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The influence of the heat transfer field on anomalous film formation under elastohydrodynamic lubrication (EHL) conditions was studied. Liquid lubricant film shapes between a transparent disc and steel ball friction pair were investigated by white light optical interferometry. The fatty alcohol 1-dodecanol was used as the representative lubricant to develop anomalous film shapes. A sapphire disc and glass disc, which have different thermal conductivities, were used as the transparent bounding surface. Experiments were performed wherein the applied load, sliding conditions and ambient temperature were varied. The temperature of the lubricant film was estimated by a simple model with the measured traction coefficient. The estimated temperature and maximum Hertzian pressure were compared with the phase diagram of 1-dodecanol obtained using a diamond anvil cell to investigate the phase state of the lubricant film. It was found that the anomalous film shape was stably formed in the solid-state regime of the phase diagram whereas the film exhibited unique characteristics such as the collapse behaviour in high sliding conditions and liquid-like behaviour of the traction with a remaining thickened film part in the liquid state regime. [ABSTRACT FROM AUTHOR]

The operating conditions and the properties of the liquid have great effects on the shape and size of the liquid film and eventually affect the efficiencies of the atomization of alternative fuels, liquid jet impingement cooling, and equipment cleaning processes. The shape and size of the liquid film are dominated by the distance from the stagnation point to the liquid film edge(r m a x). In this study, after deducing the thickness profile and the theoretical rather than the numerical solution of the initial velocity profile of the liquid film, a set of semi-empirical models about the shape, size of the liquid film, and the width of the raised zone formed by an oblique jet impinging on curved walls have been developed. In order to validate the theoretical model, a corresponding experiment has been developed, in which the jet velocities, impingement angles, liquid viscosity, surface tension, and radius of curvature have been included. The comparisons showed the theoretical results are in good agreement with the experimental data. The error for the location of the inner and outer border lines are less than 14.9% and 13.5%, respectively, except for the location in the upstream part of the film. And the effects of jet velocity, impingement angle, surface tension, dynamic viscosity, and radius of curvature were also theoretically discussed. The outer border line of the liquid film is dominated by the impingement angle and the impingement velocity, which affect the r m a x exponentially and linearly, respectively. And the liquid viscosity and surface tension coefficient also affect the r m a x approximately linearly. But the effects of the liquid viscosity and surface tension coefficient on the r m a x are much less than the impingement velocity. The radius of curvature has little effect on the outer border lines and width of the raised zone when gravity is ignored. • The thickness profile and initial velocity profile of the liquid film were deduced. • A set of semi-empirical models about the size of the liquid film were developed. • The outer border line is dominated by the impingement angle and impingement velocity. • The radius of curvature has little effect on the outer border lines when gravity is ignored. • The width of the raised zone is dominated by the liquid viscosity and impingement angle. [ABSTRACT FROM AUTHOR]

This paper describes the appearance of abnormal film thickness features formed in elastohydrodynamic contacts lubricated by a fatty alcohol. Experiments were conducted by varying the slide to roll ratio between a steel ball and a glass disk in a ball-on-disk type device. Lauric alcohol was used as lubricant and film thickness was measured in the contact area by optical interferometry. Experimental results showed that the film thickness distributions under pure rolling conditions remained classical whereas the film shape changed when the slide to roll ratio was increased. The thickness in the central contact area increased and in the same time inlet and exit film thicknesses were modified. In addition, the film shapes observed when the ball surface was moving faster than the disk one and those obtained in the opposite case were different, i.e. when opposite signs but equal absolute values of the slide to roll ratio were applied.

A mathematical model based on continuity and Navier-Stokes equations, considering laminar flow in the gap between the disks, is presented to estimate the drag torque in open multidisks wet clutches. By taking into account the effects of Poiseuille and centrifugal forces, the flow pressure and velocity fields are investigated. The model quantifies the volume fraction of fluids and predicts the evolution of film shape. The drag torque estimated by the model is the sum of drag torque due to shearing of automatic transmission fluid (ATF) and the mist (suspension of ATF in air) film. In order to validate the model, experiments are peiformed on SAE# 2 test-setup under actual operating conditions of clutches. The model is capable of predicting the drag torque under conditions of variable flow rate and different disks rotational state for higher clutch speed range. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the authors investigated the appearance of anomalous film shapes in highly sliding circular contacts when fatty alcohols such as 1-decanol, 1-dodecanol, and 1-tetradecanol were used as lubricants. The film thickness distribution between a steel ball and a glass disc was measured via white-light optical interferometry. The experimental results revealed film thickening under high sliding conditions for all three fatty alcohols. It was observed that for 1-decanol, which has the lowest melting point, the thickened part of the film was the smallest; 1-tetradecanol, which has the highest melting point, produced the largest variation of the film shape. [Copyright &y& Elsevier]