18/2/2015 20APDLCommandsEveryANSYSMechanicalUserShouldKnow|PADT,Inc.TheBlog

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ByEricMiller August29,2013

20APDLCommandsEveryANSYSMechanicalUserShouldKnow

OneofthemostpowerfulthingsaboutANSYSMechanicalisthefactthatitcreatesaninputfilethatissenttoANSYSMechanicalAPDL(MAPDL)tosolve.ThisisawesomebecauseyouasauserhavecompleteandfullaccesstothehugebreadthanddepthavailableintheMAPDLprogram.MAPDLisagoodoldfashionedcommanddrivenprogramthattakesintextcommandsonelineatatimeandexecutesthem.Sotoaccessallthosefeatures,youjustneedtoenterinthecommandsyouwant.

Formanyolderusersthisisnotaproblembecausewegrewupusingthetextcommands.ButnewusersdidnotgetthechancetobeexposedtothepowerofAPDL(ANSYSParametricDesignLanguage)sogettingaccesstothoseadvancedcapabilitiescanbetough.

Infact,Iwasinaroomnexttooneofoursupportengineerswhiletheywereshowingacustomerhowtochangetheelementsthatthesolverwouldsolve(Mechanicaldefaultstothemostcommonformulation,butyoucanchangethemtowhateverstillmakessense)andtheuserhadtoadmithehadneverreallyusedorevenseenAPDLcommandsbefore.

So,asawaytogetANSYSMechanicalusersouttherestarteddowntheroadoflovingAPDLcommands,wegottogetherandcameupwithalistof20APDLcommandsthateveryusershouldknow.Well,actually,itismorethan20becausewegroupedsomeofthemtogether.Wearenotgoingtogivetoomuchdetailontheirusage,theAPDLhelpisfantasticanditexplainseverything.Infact,ifyouuseacopyofPeDALyoucangetthehelprightthereliveasyoutype(yes,thatwasaplugforyoutogooutandplopdown$49andbuyPeDAL).

AlsonotethatwearenotgettingintohowtoscriptwithAPDL.Itisatrulyparametriccommandlanguageinthatyoucanreplacemostvaluesincommandswithparameters.Italsohascontrollogic,functionsandothercapabilitiesthatyoufindinmostscriptinglanguages.Wewillfocusonactualcommandsyouusetodothingsintheprogramhere.IfyouwanttolearnmoreabouthowtoprogramwithAPDL,youcanpurchaseacopyofourIntroductiontotheANSYSParametricDesignLanguagebook.(anotherplug)

SomeAPDLBasics

APDLwasdevelopedbackinthedayofpunchcards.Itwasmucheasiertousethantheotherprogramsouttherebecausethecommandsyouentereddidnthavetobeformattedincolumns.Insteadargumentsforcommandsareseparatedbycommas.Therefore,insteadofdefiningaNodeinyourmodelas:

34512.45617.45670.0034

(notethatthelocationofthatdecimalpointiscritical).Youcreatealineas:

N,345,12.456,17.4567,0.0034

Trustme,thatwasabigdeal.ButwhatyouneedtoknownowisthatallAPDLcommandsstartwithakeywordandarefollowedbyarguments.TheargumentsareexplainedintheCommandReferenceinthehelp.Sotheentryforcreatinganodelookslikethis:

18/2/2015 20APDLCommandsEveryANSYSMechanicalUserShouldKnow|PADT,Inc.TheBlog

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Thedocumentationisveryconsistentandyouwillquicklygetthehangofhowtogetwhatyouneedoutofit.Thelayoutisexplainedinthehelp://CommandReference//3.CommandDictionary

AnotherkeythingtoknowaboutcommandsinMAPDListhatmostentitiesyoucreate(notloadsandboundaryconditions)haveanIDnumber.YourefertoentitiesbytheirIDnumber.ThisisakeyconceptthatgetslostifyougrewupusingGUIs.Soifyouwanttomakeacoordinatesystemanduseit,youdefineanIDforitandthenrefertothatID.Samethinggoesforelementdefinitions(ElementTypes),materialproperties,etcRememberthis,ithangsupalotofnewerusers.

