Using Symmetry in Modal Analysis

Altair Forum User

Can we use symmetry in modal analysis? When I did with symmetry and without symmetry, I noticed huge difference in the first modal frequency.

 

And this forum, advices against using symmetry for modal analysis http://www.eng-tips.com/viewthread.cfm?qid=333936

 

But my part is a simple plate where even the constraints are also symmetric.

 

Can anyone adivce me on this. Thanks.

Altair Forum User

Hello,

 

you can use symmetry in modal analys, but you get only some of the results (only if the mode also full symetrical).

But you still miss a lot of modes (e.g. transverse to the boundary condition or any torsional mode).

 

I suggest to use free - free (no bc's... especially for small models).

 

Regards,

Mario

 

PS: take a look for the mode shapes in your calculations