4221946 working model chapter3

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C H A P T E R 3

Working Model FEA: SolidWorksExercises

This chapter presents simulation exercises designed to help you getstarted with Working Model FEA. The exercises are for the followingproducts:

Working Model FEA: SolidWorks

Working Model 4D

The exercises make use of the Simulation Wizards as well as theWorking Model FEA standard menus to set up the problems, submit thesimulation to analysis, solve the models, and evaluate results.

Exercise 3.1 uses the Stress Wizard to perform stress simulation ona bracket.

Exercise 3.2 uses Working Model Shape Optimization to optimize abracket design.


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Exercise 3.1 Stress Simulation on a Bracket 3-2

Exercise 3.1 Stress Simulation on a Bracket

Figure 3-1

Choosing the Stress Wizard

This exercise introduces you to the Working Model FEA stress analysisfeature. You will use the Stress Wizard to determine the failure stresses(von Mises stresses) generated in the object as a result of an appliedpressure. You will then calculate the factor of safety based on von Misesstresses (minimum acceptable factor of safety=1). The Stress Wizardleads you through the entire simulation process.

Getting Started

In this section you will open the bracket file in SolidWorks and launchthe Stress wizard.

From S olidWorks:

1. Choose Open from the File menu.

This displays the File Open dialog.


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3-3 Chapter 3Working Model FEA: SolidWorks Exercises

2. Browse the Tutorial folder Chapter 3\Exercise 3.1 and open the

Bracket.par file

This opens and displays the Bracket as shown in Figure 3-1.

Note: The default location for the Tutorials folder is ProgramFiles\Working Model

3. Choose Wizards from the Working Model FEA menu, thenchoose Stress Wizard from the Wizards submenu.

This launches the Stress Wizard as shown in Figure 3-2.

Figure 3-2

Stress Wizard

Defining the Problem and Units

In this section you will define the problem for the Stress Wizard.

1. Click Begin to initiate the simulation process.

2. Click Define.


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The Wizard creates a simulation model with a default name. The

default is the name of your part with the word Model appended.

Figure 3-3

Simulation ModelName Window

3. Click Next.

This displays the Units tab of the Stress Wizard.

4. Click Units.

This displays the Desired Units window as shown in Figure 3-4.

Since you already specified inches, the units default to the English

system.


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Figure 3-4

Desired Units Window

5. Click Finish and go to the next step.

Specifying Loads

In this section you will specify a load for the stress simulation. InWorking Model FEA, loads are grouped into named sets that can containone or more loads.

1. Click the Loads tab on the Stress Wizard window.

This displays a window that prompts you to accept a default name

for the load set.

2. Click Next.

This displays the How Loads are Applied window as shown in

Figure 3-5.


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Figure 3-5

How Loads AreApplied Window

3. Select Face and click Next.

In this problem the load is pressure, which is applied on a face.

4. Optionally click Change View.

If you need to zoom, rotate, or pan the view before you pick the face,

click the Change View button. This allows you to access the

Desktop View menu or toolbar commands and modify the view as

needed. Click OK when you are finished with view modifications.

5. Click Next.

This displays the Load Geometry window.

6. Click on the top face of the base portion of the bracket. Be sure

the correct face is selected. (You can right-mouse click to selectfaces.)

7. Click Pressure (the load type) and then click Next.

This displays the Load Value dialog.

8. Enter a load value of 50.


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Pressure has a single component perpendicular to the face.

Pressure is positive if it is pointing at the face.

9. Click Next in the Load Value dialog.

This displays the Symbol Data dialog. It lets you control the color

and size of the load symbols.

Force symbols will appear on the geometry, as shown in Figure 3-

6. A dialog prompts you to create another load.

Figure 3-6

Force Symbols onBracket Face


Specifying Restraints

In this section you will specify a restraint for the stress simulation. InWorking Model FEA, restraints are grouped in named sets.

1. Click the Restraints tab on the Stress Wizard window.

This displays a window that prompts you to accept a default name

for the load set. The default load set name is Ex1_brkt_RS.


