Create a design variable for design optimization

1. In the Solution dialog box, click the Bulk Data tab.

2. Click Create Design Variable (next to Design Variables).

3. From the Type list, select the type of attribute to allow the solver to vary.Property — Lets you choose physical properties such as the T field (thickness) in a PSHELL, the DIM1 in a PBEAML, and so on. In Nastran, this creates a DESVAR/DVPREL1 combination.Composite Property — Lets you choose composite or laminate physical properties such as the NSM field (nonstructural mass) in a PCOMP. In Nastran, this creates a DESVAR/DVPREL1 combination.Material — Lets you choose material properties such as the Young's Modulus value in a MAT1 material. In Nastran, this creates a DESVAR/DVMREL1 combination.Connectivity — Lets you choose element fields such as the ZOFFS field (Z offset) in a CQUAD4 element. In Nastran, this creates a DESVAR/DVCREL1 combination.

4. In the Design Variable (DESVAR) group, in the Label box, type a descriptive label for this design variable. After you solve, you will analyze the optimization results in the Nastran .f06 file and each design variable will be identified with this label.

Defining a Property or Composite Property design variable

1. In the Property Relation (DVPREL1) group, from the Type list, select the type of physical property to vary (for example, PSHELL).

2. From the Physical Property list, select the physical property table that contains the property to vary. If necessary, click Create Physical to create a new physical property table.

3. From the Property Field list, select the property to vary (for example, the T field in a PSHELL).

4. Continue with the steps in Specifying the Relation Definition below.

Defining a Material design variable

1. In the Material Relation (DVMREL1) group, from the Material list, select the material record that contains the material property to vary. If necessary, click Choose Material to select a different material record.

2. From the Type list, select the type of material (for example, MAT1).

3. From the Material Field list, select the material property to vary (for example, E, RHO, and so on).

4. Continue with the steps in Specifying the Relation Definition below.

Defining a Connectivity design variable

1. In the Connectivity Relation (DVCREL1) group, from the Group list, choose the group that contains the elements to modify with this variable. If necessary, click New Group to create a new group.

2. From the Type list, select the type of elements, such as CBAR.

3. From the Element Field list, select the field to modify. For example, modify the X1 field of the CBAR elements included in the group you selected.

4. Continue with the steps in Specifying the Relation Definition below.

Specifying the Relation Definition

The Relation Definition determines how the solver will use the values you enter for Initial Value, Lower Bound, and Upper Bound.

• Assigned at Export — The initial value and lower/upper bounds represent scale factors. For example, vary the shell thickness by a starting scale factor of 1.0, lower bound of 0.5, and upper bound of 2.0.

• User Defined — The initial value and lower/upper bounds represent actual values. For example, vary the shell thickness using a starting value of 0.2 mm, lower bound of 0.1 mm, and upper bound of 2 mm.

When you select User Defined, you can enter a Constant Term and Coefficient.

The general Nastran variable relation equation in this software has the form:

Pi = C0 + COEF * DVID

Where

• Pi is the actual variable range used by the solution.

• DVID is the range defined with the initial, lower, and upper values.

The meaning of these values depends on whether you selected Assigned at Export or User Defined.

• Assigned at Export — When you solve and the solver input file is exported, COEF is automatically assigned to the current property value, C0 is set to 0, the general equation becomes Pi = COEF * DVID and initial, lower, and upper values are applied as scale factors. For example, if the current value of a shell thickness variable is 0.2, COEF=0.2 is assigned during the solution export process, and the initial, lower, and upper values are applied as scale factors: initial value: 1.0lower value: 0.5upper value: 2.0In this example, the actual variable range used by the solution is 0.1 to 0.4.

• User Defined — C0 and COEF are unitless user inputs. You can use C0 and COEF to scale the variable range linearly. Or, if you set them to C0=0.0 and COEF=1.0, the general equation becomes Pi = DVID and the initial, lower and upper values are applied relative to the actual variable range. Using the previous example, if C0=0.0 and COEF=1.0, the initial, lower and upper values are explicitly applied as:initial value: 0.2lower value: 0.1upper value: 0.4

In most cases, you can use the default Constant Term of 0 and a Coefficient of 1.

Defining the Initial Value and Lower and Upper Bounds

1. In the Initial Value box, enter the starting value of the attribute to vary. For example, if you are varying membrane thickness, and the modeled thickness of the shell elements is 0.2 mm, enter 0.2. If you are entering this value as a scale factor, enter the initial scale factor, such as 1.0.Note: If you are entering actual values rather than scale factors, make sure to enter the values in the model units. For example, if the response is for displacement, and your model units are metric, enter the value in mm.

2. In the Lower Bound box, enter the lowest value (or scale factor) the solver can use when varying this property.

3. In the Upper Bound box, enter the highest value (or scale factor) the solver can use when varying this property.

4. Click OK to finish creating the design variable and return to the Modeling Objects Manager.

Adding the design variable to the solution

After you create a design variable, it appears in the Selection list in the Modeling Objects Manager. To specify that the solver should use the new design variable in the solution, select the design variable and click the Add to List button. The design variable now appears in the List and you can close the Modeling Objects Manager.

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Create a design variable for design optimization, Simcenter 3D 2021.1 Series

© 2020 Siemens

window.mainLanguage="en_US"

window.delivId=""

window.projectId=""

MathJax.Hub.Config({ TeX: { extensions: ["autoload-all.js"] }, tex2jax: { displayMath: [ ] }, "SVG": { scale: 125 } });