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Microstructural and Material Quality Effects on Rolling Contact Fatigue of Highly Elastic Intermetallic NiTi Ball BearingsRolling element bearings made from highly-elastic intermetallic materials (HIM)s, such as 60NiTi, are under development for applications that require superior corrosion and shock resistance. Compared to steel, intermetallics have been shown to have much lower rolling contact fatigue (RCF) stress capability in simplified 3-ball on rod (ASTM STP 771) fatigue tests. In the 3-ball tests, poor material quality and microstructural flaws negatively affect fatigue life but such relationships have not been established for full-scale 60NiTi bearings. In this paper, 3-ball-on-rod fatigue behavior of two quality grades of 60NiTi are compared to the fatigue life of full-scale 50mm bore ball bearings made from the same materials. 60NiTi RCF rods with material or microstructural flaws suffered from infant mortality failures at all tested stress levels while high quality 60NiTi rods exhibited no failures at lower stress levels. Similarly, tests of full-scale bearings made from flawed materials exhibited early surface fatigue and through crack type failures while bearings made from high quality material did not fail even in long-term tests. Though the full-scale bearing test data is yet preliminary, the results suggest that the simplified RCF test is a good qualitative predictor of bearing performance. These results provide guidance for materials development and to establish minimum quality levels required for successful bearing operation and life.
Document ID
20170002297
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Dellacorte, Christopher
(NASA Glenn Research Center Cleveland, OH United States)
Howard, S. Adam
(NASA Glenn Research Center Cleveland, OH United States)
Thomas, Fransua
(NASA Glenn Research Center Cleveland, OH United States)
Stanford, Malcolm K.
(NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
March 17, 2017
Publication Date
March 1, 2017
Subject Category
Metals And Metallic Materials
Mechanical Engineering
Report/Patent Number
E-19341
NASA/TM-2017-219466
GRC-E-DAA-TN38995
Funding Number(s)
WBS: WBS 401769.06.01.01.06
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
metals
tribology
bearings
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