Design Concept for an Automotive Control Arm - OS-2010 This tutorial uses OptiStruct's topology optimization functionality to create a design concept for an automotive control arm required to meet performance specifications. The finite element mesh containing designable (blue) and non-designable regions (yellow) is shown in the figure below. Part specifications constrain the resultant displacement of the point where loading is applied for three load cases to 0.05mm, 0.02mm, and 0.04mm, respectively . The optimal design would use as little material as possible. Finite element mesh containing designable (blue) and non-designable (yellow) material. A finite element model representing the designable and non-designable material (shown in f igure) is imported into HyperMesh. Appropriate properties, boundary conditions, loads, and optimization parameters are defined and the OptiStruct software is used to determine the optimal material distribution. The results (the material layout) are viewed as contours of a normalized density value ranging from 0.0 to 1.0 in the design space. Isosurfaces are also used to view the density results. Areas that need reinforcement will tend towards a density of 1.0. The optimization problem for this tutorial is stated as: Objective: Minimize volume. Constraints: SUBCASE 1 - The resulta nt displacemen t of the poi nt wh ere loading is applied must be less than 0.05mm. SUBCASE 2 - The resultant displacement of the poi nt where loading is applied must be less than 0.02mm. SUBCASE 3 - The resulta nt displacemen t of the poi nt wh ere loading is applied must be less than 0.04mm. Design variables: Microstructural void sizes and orientations in the design space. The following exercises are included: • Setting up the FE model in HyperMesh • Setting up the optimization in HyperMesh • Post-processing the results in HyperView Exercise Setting Up the FE Model in HyperMesh Step 1: Launch HyperMesh, Set the User Profile and Retrieve the File RADIOSS , MotionS olve, a nd OptiS truct T utoria ls > OptiStr uct > T opolo.. . file:/// C:/Altair/ hw10.1 /help/h wsolve rs/os2 010.ht m?zoo m_highl ightsub ... 1 of 12 9/27/2011 5:16 PM
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OS-2010 Design Concept for an Automotive Control Arm
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7/29/2019 OS-2010 Design Concept for an Automotive Control Arm
Design Concept for an Automotive Control Arm - OS-2010
This tutorial uses OptiStruct's topology optimization functionality to create a design concept for an automotive control
arm required to meet performance specifications. The finite element mesh containing designable (blue) and
non-designable regions (yellow) is shown in the figure below. Part specifications constrain the resultant displacement
of the point where loading is applied for three load cases to 0.05mm, 0.02mm, and 0.04mm, respectively. The optimaldesign would use as little material as possible.
Finite element mesh containing designable (blue) and non-designable (yellow) material.
A finite element model representing the designable and non-designable material (shown in figure) is imported into
HyperMesh. Appropriate properties, boundary conditions, loads, and optimization parameters are defined and the
OptiStruct software is used to determine the optimal material distribution. The results (the material layout) are viewed
as contours of a normalized density value ranging from 0.0 to 1.0 in the design space. Isosurfaces are also used to
view the density results. Areas that need reinforcement will tend towards a density of 1.0.
The optimization problem for this tutorial is stated as:
Objective: Minimize volume.
Constraints: SUBCASE 1 - The resultant displacement of the point where loading is
applied must be less than 0.05mm.
SUBCASE 2 - The resultant displacement of the point where loading is
applied must be less than 0.02mm.
SUBCASE 3 - The resultant displacement of the point where loading is
applied must be less than 0.04mm.
Design variables: Microstructural void sizes and orientations in the design space.
The following exercises are included:
• Setting up the FE model in HyperMesh
• Setting up the optimization in HyperMesh
• Post-processing the results in HyperView
Exercise
Setting Up the FE Model in HyperMesh
Step 1: Launch HyperMesh, Set the User Profile and Retrieve the File
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Next we will create four load collectors (SPC, Brake, Corner and Pothole) and assign each a color. Follow these steps
for each load collector.
1. Right click inside the Model Browser window and move the cursor over Create to activate the extended menu and
select LoadCollector .
