Wall slip in an EHL contact lubricated with 1-dodecanol

A study was conducted of the factors that cause anomalous EHD film shapes in 1-dodecanol lubricated contacts - i.e. a thickened central plateau and an exaggerated outlet constriction. This has led to the hypothesis that, in the region where pressures exceed ~0.44 GPa, dodecanol experiences slip, which reduces the average lubricant velocity and causes an elevated film thickness in order to maintain flow continuity. The analysis suggests that slip must be occurring at, or close to, the faster moving surface, since a discontinuity in the flow midway through the thickness of the film would not affect the average speed of the lubricant. Based on this hypothesis, an equation has been derived to predict the anomalous central film thickness as a function of applied slide-roll ratio and this has been validated by comparison with experimentally measured central film thickness values. Further support of this hypothesis is provided by traction test results showing a discontinuity occurring close to the onset of slip.