Transition from 3D elements to 2D elements

[VzHache]

Hi Guys,

I want to model a part with 2D elements AND 3D elements with MSC.Nastran. I'd like to know if somebody can give me a method or a reference that deals with the problem. The problem lies in the rotation degree of freedom of node in shell elements that are not available in 3D elements.
I have been told that I could make the shell elements penetrate the 3D mesh along one element.
I'm looking for reference to validate this method or reference to get an other method.
I hope that I have been clear (I speak sometimes broken English).

Thanks in advance

 

[GBor]

VzHache,

Your english is fine, but I'm not sure I fully understand the question. I presume that you are trying to include plate elements and brick elements in the same model and are unclear how to handle the 6 DOF shells with the 3 DOF bricks without forming a hinge where the plates freely rotate where they meet the bricks.

If this is the case, it is standard practice to overlap the bricks with the plates. If that is a critical area in the model, you may want to give the row of plates that overlap a very low modulus. Regrettably, I do not have a good reference for this.

 

[crisb]

Some codes have transition elements. They are shell elements with extra nodes at the transition (to a solid element). A quick Google found this which may or may not be helpful (I don't use MSC Nastran).

http://www.mscsoftware.com/support/library/conf/auc99/p05699.pdf

 

[torpen]

Hello,

Your FEA code allows to connect shell to solid elements with the constraint relation called RSSCON.

Another basic solution is to write the kinematic constraints between the dofs of the facets of the solid elements on both sides of the shells and the rotational dofs of the shells. The height of the solid elements on both sides of the shells should be equal to the half thickness of the shells.

It is not necessary if the common line between solid elements and shell elements is not straight (no hinge moment).

Regards,

Torpen.

 

[VzHache]

Hi,

thank you all for your answers. It really helps me.