2. In the Name: field, type SPC.
When in this popup, do not hit the Enter key on the keyboard until you are completely done.
3. Leave the Card image: field set to None.
4. Select a suitable color.
5. Click on Create.
6. Similarly, create load collectors called Brake, Corner , and Pothole.
Step 4: Apply Constraints
We need to create constraints and assign them to the SPC load collector as outlined in the following steps.
1. From Model Browser, expand LoadCollectors, right click on SPC , and click on Make Current .
2. From the Analysis page, enter the constraints panel.
3. Make sure the create subpanel is selected using the radio buttons on the left-hand side of the panel.
4. Select the node at one end of the bushing (see the figure below) by clicking on it in the graphics window.
5. Constrain dof1, dof2, and dof3; make sure dofs 1, 2, and 3 are checked and dofs 4, 5, and 6 are unchecked.
Dofs with a check will be constrained while dofs without a check will be free.
Dofs 1, 2, and 3 are x, y, and z translation degrees of freedom.
Dofs 4, 5, and 6 are x, y, and z rotational degrees of freedom.
6. Click create.
A constraint is created. A constraint symbol (triangle) appears in the graphics window at the selected node. Thenumber 123 is written beside the constraint symbol, indicating that dof1, dof2 and dof3 are constrained.
Constraining dof1, dof2 and dof3 at one end of the bushing.
7. Select the node at the other end of the bushing (see the following figure) by clicking on it in the graphics window.
8. Constrain dof2 and dof3; make sure dofs 2 and 3 are checked.
9. Click create.
A constraint is created. A constraint symbol (triangle) appears in the graphics window at the selected node. The
number 23 is written beside the constraint symbol, indicating that dof2 and dof3 are constrained.
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Constraining dof2 and dof3 at the other end of the bushing.
10. Click nodes and select by id from the extended entity selection window.
11. Type the value 3239 and press Enter key.
12. This selects node ID 3239 (see the next figure).
13. Constrain only dof3.
14. Click create.
A constraint is created. A constraint symbol (triangle) appears in the graphics window at the selected node. Thenumber 3 is written beside the constraint symbol, indicating that dof3 is constrained.
Constraining dof3 on node ID 3239.
15. Click return to go to the main menu.
Step 5: Apply Forces for Brake, Corner, and Pothole Loadcases
1. From the Model Browser , expand LoadCollectors, right click on Brake, and click on Make Current .
2. From Analysis page, select forces panel.
3. Click nodes and select by id from the extended entity selection menu.
4. Type the node number 2699 and press the Enter key.
5. Click magnitude=, enter 1000.0 and press the Enter key.
6. Set the switch below to x-axis.
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Step 10: Create Constraints on Displacement Responses
In this step we set the upper and lower bound constraint criteria for this analysis.
1. Enter the dconstraints panel.
2. Click constraint= and enter constr1.
3. Check the box for upper bound only.
4. Click upper bound= and enter 0.05.
5. Select response= and set it to disp1.
6. Click loadsteps.
7. Check the box next to Brake.
8. Click select .
9. Click create.
10. Click constraint= and enter constr2.
11. Check the box for upper bound only.
12. Click upper bound= and enter 0.02.
13. Select response= and set it to Corner .
14. Click create.
15. Click constraint= and enter constr3.
16. Check the box for upper bound only.
17. Click upper bound= and enter 0.04.
18. Select response= and set it to Pothole.
19. Click create.
20. Click return twice to return to the main menu.
Step 11: Check the Optimization Problem A check run may be performed in which OptiStruct will estimate the amount of RAM and disk space required to run the
model. During the check run, OptiStruct will also scan the deck checking that all the necessary information required to
perform an analysis or optimization is present and also that this information is not conflicting.
1. From the Analysis page enter the OptiStruct panel.
2. Click save as following the input file: field
3. Select the directory where you would like to write the OptiStruct model file and enter the name for the model,
carm_check.fem, in the File name: field.
The .fem extension is for OptiStruct input decks.
