University of Sussex
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Behaviour of elastohydrodynamic films subjected to oscillatory motion

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posted on 2023-06-08, 14:49 authored by Konstantinos Kalogiannis
The main aim of this research was to understand the influence of vibration of machine components on lubricating films formed in high-pressure contacts. In the current investigation Spacer Layer Imaging Method has been used to monitor the response of elastohydrodynamic films subjected to lateral and vertical vibrations. For both cases the EHL contact was produced by steel or tungsten carbide ball and a transparent disc which was made of glass or sapphire, loaded against each other. The contacting side of the disc was sputtered with a thin chromium layer and a silica spacer layer. White light was shown onto the contact through a specially built microscope. The interferometric fringes formed by the rays reflected by the chromium layer and by the ball’s surface are captured by a high speed CCD camera. The images were subsequently analyzed and converted to film thickness maps according to calibration curves. During the tests conducted under lateral vibrations the effect of several parameters including the frequency of lateral motion, Hertzian pressure, temperature variation and the main entrain speed were investigated. Results have shown that lateral oscillations create ripples through the lubricant film only at highest lateral frequency and low entraining speeds. The parameter which influences the formation of the perturbations in the film is the ratio between the main rolling speed and the lateral speed of the contact. The smaller the ratio the larger the transient phenomena can be identified. It has also been found that temperature change has no significant influence upon the film behaviour. The effect of vertical vibrations on the film thickness was also investigated. The analysis of the film thickness has shown that a sudden increase of load had an effect of increasing the contact diameter and at the same time modified the convergence in the inlet, an enhanced film thickness was produced at the inlet periphery of the initial contact zone and travel through the contact at a velocity equal to the average speed of the contacting surfaces.


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