2.4. Define Optimization Method and Regions

Overview

You use the Optimization Region object to specify the optimization method you want to use and then select the regions of your geometry on which to perform optimization. Using the properties of the object, you define the Design Region and the Exclusion Region for the analysis. Refer to the Optimization Region object reference page for additional information about this object.

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Select the Optimization Type

You use the Optimization Type property to select the desired optimization method.

Optimization Type Property Options

  • Topology Optimization - Density Based (default)

  • Topology Optimization - Level Set Based

  • Lattice Optimization

  • Shape Optimization

  • Topology Optimization - Mixable Density

  • Topography Optimization

See the Design Method Definitions section for more information about the requirements and limitations of each method.

Design Region Property

The properties of the Design Region category enable you to define the geometry as a Geometry Selection or a Named Selection. This is the region that you wish to optimize.

Exclusion Region Property

The properties of the Exclusion Region category enable you to specify a region (geometric entities or elements) to be excluded from optimization. You specify excluded regions using defined Boundary Conditions, Geometry Selection, or a Named Selection.

Create Multiple Optimization Regions

You can specify multiple Optimization Regions objects and mix the level set, mixable density, shape optimization, and topography methods together. When mixing the use of these methods, you can define as many Optimization Region objects as needed and attach individual manufacturing constraints to each.

Density Based optimization regions cannot be mixed with other types of optimization regions. When you are using the  density-based optimization method you have two options: you can use multiple Optimization Region objects or you can use Geometry Selection or Named Selections  to define the scope of the Manufacturing Constraints.

Important:

  • Each optimization region must be uniquely scoped. The scoping of the regions cannot overlap. The application will include all the geometries of the optimization regions in the optimization process. You can use the individual optimization regions for the scoping of geometric response constraints and of manufacturing constraints.

  • The Topology Optimization - Level Set and Shape Optimization options/method support 3D solid elements only and the Topography Optimization method supports shell elements only.

The following table outlines the methods that you can combine within an optimization problem.

 Density Based OptimizationLattice OptimizationLevel Set Based OptimizationMixable DensityShape OptimizationTopography Optimization
Density Based OptimizationX     
Lattice Optimization X    
Level Set Based Optimization  XXXX
Mixable Density  XXXX
Shape Optimization  XXXX
Topography Optimization  XXXX

Define Additional Exclusion Regions

The Optimization Region object provides the contextual (right-click) menu option Local Design Restriction that enables you to specify additional exclusion regions on your model. Inserted as a child object to the Optimization Region object, it provides the scoping options Geometry Selection and Named Selection. These options follow the same scoping requirements described below.

The Structural Optimization solution does not optimize the exclusion region defined using this Local Design Restriction object. The recommended use of the Local Design Restriction object includes scenarios wherein certain regions of interest, that may be disconnected, need to be retained even though no loads or boundary conditions exist on the region.

Specify Object Properties

Using the properties of the Details pane, specify the method optimization regions for your analysis.

CategoryProperties/Options/Description

Design Region

Scoping Method. The options for this property include:

  • Geometry Selection (default): This option indicates that the design region is applied to a geometry or geometries, which are chosen using graphical selection tools. When you specify Geometry Selection for the Scoping Method, the Geometry property will appear.

    In this case, use selection filters on the Graphics Toolbar to pick your geometric entities (only body and element selection), and then click Apply. Once complete, the property displays the type of geometry (Body, Element, etc.) and the number of selected geometric entities (for example: 1 Body, 12 Elements).

  • Named Selection: Indicates that the geometry selection is defined by a Named Selection. When you specify Named Selection for the Scoping Method, the Named Selection property will appear. This property provides a drop-down list of available user-defined Named Selections (only body-based and element-based Named Selections are supported).

Exclusion Region

Defined By. The options for this property include:

  • Boundary Condition (default):

    When you specify Boundary Condition for the Defined By property, a Boundary Condition property will appear. This property includes the following options:

    • All Boundary Conditions: Applies the locations of all loading conditions and supports from the upstream static/modal system.

    • All Loads: Applies the locations of all loading conditions from the upstream static/modal system.

    • All Supports: Applies the locations of all supports from the upstream static/modal system.

    • None: No boundary condition locations are applied.

    Note:  Ansys strongly recommends that, at a minimum, you specify the option All Loads for any Exclusion Region.

  • Geometry Selection: This option indicates that the design region is applied to a geometry or geometries, which are chosen using graphical selection tools. When you specify Geometry Selection for the Scoping Method, the Geometry property will appear. Exclusion Region geometry selections can be scoped to bodies, faces, edges, vertices, elements, and nodes.

  • Named Selection: Indicates that the geometry selection is defined by a Named Selection. When you specify Named Selection for the Scoping Method, the Named Selection property will appear. This property provides a drop-down list of available user-defined Named Selections. Exclusion Region Named Selections support body-, face-, edge-, vertex-, element-, and node-based Named Selections.

Exclusion Thickness: This property displays when you set the Optimization Type property to Topology Optimization - Level Set Based, Topology Optimization - Mixable Density, or Shape Optimization. The default setting for this property is Program Controlled or you can enter a value manually. This option enables you to specify a thickness for the Exclusion Region. The default value is two times the average element size. The unit must be a length.

Exclusion Extension: This property displays when you set the Optimization Type property to either Topology Optimization - Level Set Based or toTopology Optimization - Mixable Density. This option enables you to specify the extension type for the Exclusion Region. Options include is Isotropic (default) and Orthotropic. Use the Isotropic option to perform expansion uniformly in the three directions. Use the Orthotropic option to perform the expansion along the surface normal. The Orthotropic option is only available for surface bodies.

Optimization Option

Optimization Type: You use this property to specify the type of optimization you wish to perform. Options include:

  • Topology Optimization - Density Based

  • Topology Optimization - Level Set Based

  • Lattice Optimization (see below)

  • Shape Optimization (see below)

  • Topology Optimization - Mixable Density

  • Topography Optimization (see below)

Lattice Optimization

The following additional properties are available when you select Lattice Optimization as the Optimization Type:

  • Lattice Type: This property specifies the structure of the unit cell.

  • Minimum Density: This property specifies a minimum density in order to avoid lattice structures that are too thin.

  • Maximum Density:This property specifies a maximum density. The element will be considered as full for densities higher than the Maximum Density.

  • Lattice Cell Size: The value of this property specifies the lattice cell size to be used when rebuilding the lattice geometry for printing.

Shape Optimization and Topography Optimization

The following additional properties are available when you select Shape Optimization or Topography Optimization as the Optimization Type:

  • Move Limit Per Iteration: This property enables you to define how far each node can move at each iteration. It must be defined in length units, for example one element size. By default, this property is set to Program Controlled. Select the Manual option to change the value.

  • Total Move Limit: This property enables you to define how far each node can move in total. It must be defined in length units, for example three times the element size. By default, this property is set to Program Controlled. Select the Manual option to change the value.

  • Mesh Deformation Control: This property enables you to define how much the mesh can be stretched. It is an additional control to avoid element distortion. This unit-less value is a sort of penalty factor that ranges from 0 (no control) to 1.0. By default, this property is set to Program Controlled. Select the Manual option to change the value.