TouseMAPDLcommandsyousimplyentereachcommandonalineinacommandobjectthatyouplaceinyourmodeltree.Wedidaseminaronthisverysubjectabouttwoyearsagothatyoucanwatchhere.

TheideaofentityselectionisfundamentaltoAPDL.AbovewepointoutthatallentitieshaveanID.YoucaninteractwitheachentitybyspecifyingitsID.Butwhenyouhavealotofthem,likenodesandelements,itwouldbeapain.SoAPDLdealswiththisbylettingyouselectentitiesofagiventypeandmakingthemselectedorunselectedThenwhenyouexecutecommands,insteadofspecifyinganID,youcanspecifyALLandalloftheselectedentitiesareusedforthatcommand.Sometimeswerefertoentitiesasbeingselected,andsometimeswerefertothemasactive.ThebasicconceptisthatanyentityinANSYSMechanicalAPDLcanbeoneoftwostates:active/selectedorinactive/unselected.inactive/unselectedentitiesarenotusedbywhatevercommandyoumightbeexecuting.

IfyouwanttoseealloftheAPDLcommandthatANSYSMechanicalwritesout,simplyselectthesetupbranchofyourmodeltreeandchooseTools>WriteInputFile.Youcanviewitinatexteditor,orevenbetter,inPeDAL.

Onelastimportantnotebeforewegothroughourlistofcommands:theoldGUIforMAPDLcanbeusedtomodifyorcreatemodelsaswellasANSYSMechanical.EveryactionyoutakeintheoldGUIisconvertedintoacommandandstoredinthejobname.logfile.Manyuserswillcarryouttheactionstheywantinaninteractive

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session,thensavethecommandstheyneedfromthelogfile.

Wait,onemorething:Rightnowyouneedthesecommands.ButateveryreleasemoreandmoreofthesolverisexposedinANSYSMechanicalFUIandweendupusinglessandlessAPDLscripts.Sobeforeyouwriteascript,makesurethatANSYSMechanicalcantalreadydowhatyouwant.

TheCommands

1.!

AnexclamationpointisacommentinAPDL.Anycharacterstotherightofoneareignoredbytheprogram.Usethemoftenandaddgreatcommentstohelpyouandothersrememberwhattheheckyouweretryingtodo.

2./PREP7/SOLU/POST1FINISH

TheMAPDLprogramconsistsofacollectionof10processors(thereweremore,buttheyhavebeenundocumented.)Commandsonlyworkinsomeprocessors,andmostonlyinone.Ifyouenterinapreprocessorcommandwhenyouareinthepostprocessor,youwillgetanerror.

WhenyoucreateacommandobjectinyourANSYSMechanicalmodel,itwillbeexecutedineitherthePreprocessor,theSolutionprocessor,orinthePostprocessor.Dependingonwhereinthemodeltreeyouinsertthecommandobject.Ifyouneedtogointoanotherprocessoryoucan,yousimplyissuethepropercommandtochangeprocessors.JUSTREMEMBERTOGOBACKTOTHEPROCESSORYOUSTARTEDINwhenyouaredonewithyourcommands.

/PREP7goestothepreprocessor.Usethistochangeelements,createthings,ormodifyyourmeshinanyway.

/SOLUgoestothesolutionprocessor.Mostofthetimeyouwillstarttheresoyoumostoftenwillusethiscommandifyouwentinto/PREP7andneedtogetback.Modifyloads,boundaryconditions,andsolversettingsinthisprocessor.

/POST1goestothepostprocessor.Thisiswhereyoucanplaywithyourresults,makeyourownplots,anddosomeverysophisticatedpostprocessing.

FINISHgoestothebeginlevel.Youwillneedtogothereifyouaregoingtoplaywithfilenames.

3.TYPEMATREALSECNUM

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YouonlyreallyneedtoknowthesecommandsifyouwillbemakingyourownelementsbutoneofthosethingseveryoneshouldknowbecausetheassignmentofelementattributesisfundamentaltothewayAPDLworks.soreadonevenifyoudontneedtomakeyourownelements.

