written by changhyun, son chapter 6. ansys implementation - 1 chapter 6 ansys implementation

Written by Changhyun, SON Chapter 6. ANSYS Implementation - 1

CHAPTER 6CHAPTER 6

ANSYS ImplementationANSYS Implementation


Main StepsMain Steps

Begins with building a parametric model and creating the analysis file.Begins with building a parametric model and creating the analysis file.

AnalysisAnalysisFileFile

Explore theExplore theDesign DomainDesign Domain

Optimize theOptimize theDesignDesign

Initial DesignInitial Design

Parametric Modeling& Loading

Solution

ParametricResults


To optimize a design, an analysis file must be available.To optimize a design, an analysis file must be available.

The analysis file contains input for the parametric model: The analysis file contains input for the parametric model:

Initial parameter valuesInitial parameter values

Model geometry and meshingModel geometry and meshing

Boundary conditions, loads, and solutionBoundary conditions, loads, and solution

Results review and retrievalResults review and retrieval

Analysis FileAnalysis File


ProcedureProcedure

Four main steps (assuming that the analysis file iFour main steps (assuming that the analysis file is available):s available):

1. Identify the analysis file1. Identify the analysis file

2. Identify optimization variables - DVs, SVs, and objecti2. Identify optimization variables - DVs, SVs, and objective functionve function

3. Run the optimization3. Run the optimization

4. Review results4. Review results

These steps correspond to the menus in Main MeThese steps correspond to the menus in Main Menu > Design Opt as shown on the right.nu > Design Opt as shown on the right.

1

2

3

4


Example - Problem DefinitionsExample - Problem Definitions

We will use the rotating disk example to illustrate each step:We will use the rotating disk example to illustrate each step:

A high-speed rotating disk made of steel is to be designed for nearly uniform stresA high-speed rotating disk made of steel is to be designed for nearly uniform stres

s distribution at an operating speed of 15,000 rpm.s distribution at an operating speed of 15,000 rpm.

Properties: E = 30E6 psi,Properties: E = 30E6 psi, = 7.2E-4 lb-s= 7.2E-4 lb-s22/in/in44,, = 0.3= 0.3

rimymid

10.0R

4.0R

hub

0.6 0.4

1.6

0.5

xmid


Example - LimitationsExample - Limitations

The The von Mises stressvon Mises stress should not exceed should not exceed 25,000 psi25,000 psi

The disk’s The disk’s lowest natural frequencylowest natural frequency should be should be 1000 Hz or greater1000 Hz or greater..

The hub and the rim are of fixed dimensions, but you are allowed to The hub and the rim are of fixed dimensions, but you are allowed to

modify the shape in between.modify the shape in between.


Optimizing the Design - ProcedureOptimizing the Design - Procedure

Identify the Analysis FileIdentify the Analysis File

Identify the analysis fileIdentify the analysis file

Identify optimization variablesIdentify optimization variables

Run the optimizationRun the optimization

Review resultsReview results

Recall that the analysis file contains the input required Recall that the analysis file contains the input required

for one complete loop of the optimization run:for one complete loop of the optimization run: Parametric modeling and loadingParametric modeling and loading

SolutionSolution

Parametric resultsParametric results



Identify the Analysis FileIdentify the Analysis File

To identify the analysis file, simply choose the file name To identify the analysis file, simply choose the file name

from the Assign Analysis File dialog:from the Assign Analysis File dialog: Design Opt > -Analysis File- Assign…Design Opt > -Analysis File- Assign…

Or use the Or use the OPANLOPANL command command



Identify Optimization VariablesIdentify Optimization Variables





This step involves choosing the appropriate parameters This step involves choosing the appropriate parameters

and designating them as:and designating them as: Design variablesDesign variables

State variablesState variables

Objective functionObjective function


Design Variables (DVs)Design Variables (DVs) Design characteristics that are allowed to change in order to minimize thDesign characteristics that are allowed to change in order to minimize th

e volume (or whatever the objective function is).e volume (or whatever the objective function is).

