# Select a Lower Bound of R and Rmin

The choice of a lower bound of R is essential to achieve a result that shows the correct characteristics for low frequencies and preload dependent simulations.

The lower bound you chose for R during fitting depends on how the bushing is going to be used during simulation and on the available test data. If the application isn’t known at the time of fitting, the lower bound may be chosen only according to the test data. In a concrete application that value of R can then be modified in the simulation model by setting RMIN accordingly.

## Choose the Lower Bound of Rmin from Test Data

The desired behavior for a bushing model is that input frequencies that are smaller than the lowest provided test frequency data ${f}_{0}$ be passed into the static spline. To achieve this behavior, the lower limit of R should be set greater or equal to $2{f}_{0}\pi $ .

## Choose the Lower Bound of R Based on Anticipated Usage During Simulation

- If you desire that the simulation model have the ability to switch between two preloads within a given time $\delta T$ , then you should choose R to be greater or equal to $\frac{2\pi}{\delta T}$ .
- If you decide that these values of R are too conservative or you don’t want the entire response from the static spline, the simulation model is still capable of doing the switch between these preloads. The time it takes to complete a switch of all states from one preload to another is given by $\frac{2\pi}{R}$ .