UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Lubricated rolling over a pool Rahmani, Hatef


The focus of this research is the rolling of a cylinder over a pool of viscous fluid. This process has many industrial applications such as roll coating, lubrication of bearings, and rail transport (the primary motivator of this research). The problem is studied for Newtonian and shear-thinning fluids. The speed, width and loading of the cylinder are varied as are the initial depth and length of the viscous pool. Depending on the operating conditions, the cylinder will either ride on a lubrication film or remain in solid contact with the underlying substrate (although in the wheel/rail interface, there could also be a mixed or boundary lubrication regime). For the former situation, a lubrication theory is provided to predict the pressure underneath the cylinder and the film thickness deposited on the substrate. To account for the flux of fluid escaping towards the cylinder edges (3D effects), an approximation of the lubrication theory is used that includes an adjustable parameter. Once this single parameter is calibrated against experiment, the theory predicts peak lubrication pressures, gap sizes and film thicknesses to within about ten percent. The printer's instability arises during the splitting process, patterning the residual fluid films on the substrate and cylinder. If the pool length is less than the cylinder circumference, the fluid adhering to the cylinder is rotated back into contact with the substrate, and when there is sufficient adhered fluid a lubrication film forms that can again be modelled by the theory. Conversely, if there is insufficient adhered fluid, no contiguous lubrication film is formed; instead the pattern from the printer's instability "prints" from the cylinder to the substrate. A field experiment was conducted to understand the initial pickup of the liquid by the train wheel and subsequent carrydown along the track. Due to the high wheel-rail contact pressure, the liquid failed to form a lubrication layer (not the preferred outcome) and was squeezed out laterally, adhering to the edges of the wheel contact band. This edge liquid, however, provides tribological benefits on the curved track due to movement of the contact band as the train rounds a curve.

Item Media

Item Citations and Data


Attribution-NonCommercial-NoDerivatives 4.0 International