For the rotating disk example, the DVs arFor the rotating disk example, the DVs aree

THETAHUB, 30°~ 90°THETAHUB, 30°~ 90° THETARIM, 45°~ 135°THETARIM, 45°~ 135° XMID, 0.5 ~ 4.5 inXMID, 0.5 ~ 4.5 in YMID, 0.25 ~ 1.5 inYMID, 0.25 ~ 1.5 in rim

ymidhub

xmid




To identify DVs,To identify DVs, Design Opt > Design Variables… > Add…Design Opt > Design Variables… > Add… Or use the OPVAR command:Or use the OPVAR command:

OPVAR,OPVAR,namename,DV,,DV,min,max,tolermin,max,toler




Maximum value (MAX) is required and must be > 0.0. Maximum value (MAX) is required and must be > 0.0.

Minimum value (MIN), if specified, must be > 0.0. If not specified, MIN defaMinimum value (MIN), if specified, must be > 0.0. If not specified, MIN defaults to 0.001*MAX.ults to 0.001*MAX.

Tolerance (TOLER) is the acceptable change in the DV between loops for conTolerance (TOLER) is the acceptable change in the DV between loops for convergence.vergence.

Has same units as the DV and is Has same units as the DV and is notnot a percentage or a fraction. Default = 0.01*c a percentage or a fraction. Default = 0.01*current value.urrent value.

For example, if THETAHUB = 54.2° in loop 6 and 55.0° in loop 7, convergence basFor example, if THETAHUB = 54.2° in loop 6 and 55.0° in loop 7, convergence based on DVs has ed on DVs has notnot occurred since |54.2-55.0| = 0.8, which is > 0.55. occurred since |54.2-55.0| = 0.8, which is > 0.55.

(But convergence may have occurred based on the objective function… more on thi(But convergence may have occurred based on the objective function… more on this later.)s later.)




You can define up to 60 DVs, but we recommend using no more than You can define up to 60 DVs, but we recommend using no more than

10~20 DVs. The more DVs, the higher the chance of converging to a 10~20 DVs. The more DVs, the higher the chance of converging to a

local minimum.local minimum.

DVs are restricted to positive values. Since most DVs are geometric DVs are restricted to positive values. Since most DVs are geometric

parameters such as thickness and radius, this restriction does not gparameters such as thickness and radius, this restriction does not g

enerally pose a problem.enerally pose a problem.




State Variables (SVs)State Variables (SVs)

Constraints placed on the design, such as a maximConstraints placed on the design, such as a maximum stress or deflection.um stress or deflection.

For the rotating disk example, SVs are:For the rotating disk example, SVs are: Maximum hoop stress Maximum hoop stress 25000 psi 25000 psi First natural frequency First natural frequency 1000 Hz 1000 Hz




To identify SVs,To identify SVs, Design Opt > State Variables… > Add…Design Opt > State Variables… > Add… Or use the Or use the OPVAR OPVAR command:command:

OPVAR,OPVAR,namename,SV,,SV,min,max,tolermin,max,toler




tolertolertolertoler InfeasibleInfeasible Feasible RegionFeasible Region

SVSVs can be one-sided or two-sided.s can be one-sided or two-sided. One-sided: only MIN or only MAX specifiedOne-sided: only MIN or only MAX specified Two-sided: both MIN and MAX specified.Two-sided: both MIN and MAX specified.

TOLERTOLER is the feasibility tolerance… how far the design can go beyond M is the feasibility tolerance… how far the design can go beyond MAX and MIN before it is considered infeasible.AX and MIN before it is considered infeasible.

Has same units as the SV and is Has same units as the SV and is notnot a percentage or a fraction. Default = 0. a percentage or a fraction. Default = 0.01*(MAX-MIN).01*(MAX-MIN).

For example, if the disk’s first natural frequency is FREQ1 = 991.3 Hz, the deFor example, if the disk’s first natural frequency is FREQ1 = 991.3 Hz, the design is still feasible since the actual threshold is 1000-(0.01*1000) = 990 Hsign is still feasible since the actual threshold is 1000-(0.01*1000) = 990 Hz.z.