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2. Click Next.

This displays the Restraints window as shown in Figure 3-7.

Figure 3-7

How RestraintsAre Applied Window

3. Select Face and click Next.

In this problem the restraint is applied on the face.

4. Click on the back vertical face of the bracket. Be sure the back

vertical face is selected.

5. Click Next.

This displays the Restraint Types window as shown in Figure 3-8.


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Figure 3-8

Restraints Types Window

6. Select Fixed in the Restraint Type window and click Next.

This prevents the back of the bracket from moving or rotating in any

direction. The Wizard displays the Symbol Data dialog, which lets

you control the color and size of the Restraint symbols.

7. Change the symbol size to 0.5 inches and click Next in the

Symbol Data dialog.

Force symbols will appear on the geometry, as shown in Figure 3-

9. A dialog prompts you to create another restraint.


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Figure 3-9

Restraints and Loads

on Bracket


Specifying Mesh and Getting Results

In this section you will analyze your model to get results. You will firstspecify a mesh for the stress simulation. In Working Model FEA thematerial used for analyzing the model is actually assigned to the mesh.

1. Click the Analyze tab on the Stress Wizard window and select

Analyze.

This displays the Materials for Mesh dialog.

2. Select Choose an existing material and click Next.

This displays the Select Existing Material for Mesh window as

shown in Figure 3-10.


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Figure 3-10

Select Existing Material

or Mesh Window

3. Scroll the material list to display Steel-ANSI 304. Select it and

then click Next.

You are now ready to select the geometry to mesh.

4. Click Next.

This displays the Analysis Execution window, which specifies the

analysis start time.

There is an abrupt geometric change where the top edge of the rib

joins the vertical part of the bracket and this is likely to cause higher

stress concentrations. To get a better picture of the stresses there,

you need a fine mesh in that area. To save meshing and analysis

time, it is better to specify larger elements in most of the body andapply mesh refinements in the critical areas than to use small

elements overall. For this reason, we will use h-adaptivity.

5. Select h-adaptivity.

Use default values for Map Iterations and Target Error.

6. Accept Now and Click Finish to submit the model.


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The program will first display a Working Model dialog that shows

the progress of the Meshing process. Then the MSC.Nastran dialog

(Figure 3-11) displays the progress of the analysis process.

Figure 3-11

MSC.Nastran Dialog

When the first iteration is complete, the program will refine the mesh

where necessary to achieve the most accurate results. It will iterate

several times until it reaches your desired accuracy setting. When

the analysis is completed, the window displays: Analysis job

completed successfully.

Working Model FEA calculates an extensive range of analysis

solutions. The Wizard, however, returns only those responses that

can give you the quickest visual and numerical feedback about the

success or failure of your part. For more comprehensive results you

must use the dialogs activated by the Working Model FEA menu.

These will be shown in other exercises.

Using the Design Doctor to Analyze Results

The Design Doctor is an analysis expert designated to examine andinterpret your analysis results. The Design Doctor checks aspects of youranalysis results against various pre-established criteria and tells you whatto correct should any of your results fail the test. Sometimes the DesignDoctor can make the necessary repairs to your simulation data.

1. Click Results in the Stress Wizard window.

This displays the Design Doctor window as shown in Figure 3-12.


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Figure 3-12

Design Doctor

2. Click Next.

The Design Doctor displays the list of criteria against which your

results will be tested (Figure 3-13).

Figure 3-13

Design Doctor Options

3. Enter the minimum factor of safety value you consider

acceptable for your design.


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Working Model FEA will obtain the maximum yield stress of the

material from the material library and get the von Mises stresses

from the analysis results.

4. Click Next.

The Design Doctor will proceed with the diagnostic tests for each

criteria. If the results pass the test, the Design Doctor puts a check

mark next to the criteria name. The dialog below (Figure 3-14)

shows that all tests have completed successfully.

Figure 3-14

Design Doctor Results

To get more details from the Design Doctor:

5. Highlight Design Intent/Animation and then click Diagnosis.

This displays the diagnosis for the Design Intent.

