147 - understanding global sensitivity design studies

8/13/2019 147 - Understanding Global Sensitivity Design Studies

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DesignandSensitivityStudiesUnderstandingGlobalSensitivityDesignStudiesLecture

UnderstandingGlobalSensitivityDesignStudies.mp3

Understanding Global Sensitivity Design Studies

Global Sensitivity Studies are used to generate a much larger

picture of how measures respond to changing a design variable over

a specified range.

Global Sensitivity Design Studies

Design variable changed over defined range Options:

o Repeat P-Loop Convergenceo Remesh after each shape updateo Shape animate the model

Provides more information than Local Sensitivity Design Studies

Radial Offset vs. Maximum von Mises Stress


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p-level for each element on the first pass of the analyses and use those p-levelsfor all of the remaining steps. You may want to check this option if yourgeometry changes during the design study are such that some edges mightrequire higher p-levels.

Remesh after each shape update: This option causes Mechanica to remesh yourmodel after each shape update. It is useful in cases where shape changes may

affect the mesh such that the accuracy of an analysis may decreasesignificantly. For example, geometry that starts out thick when it is originallymeshed, but can end up thin due to design variables changes.

Shape Animate the Model: This option enables you to view the shape changesfor each step that will be encountered during a Global Sensitivity Study.Mechanica does this by regenerating the model and displaying the geometrythat will result for each step. You should use the Shape Animate option topreview shape changes and verify that the geometry regenerates as expected(and doesn't enter resolve mode) for each step before running a design study.

UnderstandingGlobalSensitivityDesignStudiesDemonstrationUnderstandingGlobalSensitivityDesignStudies_demo.mp4

UnderstandingGlobalSensitivityDesignStudiesProcedureProcedure: Understanding Global Sensitivity Design

Studies

ScenarioCreate a Global Sensitivity Study.

Global_Sens_DS global_bracket_orig.prt

Task 1.Open the Mechanica application and define a Global Sensitivity Design Study.

1. Click Applications > Mechanica.

The simulation features (material, load, constraints, parameters, static

analysis) are already defined in this model.

2. Click Mechanica Analyses/Studies from the main toolbar.

3. Click File > New Sensitivity Design Study....


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4. In the Name field, type GLOBAL_SENS_STUDY.

5. Verify Global Sensitivityis selected from the Typedrop-down menu.

6. In the Analysessection of the dialog box, select the BRACKET_STATIC (Static)analysis.

7. Click Select Dimension in the Sensitivity Study Definition dialog.

8. Select the round feature under the mouse cursor in the figure. Select the R1.00dimension.

9. Select d4in the Variables area of the dialog box and type INNER_FILLET.

10. Type the following values for the INNER_FILLET row in the Variables area of thedialog box.


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Variable Current Start End

INNER_FILLET 1 .75 2.75

11. Click Select Dimension in the Sensitivity Study Definition dialog box.

12. Select the Extrude feature as shown in the figure. Select the 7.00dimension.

13. Select d1in the Variables area of the dialog box and type FLANGE_LENGTH.

14. Enter the following values for the FLANGE_LENGTH row in the Variables area ofthe dialog box.

Variable Current Start End

FLANGE_LENGTH 7 4 8

15. Type 5in the Stepsfield.

Mechanica divides the difference between the start and end values by the

number of steps you specify and calculates values for your model's

measures at each interval. You can enter from 1 to 999 intervals. For

example, INNER_FILLET has a range of variation between .75 and 2.75. If

the number of steps is 5 then, Mechanica will compute values at .75, 1.25,

1.75, 2.25, and 2.75.


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16. Click Options...from the Sensitivity Study Definition dialog box.

17. Click Shape Animate the Model.

18. Click Accept Value for every interval which Mechanica updates the geometryand visually inspect that the design changes as expected with no regeneration

failures.19. Click Yesin the Question dialog box to restore the model to its original shape.

20. Click Close > OK > Closeto close all of the open dialog boxes.

21. Return to the Standard Pro/ENGINEER mode by clicking Applications >Standard.

22. Click Save from the main toolbar and click OKto save the model.

23. Click File > Erase > Current > Yesto erase the model from memory.

This completes the procedure.

UnderstandingGlobalSensitivityDesignStudiesExerciseExercise: Understanding Global Sensitivity Design

Studies

Objectives

After successfully completing this exercise, you will be able to:

Use information from a local sensitivity study to prepare the model for a globalsensitivity design study.

Interpret results from a global sensitivity design study and use them to set up foran optimization study.

ScenarioAfter evaluating the results from a local sensitivity study, you have learned howsensitively Mechanica measures (max displacement, von Mises stresses and so on) reactto local changes of some design variables. Based on this study, you have decided to keep

only the variables that cause dramatic changes in the Mechanica measures of interest.

In this exercise, you will oscillate the remaining design variables over a larger range(thus, the name global as opposed to local) and examine the effects these changes have

on the important Mechanica measures. Based on this design study, we can establish whatthe range of variation for each of the design variables should be and use these ranges in

an optimization design study. Our ultimate goal is to bring the structural stresses below240 MPa and minimize the mass of the bracket (and ultimately the mass of the assembly

model that contains it).


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JackGlobal up_link.prt

Task 1.Open Mechanica Structure mode.

1. Click Applications > Mechanica.

Since the structural simulation features (loads, constraints, materials, static

analysis, and local sensitivity study) are already defined, Mechanica

automatically places you in Structure mode.

Task 2.Define a global sensitivity design study.

1. Click Mechanica Analyses/Studies from the main toolbar.

2. Click File > New Sensitivity Design Study...from the Analyses and DesignStudies dialog box.

3. Type LINK_GSDSin the Name field.

4. Verify that the Type drop-down menu is set to Global Sensitivity.

5. Select Static_Analysis_3D_Shell (Static)from the list of analyses.

The design variables you will select in the next few steps are based on

conclusions made from the results of a local sensitivity study completed for

this mode.