MAXMIN




State variables are not required for optimization, State variables are not required for optimization, but they are usually specified since most designbut they are usually specified since most designs need to be constrained in some fashion.s need to be constrained in some fashion.

You can define You can define up to 100 SVsup to 100 SVs..




Objective Function (OBJ)Objective Function (OBJ)

The parameter that is minimized by the optimizer. Examples are voThe parameter that is minimized by the optimizer. Examples are vo

lume, weight, and the temperature at a location.lume, weight, and the temperature at a location.

For the rotating disk example, the objective is to minimize the variaFor the rotating disk example, the objective is to minimize the varia

tion in stress. Hence the OBJ is the standard deviation of the von tion in stress. Hence the OBJ is the standard deviation of the von

Mises stress, SDEV.Mises stress, SDEV.




To identify the objective function,To identify the objective function, Design Opt > Objective…Design Opt > Objective… Or use the Or use the OPVAROPVAR command: command:

OPVAR,OPVAR,namename,OBJ,,OBJ,,,toler,,toler




Tolerance (TOLER)Tolerance (TOLER) is the acceptable change in the OBJ between loops fo is the acceptable change in the OBJ between loops fo

r convergence.r convergence. Has same units as the OBJ and is Has same units as the OBJ and is notnot a percentage or a fraction. Default = 0. a percentage or a fraction. Default = 0.

01*current value.01*current value.

For example, if the standard deviation SDEV = 3900 in loop 7 and 3850 in loFor example, if the standard deviation SDEV = 3900 in loop 7 and 3850 in lo

op 6, convergence based on OBJ has op 6, convergence based on OBJ has notnot occurred since |3900-3850| = 50, w occurred since |3900-3850| = 50, w

hich is > 39.0.hich is > 39.0.

(But convergence may have occurred based on DVs… more on this later.)(But convergence may have occurred based on DVs… more on this later.)




You can specify only one OBJ.

ANSYS always minimizes the OBJ. If you want to maximize

something, say the parameter y, specify 1/y or A-y as the

OBJ (where A >> y).

We recommend that the OBJ remain positive. Add a

constant value to the parameter if needed to ensure this.




Optimizing the Design - Procedure Optimizing the Design - Procedure






This step involves:This step involves:

A.A. Specifying run-time controlsSpecifying run-time controls

B.B. Choosing the optimization methodChoosing the optimization method

C.C. Saving the optimization databaseSaving the optimization database

D.D. Initiating the optimization runInitiating the optimization run


A. Run-Time ControlsA. Run-Time Controls

These include:These include: Optimization database file name (Optimization database file name (OPDATAOPDATA). ).

Default: Default: jobnamejobname.opt.opt..

Controls on how to read the analysis file (Controls on how to read the analysis file (OPLOOPOPLOOP). ).

Default: read from the first line, ignore DV parameter definitions.Default: read from the first line, ignore DV parameter definitions.

Printout controls (Printout controls (OPPRNTOPPRNT). Default: suppress printout.). Default: suppress printout.

Save-best-design option (Save-best-design option (OPKEEPOPKEEP). Default: OFF.). Default: OFF.




Most controls are best left to default values except perhaps the save-Most controls are best left to default values except perhaps the save-

best-design option.best-design option.

This option saves the best design to date as it occurs:This option saves the best design to date as it occurs:

model geometry, mesh, loading, etc. on model geometry, mesh, loading, etc. on jobnamejobname.bdb.bdb

results on results on jobnamejobname.brst..brst.




Design Opt > Controls...Design Opt > Controls...




Notes on the Save-Best-Design OptionNotes on the Save-Best-Design Option

The best database is saved by a SAVE operation to the file The best database is saved by a SAVE operation to the file jobnamejobname.b.b

db.db.

The best results file is saved by simply copying the results file The best results file is saved by simply copying the results file jobnamjobnamee.rst to .rst to jobnamejobname.brst (or .rth to .brth, .rmg to .brmg, .rfl to .brfl)..brst (or .rth to .brth, .rmg to .brmg, .rfl to .brfl).

