A ball bearing is characterized by basic static capacity is I and dynamic capacity is 18000 N. This bearing is subjected to equivalent static load Of 5500 N. What is the life in million revolutions. 

Concept:-

Bearing loading ratio = C/P

Where,

C = Basic dynamic load rating in N

P = Equivalent static load in N

Basic rating life - 

The basic rating life is based on a 90% statistical model, expressed as the total number of revolutions in 90% of the bearings in an identical group of bearings subjected to identical operating conditions will attain or surpass before flaking due to material fatigue.

For ball bearings,  \(L_{10}= \left ( \frac{C}{P} \right )^3\;\).....Eqn(1)

For roller bearings, \(L_{10}= \left ( \frac{C}{P} \right )^\frac{10}{3}\;\).......Eqn(2)

Where L10 = Basic rating life 106 revolutions

Calculation:-

Given:-

A ball bearing having,, Static capacity = C1 = 11000 N, C = 18000 N, P = 5500 N

The bearing loading ratio is = C/P

 ⇒ C/P = 18000/5500 = 3.2727

Now, for life in millions of revolutions, we can use equation 1.

 \(L_{10}= \left ( \frac{C}{P} \right )^3\;\)

 \(L_{10}= \left ( \frac{18000}{5500} \right )^3= 35.053\;\)

L10 = 35.053 Million revolutions