Problem with ridgid elements

[y32k]

I'm having a problem with ridged elements that don't seem to be working they way they should be - they are not transferring displacements 100%. That is to say, the dependant nodes are not displacing as much as the dependant nodes.

Here is a simple model:
I have a solid cube hex meshed. The bottom corners are pinned. Above the cube is a node off-center from the CG of the top surface with a load in the downward direction (perpendicular to the top surface of the cube). The loaded node is connected to each node on the top surface of the block with ridged links in all 6 degrees with the loaded node as the independent node.
The solution that I get depicts that the surface of the block does not displace downward equally. Instead, the edge closest to the load is deflected the most and varies linearly to the edge away from the load, which is deflected much less that other edge. The surface remains planar, and the results given is what I would expect to see if I had loaded it with a triangular pressure.

My understanding about ridged links is that the displacement/rotation at one end of the link is transferred to the other end without any changes. The output on the nodes indicated that the rotation is transferred, but not the displacement.

Is my understanding incorrect, or have I missed something? Any help would be appreciated.

 

[Spirit]

y32k,

the RBE2 element forces the nodes connected to move only with a rigid body movement, with reference to the DOFs defined in the rigid element itself. If you look at the RBE2 definition, it is 'A rigid body connected to an arbitrary number of grid points', and a rigid body in rotation can definitely have different displacements in different positions. Think of a spinning wheel: the rotation of each one of his points is identical, but the displacements vary for different locations. So I see nothing strange in the behaviour you are describing.

If you want both rotations and displacements to be identical, just ground the rotational DOFs of the master node and see what happens.

Regards,

Spirit




'Ability is 10% inspiration and 90% perspiration.'

 

[y32k]

Spirit,

Thanks for the clarification, I wasn't fully grasping the definition. The rotaional constraints did exactly what I was looking for. Thanks

 

[40818]

Were you using RBE2 elements or another type? i.e RBE3 etc?