Coupling ref nodes to solids in Abaqus

[b.overdorp]

Hi,

I'm a little new to abaqus and having trouble with the following:

I've created a beam in C3D8I elements which I want to load in pure bending,
therefore, I have created 2 ref nodes at both ends. I have coupled the ref
nodes to the end surfaces of the beam using Coupling constraint. When I
apply a rotation to the ref nodes it does not transfer the rotation to the
beams surfaces, and the Riks analysis terminates. Now I'am aware this is wrong since Solids do not have
rotational DOF's, but I have not found another method to accomplisch what
I'm trying to do. Any suggestions?

 

[Mustaine3]

The chances are very low, that two loads and the responses balance each other numerically exactly and create an equilibrium. So you should think about boundary conditions (recommended) or try options like Inertia Relief or Stabilization.

 

[b.overdorp]

I have used a Displacement/Rotation BC on both sides of the beam. Moreover, I found an earlier (Closed) thread which deals with the same kind of situation:

http://www.eng-tips.com/viewthread.cfm?qid=334975

I have used the same approach, but the rotation of the ref node still seems to not be coupled to the surface. As abaqus return the following error:

 

[Mustaine3]

Try first to couple all DOF. Also check what happens with a regular static procedure, not Riks.

 

[b.overdorp]

Coupling DOFs U1, U2, U3, works, Rigidbody aswell. However, I'm still curious why coupling UR3 works in the other thread. Maybe it's the Riks analyses indeed, although I see no reason why. I will consider this one closed (solved-ish).

 

[Mustaine3]

Nodes at solid elements have no rotational DOF, so you cannot couple them to something else.
And in the other thread it wasn't mentioned that it worked - it was just asked.

 

[IceBreakerSours]

Why do you need to do Riks analysis for a pure bending deformation of a beam?

Also, the reference node you created is probably left unconstrained in the translation DOFs. Have you checked the warning/error messages in the log (.dat/.msg) files?

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