Design constraints in topology optimization

Design constraints are limitations that ensure that the optimization results satisfy any important requirements. For example, you might want to make a part as stiff as possible while using only half of the part's original weight. The weight requirement would be a design constraint.

Each design constraint is a modeling object. You can create multiple design constraints and use one or more for each topology optimization solution, subcase, or both. For example, you might create one design constraint for the solution that specifies the acceptable weight range for the model, and another for a statics subcase that specifies the maximum displacement for a selected node.

You can use a design constraint for weight or volume only at the solution level. For all other responses—such as displacement or the frequency of normal modes—you must create the design constraint at the subcase level.

Tip:

Do not add design constraints that might make convergence more difficult. For example, do not add a design constraint that sets the lower limit on von Mises stress to zero; von Mises stress must always be a positive value.

Creating design constraints

You can create design constraints using the following approaches:

• Use the Modeling Objects command.For a topology optimization design constraint, you can use any of the following modeling object types:Design Constraint - GlobalDesign Constraint - StaticsDesign Constraint - Normal ModesDesign Constraint - Direct FrequencyDesign Constraint - Modal Frequency****Design Constraint - BucklingWhen you use the Modeling Objects command, the design constraint 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 Constraint 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 Constraint node at any time.You can use a global design constraint only at the solution level. You can use the others only with the corresponding subcase. For example, you can use a statics design constraint only with a Nastopt - Statics subcase.

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

Working with design constraints

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

• To remove a design constraint from a solution or subcase, right-click the design constraint and choose Remove. To remove all of the design constraints, right-click the Design Constraint node and choose Remove All.You can remove a design constraint only when the solution is active.Removing a design constraint 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 Constraint node under the solution or subcase→New Design Constraint

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

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Impact of rigid elements in topology optimization

Design objectives in topology optimization

Design areasin topology optimization

Manufacturing constraints in topology optimization

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Design constraints in topology optimization, Simcenter 3D 2021.1 Series

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