Pattern Repetition using Topology Optimization - OS-2050



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This tutorial demonstrates how to perform topology optimization using pattern repetition. The model is a rectangular plate with a concentrated force on one edge and two constraints on the opposite edge. Two other rectangular plates with a scaled size of 0.6 and 0.3 from the original plate with forces and boundary conditions applied in different directions are also modeled to highlight the difference in the topology results between with and without pattern repetitions.

The tutorial input file can be found in <install_directory>/tutorials/os/. Copy the files from this directory to your working directory.

The steps in the tutorial are:

·    Retrieve the OptiStruct input file

·    Set up the optimization problem without pattern repetition

·    Run OptiStruct

·    Post-process the results

·   Add the pattern repetition cards

·    Rerun the optimization problem

·    Post-process the new results

The following file is needed to perform this tutorial:

no_repeat.fem

Original ASCII OptiStruct input deck.

This file can be found in <install_directory>/tutorials/os/ and copied to your working directory.

The objective is to minimize the compliance for the single subcase. The volume fraction of the design space is limited to 0.3. The design spaces are the three plates.

image\2050_1.gif

To retrieve an existing OptiStruct finite element (FE) model:

  1. Launch HyperMesh.

  2. Choose OptiStruct in the User Profiles dialog and click OK.

User Profiles… can also be accessed from the Preferences pull-down menu.

This loads the OptiStruct user profile. It includes the OptiStruct template, macro menu, and import reader. It simplifies the menu systems to give access to only the functionality of HyperMesh that is necessary for using OptiStruct.

  1. Select the Files panel toolbar button image\files_panel.gif.

  2. Select the import subpanel using the radio button on the left side of the panel.

  3. Select FE using the radio button.

  4. Click the switch in the center of the panel and select OPTISTRUCT.

  5. Click import….

  6. Select the no_repeat.fem file, located in the HyperWorks installation directory under <install_directory>/tutorials/os/, and click Open.

The no_repeat.fem model is loaded into the current HyperMesh session.

  1. Click Return.

To define the design space:

  1. Go to the Analysis page.

  2. Click optimization.

This brings up the optimization module.

  1. Click topology.

  2. Select the create subpanel using the radio buttons on the left-hand side of the panel.

  3. Set the selector to PSHELL.

  4. Click comps and select the component labeled first by checking the box beside it.

  5. Click return.

  6. Click base thickness = and enter a value of 0.0.

  7. Click desvar = and enter dv1.

  8. Click create.

  9. Select the parameters subpanel using the radio buttons on the left-hand side of the panel.

  10. Toggle minmemb off to mindim=.

  11. Click mindim= and enter 2.0.

  12. Click update.

Repeat steps 4 through 13 for the components called second and third with desvar names dv2 and dv3 respectively.

This defines the design space.

  1. Click return.

To define the responses:

  1. Click responses.

  2. Set the switch under response type: to volumefrac.

  3. Verify that the toggle in the center of the panel is set to total.

  4. Click response = and enter volfrac.

  5. Click create.

This defines the volume fraction response.

  1. Set the selector under response type: to compliance.

  2. Verify that the toggle in the center of the panel is set to total.

  3. Click response = and enter comp.

  4. Click create.

This defines the compliance response.

  1. Click return.

To define the constraint and objective:

  1. Click dconstraints.

  2. Click response = and select volfrac.

  3. Check the box next to upper bound =.

  4. Click upper bound= and enter 0.3.

  5. Click constraint = and enter yconstr.

  6. Click create.

This defines the volume fraction constraint.

  1. Click return.

  2. Click objective.

  3. Click response = and select comp.

  4. Set the objective selector to min.

  5. Click loadstep and select sub.

  6. Click create.

This defines the compliance response as the objective.

  1. Click return twice to return to the main menu.

This completes the definition of the topology optimization problem without pattern repetition.

To perform the OptiStruct run:

  1. Click OptiStruct to enter the panel to run OptiStruct.

  2. Click save as… following the input file: field.

A Save file… browser window pops up.

  1. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, no_repeat.fem, in the File name: field.

The .fem filename extension is the suggested extension for OptiStruct input decks.

  1. Click Save.

Note the name and location of the no_repeat.fem file now displays in the input file: field.

  1. Set the switch under run options: to optimization.

  2. Click OptiStruct.

This will export the input deck and start the execution of OptiStruct in a DOS or UNIX window. The HyperMesh result file is automatically loaded once the run completes.

  1. Click return to exit the OptiStruct panel.

To view an isosurface plot of the density results:

  1. Click the HyperView button in the OptiStruct panel.

This will launch HyperView and load the no_repeat_des.h3d file.

  1. Click Close in the Message Log window that appears.

  2. Click the Contour panel toolbar button image\contour.gif.

  3. Under Result type:, select Element Densities(v) from the drop-down list and review the Density component.

A contour plot of the Element Densities(v) is displayed with the corresponding legend.

