Engine Hybrid Ceramic Bearings.

The objective of this program was the development of additional performance data and condition-monitoring techniques for silicon nitride Si3N4 bearings. Induced-defect testing was performed to assess the ability of silicon nitride balls to withstand the high shock loads experienced during the growth of a race spall. The defect was placed in the outer ring of a hybrid bearing. Conclusions were made as to the survivability of ceramic balls under such severe conditions. High-speed thermal performance was compared between an all-steel bearing, a hybrid with the same internal geometry, and a hybrid with tightened internal geometry to lower the hertzian contact stress. Conclusions were made as to whether the hybrid bearings offer any improvement in thermal performance over an all-steel bearing. A condition-monitoring methodology was developed for early detection of an impending bearing failure. A technique was developed to find both metallic and ceramic debris from bearings. A monitoring device was developed, constructed, and demonstrated.