Insufficient Constraint Problem

[PaulAchard]

Hello,

I am trying to model a shaft-like part in torsion (Tripod CV Joint). I've been getting messages telling me some elements are insufficiently constrained, so I tried a simple modal analysis to verify my constraints. No matter how many surfaces are constrained on the model, however, I always get the same message that one or two elements are insufficiently constrained, which really doesn't make sense to me. The problem elements usually have either a node on a surface or a corner.

Has anyone had similar problems?

I have attached the file in question, but it has been created using a university license so there might be incompatibility with professional licenses.

Thanks!

[JonathanHodgson · Accepted solution]

Hello Paul,

Mechanica can be rather obtuse with its errors at times!

Just a simple one to check: have you assigned a material (via a Material Assignment within Mechanica), and does it have a Young's Modulus value? Having a zero-stiffness material can also give under-constraint!

Failing that, do the modal analysis results let you look at the first mode shape?

[PaulAchard]

Aha, I knew I was missing something fundamental. I had the material assigned with mass, but no modulus... This seems to work now.

Thanks!