  1. Click the IsoValue image\iso.gif toolbar button.

  2. Click Select Load Case from the Graphics pull-down menu to open the Load Case and Simulation Selection dialog.

  3. Choose the last iteration from the Simulation list and click OK.

  4. Set Current value: to 0.4.

  5. Set Show: to Above.

  6. Check the boxes beside Features and Transient under Clipped geometry:.

  7. Click Apply.

An isosurface plot is displayed in the graphics window. Those parts of the model with a density greater than the value of 0.4 are shown in color, the rest are transparent.

image\2050_2.gif

  1. From the File pull-down menu, choose Exit to quit HyperView.

Rerun the problem with Pattern repetition

The pattern repetition cards can now be defined in HyperMesh.

  1. From the Tool page, select the numbers panel.

  2. Click the nodes button and select by id.

  3. Enter all of the following values after id=, separating them with commas:

1329

66

6

46

507

447

487

928

892

908

  1. Press Enter.

  2. Click the green on button on the right.

  3. Click return to exit the Numbers panel.

  4. From the Disp macro page, after Comps:, select Only to display only component collectors.

image\comp2050.gif

  1. Go to the Analysis page and select the optimization panel.

This brings up the optimization module.

  1. Click topology.

  2. Select the pattern repetition subpanel using the radio buttons on the left side of the panel.

  3. Click the desvar= and select dv1.

  4. Make sure the switch is pointing to master.

  5. Toggle from system to coordinates.

  6. Toggle to global system.

  7. Click the green first button and choose node ID 6.

  8. Click the second button and choose the node ID 46.

  9. Click the third button and choose the node ID 1329.

  10. Click the anchor button and choose the node ID 66.

  11. Click update on the right side to create a master DTPL card.

  12. Click the desvar= and select dv2.

  13. Click the switch and select slave.

  14. Make sure the master= is pointing to dv1.

  15. Set the following values: sx= 0.6, sy= 0.6, sz= 1.0.

  16. Click the first button and choose the node ID 447.

  17. For the second button, choose the node ID 487.

  18. For the third button, choose the node ID 1329.

  19. For the anchor button, choose the node ID 507.

  20. Click the update button on the right side to create the slave DTPL card.

  21. Click the desvar= and select dv3.

  22. Click the switch button and change to slave.

  23. Make sure the master= button is pointing to dv1.

  24. Set the following values: sx= 0.3, sy= 0.3, sz= 1.0.

  25. Click the first button and choose the node ID 892.

  26. For the second button, choose the node ID 928.

  27. For the third button, choose the node ID 1329.

  28. For the anchor, choose the node ID 948.

  29. Click the update button on the right side to create the slave DTPL card.

The above modification identifies the first DTPL card with ID 1 (on the first component) as the master. The DTPL’s of ID 2 (second component) and ID 3 (third component) are slaves and dependent on DTPL of ID1. The second component is scaled 0.6 in both the x and y axis, while the third component is scaled 0.3 in both the x and y axis with respect to the first component.

  1. Click return twice.

  2. Click OptiStruct from the Analysis page to run the solver.

  3. Click save as… following the input file: field.

A Save file… browser window pops up.

  1. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, repeat_opt.fem, in the File name: field.

The .fem file name extension is the suggested extension for OptiStruct input decks.

  1. Click Save.

Note that the name and location of the repeat_opt.fem file is now displayed in the input file: field.

  1. Set the switch under run options: to optimization.

  2. Click OptiStruct.

This will export the input deck and start the execution of OptiStruct in a DOS or UNIX window. The HyperMesh result file is automatically loaded once the run is complete.

To view an isosurface plot of the pattern repetition density results:

  1. From the OptiStruct panel, click the green HyperView button.

This launches HyperView and loads the repeat_opt_des.h3d file.

A Message Log window will appear, indicating the location of the .h3d file.

  1. Click Close to exit the Message Log window.

  2. Click the Contour panel toolbar button image\contour.gif.

  3. Under Result type:, select Element Densities(v) from the drop-down list and review the Density component.

  4. A contour plot of the Element Densities(v) is displayed with the corresponding legend.

  5. Click the Iso Value toolbar button image\iso.gif.

  6. Choose Select Load Case from the Graphics pull-down menu to open the Load Case and Simulation Selection dialog.

  7. Choose the last design under Simulation, Iteration54.

  8. Set current value: to 0.38.

  9. Set Show: to Above.

  10. Check the boxes for Features and Transparent under Clipped geometry:.

  11. Click Apply.

An iso surface plot is displayed in the graphics window. Those parts of the model with a density greater than the value of 0.38 are shown in color, and the rest are transparent.

image\2050_5.gif

  1. Click File on the menu bar and choose Exit to quit HyperView.

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