Influence of Elastic Modulus Variation on L10 Bearing Life Prediction of Case Hardened Steels
The variation in carbide volume fraction, metal matrix and composite
modulus of case layer as a function of case depth has been carefully
measured for case hardened bearing steels, using micro/nano
indentation and ultrasonic measurements [Klecka, Subhash & Arakere,
Tribology Transactions, 2013, DOI: 10.1080/10402004.2013.818393].
Conventional bearing L10 life calculations doesn’t account for variation
of elastic modulus as function of case depth and temperature. The
experimentally measured modulus variation with depth is incorporated
into FE model to compute subsurface Hertzian stress fields which are
used to compute L10 life for rolling element bearings. Two L10 life
models developed by Harris and Zaretsky were implemented [Harris,
McCool, JOT, April 1996, Vol. 118 and Zaretsky, Vleck & Hendricks,
NASA/TM-2005-213061]. The L10 life was found to be sensitive to
gradients in elastic modulus, especially for Zaretsky’s model, leading to
improved correction factors for life.