Optimization and Enhancement of Oil Supply for Hydrodynamic Slider Bearing through Tailored Surface Effects
DescriptionThe oversupply of lubricant to machine elements is quite common in practice because individuals usually err on the side of caution since an undersupply may result in catastrophic failure of an engine or a machine. However, oversupplying lubricant, particularly to small-scale devices e.g. micro-electro-mechanical systems (MEMS), is more than an issue of wastage because the resistance generated by an excessive amount of lubricant may interrupt the running. This study addresses this important issue in two aspects: first, to fundamentally understand the correlation between quantity of lubricant supply and the effective hydrodynamic lubrication of slider bearing contact; and second, to enhance the supply of oil to the bearing contact through tailored surface effects, such that the total required volume of lubricant can be optimized.What would happen if only limited lubricant is supplied to the bearing contact? Studies on elastohydrodynamic lubrication (EHL) under limited lubricant supply (usually referred to as “starvation”) conditions show that starved EHL leads to a reduction in overall lubricating film thickness, which is substantially affected by the lubricant replenishment. The lubricant would flow back to the bearing track while waiting for the next bearing roll- or slide-over. Apart from being dragged into the bearing contact from the inlet, lubricant can also be locally replenished from the vicinity of the contact by surface effects. Therefore, the use of supplied lubricant can only be optimized if the lubricating film building and fundamental knowledge therein are understood. Furthermore, our recent studies confirmed that the wettability or spreading capability of oil on a solid surface depends on surface or interfacial properties. Thus, tailored surface effects generated through appropriate bearing surface design may increase the entrainment of lubricant into the contact and reduce side-leakage by improving confinement of the lubricant.The scope of this study is confined to hydrodynamic lubricated flat-on-flat sliding contacts. The experiment will be conducted using an optical slider bearing tester. Flat-on-flat conformal contact is common in practical engineering and particularly in micro- and meso-scale devices, in which surface effects can be dominating due to their high surface-to-volume ratio and any excessive lubricant can be detrimental or even fatal. The study aims to facilitate effective thin film hydrodynamic lubrication under limited lubricant supply conditions through experimental and theoretical studies.The most original aspect of this proposed work is the experimental approach to the study of the tailored surface application in hydrodynamically lubricated bearings under limited amount of lubricant.When the project is completed, we can clarify the relationship between film building capacity and quantity of lubricant supply, as well as enable desirable lubrication through appropriate interface design. The knowledge and insight acquired in the project are certainly valuable to the lubrication design of advanced miniature devices and MEMS, which are multi-billion dollar industries and expected to continue to grow.
|Effective start/end date||1/01/17 → …|
- limited lubricant supply , thin liquid film lubrication , surface effect , starvation , optcal interferometry