AutoSPC and RBE2

LisaK
LisaK Altair Community Member
in Community Q&A

Hello,

I have a model with solid mesh (tetras) with membrane elements at the surface. All are 2nd order. The part I am analyzing is attached by three bolts, which are modelled as RBE2. The SPC is applied to the master of these. When I run eigenmodes analysis I need the AUTPSPC function in order to get the correct eigenmodes. This creates dof 456 at the slave nodes of the RBE2. Why is this needed? Is there any other way to solve this so that I don't need to use AUTOSPC?

BR

Lisa

Answers

  • Chayan
    Chayan
    Altair Employee

    Hi Lisa,
    Are you using OptiStruct as your solver. By default the OptiStruct shell elements have 6DOF per node. Since you are connecting the RBE2's to the shell elements, those 6 DOF's get transferred from the shell nodes to the Independent node of the RBE2.

    If using the membrane to extract surface stresses, instead of shell membrane, you could request for GPStresses for a nodeset that contains the surface nodes of your solid. That should get rid of the AUTOSPC.

    If you need to use membrane, pls check and make sure you are turning off the MID2 on your membrane elements, to simulate membrane behavior, otherwise the surface elements will introduce additional stiffness to your part. .

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