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Modal analysis on hollow beam
Mon, 2008-06-02 06:28 - Stefano Galiasso
Good morning, I am studying a cantilever hollow beam both with FEM (Ansys) and MULTYBODY (MSC Adams).
Do anybody knows why I get different mode shapes performing modal analysis with the two codes? (e.g. 3rd mode in Adams is torsional while ansys has not any torsion modes!!)
Thank you very much
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Re: Modal analysis on hollow beam
Do you have the same degrees of freedom in both cases? i.e. in Ansys, do you use a 2D or a 3D beam?
Need Info on Adams:
Stefano
I agree with rayoly's comments. Please use beam4 or other 3D beams. (So I presume that your Adams solution is correct).
I have a small doubt in using Adams view package, Is that not a rigid body dynamics tool? Did you use flexible body for the analysis?
Can you please explain on how you used Adams/View package to do modal analysis? Thank you.
Gopinath
University of Oklahoma
I used beam4 elements with
I used beam4 elements with ansys (5 elements) while I used 5 elements in ADAMS linking their center of masses with a beam --> elastic property.
In this way I thought I get a flexible beam even with ADAMS, and ADAMS simulations give me this idea too.
I am gonna check how to explain better what I did with the two codes, thank you for your willingness.
Stefano Galiasso
Automotive Engineer (Bachelor)
Mechanical Engineer (Master degree, currently attending)
Did you check with the analytical solution:
Stefano
Did you try to compare with the analytical solution, ωn2=(E I/ρ A)βn4 where Cos[βn L] Cosh[βn L]+1=0, and n=1,2,3...
(read as Omega_squared=(E I/ρ A) (beta raised to power 4), subscript n for nth mode)
βn=1.8751, 4.6941, 7.8548, ...
Regards,
Gopinath