OS-T: 3010 Topography Optimization of an L-bracket
In this tutorial you will perform a topography optimization on a L-bracket modeled with an attached mass.
![3010_l_bracket](../../../images/solvers/3010_l_bracket.png)
- Objective
- Maximize 1st frequency mode.
- Constraints
- Bead dimensions and layout.
- Design Variables
- Perturbation of nodes normal to the shell's mid-plane.
Launch HyperMesh and Set the OptiStruct User Profile
-
Launch HyperMesh.
The User Profile dialog opens.
-
Select OptiStruct and click
OK.
This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.
Open the Model
- Click .
- Select the Lbkttopog.hm file you saved to your working directory.
-
Click Open.
The Lbkttopog.hm database is loaded into the current HyperMesh session, replacing any existing data.
Set Up the Optimization
Define Topography Design Variables
For a topography optimization, a design space and a bead definition need to be defined.
In this step, the values of a bead width of 15mm, a bead height of 5mm, and draw angle of 85 degrees will be used. Symmetry of the bead pattern should be forced along the symmetry line of the design space.
- From the Analysis page, click the optimization panel.
- Click the topography panel.
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Create a topography design space definition.
- Select the create subpanel.
- In the desvar= field, enter topo.
- Using the props selector, select design.
- Click create.
A topography design space definition, topo, has been created. All elements organized into the design component collector(s) are now included in the design space. -
Create a bead definition for the design space topo.
A bead definition has been created for the design space topo. Based on this information, OptiStruct will automatically generate bead variable definitions throughout the design variable domain.
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Adding pattern grouping constraints.
- Select the pattern grouping subpanel.
- Click desvar = and select topo.
- Set the pattern type to 1-pln sym.
- Click anchor node, and enter 337 in the id= field.
- Click first node, and enter 613 in the id= field.
- Click update.
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Update the bounds of the design variable.
The upper bound sets the upper bound on grid movement equal to UB*HGT and the lower bound sets the lower bound on grid movement equal to LB*HGT.
- Click return to go to the Optimization panel.
Create Optimization Responses
- From the Analysis page, click optimization.
- Click Responses.
-
Create the frequency response.
- In the responses= field, enter FREQ.
- Below response type, select frequency.
- For Mode Number, enter 1.0.
- Click create.
A response, FREQ, is defined for the frequency of the first mode extracted. - Click return to go back to the Optimization panel.
Define the Objective Function
- Click the objective panel.
- Verify that max is selected.
- Click response and select FREQ.
- Using the loadsteps selector, select STEP.
- Click create.
- Click return twice to exit the Optimization panel.
Save the Database
- From the menu bar, click .
- In the Save As dialog, enter Lbkttopog.hm for the file name and save it to your working directory.
Run the Optimization
- From the Analysis page, click OptiStruct.
- Click save as.
-
In the Save As dialog, specify location to write the
OptiStruct model file and enter
Lbkttopog for filename.
For OptiStruct input decks, .fem is the recommended extension.
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Click Save.
The input file field displays the filename and location specified in the Save As dialog.
- Set the export options toggle to all.
- Set the run options toggle to optimization.
- Set the memory options toggle to memory default.
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Click OptiStruct to run the optimization.
The following message appears in the window at the completion of the job:
OPTIMIZATION HAS CONVERGED. FEASIBLE DESIGN (ALL CONSTRAINTS SATISFIED).
OptiStruct also reports error messages if any exist. The file Lbkttopog.out can be opened in a text editor to find details regarding any errors. This file is written to the same directory as the .fem file. - Click Close.
- Lbkttopog.hgdata
- HyperGraph file containing data for the objective function, percent constraint violations, and constraint for each iteration.
- Lbkttopog.hist
- The OptiStruct iteration history file containing the iteration history of the objective function and of the most violated constraint. Can be used for a xy plot of the iteration history.
- Lbkttopog.html
- HTML report of the optimization, giving a summary of the problem formulation and the results from the final iteration.
- Lbkttopog.oss
- OSSmooth file with a default density threshold of 0.3. You may edit the parameters in the file to obtain the desired results.
- Lbkttopog.out
- OptiStruct output file containing specific information on the file setup, the setup of the optimization problem, estimates for the amount of RAM and disk space required for the run, information for all optimization iterations, and compute time information. Review this file for warnings and errors that are flagged from processing the Lbkttopog.fem file.
- Lbkttopog.sh
- Shape file for the final iteration. It contains the material density, void size parameters and void orientation angle for each element in the analysis. This file may be used to restart a run.
- Lbkttopog.stat
- Contains information about the CPU time used for the complete run and also the break-up of the CPU time for reading the input deck, assembly, analysis, convergence, and so on.
- Lbkttopog_des.h3d
- HyperView binary results file that contain optimization results.
- Lbkttopog_s#.h3d
- HyperView binary results file that contains from linear static analysis, and so on.
- Lbkttopog.grid
- An OptiStruct file where the perturbed grid data is written.
View the Results
Shape contour information is output from OptiStruct for all iterations. In addition, Eigenvector results are output for the first and last iteration by default. This section describes how to view those results in HyperView.
View a Transient Animation of Shape Contour Changes
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From the OptiStruct panel, click HyperView.
HyperView launches within the HyperMesh Desktop and loads the Lbkttopog_des.h3d file.
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On the Animation toolbar, set the animation mode to
Transient.
Figure 2.
-
Click
to start the animation.
-
Click
to open the Animation Controls panel.
- Move the Max Frame Rate slider to adjust the animation speed.
Review the Optimized Frequency Difference
-
In the top, right of the application, click
to proceed page 3, which contains the results for first and the last iterations.
- In the Results Browser, select the first iteration (Iteration 0).
![os_3010_iter0](../../../images/solvers/os_3010_iter0.png)
![os_3010_iter12](../../../images/solvers/os_3010_iter12.png)
Apply Optimized Topography
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In the top, right of the application, click
to go back to the Design History page (page 2).
-
On the Animation toolbar, click
to set the Current time to the last step.
Figure 5. Topography Results