying degree of success. However, each of these techniques has limitations and difficulties due to characteristics of lubricated elastomer contacts including:…”

Oil Film Formation of Reciprocating Seals Observed by Interferometry

“…One of the first direct measurements was reported by Jagger [5], which was performed by an electrical method. Since then, several measurement methods have been reported, such as a magnetic resistance method [6] and a fluorescence method [7]. Interferometry is another possible method for measuring oil film thickness.…”