6. Click Close, Finish, and Close to end the exercise.

You have completed this exercise.


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Exercise 3.2 Optimizing the Shape of a Bracket

This exercise introduces you to shape optimization and Working ModelShape. The Optimization Wizard will lead you through the sequence ofsteps required to optimize the design of a bracket.

Using Working Model Shape Optimization

Working Model Shape Optimization links finite element analysis and

parametric geometric construction in a process called shapeoptimization. Shape optimization automates the search for an optimaldesign by varying dimensions to achieve a design objective, for example,minimum mass, while observing certain design criteria, such asmaximum allowable stress limits.

Working Model Shape Optimization must be used with Stress, Vibration,or Buckling Simulations. The following is a short outline of the

optimization strategy. You will see each step in greater detail as youwork your way through the exercise in this section.

7. Start with your SolidWorks part geometry. Identify the dimensions

that you will vary. Define the global design variables in Solid-

Works.

8. Create a simulation model of the appropriate analysis type. Add

loads (except in aVibration Simulation), restraints, and mesh. Run

the analysis of this model if you need to simulate the behavior of

the part with its initial dimensions.

9. Define a shape optimization model and associate with it the follow-

ing input criteria:

Design ObjectiveThe goal of the optimization process. Acommon design objective is to minimize the mass of the part

Design VariablesIdentified dimensional parameters that arepermitted to change during the optimization process

Design constraintsPhysical characteristics and responsesthat must be maintained (e.g., maximum allowable stress ordisplacement)

10. Run the shape optimization analysis.

11. Review the shape optimization results and observe the sensitivity of

the overall design to each variable.

12. Update the SolidWorks part based on the new optimized dimen-

sions.


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Exercise 3.2 Optimizing the Shape of a Bracket 3-16

Preparing the Part

Open a Part The part for this example is in Tutorials\Chapter 3\Exercise 3.2. Thename of this part is Bracket_opt.par.

Define the DesignVariable(s)

For this exercise, we have already defined the design variables. Designvariables are defined in SolidWorks as Independent Global DesignVariables. The equation field should contain the value with which thegeometry was constructed.

Associate DesignVariables and Dimensions

In this exercise, the design variables are already associated with thedimensions. Design variables and dimensions are associated through theSolidWorks Part menu. Choose Edit Feature to associate the variableswith the dimensions.

Figure 3-15

Bracket

The design variables and dimensions for the bracket shown in Figure 3-15 are as follows:

Unit systemEnglish

Load2500 lbf total force pushing down on the top face of the baseportion of the bracket.

RestraintThe back face of the bracket is fully restrained.

MaterialStainless Steel

Design ObjectiveMinimize the mass of the part by changing thethickness of the base and of the rib. Initial mass= 26.5 lbm.

Design ConstraintAllowable von Mises stress = 38000 psi.


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Design VariablesTwo dimensions of the bracket will serve asdesign variables:

Base thicknessInitial value = 1.0 in (Minimum value allowed =0.1 in./Maximum value allowed = 1.1 in.)

Rib thicknessInitial value=0.75 in (Minimum value allowed= 0.1in./Maximum value allowed=1.0 in)

Getting Started

In this section you will open the bracket file and define the simulationmodel required for optimization. If you need help with these steps, please

refer to the first exercise in this chapter.

From S olidWorks:

1. Choose Open from the File menu.

This displays the File Open dialog.

2. Browse the Tutorials\Chapter 3\Exercise 3.2 folder and open the

bracket_opt.par file.

This opens and displays the Bracket as shown in Figure 3-15.

Note: The default location for the Tutorials folder is ProgramFiles\Working Model

3. Create a new simulation model, load set, and restraint set.

See Exercise 3.1 for help with these steps.

The simulation type is Stress. Use the following parameters:

Loads Total Force2500 lbf in the Global Y direction on the top face of thebase portion of the bracket.

Restraints Fully restrain the back face of the bracket.


