Learning Forum

[afshintaghvaeipour]

Dear Experts,

I have a clamped beam, first, I try to conduct a modal analysis to extract natural frequencies. Then, around the first natural frequency, I conducted a Harmonic analysis, with a force at the end tip. I got the response spectrum of the end tip displacement. Now, I am trying to conduct a transient dynamic analysis while a simple harmonic force with the same amplitude as the the harmonic and a frequency close to the natural frequncy is applied at the end tip. I expect to get the steady displacement amplitude same as a value on the response spetrum corresponding to the applied frequency. However, they are diffrenet. Would you answer why it happens. Noteworthy to mention that I defined similar damping on both analyses. 

Thanks

[Erik Kostson]

 

 

Hi

Should be the same (same frequency force and amplitude – so at resonance  – aslo both need same damping) – use though MSUP transient and MSUP harmonic for best comparison.

MSUP Transient:

https://www.youtube.com/watch?v=3fHu5fMHNeU

MSUP Harmonic:

https://www.youtube.com/watch?v=_1BASk_VyCQ

If you do that they are the same (displacement at the same location say at the tip).

All the best

Erik