HOW TO HANDLE SYMMETRY CONSTRAINTS AND RBE3 COUPLINGS | ERROR #2933

alex_ander
alex_ander Altair Community Member
edited October 2020 in Community Q&A

Hello, I have a problem to create a feasible model while using geometric symmetry (symmetry constraints). The model has 2 symmetries (xy plane and yz plane). The concentrated force is applied into an reference node which connects the inner node of the structure through a rbe3 element. The other side is also connected through RBE3 to a refrence node which is contrained.

 

While strictly constraining the nodes which are in the symmetry plane, e.g. xy plane the nodes will be contraint in dof 3 (z), 4(rx), 5(ry). But then I got following error massage:

 

 *** ERROR # 2933 ***
 There are more number of degree of freedoms with double dependency
 than the number of independent degree of freedom near grid ID
 2. PARAM,AUTOMSET is ineffective in this situation.
 
 *** Run terminated because of error(s) in the input data.
 

 

Solver FAILED

optistruct:: Solver run finished.

 

My interpretation was that the problem is because some of the nodes are constraint in symmetry and the rbe3 coupling doublewise.

Excluding the dof leads to a weird behaivour of the coupling. The reference point is moving I guess and I could not fix it. Running the model in a full volume runs well, but it has too many elements and is too slow. The quarter model runs very quickly although it is very fine.

 

I need to calculate with rbe3 element because I need to apply concentrated force. So I cannot use nodal force instead.

 

I hope the community here could help me.

 

 

 

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