Analysis of Thermal Deformation of a Rough Slider and Its Asperities and Its Impact on Load Generation in Parallel Sliders
Heating is inevitable in any bearing operation. This leads to not only the thinning of the lubricant but also could lead to a thermal deformation of the bearing. The present work is an attempt to analyze the influence of thermal deformation on the thermohydrodynamic lubrication of infinitely long tilted pad slider rough bearings. As a consequence of heating the slider is deformed and is assumed to take a parabolic shape. Also the asperities expand leading to smaller effective film thickness. Two different types of surface roughness are considered: longitudinal roughness and transverse roughness. Christensen’s stochastic approach is used to derive the Reynolds-type equations. Density and viscosity are considered to be temperature dependent. The modified Reynolds equation, momentum equation, continuity equation and energy equation are decoupled and solved using finite difference method to yield various bearing characteristics. From the numerical simulations it is observed that the performance of the bearing is significantly affected by the thermal distortion of the slider and asperities and even the parallel sliders seem to carry some load. Keywords—Thermal Deformation, Tilted pad slider bearing, longitudinal roughness, transverse roughness, load capacity.
The Viscosity Wedge
In a previous paper (6) it was shown that a viscosity gradient across an oil film allowed a hydrodynamic load to be carried between contra rotating discs. If there is a temperature (and viscosity) gradient, not only through the oil film but also in the direction of motion, a considerable load can be borne. The equations are set up and solved numerically giving coefficient for oil film thickness and friction. The oil film thickness is comparable (three quarters) of that carried by Michell pads. The computed results are applied to the parallel surface thrust bearing described by Fogg (2) in 1946 and shown to give tolerable agreement with the experimental findings. Contributed to the American Society of Lubrication Engineers by the author.
Surface Roughness Effects in Infinitely Long Porous Journal Bearings
Christensen's stochastic theory of hydrodynamic lubrication of rough surfaces is used to study the effect of surface roughness in an infinitely long porous journal bearing operating under steady conditions. It is shown that the surface roughness considerably influences the bearing performance; the direction of the influence depends on the roughness type.