Experimental Investigation of Thrust Surfaces with Deterministic Micro Asperities

Surfaces at the micro/nano scale are comprised of many peaks and valleys (asperities) that together determine the surface roughness. It has long been shown that if one could control the size, shape and distribution of the asperities, then the lubrication properties of such surfaces could be enhanced substantially. The objectives of this project are to experimentally quantify the effects of micro asperity pattern/geometry on hydrodynamic lubrication in conformal contacts, and to evaluate the effectiveness of a modified LIGA MEMs fabrication process in manufacturing controllable and repeatable micro-asperities of a specified geometry (deterministic micro asperities). Thrust bearing samples will be fabricated with various asperity patterns and geometries (e.g. - hexagons, cylinders, squares) with heights in the range of 500 nm to 50 mm. The friction coefficient, film thickness, load capacity and operating temperature of the thrust surfaces will be measured and the data compared to existing theoretical models. The thrust surfaces will also be analyzed using 3-d surface metrology and SEM techniques. The project results can be used by future researchers for further model/theory refinement and by industry engineers for the design of innovative bearing and seal systems. The research and education infrastructure will also be enhanced by making the results available to students and researchers via the world wide web. A sample industrial application of the expected results indicates a long term cost savings in excess of 160 M$ and an energy savings in excess of 1.2 Trillion BTU/yr, showing a potential benefit to businesses and the environment.