Surface texturing is a representative technology of low friction and wear resistance and is the latest surface treatment technology that processes fine-sized grooves, dimples, or pockets on a lubricating surface. Recently, its application has expanded widely, including thrust bearings, mechanical seals, piston-ring, and cylinder liners. So far, most of the theoretical studies related to surface texturing have been interpreted as isothermal (ISO) with constant lubricant viscosity. However, when operating the bearing, it is necessary to consider the increase in oil temperature due to the viscous shear and its effect. Maintaining the temperature of the lubricating surface at a constant state is difficult. Therefore, to more accurately predict the lubrication characteristics of parallel thrust bearings, it is necessary to analyze them by applying appropriate temperature boundary conditions to continuity, Navier-Stokes, and energy equations for oil. The problem requires thermohydrodynamic (THD) lubrication analysis that allows the effect of temperature changes, and this thesis uses computational fluid dynamics (CFD) analysis. This thesis presents the results of the effect of temperature boundary conditions and the effect of groove number and depth on the parallel thrust bearing through CFD analysis.
There is the number and groove depth with maximum load-carrying capacity (LCC) for isothermal (ISO) cases and four temperature boundary conditions. The LCC is maximum near the groove depth where the vortex starts to occur, and the THD result is lower than the ISO result. However, the results for the A-A and T-A conditions in the case of deep grooves were more significant than the ISO results. As the number of grooves increases, the frictional force acting on the slider decreases almost linearly except for the A-A condition. In the A-A condition, the effect of the viscosity decrease due to the high temperature was dominant to the friction reduction than the grooves. Flow rate is highest in A-T condition and lowest in T-A condition. In addition, the flow rate was maximized at the groove depth where the LCC was maximum.
The ISO analysis result of the surface textured bearing overestimates the LCC but underestimates the friction reduction. Therefore, THD analysis should be performed with appropriate temperature boundary conditions to derive accurate design specifications. The numerical analysis method and results used in this paper can be applied to improve the lubrication performance of various sliding bearings with surface texture.
In order to derive the optimal texturing specifications with maximum LCC and minimum friction, additional research considering the effects of cavitation, heat transfer to the bearing surface, and deformation of the bearing surface due to generated pressure and temperature is required.