BALL
BEARING
 EHL



Body 1 (ball) 
Body 2 (race outer ring) 
Young's modulus E 
GPa 
GPa 
Poisson's constant v 


Radius r_{x} 
10^{3}
m 
10^{3}
m 
Radium r_{y} 
10^{3} m 
10^{3} m 

Lubricant viscosity η_{0} 
Pa·s 
Viscosity pressure coeff α 
1/GPa 
Number of balls z 

Rotational speed n 
rpm 
Bearing load P 
N 

Effective Young's modulus E' 
GPa 
Effective contact radius R' 
10^{3}
m 
Semi contact radius a 
10^{3}
m 
Semi contact radium b 
10^{3}
m 
Mean contact pressure p_{m} 
GPa 
Max contact pressure
p_{max} 
GPa 
Viscosity number L 

Load number N 

Film height number H 

Couette flow film thickness h_{c} 
10^{6}
m 

The lubrication regime in which the bearing operates depends
on the rotational speed. At low speed Boundary Lubrication
prevails (hc/Ra<1). Representative values for the Ravalue of
the ball and raceway are Ra=0.001 and
Ra=0.1 μm respectively. It follows that hc>0.2 results in full film lubrication (EHL: hc/Ra>2).
This situation can easily be considered by measuring the
electric conduction over the inner and outer ring of the bearing
(EHLhigh electrical resistance, BLconduction) 

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