Pressure Vessel Simulation - "The model is insufficently constrained"

[zwantz]

I am working on a simulation of a pressure vessel.

Here are some pictures:

All components:

Stripped down with supports:

I am getting errors during the run. It says that the Model is Insufficiently Constrained.

I dont understand how this could be. The default connection setting is set to bonded, there are ignored contact interfaces which are treated as "Free". These are located between the end caps and the central cylinder.

Any Ideas?

[346gnu]

Zach,

If you are not using contact and are treating the connectivity as 'free' where the contacts would otherwise be then you can use modal to identify the culprit.

Method 1:  run a constrained model and ask for rigid modes. remember to ask for number of parts x 6 as + 1 as the number of modes. Keep the mesh simple and unrefined. Review the rigid modes

Method 2: (useful if you have contacts) constrain each part fully with it's own constraint. suppress each in turn until the model fails. Use bisection method to home more quickly on the problem if you have a lot of parts/constraints.

Method 3: Review geometry again and pedantically ensure that every component is bonded to something that eventually leads to ground.

To get quick failures use Multi-pass adaptive and limit the maximum edge order to 1. No mesh refinement or anything fancy.

It will be obvious when you find it.

How are you accounting for the axial loads?

Keep us posted

[zwantz]

Thanks for your quick answer.

I'm running the Modal analysis right now. The contact interfaces have been ignored and treated as free by Simulate. Everything else is a bonded connection, even though in the real world the part simply rests on the supports and are not bonded.