If multiple analyses are done, such as thermal followed by stress, only If multiple analyses are done, such as thermal followed by stress, only

the the lastlast results file is copied. results file is copied.

Consider using the Consider using the /ASSIGN/ASSIGN function ( function ( Utility Menu > File > ANSYS Utility Menu > File > ANSYS

File Options…File Options… ) if you want a different results file to be copied. ) if you want a different results file to be copied.




B. Optimization MethodB. Optimization Method

Two optimization methods are available in ANSYS:Two optimization methods are available in ANSYS:

Sub-problem approximation methodSub-problem approximation method

First-order methodFirst-order method

The sub-problem approximation method is generally The sub-problem approximation method is generally

recommended for most applications because of its recommended for most applications because of its

generality of approach and speed of execution.generality of approach and speed of execution.

Details of when to choose the first-order method will be Details of when to choose the first-order method will be

presented later.presented later.




Use the Use the OPTYPE OPTYPE and and OPSUBPOPSUBP commands. commands. Or Or Design Opt > Method/Tool…Design Opt > Method/Tool…

Choosing a method brings up a second dialog box with Choosing a method brings up a second dialog box with additional options. These options (discussed later) are best additional options. These options (discussed later) are best left to default values.left to default values.




C. Save the Optimization DatabaseC. Save the Optimization Database

The optimizer works with its own database, which consists of:The optimizer works with its own database, which consists of: DV, SV, and OBJ specifications.DV, SV, and OBJ specifications. Analysis file name, optimization method and controls, total number of iAnalysis file name, optimization method and controls, total number of i

terations completed to date, etc.terations completed to date, etc. Parameter values for each design generated to date.Parameter values for each design generated to date.

At the end of each iteration, ANSYS automatically saves this inforAt the end of each iteration, ANSYS automatically saves this information on the OPT database file specified in the Run-Time Controlmation on the OPT database file specified in the Run-Time Controls dialog (which defaults to s dialog (which defaults to jobnamejobname.opt)..opt).




You can check the OPT You can check the OPT

database status at any database status at any

time using:time using: Design Opt > -Opt Design Opt > -Opt

Database- StatusDatabase- Status

Or the Or the STATUSSTATUS command command




Saving the OPT database before initiating the optimization run allows you tSaving the OPT database before initiating the optimization run allows you to resume from this point conveniently if needed.o resume from this point conveniently if needed.

Use the Use the OPSAVEOPSAVE command. command. Or Or Design Opt > -Opt Database- Save...Design Opt > -Opt Database- Save...

Choose a name different from the default (since the default file gets updated eaChoose a name different from the default (since the default file gets updated each iteration). Example: ch iteration). Example: jobnamejobname.opt0..opt0.




D. Initiate the Optimization RunD. Initiate the Optimization Run Use the Use the OPEXEOPEXE command. command. Or Or Design Opt > Run…Design Opt > Run…

Check the settings, then press OK to start the Check the settings, then press OK to start the optimization.optimization.




The optimizer will then loop through the analysis file multiple The optimizer will then loop through the analysis file multiple

times with new DV values each time until the design has times with new DV values each time until the design has

convergedconverged or until the maximum number of iterations is reached. or until the maximum number of iterations is reached.




What is convergence?What is convergence?

A design has converged to a possible optimum if it is feasible A design has converged to a possible optimum if it is feasible andand if if oneone of of

the following four conditions is true:the following four conditions is true:

1.1. The change in objective function between the current design and the The change in objective function between the current design and the

best feasible design is less than the tolerance.best feasible design is less than the tolerance.

|OBJ|OBJcurrentcurrent - OBJ - OBJbestbest| < TOLER| < TOLERobjobj

2.2. The change in objective function between the current and previous deThe change in objective function between the current and previous de

signs is less than the tolerance.signs is less than the tolerance.

