Learning Forum

[Danial Hakim]

I'm conducting a random vibration analysis on a fixed-wing VTOL model aircraft to measure the amount of vibration exerted towards the wing during flight process. I can't seem to understand the output which is the response PSD obtained from the analysis. In my case, I used PSD displacement as the PSD input. How can I relate the amount of vibration exerted with the Response PSD (m2/Hz) obtained? Can anyone help me explain the relation? Thank you.

[Chandra Sekaran]

The output is the 1 sigma response (displacement, stress etc) which is the square root of the area under the response PSD curve. The RPSD curve shows the degree to which various natural frequencies of the structure are contributing to the response. For example, you might apply a PSD input that goes from 100 to 200 Hz in the Z direction. A natural frequency (mode) may be at 140 Hz but it may not be in the Z direction (very low participation factor in Z direction). So you won't see a peak at 140 Hz in the RPSD curve.

[Armin_A]

Hi Danial,

To add to Chandra's comment, please see the course (video) below that you may find helpful for random vibration analysis:

How to Correctly Interpret PSD results| Ansys Courses