Frequency response analysis using NASTRAN

[sasank]

Hallo!
I am running point mobility to find out the '0' Hz equivalnet static stiffness of bracketry of a typical SUV frame.Calculating the deflections and from deflections calculating the stiffness. Aim is to find out the equivalent static stiffness in a free-free conditions. But, I do nothave any tool or back ground to support my results. Can any body suggest a way for that.

Kamalakar

 

[GregLocock]

So, do you have a plot of mobility for the driving point? ie velocity per unit force, vs frequency?



Cheers

Greg Locock

 

[sasank]

Let me be more clear. My intention is to find the equivalent static stiffness at '0'Hz. displacements are my outputs from the analysis. (SOL111). I am finidng the static stiffness only without constraining the frame

Regards
Sasank

 

[GregLocock]

Oh, so is the plotted curve horizontal at very low fgrequencies? If so then the stiffness is just the test load (1 N?) divided by that displacement.



Cheers

Greg Locock

 

[sasank]

Greg
Thanks for the reply. But, my question is can we validate this stiffness with some kind of test or theotically?

Regards
kamalakar

 

[GregLocock]

Yes, by hitting it with an impact hammer and measuring the resulting vibration. The technique is called experimental modal analysis. Your noise and vibration laboratory will be able to do this for you.

Cheers

Greg Locock