|OBJ|OBJcurrentcurrent - OBJ - OBJcurrent-1current-1| < TOLER| < TOLERobjobj




3.3. For each DV, the change between the current design and the best feasiFor each DV, the change between the current design and the best feasible design is less than its tolerance.ble design is less than its tolerance.

|DV|DVcurrentcurrent - DV - DVbestbest| < TOLER| < TOLERdv dv for all DVs for all DVs

4.4. For each DV, the change between the current and previous designs is lFor each DV, the change between the current and previous designs is less than its tolerance.ess than its tolerance.

|DV|DVcurrentcurrent - DV - DVcurrent-1current-1| < TOLER| < TOLERdv dv for all DVs for all DVs

Again, if one of these four conditions is true Again, if one of these four conditions is true andand if the current design is feasi if the current design is feasible, we have a ble, we have a convergedconverged or or optimumoptimum design. design.




The ANSYS Output window (or output file if batch) shows the basis for The ANSYS Output window (or output file if batch) shows the basis for

convergence.convergence.

For the rotating disk example, design no. 9 (also called set 9) For the rotating disk example, design no. 9 (also called set 9)

converged based on OBJ comparison to the best design (set 3). And converged based on OBJ comparison to the best design (set 3). And

set 9 is considered the “optimum” design since it has a lower OBJ value set 9 is considered the “optimum” design since it has a lower OBJ value

than set 3.than set 3.




Does convergence indicate an optimum design?Does convergence indicate an optimum design?

Not necessarily. It simply indicates that the current design is Not necessarily. It simply indicates that the current design is

feasible and meets one of the four convergence criteria.feasible and meets one of the four convergence criteria.

It is up to you, the engineer, to determine whether the design is It is up to you, the engineer, to determine whether the design is

indeed optimum.indeed optimum.

One way to do this is by continuing (restarting) the One way to do this is by continuing (restarting) the

optimization with different tolerance values or with a different optimization with different tolerance values or with a different

set of designs. More on restarts later.set of designs. More on restarts later.




The output window also lists a design sensitivity summary table, The output window also lists a design sensitivity summary table, which can be used as a guide to determine which DV has the which can be used as a guide to determine which DV has the most (or least) effect on design parameters.most (or least) effect on design parameters.

For the rotating disk example, notice that a unit change in YMID For the rotating disk example, notice that a unit change in YMID has a large effect on the maximum stress. The design is also has a large effect on the maximum stress. The design is also sensitive to changes in XMID.sensitive to changes in XMID.





Review the ResultsReview the Results





You can review optimization results by:You can review optimization results by: first restoring the OPT database (if needed)first restoring the OPT database (if needed)

listing design setslisting design sets

creating graphscreating graphs

restoring the geometry and results for the best designrestoring the geometry and results for the best design




Restoring the OPT DatabaseRestoring the OPT Database

This step is needed only if you exited ANSYS after the optimization rThis step is needed only if you exited ANSYS after the optimization run.un.

Use the Use the OPRESUOPRESU command. command.

Or Or Design Opt > -Opt Database- Resume…Design Opt > -Opt Database- Resume… File name defaults to the OPT database file name specified in tFile name defaults to the OPT database file name specified in t

he Run-Time Controls dialog (which in turn defaults to he Run-Time Controls dialog (which in turn defaults to jobnamejobname..OPT).OPT).



Review the ResultsReview the ResultsListing Design SetsListing Design Sets

Allows you to review parameter values for a desired design or Allows you to review parameter values for a desired design or a range of designs.a range of designs.

You can choose to list optimization parameters only or all You can choose to list optimization parameters only or all parameters.parameters.

Use the Use the OPLISTOPLIST command. command. Or Or Design Opt > -Design Sets- List…Design Opt > -Design Sets- List…




Note that the listing indicates whether a design is feasible or infeasible and also the reason for infeasibility.

For the rotating disk example:

The initial design is infeasible because SMAX is out of range.

The two feasible designs are also the best designs.




Creating GraphsCreating Graphs

Use the PLVAROPT command.Use the PLVAROPT command.