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6. Click Select Dimension from the Variables area of the dialog box.

7. Select Cut id 91from the model tree.

8. Select the resulting 12.7dimension from the display area.

9. Adjust the design variable range settings as shown in the table below:

Design Variable Current Start End

radial_offset 12.7 8 18

Note: The range settings for the design variables are ultimately based on

engineering judgment. The Start and End values are set to change the

design by minimizing/maximizing the measures of interest.

Keep in mind that the model should not fail regeneration - you will use the

Shape Animate the Model functionality to verify this.

10. Type 6in the Steps field. The dialog box should now appear as shown in the

figure.


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11. Click Options...and select the Repeat P-Loop Convergenceand Remesh after

each shape updatecheck boxes as shown in the figure.

12. Click Shape Animate the Modelto animate the model and verify that it will

regenerate properly at each of the steps.

13. Press ENTERwhen prompted if you want to continue to the next step. You willneed to do this a total a five times.

14. Click Yeswhen you are prompted if you want to restore the model to its originalshape.

15. The dialog box should appear as shown in the figure. Click Closeto close the

Design Study Options dialog box.16. Click OKto complete the Sensitivity Study Definition and close the dialog box.


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Task 3.Run the global sensitivity study.

1. If necessary, select LINK_GSDSfrom the list of analyses as shown in the figure.

2. Click Start Run > Yesto start the design study.

3. Click Display Study Status once the analysis is started.

Note: Since you have select six steps, there are seven steps in the Global

Design Sensitivity Study. The first set of calculations is done at the Start

settings of the design variable (radial_offset = 8 mm). This value is then

increased and the calculations are repeated. The amount that the design

variable is increased is set by taking the difference between the End and

Start values and dividing it by the number of steps. In out case, this means

(18-8)/6= 1.6667 mm increments.

4. When the analysis is complete, click Closeto close the Diagnostics window and

click Closeto close the Run Status window.


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Task 4.Explore the results of the LINK_GSDS design study.

1. Verify that LINK_GSDSis still selected in the Analyses and Design Studies dialogbox and click Results to start Results mode.

2. Type VM_STRESSin the Name field and Von Mises Stress vs. Radial Offset

Design Variablein the Title field.

3. Verify that the Display type field is set to Graph.

4. Click Define Measure to open the Measures dialog box.

5. Select max_stress_vmfrom the list of Measures and click OKto close theMeasures dialog box.

6. The dialog box should appear as shown in the figure. Click OK and Showto showthe resulting graph.


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7. Click Copy from the main toolbar in the Results window.

8. Type TOTAL_MASSin the Name field and Total Mass vs. Radial Offset Design

Variablein the Title field.


10. Select total_massfrom the list of Measures and click OKto close the Measuresdialog box.

11. The dialog box should appear as shown in the figure. Click OK and Showto show

the resulting graph.


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From the graphs and results evaluated by Pro/MECHANICA we can easily

identify that the radial_offset design changes are dramatically decreasing

the von Mises stress in the model. The stress decreases from 1140 MPa to

roughly 200 MPa and the mass increases to about 0.190 Kg for radial_offset

varying between 8 and 18 mm. Since our plan is to lower the von Mises

stress below 240 MPa and minimize the mass, we can now narrow down the

proper range of the radial_offset variable for an Optimization Study insteadof using larger design ranges used in this study. This is advantageous

because a large design variable range in an Optimization study can become

very time consuming and require a substantial amount of disk space and

memory to solve.

2. When you are through examining the graphs, click File > Exit Results > Notoexit the Result window without saving any results.

Task 6.[Optional] Evaluate the global sensitivity of Mechanica measures based onthick design variable.

Perform the same process detailed in Tasks 2 through 5 above for the

thick design variable. Use the steps below if you need more guidance.

1. If necessary, click Applications > Mechanica.

2. If necessary, click Mechanica Analyses/Studies from the main toolbar.

3. If necessary, select LINK_GSDSfrom the list of analyses and click Copy fromthe Analyses and Design Studies dialog box.

4. Right-click Copy_of_LINK_GSDSand select Edit...

5. Type LINK_GSDS_THICKin the Name field.

6. Select radial_offsetfrom the list of Variables and click Delete Row toremove it.

7. Click Select Dimension from the Variables area of the dialog box.

8. Select Shell id 528from the model tree.

9. Select the resulting 3.81dimension from the display area.10. Adjust the design variable range settings as shown in the table below:

Design Variable Current Start End


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thick 3.81 2.15 4.50

11. Click OKto complete the sensitivity study definition and close the dialog box.

12. Click Start Run > Yesto start the design study.

13. Click Display Study Status once the analysis is started.

14. When the analysis is complete, click Closeto close the Diagnostics window and

click Closeto close the Run Status window.

15. Verify that LINK_GSDS_THICKis still selected in the Analyses and Design

Studies dialog box and click Results to start Results mode.

16. Type VM_STRESS2in the Name field and Von Mises Stress vs. Thickness

Design Variablein the Title field.


18. Select max_stress_vmfrom the list of Measures and click OKto close theMeasures dialog box.

19. Click OK and Showto show the resulting graph.

20. Click Copy from the main toolbar in the Results window.

21. Type TOTAL_MASS2in the Name field and Total Mass vs. Thickness DesignVariablein the Title field.


23. Select total_massfrom the list of Measures and click OKto close the Measuresdialog box.

24. Click OK and Showto show the resulting graph.

25. Examine the resulting graphs.


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147 - understanding global sensitivity design studies

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