How to constrain non-touching surfaces to move as one?

[Anonymous]

The accompanying picture is of a structural linear stress analysis under a temperature/differential thermal contraction load.

One stainless steel plank [green in attached jpg] is sandwiched between two other planks of a differing steel [gray]. These two materials have slightly different mean coef. of thermal contraction, so if both ends' surfaces are (independently) tied together such that all three planks' ends move as one in the X-direction, the more shrunken steel (green) will be held in tension under the less shrunk steel planks's ends. (Of course, the gray steel planks will reciprocally be under compression via the green's relatively tugging both its ends together.)

I know how to tie everything together at the far end surfaces using general constraints in Tx, Ry, & Rz.

(Also, I'm using a sliding/no separation contact for both touching surfaces and 'anchoring' the whole assembly to one node's fully fixed general constraint so the whole thing doesn't go spinning off into space.)

What I'm after is how do I keep the pictured near ends' surfaces tied together (with regard to Tx, Ry, & Rz) while still allowing them to displace (as one) in the X direction under their individual pieces thermal differential contractions' loading?

FWIW, my model's default temperature is 70F, while its load temperature is -320F. (i.e., the model represents chilling the assembly down to -250F.)

Thanks!

[John_Holtz · Accepted solution]

Hi @Anonymous

I think that you should be able to use a rigid element in which one node on the end ("pick a node, any node") is connected to all of the other nodes on the end. Set the rigid element to work in the Tx direction. This should keep all of the nodes displacing the same distance in the X direction.

The command "Draw > Design > Contact Elements" will make it easy to connect all of the nodes to one node.

I did not try a test, and it has been a long time since I wrote the attached article, but I think it will work.

[Anonymous]

That did it.

Thank you.  

I kept looking for such under the Setup tab and never tried under the Draw tab.