iMechanica - Modal analysis on hollow beam - Comments

Did you check with the analytical solution:

Gopinath Venkatesan — Wed, 04 Jun 2008 10:15:57 -0400

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

I used beam4 elements with

Stefano Galiasso — Wed, 04 Jun 2008 05:44:36 -0400

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)

Need Info on Adams:

Gopinath Venkatesan — Tue, 03 Jun 2008 10:15:14 -0400

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

Re: Modal analysis on hollow beam

rayoly — Mon, 02 Jun 2008 08:58:41 -0400

Do you have the same degrees of freedom in both cases? i.e. in Ansys, do you use a 2D or a 3D beam?

Modal analysis on hollow beam

Stefano Galiasso — Mon, 02 Jun 2008 06:28:07 -0400

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