The paper outlines recent and ongoing studies of the influence of vibration effects on ball bearing and their lubricant systems. The maximum peak loads on spacecraft bearings occur at the beginning of their service life due to effects of the launch vibration environment subjecting high contact stresses which could cause permanent deformation of balls or raceway or lubricant degradation. If the launch vibration forces are much higher than the bearing preload, the bearing may momentarily offload, allowing a gap between ball and raceway (gapping) and inducing a change in the dynamic behaviour of the system and damage to the bearing. During static tests loads up to a peak Hertzian stress of 10940 MPa were applied to bearing rings lubricated by Braycote 601, MoS2, ion-plated lead and un-lubricated rings. Detectable indentation were found at peak Hertzian stresses above 4000 MPa, better visible on solid lubricant coated rings. Dynamic tests were carried out with preloaded axial thrust bearings, as there contact angle does not change under load. By torque measurements little correlation between maximum bearing gapping or maximum acceleration and increases in bearing torque noise were found. Greased and un-lubricated bearings showed very slight surface damage whereas the witness of vibration was much more noticable on solid lubricated bearings. Exposed to a combination of high stresses and gapping at an acceleration of 5g leading to a peak Hertzian stress of 4105 MPa and a maximum gapping of 5,5 micron the ion-plated lead film was almost completely removed (EDX-controled). The MoS2 lubricated bearings showed less reduction of lubricant film in EDX-analysis. The damage to grease lubricated bearings was much less, as vibration affected zones were barely detectable. The gapping investigation showed a ring displacement with very small tilt angles, suggesting rings remain substantally parallel with unifomly distributed ball loads. The CABARET-predicted and measured gapping values were found to be in good agreement. An ongoing work will use direct non-contacting displacement transducers to monitor axial and radial ring motions of solid and liquid lubricated bearings during simulated flight practice conditions.
Observations on the influence of launch vibration on bearing torque and lubricant performance
Untersuchung zum Einfluss der Startvibrationen von Raketen auf das Lagermoment und die Schmierstoffleistungsfähigkeit bei Kugellagern
2001
8 Seiten, 10 Bilder, 5 Tabellen, 4 Quellen
Conference paper
English
Observations on the influence of launch vibration on bearing torque and lubricant performance
British Library Conference Proceedings | 2001
|Lubricant Contaminants and Their Effects on Bearing Performance
SAE Technical Papers | 1975
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