Creating a member size restriction

For a topology optimization you can specify the minimum or maximum size of selected regions of your model; for example, the minimum size of a region in which the optimization creates trusses. You can also specify the minimum distance between trusses. Specifying a maximum member size forces the optimization to split thick regions into several smaller regions and prevents it from creating large contiguous regions that may be difficult to cast. Specifying a minimum member size avoids thin trusses that may be difficult to manufacture. The minimum member size must be greater than twice the average element size to prevent the results from being dependent on the mesh size.

Related Topics
Creating a geometric restriction in a topology or sizing optimization
Creating a geometric restriction in a shape optimization

Context:

In most cases you can specify the same value for both the minimum and maximum member size, and the Optimization module creates trusses that are approximately equal to the specified value. To prevent the structure from collapsing, the Optimization module tries to avoid creating thin trusses in regions where prescribed conditions are applied.

Specifying the minimum or maximum member size is very computationally expensive and should be used only where necessary. You should perform an optimization without member size restrictions to identify any regions where the restrictions should be applied.

Note:

You can combine a member size constraint and a demold constraint only for a general topology optimization.

  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 Member size (Topology) from the list of geometric restrictions, and click Continue.

  4. From the viewport, select the region to which the member size restriction will be applied or click Done to apply the member size restriction to the entire model.

    By default, Abaqus/CAE allows you to select all of the model. To select faces or cells, use the Selection toolbar to change the type of object that you can select to Face or Cells. For more information, see Filtering your selection based on the type of object.

    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 the geometric restriction region, click Done in the prompt area. For more information on selecting objects, see Selecting objects within the viewport.”

    The Edit Geometric Restriction dialog box appears.

  6. Do one of the following:

    • Select Minimum thickness, and enter the minimum member thickness.

    • Select Maximum thickness, and enter the maximum member thickness.

    • Select Envelope, and enter the following:

      • The Minimum member thickness.

      • The Maximum member thickness.

      • The Minimum gap between members.

  7. Click OK to create the frozen area geometric restriction and to exit the editor.