Surface defects effects on bearing dynamics

Abstract

Influence of race defects on the motions of bearing components (i.e. inner and outer races, cage, and balls) was investigated using a six degrees of freedom dynamic model for deep groove and angular contact ball bearings. Surface defects such as dents and bumps on bearing surfaces cause the elements (balls and cage) of bearings to vibrate and impact the inner and outer races. To model the effects of surface defects on bearing dynamics, the superposition principle was used to include the effects of a dent or bump on bearing dynamics. A bump having a general geometry was modelled as an equivalent ellipsoid in contact with the original bearing components geometry while a dent was modelled as an equivalent ellipsoidal depression on the bearing surface in contact with bearing component. Therefore, the net forces acting on the contacting body is superposition of forces acting on the bodies without any defect and forces corresponding to defect alone. This approach was also used to investigate and model the effects of debris contaminants on bearing performance. The effects of the debris are calculated similar to bumps with an exception that debris is free to move within the bearing component domain. The results indicate that surface defects and irregularities such as dents and bumps have a significant effect on bearing motion and forces. The results also demonstrate that a single defect can affect the forces and motion throughout the entire bearing and on all bearing components.