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carm_complete.html HTML report of the optimization, giving a summary of the
problem formulation and the results from the final
iteration.
carm_complete.oss OSSmooth file with a default density threshold of 0.3.
The user may edit the parameters in the file to obtain the
desired results.
carm_complete.out OptiStruct output file containing specific information onthe file setup, the setup of the optimization problem,
estimates for the amount of RAM and disk space required
for the run, information for each optimization iteration,
and compute time information. Review this file for
warnings and errors that are flagged from processing the
cclip_complete.fem file.
carm_complete.res HyperMesh binary results file.
carm_complete.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. The .sh file may beused to restart a run and, if necessary, run OSSmooth
files for topology optimization.
cclip_complete.stat Summary of analysis process, providing CPU information
for each step during analysis process.
Post-processing the Results in HyperView
Element density results are output to the carm_complete_des.h3d file from OptiStruct for all iterations. In addition,
Displacement and Stress results are output for each subcase for the first and last iterations by default intocarm_complete_s#.h3d files, where # specifies the sub case ID. This section describes how to view those results in
HyperView.
Step 13: View the Deformed Structure
1. Once you see the message Process completed successfully in the command window, click the green
HyperView button.
HyperView is launched and the results are loaded. A message window appears to inform about the successful
loading of the model and result files into HyperView. Notice that all three .h3d files get loaded, each in a different
page of HyperView.
2. Click Close to close the message window.
It is helpful to view the deformed shape of a model to determine if the boundary conditions are defined correctly,
and also to find out if the model is deforming as expected. The analysis results are available in pages 2, 3, and 4.
The first page contains the optimization results.
3. Click the Next Page toolbar button to move to the second page.
The second page has the results from the carm_complete_s1.h3d file. Note that the name of the page is
displayed as Subcase 1 – Brake to indicate that the results correspond to subcase 1.
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Step 14: Review Contour Plot of the Density Results
The optimization iteration results (Element Densities) are loaded in the first page.
1. Click the Previous Page button until the name of the page is displayed as Design History , indicating that the
results correspond to optimization iterations.
2. Click the Contour toolbar button .
Note the Result type: is Element Densities [s] ; this should be the only results type in the
“file_name”_des.h3d file.
The second drop-down menu shows Density .
3. In the Averaging method: file, select Simple.
4. Click Apply to display the density contour.
Note the contour is all blue this is because your results are on the first design step or Iteration 0.
5. At the bottom of the GUI, click on the name Design or Iteration 0 to activate the Load Case and Simulation
Selection dialog.
6. Select the last iteration by double clicking on the last Iteration #.
Each element of the model is assigned a legend color, indicating the density of each element for the selected
iteration.
Have most of your elements converged to a density close to 1 or 0?
If there are many elements with intermediate densities, the DISCRETE parameter may need to be adjusted. The
DISCRETE parameter (set in the opti control panel on the optimization panel) can be used to push elements
with intermediate densities towards 1 or 0 so that a more discrete structure is given.
In this model, refining the mesh should provide a more discrete solution; however, for the purposes of this tutorial,
the current mesh and results are sufficient.
Regions that need reinforcement tend towards a density of 1.0. Areas that do not need reinforcement tend towards
a density of 0.0.
Is the max= field showing 1.0e+00?
In this case, it is.
If it is not, the optimization has not progressed far enough. Allow more iterations and/or decrease the OBJTOL
parameter (also set in the opti control panel).
If adjusting the discrete parameter, refining the mesh, and/or decreasing the objective tolerance does not yield a
more discrete solution (none of the elements progress to a density value of 1.0), review the set up of the
optimization problem. Some of the defined constraints may not be attainable for the given objective function (or
vice versa).
Step 15: View an Iso Value Plot on Top of the Element Densities Contour
This plot provides the information about the element density. Iso Value retains all of the elements at and above acertain density threshold. Pick the density threshold providing the structure that suits your needs.
1. From Graphics pull down menu, click on Iso Value, and choose Element Densities as the Result type.
2. Click Apply .
3. Set the Current Value: to 0.15.
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