Each model has its own unique failure rate equations for the parts that it supports. The failure rate equation for a part consists of system parameters and multiple Pi (Π) factors, which when calculated provide the failure rate of the part. Each parameter in the Prediction Data pane affects the values of one or more Pi factors (or C factors for a mechanical part).

In the Prediction Data pane, clicking Pi Factors opens the Pi Factors window, which shows the Pi factors used by the selected model to calculate the failure rate for the part. Near the bottom of the Pi Factors window are Model Failure Rate and Failure Rate.

Base failure rates calculated by the model are adjusted when one or more of the following conditions occur:

If the part is overstressed based on derating limits specified in Prediction Derating fields, the Pi Factors window notes the cause for the overstress beneath the calculated failure rates. For more information, see Prediction Derating Files.

If the failure rate for the part is allocated, the Pi Factors window displays a message indicating that no Pi factors are associated with parts that have allocated failure rates. For more information, see Reliability Allocation.

To report on the Pi factors for parts, you can use the supplied Report Design file, Prediction Pi Factors. This report includes Pi Factors, which stores the values for all Pi factors that the selected calculation model uses to compute the part’s failure rate. You can also use the Format Builder to insert Pi Factors in the System Tree Items table and Parts Table. Additionally, you can include this field in an export.

In the Pi Factors window, you can click Copy Data to copy the data to the Windows Clipboard. You can then paste the copied data into any Windows document or spreadsheet. To close the Pi Factors window, you click Close.