Question

A ball bearing is subjected to a radial load of 5 kN is expected to have life of 8000 hr at 1450 rpm with reliability of 99%. life of bearing with 90% reliability is _______ million revolutions.

Answer 1

$P_e=5kN,L_{99}=8000hr,N=1450rpm$

$L_{99}=8000\times 60\times 1450$

$=\text{696 million revolutions}\frac{L_{90}}{L_{99}}={\left[\begin{array}{c}\frac{ln\left(1/R_{90}\right)}{ln\left(1/R_{99}\right)}\end{array}\right]}^{1/1.17}$

$L_{90}=L_{99}\times 7.45$

$L_{90}=\text{5185.96 million revolutions}$