Element type for Modal Analysis

[harid]

Hello friends,

I am doin modal analysis to get natural frequencies of a 450mm tube. I used Brick 8node Solid 45 and got the first mode frequency of 550Hz. Then I tried changing the element type to 20NODE Solid 95. I got the the first mode frequency at 460Hz. Could anyone suggest which elemnt type is good for modal analysis . Also could anyone explain me wat are second order element types and examples of such higher order element types.
Thank you very much for ur precious answers.

Cheers
Harid

 

[Drej]

I guess the reason that your 20-noded brick elements are giving you a different frequency is because it is a more accurate solution, compared to the 8-noded brick. If you need to model a tube there are a number of ways. For instance, you could always use the 63 or 93 shells. I would guess the difference between these would not be so great for the same mesh densities used for the solid elements.

First order elements are those having nodes at each corner of the element only, whereas second (higher) order elements have what are known as "mid-side" nodes. For example, a shell63 is first order, shell93 second order (compare also solids 45 and 95).

Hope this helps
-- drej --

 

[harid]

Thanks a lot Drej...Ur help is greatly appreciated....
Thank u all guys...
cheers
harid