Or Design Opt > Graphs/Tables…Or Design Opt > Graphs/Tables…

You can graph optimization You can graph optimization

variables versus set number variables versus set number

(default) or versus other (default) or versus other

optimization variables.optimization variables.



Review the ResultsReview the Results This is a graph of objective function SDEV vs. set number.This is a graph of objective function SDEV vs. set number.

PLVAROPT,SDEVPLVAROPT,SDEV



Review the ResultsReview the Results State variable FREQ1 vs. set number.State variable FREQ1 vs. set number.

PLVAROPT,FREQ1PLVAROPT,FREQ1



Review the ResultsReview the Results SMAX (maximum von Mises stress) vs. set number.SMAX (maximum von Mises stress) vs. set number.

PLVAROPT,SMAXPLVAROPT,SMAX




Working with Graphs

Many graph controls are available to alter the way the graph shows on the screen:

Axis controls: change the axis label, number of divisions, range of values, etc.

Curve controls: thickness of curve, filling of area under curve, etc.

Grid controls: grid on/off; X-grid only, Y-grid only, or both; etc.

Utility Menu : PlotCtrls > Style > Graphs




As an example, we will change the previous graph as

follows:

Set Y-axis label to SMAX

Change number of X-axis divisions to 8 (9 sets, therefore 8

divisions)

Increase curve thickness




Utility Menu : PlotCtrls > Style > Graphs > Modify Axes ...

Utility Menu : PlotCtrls > Style > Graphs > Modify Curve ...




Restoring the Best Design Geometry and ResultsRestoring the Best Design Geometry and Results

To do this, simply exit the optimizer and resume the file To do this, simply exit the optimizer and resume the file jobnamejobname.bdb (be.bdb (best db).st db).

Main Menu > FinishMain Menu > Finish Utility Menu > File > Resume from… Utility Menu > File > Resume from… Utility Menu > Plot > ElementsUtility Menu > Plot > Elements

Or issue these commands:Or issue these commands: FINISHFINISH RESUME,RESUME, jobname,jobname,bdbbdb EPLOTEPLOT




Results are available on the file Results are available on the file jobnamejobname.brst..brst.

Enter POST1 and specify Enter POST1 and specify jobnamejobname.brst as the results file .brst as the results file

(using the (using the FILEFILE command command

or or Main Menu : General Postproc > Data & File Opts…Main Menu : General Postproc > Data & File Opts… ). ).

Then use standard POST1 functions to review results.Then use standard POST1 functions to review results.

Note: .bdb and .brst are written only if you activate the save-best-design opNote: .bdb and .brst are written only if you activate the save-best-design op

tion in the Optimization Controls dialog.tion in the Optimization Controls dialog.


Optimizing the DesignOptimizing the Design

ProcedureProcedure





Next we will briefly discuss how to work with the optimization Next we will briefly discuss how to work with the optimization

database and continue (restart) the optimization if needed.database and continue (restart) the optimization if needed.



C. RestartsC. Restarts

A restart is a continuation of a previous optimization run.A restart is a continuation of a previous optimization run. Its purpose is usually one or both of the following:Its purpose is usually one or both of the following:

to further hone in on the optimum by changing tolerances and/or to further hone in on the optimum by changing tolerances and/or DV limitsDV limits

to force a different optimization “path” by starting from a different to force a different optimization “path” by starting from a different set of designsset of designs

DV

OBJ

Current optimum

Possible new optimum

OBJ

Current optimum

Possible new optimum

DV



RestartsRestarts

A typical restart involves four steps:A typical restart involves four steps:

1.1. First save the current OPT database to a named fileFirst save the current OPT database to a named file

2.2. Select a subset of design sets if neededSelect a subset of design sets if needed

3.3. Modify optimization variables (tolerances and limits)Modify optimization variables (tolerances and limits)

4.4. Run the optimizationRun the optimization



RestartsRestarts

1. Save the Current OPT Database1. Save the Current OPT Database

This allows you to restore it later if needed.This allows you to restore it later if needed.

