HS-4210: Multi-Disciplinary Optimization Study

Learn how to perform a multi-disciplinary size optimization for two finite element models defined for OptiStruct that have common input variables.

Before you begin, copy the model files used in this tutorial from <hst.zip>/HS-4210/ to your working directory.
The objective is to minimize the volume of the plate under a stress and a frequency constraint. The input variables are the thickness of each of the three components, defined in the input deck via the PSHELL card. The thickness should be between 0.05 and 0.15; the initial thickness is 0.1. The optimization type is size. To demonstrate the use of the optimization tool in a multi-disciplinary optimization, two models are created. One model is used for the stress analysis and one for the frequency analysis. Both models must have the same input variables.
Figure 1. Double Symmetric Plate Model


Perform the Study Setup

  1. Start HyperStudy.
  2. Start a new study in the following ways:
    • From the menu bar, click File > New.
    • On the ribbon, click .
  3. In the Add Study dialog, enter a study name, select a location for the study, and click OK.
  4. Go to the Define Models step.
  5. Add a Parameterized File model.
    1. From the Directory, drag-and-drop the plate1.tpl file, located in approaches/setup_1-def/run__00001/m_1, into the work area.
      Figure 2.


    2. In the Solver input file column, enter plate1.fem.
      This is the name of the solver input file HyperStudy writes during the evaluation.
    3. In the Solver execution script column, select OptiStruct (os).
  6. Add a Parameterized File model.
    1. From the Directory, drag-and-drop the plate2.tpl file, located in approaches/setup_1-def/run__00001/m_2, into the work area.
      Figure 3.
    2. In the Solver input file column, enter plate2.fem.
    3. In the Solver execution script column, select OptiStruct (os).
  7. Click Import Variables.
    Six input variables are imported from the plate1.tpl and plate2.tpl resource file.
  8. Go to the Define Input Variables step.
  9. Review the input variable's lower and upper bound ranges.
  10. Link Property 21 to Property 11.
    1. Click the Links tab.
    2. In the Expression column of the input variable Property 21, click .
    3. In the Expression Builder, click the Input Variables tab.
    4. In the work area, select Property 11.
    5. Click Insert Varname.
      The expression var1 appears in the Evaluate expression field.
      Figure 4.


    6. Click OK.
      Property 21 of Model 2 is linked to Property 11 of Model 1.
  11. Create two more links.
    1. Link Property 22 to Property 12.
    2. Link Property 23 to Property 13.
    Figure 5.


Perform Nominal Run

  1. Go to the Test Models step.
  2. Click Run Definition.
    An approaches/setup_1-def/ directory is created inside the study directory. The approaches/setup_1-def/run__00001/m_1 and approaches/setup_1-def/run__00001/m_2 sub-directories contain the plate2.out (for the structural volume and frequency) and plate1.h3d (for the stresses) files, which are the results of the nominal run, and will be using during the Optimization.

Create and Evaluate Output Responses

In this step you will create three output responses: Volume, Stress43, and Frequency1.

  1. Go to the Define Output Responses step.
  2. Create the Volume output response, which represents the volume of the plate.
    1. From the Directory, drag-and-drop the plate2.out file, located in approaches/setup_1-def/run__00001/m_2, into the work area.
    2. In the File Assistant dialog, set the Reading technology to Altair® HyperWorks® and click Next.
    3. Select Single item in a time series, then click Next.
    4. Define the following options, then click Next.
      • Set Type to Volume.
      • Set Request to Volume.
      • Set Component to Value.
      Figure 6.


    5. Label the output response Volume.
    6. Set Expression to First Element.
      Note: Because there is only a single value in this data source, [0] is inserted after m_2_ds_1, thereby choosing the first (and only) entry in the data source.
      Figure 7.


    7. Click Finish.
    The Volume output response is added to the work area.
  3. Create the Stress43 output response, which represents the von Mises Stress of Element 43.
    1. From the Directory, drag-and-drop the plate1.h3d file, located in approaches/setup_1-def/run__00001/m_1, into the work area.
      The file contains the analysis results, including the stresses.
    2. In the File Assistant dialog, set the Reading technology to Altair® HyperWorks® and click Next.
    3. Select Single item in a time series, then click Next.
    4. Define the following options, then click Next.
      • Set Subcase to Subcase 1 (Load).
      • Set Type to Element Stresses (2D & 3D) (2D).
      • Set Requests to E43.
      • Set Component to vonMises (Mid).
    5. Label the output response Stress43.
    6. Set Expression to First Element.
    7. Click Finish.
      The Stress43 output response is added to the work area.
  4. Create the Frequency1 output response, which represents the frequency results.
    1. From the Directory, drag-and-drop the plate2.out file, located in approaches/setup_1-def/run__00001/m_2, into the work area.
    2. In the File Assistant dialog, click Next.
    3. Select Single item in a time series, then click Next.
    4. Define the following options, then click Next.
      • Set Type to Frequency1.
      • Set Requests to Mode 1.
      • Set Component to Value.
    5. Label the output response Frequency1.
    6. Set Expression to First Element.
    7. Click Finish.
      The Frequency1 output response is added to the work area.
  5. Click Evaluate to extract the output response values.
    Figure 8.


Run Optimization

  1. Add an Optimization.
    1. In the Explorer, right-click and select Add from the context menu.
    2. In the Add dialog, select Optimization.
    3. For Definition from, select Setup and click OK.
  2. Go to the Optimization 1 > Definition > Define Output Responses step.
  3. Click the Objectives/Constraints - Goals tab.
  4. Apply an objective on the Volume output response.
    1. Click Add Goal.
    2. In the Apply On column, select Volume.
    3. In the Type column, select Minimize.
    Figure 9.


  5. Apply a constraint on the Stress43 output response.
    1. Click Add Goal.
    2. In the Apply On column, select Stress43.
    3. In the Type column, select Constraint.
    4. deterministic
    5. In column 1, select <= (less than or equal to).
    6. In column 2, enter 22.
    Figure 10.


  6. Apply a constraint on the Frequency1 output response.
    1. Click Add Goal.
    2. In the Apply On column, select Frequency1.
    3. In the Type column, select Constraint.
    4. deterministic
    5. In column 1, select >= (less than or equal to).
    6. In column 2, enter 32.
  7. Go to the Optimization > Specifications step.
  8. In the work area, set the Mode to Adaptive Response Surface Method (ARSM).
    Note: Only the methods that are valid for the problem formulation are enabled.
  9. Click Apply.
  10. Go to the Optimization > Evaluate step.
  11. Click Evaluate Tasks.
  12. Plot the progress of the Optimization iteration.
    1. Click the Iteration Plot tab.
    2. Using the Channel selector, select Goal 1, Goal 2, and Goal 3.
    3. Above the Channel selector, activate and enable the Bounds setting.
    Over the course of the optimization, the objective is minimized and at the conclusion, the constraints are satisfied. In the plots, the large markers indicate a design which has at least one violated constraint and a small marker indicates a feasible design. At the optimal design, the only active constraint is Constraint 1. In contrast, constraint 2 is not active at the optimum; this indicates Constraint 2 does not have an influence on the result.
    Figure 11.