As bearings rotate under load the components see material fatigue. The basic life formula, also know as the L10 life formula is used to calculate the number of revolutions before a failure occurs. Life can vary considerably, it is affected by many variables that the formulas cannot account for. The formulas are simply a guideline and should no be relied upon for critical applications.
Basic Bearing Life
L10=(Cr/P)3 • 106 Revolutions
L10h=500 • f3h fh=fn • (Cr/P), fh=(33.3/n)1/3
L10=Basic rating life
Cr=Basic dynamic load rating(kgf)
n=R.P.M.
fn=Speed factor L10h=Basic rating life in hours
P=Equivalent load(kgf)
fh=Life factor
Life equation for Ceramic Bearings
L=aCL • aCM (Cr/P)3
Lubrication CL Bearing type a CM
Oil or Grease 1 Hybrid 4
Full ceramic 1
Water 0.02 Hybrid 0.1
Full ceramic 1
L= Basic rating life (90% reliability life), 106 revolutions
Cr= Basic dynamic load rating of steel bearing of same size, N
P: Dynamic equivalent load, N
aCL : Lubrication coefficient
aCM : Material coefficient
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