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# Symmetry Fixture on Assembly

## Symmetry Fixture on Assembly

(OP)
I am trying to do a structural load analysis on a Geodesic dome which is symmetrical and can be divided way down which could really help with the setup and run time of the model. I used an Extruded-Cut to narrow the assembly down to the pie piece I want to do the analysis on but when running the model it still includes then entire model and all the parts in the analysis. Is there any way to make the Symmetry Fixture work in an assembly?

### RE: Symmetry Fixture on Assembly

What you probably need is cyclic symmetry and that is not supported in Cosmos/M or Simulation.

Cyclic symmetry constrains nodes on symmetry faces to move together.

If this dome is made of thin members, you could use beams, make one section and then rotate copy it around.

TOP
CSWP, BSSE
www.engtran.com  www.niswug.org
Phenom IIx6 1100T = 8GB = FX1400 = XP64SP2 = SW2009SP3
"Node news is good news."

### RE: Symmetry Fixture on Assembly

(OP)
Thanks for the response kellnerp, I'll give that a look.

### RE: Symmetry Fixture on Assembly

Could you apply a microscopic chamfer on all of the edges of the surface the cyclic symmetry constraint is applied to?  When you apply cyclic symmetry, only select  the face and not the chamfers.  This should help prevent the nodes from closing in on themselves.

### RE: Symmetry Fixture on Assembly

@moreinr
The problem with a geodesic dome is the symmetry faces|edges|vertices are not on planes. A dome of this nature is not amenable to modeling with solids so chamfers make little sense as a surface or beam element can't be geometrically chamfered.

The issue with this type of symmetry is to get the nodes on the symmetry faces to move together and this requires two things:
1. The nodes are defined in a cylindrical or spherical coordinate system based on the axis of rotation
2. The nodes on the symmetry faces that would join with the face on the opposite symmetry face must be forced to move together. This requires using the CPDOF command in Cosmos/M. There is no corresponding method in Simulation.

This is a long standing deficit in the SRAC/SolidWorks FEA products. ANSYS and other FEA products have had this capability for a long time.

TOP
CSWP, BSSE
www.engtran.com  www.niswug.org
Phenom IIx6 1100T = 8GB = FX1400 = XP64SP2 = SW2009SP3
"Node news is good news."

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