Inlet shear heating reduction factor

Compared with the quantity of lubricant available in the bearing, not all of it can go through the contact area. Only a tiny amount of lubricant is used to form a hydrodynamic film. Therefore, some of the oil close to the contact area inlet is rejected and produces a reverse flow (fig. 1). This reverse flow shears the lubricant, generating heat, which lowers the oil viscosity and reduces the film thickness and rolling friction.
For the effect described above, the inlet shear heating reduction factor can be estimated using

Φish Inlet shear reduction factor

=inlet shear heating reduction factor (diagram 1)
=rotational speed [r/min]
dm =

bearing mean diameter [mm] 

= 0,5 (d + D)

ν =kinematic viscosity at operating temperature of the oil or the base oil viscosity of the grease [mm2/s]
SKF logo