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Mesh MaterialSteelElement Size Accept the default

Figure 3-16

The Simulation Model

4. Choose Wizards from the Working Model FEA menu and then

choose Working Model Shape Wizard from the Wizards

submenu.

5. Click Begin, then Define.

6. Accept Start a New Model and click Next.

The Model Name and Simulation Model page as shown in Figure 3-

17is displayed.


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Figure 3-17

Model Name and

Simulation Model Page

7. Accept the default Optimization Model Name and the Simulation

Model Name.

8. Click Finish and continue with the next section.

Specifying a Design Objective

Before you can optimize a designs performance or response, you mustdefine what it is that you consider optimal. It may be a minimum mass,maximum first natural frequency, etc. Whatever you choose, this will be

the design goal, or objective. For this project, the design objective is tominimize the mass of the part.

1. Click the Objective tab in the Wizard window.

This displays the Design Objective page as shown in Figure 3-18.


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Figure 3-18

Design Objective Page

2. Accept the default design objective action as Minimize and the

default design objective response as mass.


Specifying Design Variables

In this step you will identify the design variables. Working Model Shapeenters the initial value of a predefined variable dimension and specifiesdefault maximum and minimum allowable boundaries (+/- 10%). Youcan modify these boundary values to suit your optimization criteria.

1. Click the Variables tab in the Wizard window.

This displays the Design Variable page as shown in Figure 3-19.


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Figure 3-19

Design Variable Page

2. Select Thickness from the Name list.

3. Accept the upper bound as 1.1 inches and set the lower bound

to 0.1 in. in the Design Variable Bounds region.

4. Click Next.

The Wizard prompts you to create another variable.

5. Click Yes.

This redisplays the Design Variable window.

6. Select RibThick

7. Set the upper bound to 1.0 inch and the lower bound to 0.1 in.

8. Click Next.

The Wizard prompts you to create another variable.


Specifying Constraints

A design constraint is a design response whose upper or lower limit valueplaces certain restrictions on the magnitude of the design variable(s)changes. For example, by decreasing the thicknesses, this part can be


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made lighter but the maximum allowable stress will limit how far youcan reduce these dimensions. In this case, the maximum allowable stress

is your design constraint.

1. Click the Constraints tab in the Wizard window.

A dialog prompts you to accept a default constraint name.

2. Accept the default constraint name and click Next.

This displays the Design Constraints Response page as shown in

Figure 3-20.

Figure 3-20

DesignConstraint ResponsePage

3. Accept Response = stress and Component = von Mises and

Click Next.

The design constraint is applied to All Solids.

4. Click Next.

This displays the Design Constraint Limit page as shown in Figure

3-21.


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Figure 3-21

Design Constraint Limit

Page

The Type of Constraint defaults to stress, and upper bound


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The Simulation Parameters tree-diagram displays the simulation

components. A default result set is created, displaying the load set

and restraint set that will be applied in the analysis.

2. Click Next.

The General Job Information page (Figure 3-22) displays the

parameters of the optimization job.

Figure 3-22

General Job InformationPage

3. Accept the default Optimization Result Set name, set the

maximum number of design cycles to 10 and accept the default

optimization type - Optimization plus sensitivity.

4. Click Next to continue.

This displays the execution option dialog.

5. Accept the default execution option Immediate automatic

execution and Click Finish.

This sends the optimization job to the solver. The message in the

MSC.Nastran window will inform you that the job has completed.

6. Click OK and continue with the next section.

3 25 Chapter 3 Working Model FEA: SolidWorks Exercises


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Processing Optimization Results

When the solver completes the job, the Results Wizard (Figure 3-23)displays. The Results Wizard contains all information about youroptimization results.

Figure 3-23

Results Wizard

The Results Wizard includes the following:

Optimization result setAccept the default current set.

Optimization exit statusProvides information about how theoptimization completed. For example, Optimization converged to anoptimal solution indicates that the optimization converged to a set ofdesign variables and all constraints are satisfied.

Information at final design cycleDisplays the optimized valueof the objective and the value(s) of the design variables.

