Question:

How do I create a passive region for running a Topology or Field Optimization?

Applies to:

• Topology Optimization
• Field Optimization

A passive region during optimization is defined as a region that will remain constant and not change from iteration to iteration. The region will remain solid for topology optimization with the default initial value, and mesh elements contained in a regional constraint will remain regardless of thresholding. By utilizing an initial value field for a topology optimization, users can also ensure some areas remain void, solid, or void/solid depending on the selected thresholding value at the end of the topology optimization.

For field optimization, the density value of the mesh element is not affected by the passive region as there is no thresholding occurring; instead, the selected design variable will remain constant throughout the optimization process. For example, a region of a parametric voronoi component that is included in a passive region constraint will keep the “initial cell size” and “initial beam thickness” throughout each iteration, and only the cells outside of the region will have their parameters changed to achieve the objectives/constraints.

Note: This workflow will not cover setting up an optimization workflow. It only covers setting up a passive region in both optimization scenarios. To learn how to run an optimization, we first recommend reviewing the following articles:

Different approaches are required for field and topology optimization to preserve solid topology throughout optimization. They are detailed below:

Preserving Solid Geometry in Topology Optimization:

For Topology Optimization, we use the Passive Region Constraint block. This block requires you to define a region that overlaps with the body being optimized. In the example below, mounting holes from the original CAD body have been thickened using a Thicken Body block. The extra material this creates will prevent the Topology Optimization from removing necessary material around the holes. Once the Topology Optimization is complete, you can see that the defined area is unaffected.

Preserving Solid Geometry in Field Optimization:

For Field Optimization, the Passive Region block maintains initial design variables. For passive (solid) regions, we must instead use an additional component and tie them together with a constraint. For the solid region, we can use an FE Solid Component, and for the area to be optimized, we can use one of the available “Parametric FE Components” such as Voronoi, lattice, or shell. The example below consists of a robotic arm frame we want to keep solid and a central area we want to optimize. We need to create a component and a boundary for each entity.

The central area is defined by a Parametric Lattice Component (Beta) and an FE Boundary by Body block. This isolates the specific region that we want to become the optimized lattice. An FE Component and an FE Boundary by Body block define the frame. This keeps the frame solid and separate from the lattice region. These two bodies are combined under the Parametric FE Model (Beta) block. The components are listed under the Parametric FE Components List (Beta), while the last step is to insert a Tie Constraint block under the input of the connector. This block ties the two boundaries together and establishes a relationship between them. Once the Field Optimization is complete, you can see that only the lattice region was affected.

And that’s it! You’ve successfully created passive regions!

Are you still having issues? Reach out to the support team, and we’ll be happy to help!