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Hi Michael,

Since you are using an older version (5.2a), the technique is not identical to what you would use today (it is more streamlined now). Here is what to do:

• Add a Solid Connection node in the Beam interface (at point level). Use Connection type = Simplified
• Add a Beam Connection node in the Solid Mechanics interface (at boundary level)
• In the Beam Connection node you can reference the node you just created in the Beam interface.
• For other settings, consult the documentation for these features.

Regards,
Henrik

Hi Henrik,

Thank you for your reply and suggestion. I have actually already tried that and it still does not work. Let me illustrate my troubles. I attach a couple of models and I will now explain what is going on in the first attached model (model1e.mph) ... 1. There is the central rigid domain which is constrained by a spring foundation. 2. There is the second rigid domain around it which is not constrained directly but has a hinge joint on the boundary with the inner domain. Together, these two domains from the outside look like an object which is hooked up to a spring at the coordinate origin and free to rotate around the shape's center (wherever that center is - it may not be at the origin if the spring is stretched).

Now we apply a tangential load to a point on the surface. The tangent force will rotate the shape by 90 degrees and stretch the spring. If you look at the displacement of the point where the force is applied, it all seems to work.

Now let's add the beam. As you suggested, I added the beam using solid and beam connections. Now if I examine the free end of the beam, I expect to see it also rotate and displace. Instead I get an error.

I tried to see if there was a way to get around the error (model1f_1). In this second model, we have almost the same setup, except the beam is oriented differently and there is a new rigid domain at the end of it. The rigid domains at the ends of the beams are connected to the beam as you suggested. However if I apply force to move either domain, the simulation reports values as if there is no connection between these rigid domains, i.e. as if there is no beam.

I would appreciate any help or advice of hint you might provide.

Sorry, here is a simplified model. Just two circles (solid domains) connected by a beam. One circle (say #1) is held by a spring foundation, the other (#2) is pulled with a point load. The spring never stretches and the circle #1 never moves. However circle #2 moves in the direction it is pulled with constant acceleration, as if there is no restoring force.

An even simpler model is attached. Just a rigid domain held in place via a spring foundation. A beam is attached to it using solid and beam connections. Now I apply an edge load to the beam and I expect the rigid domain to move until the spring foundation provides enough restoring force to balance out the pulling force. However, the rigid domain does not move as far as I can tell. // P.S. Not shown here is a similar model where I applied a body load to the rigid domain. Sure enough, the domain moved, the spring got stretched, I even saw nice oscillations which I could the then damp via damping terms in the spring foundation. In other words, pulling on the domain itself produces meaningful results. Pulling on the beam does not.

The really interesting part here is that the beam definitely feels the stress, suggesting that it "knows" it is connected to a rigid domain. But the forces from the Solid Mechanics just never seems to couple into the MBD module.

And just to be clear, I need MBD hooked up to the model because I need hinge coupling elsewhere. I cannot just delete MBD from the simplified model. If solid mechanics module had hinges then I would not need MBD at all.

Hi Michael,

Some suggestions:

• The Beam-Solid Connection needs at least three nodes on the solid to be connected to the beam to be 'welded'. In your configuration it will be a 'hinge' since only the point where the beam is attached is 'seen' by the connection due to the curvature of the boundary. Solutions: Increase Connection Tolerance and/or refine the mesh. However: since the domain is rigid anyway, it is easier to set Connected area defined by to Selected Boundaries.
• If you a just going to borrow the joints from the MBD interface, you should not have any domains at all selected in the Multibody Dynamics node. You add Attachment nodes in Solid Mechanics or Beam, and then reference them in the Hinge Joint node.

Regards,
Henrik