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The Effect of Indenter Ball Radius on the Static Load Capacity of the Superelastic 60NiTi for Rolling Element BearingsStatic load capacity is a critical design parameter for rolling element bearings used in space mechanisms because of the potential for Brinell (surface dent) damage due to shock and vibration loading events during rocket launch. Brinell damage to bearing raceways can lead to torque variations (noise) and reduced bearing life. The growing use of ceramic rolling elements with high stiffness in hybrid bearings exacerbates the situation. A new family of hard yet resilient materials based upon nickel-titanium is emerging to address such bearing challenges. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (~100GPa) and has been shown to endure higher indentation loads than conventional and high performance steel. Indentation load capacity has been reported for relatively large (12.7mm diameter) ceramic (Si3N4) indenter balls pressed against flat plates of 60NiTi. In order to develop damage load threshold criteria applicable to a wide range of bearing designs and sizes, the effects of indenter ball radius and the accuracy of interpolation of the Hertz contact stress relations for 60NiTi must be ascertained. In this paper, results of indentation tests involving ceramic balls ranging from 6.4 to 12.7mm in diameter and highly polished 60NiTi flat plates are presented. When the resulting dent depth data for all the indenter ball sizes are normalized using the Hertz equations, the data (dent depth vs. stress) are comparable. Thus when designing bearings made from 60NiTi, the Hertz stress relations can be applied with relative confidence over a range of rolling element sizes and internal geometries.
Document ID
20140008619
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Dellacorte, Christopher
(NASA Glenn Research Center Cleveland, OH United States)
Moore, Lewis E.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Clifton, Joshua S.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
June 30, 2014
Publication Date
May 19, 2014
Subject Category
Metals And Metallic Materials
Mechanical Engineering
Report/Patent Number
GRC-E-DAA-TN10811
Meeting Information
Meeting: 2014 Society of Tribologists and Lubrication Engineers (STLE) Annual Meeting
Location: Orlando, FL
Country: United States
Start Date: May 19, 2014
End Date: May 22, 2014
Sponsors: Society of Tribologists and Lubrication Engineers
Funding Number(s)
WBS: WBS 869021.05.03.03.15
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
bearings
materials
metals
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