Symmetry not working correctly

[TerryR1]

I'm getting very different results when I try to use symmetry in Ansys 12.

I have a simple box with a force on the bottom; see picture.

When I run FEA on the whole thing, the box bottom deflects 0.1".
When I run it in symmetry, ansys tells me the box bottom deflects 0.4".


Setup for FEA on entire model:
4000lbs force on the bottom
Fixed support around the rim

Setup for FEA on symmetric model:
Only analyzing 1/4 of model
1000lbs force on the bottom
Fixed support around the rim
Frictionless support around cut faces.


Am I missing something? Thanks!

 

[TerryR1]

Wow I just answered my own question. The results of the symmetry FEA are correct.

When I matched the mesh size of the whole model to the symmetry model, the results match.

Scary that the results can be off by 600% with the default mesh size....