How to use the FFT of Acceleration Data in Dynamic Frequency Analysis and Dynamic Random Analysis?

[cwu-3]

How to use the FFT of Acceleration Data of three directions in Dynamic Frequency Analysis and Dynamic Random Analysis?

Our product is an electronic box with two fans. We have obtained data about their fan vibration from the fan supplier, as shown in the attachment.

We want to analyze the impact of fan vibration on our products. Is it possible to use dynamic frequency analysis or dynamic random analysis? How do I apply attachment data? How to convert the acceleration-related data to force-related data? How to judge the results of the analysis？

[rjakel]

Hi Caiming Wu,

You may download my presentation about dynamic analysis here:

Linear Dynamic System Analyses with Creo Simulate – Theory & Application Examples, Capabilities, Limitations

It should help you regarding dynamic frequency/random analysis in Creo Simulate.

First of all you need a FEM model of the measurement set-up of the fan. Otherwise you cannot transfer the measured acceleration into a force excitation for a dynamic frequency analysis of your housing, since you can just apply forces or base point acceleration in a dynamic analysis. The fan vibration may be caused by many reasons, not only fan unbalance (an example for unbalance excitation is shown in my presentation). With help of the fan FEM, you may try to compute the underlying unbalance from the measured acceleration, but this needs some assumptions you usually do not know (like damping). It is better to measure the bearing forces of the fan as function of rotating frequency directly and apply that force to your housing in a dynamic frequency analysis.