Bearings: Technology and needs
A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.
The effect of cleanliness on the attainable bearing life in aerospace applications
Surface-initiated fatigue and wear caused by contamination is one of the major causes for bearing failures in aerospace applications. This paper outlines a method to precisely define cleanliness with the help of the cleanliness factor s and the contamination factor V. Particle sizes and filtration ratios are defined and allocated to certain V factors. These factors can then be entered into a proposed bearing life calculation method to quantity the effect of system cleanliness/contamination on the attainable bearing life. A procedure to improve system cleanliness is described (pre-cleaning concept) so that contamination related damage can be eliminated.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.