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 % 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.