Fatigue Life

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Fatigue life, L10 [rev, hrs], is a statistical measure of the life which 90% of a large group apparently identical rolleing element bearings will complete or exceed. For a single bearing, L10 also refers to the life associated with 90% reliability.

The relationship between fatigue or rating life, capacity and load is:

(6)
where   

L10 rev = Rating Life [106 rev]
C = Dynamic capacity [lbf]
Pe = Equivalent radial load

To obtain the rating life in [hours], use

(7)
where   

L10 hrs = Rating Life [hours]
ne = Equivalent radial load

In case of constant speed, the equivalent speed equals the constant bearing speed. In all other cases the quivalent speed is the weighted average of all individual speed components.

(8)
where   

ni = individual speed component [rpm]
ti = time interval in [percent] of total time

In cases of constant load, the equivalent radial load equals the constant load. To compute the equivalent load for all other cases, use:

(9)
where   

q = 10/3 for roller bearings
Ft = individual radial load [lbf]