7 Replies Latest reply on Jun 13, 2012 8:46 AM by Phil Perlich

    How does the Symmetry Fixture Work?

    Phil Perlich
    Phil Perlich May 25, 2012 2:44 PM

      I have a circular assembly the is symmetric across the front and right planes. How can I take advantage of the symmetry fixture?

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        • Re: How does the Symmetry Fixture Work?
          Anthony Botting
          Anthony Botting May 25, 2012 2:54 PM (in response to Phil Perlich)

          Hi Phil: If not already done, you will probably have to make an assembly cut to expose the symmetry faces. Presumably you could then select the face and apply the symmetry fixture.

          I tend to stick with the "old-fashioned" (manual) method so I can more clearly see what is going on, esp. if you have shell elements, they can be a bit tricky. For a solid element model, I will select the symmetry face and a reference plane parallel to that face and apply a displacement value of zero, normal to the reference plane (in SW 2012, you can select the same face for the reference plane - assuming it is flat). Hope that helps! - Tony

            • Re: How does the Symmetry Fixture Work?
              Phil Perlich
              Phil Perlich May 29, 2012 1:33 PM (in response to Anthony Botting)

              Thanks for the reply Mr. Botting,

              I am working with a solid element model. After I do the 'symmetry cut,' do I need to select the symmetric face on each part or will just one work?

               

              Also will the symmetry fixture work for a 1/4 piece or only a 1/2 piece?

               

              Do designers use the symmetry feature to ensure they have a symmetric mesh?

                • Re: How does the Symmetry Fixture Work?
                  Anthony Botting
                  Anthony Botting May 29, 2012 4:37 PM (in response to Phil Perlich)

                  Hi Phil:

                  Yes, normally you would select any cut face on each component.

                  It is supposed to work for 1/4 piece, too. I have done "pizza slices" on circular components as small as 1/16 slice - leaving enough "meat" to see some sort of result. The algorithm is supposed to locate a restraint value of zero, in the direction normal to the cut face. I am unsure if it works on a curved surface, however (i.e., not a flat surface).

                  I have used the feature to obtain symmetry in the mesh along that plane, too. However, note that if you were to mesh another pizza slice and assemble the slices, the elements that face each other across the boundary might not have a perfect size match. In this case, a common mesh control can be applied at the boundary in an attempt to match element size.

                  Another option that might be appropriate for your case is the "Axisymmetric 2D" method, where you mesh only a symmetry cut face with 2D elements. It automatically applies the boundary conditions for circular symmetry. If you create a new study, you should see an option at the bottom labeled something like "2D simplification". After that, there are choices for plane stress, plane strain or axisymmetric.

                  I hope that helps!