Design Opt > -Opt Database- Save…Design Opt > -Opt Database- Save… (or (or OPSAVEOPSAVE))

Be sure to specify a non-default file nameBe sure to specify a non-default file name



RestartsRestarts

2. Select a Subset of Design Sets2. Select a Subset of Design Sets

Design Opt > -Design Sets- Select/Delete…Design Opt > -Design Sets- Select/Delete… (or (or OPSELOPSEL and and OPDELEOPDELE)) Allows you to keep a desired set of designs (such as all feasibles) and discarAllows you to keep a desired set of designs (such as all feasibles) and discar

d the rest.d the rest. Caution:Caution: Selecting a subset Selecting a subset

actually actually removesremoves the unselected the unselected

design sets from the database. design sets from the database.

(That’s why the first step is to (That’s why the first step is to

save the OPT database!)save the OPT database!)



RestartsRestarts

For the rotating disk example, selecting all feasible sets discards For the rotating disk example, selecting all feasible sets discards

seven design sets and keeps two.seven design sets and keeps two.

Use the List function to list all currently selected design sets.Use the List function to list all currently selected design sets. Design Opt > -Design Sets- List… > All SetsDesign Opt > -Design Sets- List… > All Sets

Notice that the original set numbers are retained. That is, deleted set Notice that the original set numbers are retained. That is, deleted set

numbers are numbers are notnot reused. reused.



RestartsRestarts

3. Modify Optimization Variables3. Modify Optimization Variables

You can modify tolerances, change limits, and even delete a DV or SV for the You can modify tolerances, change limits, and even delete a DV or SV for the restart.restart.

Modifying TolerancesModifying Tolerances For DVs and OBJ, allows you to change the convergence basis. For exaFor DVs and OBJ, allows you to change the convergence basis. For exa

mple, tightening the OBJ tolerance may “force” convergence based on Dmple, tightening the OBJ tolerance may “force” convergence based on DV tolerances.V tolerances.

For SVs, allows you to increase or decrease the feasibility threshold.For SVs, allows you to increase or decrease the feasibility threshold.



RestartsRestarts

For the rotating disk, we will tighten the OBJ tolerance (SDEV) to For the rotating disk, we will tighten the OBJ tolerance (SDEV) to 0.5.0.5.

Design Opt > Objective… > ModifyDesign Opt > Objective… > Modify



RestartsRestarts

Changing LimitsChanging Limits

Allows you to constrain or expand the design Allows you to constrain or expand the design

domain.domain.

Design Opt > Design Variables… > Edit…Design Opt > Design Variables… > Edit…

Design Opt > State Variables… > Edit…Design Opt > State Variables… > Edit…

For the rotating disk, we will change DV limits as For the rotating disk, we will change DV limits as

follows:follows:

– THETARIM: 45°-90°THETARIM: 45°-90°

– XMID: 2.0-3.0 inXMID: 2.0-3.0 in



RestartsRestarts



RestartsRestarts

4. Run the optimization4. Run the optimization

First save the new settings to a named file:First save the new settings to a named file:

Design Opt > -Opt Database- Save…Design Opt > -Opt Database- Save…



RestartsRestarts

Then initiate the optimization run. The new run will most likely Then initiate the optimization run. The new run will most likely

converge to a different design. Again, it is up to you, the engineer, converge to a different design. Again, it is up to you, the engineer,

to verify the validity of the optimum design.to verify the validity of the optimum design.

Design Opt > Run…Design Opt > Run…



RestartsRestarts

The rotating disk The rotating disk

example took 12 example took 12

iterations to converge iterations to converge

based on DV tolerances. based on DV tolerances.

The best design is set The best design is set

21.21.



RestartsRestarts

Compared to the previous best design (set 9, which is now Compared to the previous best design (set 9, which is now

infeasible because of the new DV limits), the new best design infeasible because of the new DV limits), the new best design

(set 21) has a lower OBJ. (set 21) has a lower OBJ.



RestartsRestarts

written by changhyun, son chapter 6. ansys implementation - 1 chapter 6 ansys implementation

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