Creating a point symmetry restriction

You can specify a point symmetry geometric restriction for a shape optimization. A rotational symmetry geometric restriction forces selected faces of the optimized model to be symmetric about a specified point of symmetry. You specify the point of symmetry by selecting a coordinate system (the point of symmetry is assumed to be the origin of the coordinate system). You can use the global coordinate system, or you can create a datum coordinate system (see Methods for creating a datum coordinate system, for more information).

See Also
Creating a geometric restriction in a topology or sizing optimization
Creating a geometric restriction in a shape optimization

Context:

The mesh must be approximately symmetric about the point before the optimization starts so that the Optimization module can identify pairs of nodes on either side of the point of symmetry—the main node and the secondary node. By default, the main node is the node that the optimization moves out the most (the most growth) or moves in the least (the least shrinkage). The optimization displaces the main node, and the symmetry condition applies an equal displacement to the secondary node so that it remains symmetrical to the main node. Alternatively, if you are trying to optimize surfaces that are in contact, you can force the Optimization module to select the main node as the node to which the optimization is applying the least growth or the most amount of shrinkage.

  1. From the main menu bar, select Geometric RestrictionCreate.

    The Create Geometric Restriction dialog box appears.

    Tip: You can initiate the Create procedure in two other ways:

    • Click Create in the Geometric Restriction Manager. (You can display the Geometric Restriction Manager by selecting Geometric RestrictionManager from the main menu bar.)

    • Click the tool in the Optimization module toolbox.

  2. From the Create Geometric Restriction dialog box that appears, enter the name of the geometric restriction.
  3. Select Point symmetry (Shape) from the list of geometric restrictions, and click Continue.
  4. From the viewport, select the faces in which the point symmetry will be enforced. For more information, see Using the face curvature method to select multiple faces.

    If you would rather select from a list of existing sets, do the following:

    1. Click Sets on the right side of the prompt area.

      Abaqus/CAE displays the Region Selection dialog box containing a list of available sets.

    2. Select the set of interest, and click Continue.

    Note:

    The default selection method is based on the selection method you most recently employed. To revert to the other method, click Select in Viewport or Sets on the right side of the prompt area.

  5. When you have finished selecting faces, click Done in the prompt area.

    The Edit Geometric Restriction dialog box appears.

  6. Select the coordinate system. The point of symmetry is assumed to be the origin of the selected coordinate system.
  7. Select the method that the optimization will use to determine the main point. In most cases you should select Determine from most growth and least shrinkage. You should select Determine from least growth and most shrinkage only if you are trying to optimize faces that are involved in contact.
  8. Enter the tolerance in the X-, Y-, and Z-planes that will be used to determine symmetric points .

    The Optimization module uses the tolerance to identify the nodes that are symmetric to the point of symmetry.

  9. If desired, toggle on Ignore in first design cycle (default). When the optimization starts, it assumes the faces are already symmetric about the point. If the faces are not symmetric, the Optimization module issues a warning and tries to continue. If you toggle off Ignore in first design cycle and the faces are not symmetric, the Optimization module issues an error message and stops execution.
  10. Click OK to create the point symmetry geometric restriction and to exit the editor.