Bearing modulus is a modulus used in journal bearing design. It is a dimensionless number.
Formula
Bearing Modulus (C) is C = (Zn/p) where
- Z = oil viscosity
- n = speed of rotation (rpm)
- p = bearing pressure(N/MM2)
For any given bearing, there is a value for indicated by C, for which the coefficient of friction is at a minimum. The bearing should not be operated at this value of bearing modulus, since a slight decrease in speed or a slight increase in pressure will make the part of a shaft or axle that rests on bearings operate in partial lubrication state resulting in high friction, heating and wear.
To prevent this, the average value of Bearing modulus should be
- Zn/p >= 3C
or for large fluctuations and heavy impact loads
- Zn/p = 15C (approx)
References
- Karwa, Rajendra (2002). A Text Book of Machine Design. Firewall Media. ISBN 978-81-7008-833-2. Retrieved 2 January 2012.