Speaker:

Michael O’Brien, The Aerospace Company

Title

“Failure Analysis of Si3N4 Balls used in Hybrid Bearings”

Abstract:

A test series was undertaken to demonstrate the rolling-element fatigue life and Weibull distribution of advanced material bearings consisting of silicon nitride balls and Rex 20 tool steel races. Compared to conventional 52100 steel bearings, the advanced bearings demonstrated much greater lives (6.7 times greater life at 90% confidence and 10 times greater life at 50% confidence).

A fractographic analysis of three failed ceramic balls was performed. In each instance, the initiation of the final fracture was traced back to a relatively small initiation site. In two cases, interesting features were identified that may represent the potential cause for the failure. These potential causes were identified as small defects that are believed to be sintering voids with diameters of less than 2 microns. It is possible that such small defects should be considered defects inherent to the material rather than manufacturing defects.

Biography:

Michael O'Brien received his BS in Mechanical Engineering from MIT and his PhD in Materials Science from Brown University. He has been employed at The Aerospace Corporation since 2000. His interests are in the mechanical behavior of materials and computational solid mechanics. He has also served as membership chair, secretary and treasurer of the Los Angeles chapter of ASM International

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