98 - understanding cyclic symmetry constraints.pdf

7/27/2019 98 - Understanding Cyclic Symmetry Constraints.pdf

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StructuralConstraintsUnderstandingCyclicSymmetryConstraintsLecture

UnderstandingCyclicSymmetryConstraints.mp3Understanding Cyclic Symmetry Constraints

You can use symmetry constraints to significantly reduce model

size.

Before Cyclic Symmetry

After Cyclic SymmetryLectureNotes

Symmetry Constraints

When the loads, constraints, and geometry of a model are symmetrical, you can takeadvantage of symmetry to analyze a portion of the model instead of the entire model.Symmetric constraints work by preventing the model from deforming through theplane(s) of symmetry. There are two types of symmetry constraints that can be


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created in Mechanica: Mirror and Cyclic. We will focus on Cyclic symmetry in this

topic.

Cyclic symmetry is applied to models that are symmetrical about an axis. This isdifferent from axisymmetric models in that the model does not have to be a body ofrevolution. The model can have patterns of features that are repeated at the sameinterval about an axis. Using cyclic symmetry requires that the user create a cut

feature that reduces the model to a single slice.

Best Practices

It should be noted that symmetry can only be used when the model, loads, andconstraints are symmetrical. If only the model is symmetrical, then the resultsgenerated will not be correct, or may be correct for stress but not displacement,or vice versa. The symmetry requirement for loads and constraints is oftenoverlooked.

In cyclic symmetry, the angular dimension of the slice being used must returnan integer when 360 degrees is divided by the dimension. Therefore dimensions

such as 15, 18, 30, 45, 60 are all valid. In addition, the surfaces selected forcyclic symmetry must map to one another.

Finally, users should note that when taking advantage of symmetry in models, amodal analysis or buckling analysis will only report the modes that aresymmetrical. As such, not all modes may be captured. For such analyses it isrecommended to not use symmetry.

UnderstandingCyclicSymmetryConstraintsDemonstrationUnderstandingCyclicSymmetryConstraints_demo.mp4

UnderstandingCyclicSymmetryConstraintsProcedureProcedure: Understanding Cyclic Symmetry Constraints

ScenarioCreate a cyclic symmetry constraint.

CreateCycSymCons impeller.prt

Task 1. Resume a cut feature and open the Mechanica application.

1. From the main menu, click Edit > Resume > Resume All.

This operation resumed a cut feature that removes all of the geometry in the

model except for the piece to which you are going to apply the cyclic


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symmetry constraint.

2. Click Applications > Mechanica.

Task 2. Create a cyclic symmetry constraint.

1. Click Symmetry Constraint from the Mechanica toolbar.

2. Select Cyclic from the Type drop-down menu.

3. Query select the hidden surface on the far side of the slice as the first reference as

shown.

4. Right-click anywhere in the display area and select Second Side.

5. Select the surface on the near side of the slice as the second reference as shown.

6. The dialog box should now appear as shown. Click OK to complete the symmetryconstraint.


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7. The models should now appear with the Cyclic Symmetry icon as shown.

Task 3. Save the model and erase it from memory.

1. Return to the Standard Pro/ENGINEER mode by clicking Applications > Standard.

2. Click Save from the main toolbar and click OK to save the model.

3. From the main menu, click File > Close Window.

4. Click File > Erase > Not Displayed > OK to erase the model from memory.

This completes the procedure.


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98 - understanding cyclic symmetry constraints.pdf

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