Lubrication Oil Film Thickness Research Articles

Current tools and techniques for EHL modelling

We describe the construction of genuine black box software to model in detail elastohydrodynamically lubricated contacts. Such models are necessarily built on a basis of sophisticated numerical software, since the operating parameters encountered in engine and machine components (e.g. an automotive valve train) span a very wide range of conditions from the nearly steady and hydrodynamic case to extreme EHD conditions with rapid transients. As transient phenomena are responsible for the non-failure of many machine components under EHD conditions, we regard the ability to model them as critical. The traditional correlations for lubricant oil film thickness (survey functions) do not account for transients. We are therefore using EHD modelling software as the core of several engine component simulation programs.

Measurement of Oil Film Thickness Distribution on Piston Surface using Fluorescence Method. Analysis of Oil Film Behavior on Piston Skirt.

A new method using an induced fluorescence technique with a filter-covered Xe-flash lamp and a CCD camera has been developed, by which the 2-dimensional distribution of lubricating oil film thickness between piston and cylinder liner in an operating engine can be measured. The results show that it is possible to estimate the oil film boundary position on the skirt from the oil film thickness distribution. Analysis of the wrist pin offset effect shows that excessive pin offset increases the piston friction force during the compression stroke in motoring, because the piston tilts unfavorably and consequently the oil film on the upper side of the skirt becomes thinner at the antithrust side.

Effects of Lubricant Oil Film Thickness on Seizure Initiation in Cold Extrusion of Aluminium

A critical condition for seizure initiation has been investigated under a relatively low extrusion speed using an extrusion-type friction testing machine. To examine the effects of lubricant oil film thickness on seizure initiation, the oil film thicknesses at the tool-workpiece interface were estimated theoretically, and paraffinic mineral oils with three grades of viscosity were tested with various thicknesses of oil film applied, using commercially pure aluminium as the workpiece. The seizure phenomenon was always near the die exit. The lower the viscosity grade of oil used and the thinner the oil film applied, the shorter the critical punch stroke for seizure initiation became. Consequently, it has been clarified that the critical oil film thickness for seizure initiation was about 0.2 μm.

A seizure initiation mechanism in cold metalworking processes. 4th report. Effect of tool surface roughness on the critical oil film thickness.

An extrusion-type friction test and a forced sliding test have been carried out to examine the critical conditions for seizure initiation in different tool surface roughnesses using a commercially pure aluminium as a workmetal. The thinner the applied lubricant oil film thickness was, the earlier the seizure occured in every tool surface roughness. However, the critical punch stroke for seizure initiation decreased remarkably with the increasing of tool surface roughness. The oil film thickness trapped in the tool-work interface was measured experimentally and estimated theoretically. As a result, it has been clarified that the critical oil film thickness for seizure initiation increases with the increasing of tool surface roughness.