Load Life Analysis for Combined Load

The analysis done in Rolling Element Bearing Load Life and Size Selection is primarily for radial load only.

When there is an axial load, we can still use the load rating values ($C$ and $C_0$), but we need to re-compute the equivalent dynamic load $P$.

Specifically, we get the weighted average as:

$$\begin{array}{rl}{P}_0& =X_0{F}_r+Y_0{F}_a(\text{for static load})\\ P& =X{F}_r+Y{F}_a(\text{for dynamic load})\end{array}$$

where $X$ or $X_0$ is the radial factor and $Y$ or $Y_0$ is the axial factor.

Bearing manufacturers provide a detailed guideline on how to compute the equivalent load, e.g. in the NSK catalogue.

• The equivalent load $P$ (or $P_0$) is determined by the linear combination of $F_r$ and $F_a$
• Radial/axial factors depend on other factors, $e$ and $f_0$
• If $F_a$ is relatively small (not bigger than $e$), then it can be ignored

Example