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PaulAchard1-Visitor
1-Visitor
Jan 16, 2013 6:37 AM UTC
Solved

Insufficient Constraint Problem

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!

JonathanHodgsonAnswer
13-Aquamarine
Jan 16, 2013 1:56 PM UTC

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?

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2 replies

JonathanHodgson13-AquamarineAnswer
13-Aquamarine
Jan 16, 2013 1:56 PM UTC

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?

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    PaulAchard1-VisitorAuthor
    1-Visitor
    Jan 16, 2013 3:06 PM UTC

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

    Thanks!

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