1. Click Next and proceed to the next section.

Exercise 3 2 Optimizing the Shape of a Bracket 3-26


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Interpreting Optimization Results

A number of graphs and bar charts are used to illustrate the outcome ofshape optimization. The Optimization Results window (Figure 3-24) liststhe three major categories of results that can be displayed in a graphicalform. The last option on this page updates the model geometry to thedimensions calculated for any one of the design cycles.

Figure 3-24

Optimization ResultsWindow

The following sections describe each of these results categories.

Design Cycle History Graphs

Design cycle history graphs show how a specific optimizationcomponent changes from its initial value to its final value through theoptimization process.

1. Select Design Cycle History Graph and click Next.

This displays the Design Cycle History Data window as shown in

Figure 3-25.



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3 27 Chapter 3 Working Model FEA: SolidWorks Exercises

Figure 3-25

Design Cycle History Data

A design cycle history graph can be created for any of the followingresult data:

Objective Function Shows how the design objective changedwith each design cycle.

Design Variable(s)Shows how one or more design variableschanged with each design cycle.

Design Constraint(s)Shows how one or more design constraints

changed with each design cycle. Maximum Constraint ViolationShows how the maximum

constraint violation changed with each design cycle (expressed as apercentage of constraint violation).

2. Select Design Variable(s).

The checklist box window shows the design variables Thickness and

RibThick. You can select either one of them, but for this display

accept both.

3. Click Next and continue with the next section.



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p g p

Design Cycle History Scaling

You use the Design Cycle History Scaling window (Figure 3-26) tocreate and display a results graph.

Figure 3-26

Design Cycle HistoryScaling Window

.

1. Select No Scaling (true value) and click Next.

This displays a window that prompts you to create a graph. The

selections are as follows:

2. Select Create a Graph and click Next.

This creates and displays the graph.



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p g

Figure 3-27

Design Variable History

Graph

Note: In the following steps, a number of graphs will be displayed. Youcan close the graphs after viewing or keep them open to compare resultsbetween graphs.

3. Click Yes to display more optimization results and continue with

the next section.

This displays a window with more results graph selections.

Updating the ModelTo see how the geometric model changes is shape in each design cycle,open the Explorer or click on the Working Model FEA tab of yourDesktop Browser. Look for the Ex1_brkt_opt_Model and double clickon one of the model shape design cycle listings. Before updating themodel you can view stress results as described in this exercise. You canalso update the geometric model and the mesh to match any of the design



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cycles. The purpose of updating the mesh is to be able to run a simulationanalysis of the updated model and get new stress, deformation, vibration,

or buckling results.

In the Optimization Wizard Results window:

1. Select Update the Model.

This displays the Model Update window as shown in Figure 3-28.

Figure 3-28

Model Update Window

2. Select the last design cycle from the list in the Select Design

Cycle region.

The Select Design Cycle list shows all design cycles that the

optimizer evaluated. Your selection is used to update the model.

3. Accept the default to update the mesh with the model.

The Information at selected design cycle provides the following

information:

ObjectiveThe value of the objective function at the end ofthe selected design cycle.

Design variablesThe value of the design variables at the endof the selected design cycle.



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Note: The values found for the last design cycle and the next-to-last

design cycle are generally identical, indicating that the results haveconverged.

4. Click Next.

The update will be based on the design variables found for the

selected design cycle. A dialog prompts you to update the model.

5. Click Yes to update.

This procedure will update the mesh and delete any results

associated with the original model.

6. Click on Finish to close the Results.

7. Click Close to exit the Wizard.

The bracket is updated as shown in Figure 3-29.

Figure 3-29

Updated Bracket



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Viewing Stress Simulation Results

In this section you will display the stress simulation results of theoptimized model to verify stress constraints and see deflection values.

1. Choose Explorer from the Working Model FEA menu expand

Ex1_brkt_opt_Model_OptResults1.

2. Double Click on StressResultSet.

3. Close the Explorer.

View the stress simulation result contour as shown in Figure 3-30.

Figure 3-30

Stress Simulation ResultContour

You have completed this exercise.



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4221946 working model chapter3

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