A simplified semi-analytical solution for the film thickness fluctuations in the normal-approach problem of elastohydrodynamic lubrication (EHL) contacts has been obtained. The model is based on an inlet analysis to include squeeze-film effects together with the variation of lubricant entrainment speed that is induced by the changes of contact radius as the load oscillates. The results obtained are in excellent agreement with numerical solutions and suggest that the fluctuations in entrainment speed are the main cause for the observed film modulations. The modified semi-analytical solution seems applicable in many practical cases. The amplitude of the film thickness fluctuations produced by fluctuations in the load is in this way related to a single parameter.
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