Bearing modulus

Bearing modulus is a modulus used in journal bearing design. It is a dimensionless number.^[1]

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)