Design objectives in topology optimization

The design objective indicates the goal of the optimization process, which is to minimize or maximize a particular response, such as weight or compliance.

Each design objective is a modeling object. You can create multiple design objectives, but each topology optimization solution should have only one at either the solution or subcase level.

Some responses—such as weight or volume—can be used only at the solution level. Others—such as displacement or the frequency of normal modes—can be used at either the solution level or subcase level.

When you create a design objective at the subcase level, if the response can span several nodes or elements, you must specify how to combine the individual values into a single value for use for the optimization process. For example, a statics design objective might be to minimize the displacement of several nodes. You could specify that you want to use the maximum displacement value of all the selected nodes, the minimum value, the average of all the values, and so on. You can also do this for a solution-level design objective if the response is subcase-specific.

For a solution-level design objective with a subcase-specific response, you must specify the single response value to use for the optimization process from across multiple subcases. For example, a global design objective might be to minimize a stress response. The stress values would come from the statics subcases. If the solution has multiple statics subcases with different loads, the stress value for each subcase would be different. To get the single stress value to use for the optimization process, you must combine the stress values for the selected elements of each subcase into a single value (such as the maximum, minimum, or average value). You must then combine the single subcase values into a single overall value. This single overall stress value is then used in the topology optimization calculations.

Creating design objectives

You can create design objectives using the following approaches:

• Use the Modeling Objects command.For a topology optimization design objective, you can use any of the following modeling object types:Design Objective - GlobalDesign Objective - StaticsDesign Objective - Normal ModesDesign Objective - Direct FrequencyDesign Objective - Modal Frequency****Design Objective - BucklingWhen you use the Modeling Objects command, the design objective appears only under the Modeling Objects node in the Simulation Navigator. To apply it to your topology optimization solution, you must either right-click the modeling object and choose Add to Active Solution or Step, or drag the modeling object from the Modeling Objects node to the Design Objective node for the solution or subcase. You can use the Add to Active Solution or Step command only if the solution or subcase is active, but you can drag a modeling object to the Design Objective node at any time.You can use a global design objective only at the solution level. You can use the others only with the corresponding subcase. For example, you can use a statics design objective only with a Nastopt - Statics subcase.

• In the Simulation Navigator, right-click the Design Objective node under a topology optimization solution or subcase and choose New or Replace Design Objective.You can add a solution-level design objective only when the solution is active. If the solution is active, you can add a subcase-level design objective even if the subcase is not active.This approach adds the modeling object under both the selected Design Objective node and the Modeling Objects node.

If you use the Add to Active Solution or Step or New or Replace Design Objective command when a design objective already exists for the solution or subcase, the new objective replaces the existing one. However, both modeling objects continue to appear under the Modeling Objects node, and you can change the objective as needed.

Note:

If your topology optimization solution has more than one design objective (for example, if you create one at the solution level and one at the subcase level), your solution might fail.

Working with design objectives

• To see the information that will be sent to Simcenter Nastran when you solve the solution, right-click the design objective and choose Solver Syntax Preview.

• To remove a design objective from a solution or subcase, right-click the Design Objective node or the design objective itself and choose Remove.You can remove a design objective only when the solution is active.Removing a design objective from a solution or subcase does not delete the modeling object, so you can restore it later.

Where do I find it?

Application	Pre/Post
Prerequisite	A Simulation file as the work part and displayed part
Command Finder	Modeling Objects
Simulation Navigator	Right-click the Design Objective node under the solution or subcase→New or Replace Design Objective

How do I

Create a topology optimization solution

Create the design objective for topology optimization

Create a design area for topology optimization

Create a design constraint for topology optimization

Create a manufacturing constraint

Learn more

Simcenter Nastran Topology Optimization

Topology optimization workflow

Impact of rigid elements in topology optimization

Design areasin topology optimization

Design constraints in topology optimization

Manufacturing constraints in topology optimization

Lattice structures

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Design objectives in topology optimization, Simcenter 3D 2021.1 Series

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