Everyelementinyourmodelisassignedpropertiesthatdefinetheelement.Whenyoudefineanelement,insteadofspecifyingallofitspropertiesforeachelement,youcreatedefinitionsandgivethemnumbers,thenassignthenumbertoeachelement.Thesimplestexamplearematerialproperties.Youdefineasetofmaterialproperties,giveitanumber,thenassignthatnumbertoalltheelementsinyourmodelthatyouwanttosolvewiththoseproperties.

ButyoudonotspecifytheIDswhenyoucreatetheelements,thatwouldbeapain.Instead,youmaketheIDforeachpropertytypeactiveandeveryelementyoucreatewillbeassignedtheactiveIDs.

Thecommandsareselfexplanatory:TypesetstheElementType,MATsetsthematerialID,REALsettherealconstantnumber,andSECNUMsetstheactivesectionnumber.

So,ifyoudothefollowing:

type,4real,2mat,34secnum,112e,1,2,3,4,11,12,13,14

youget:

ELEMMATTYPRELESYSECNODES13442011212341112131423440200101102103104111112113114

4.ET

TheMAPDLsolversupportshundredsofelements.ANSYSMechanicalpicksthebestelementforwhateversimulationyouwanttodofromageneralsense.Butthatmaynotbethebestforyourmodel.Insuchcases,youcanredefinetheelementdefinitionthatANSYSMechanicalused.

Note:Thenewelementmusthavethesametopology.Youcantchangea4nodedshellintoan8nodedhex.Butifthenodeorderingisthesame(thetopology)thenyoucanmakethatchangeusingtheETcommand.

5.EMODIF

Ifyoudefinearealconstant,elementtype,ormaterialIDinAPDLandyouwanttochangeabunchofelementstothosenewIDs,youuseEMODIF.Thisisthefastestwaytochangeanelementsdefinition.

6.MPMPDATAMPTEMPTBTBDATATBTEMP

ProbablythemostcommonlyneededAPDLcommandforANSYSMechanicalusersarethebasicmaterialpropertycommands.LinearpropertiesaredefinedwithMPcommandforapolynomialvs.temperatureorMPDATAandMPTEMPforapiecewiselineartemperatureresponse.NonlinearmaterialpropertiesaredefinedwiththeTB,TBDATA,andTBTEMPcommands.

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Itisalwaysagoodideatostickyourmaterialdefinitionsinatextfilesoyou1)havearecordofwhatyouused,and2)canreusethematerialmodelonothersimulationjobs.

7.RRMODIF

IfyoudefineanelementsformulationwithoptionsontheETcommand,andthematerialpropertiesonthematerialcommands,wheredoyouspecifyotherstufflikeshellthickness,contactparameters,orhourglassstiffness?Youputtheminrealconstants.IfyouarenewtotheMAPDLsolvertheideaofRealconstantsisabithardtogetusedto.

Theofficialexplanationis:

Datarequiredforthecalculationoftheelementmatricesandloadvectors,butwhichcannotbedeterminedbyothermeans,areinputasrealconstants.Typicalrealconstantsincludehourglassstiffness,contactparameters,strandedcoilparameters,andplanethicknesses.

Itreallyisaplacetoputstuffthathasnootherplace.Rcreatesarealconstant,andRMODIFcanbeusedtochangethem.

8.NSELESEL

Asmentioned,selectionlogicisahugepartofhowMAPDLworks.Youneverwanttoworkoneachobjectyouwanttoview,change,load,etcInsteadyouwanttoplaceentitiesofagiventypeintoanactivegroupandthenoperateonallactiveentities.(youcangroupthemandgivethemnamesaswell,seeCMCMSELCMDELEbelowtolearnaboutcomponents)

WhenaccessingMAPDLfromANSYSMechanicalyouaremostoftenworkingwitheithernodesorelements.NSELandESELareusedtomanagewhatnodesandelementsareactive.Thesecommandshavealotofoptions,soreviewthehelp.

9.NSLEESLN

Youoftenselectnodesandthenneedtheelementsattachedtothosenodes.Oryouselectelementsandyouneedthenodesonthoseelements.NSLEandESLNdothat.NSLEselectsallofthenodesonthecurrentlyactiveelementsandESLNdoestheopposite.

10.ALLSEL

AverycommonmistakeforpeoplewritinglittlescriptsinAPDLforANSYSMechanicalistheyuseselectionlogictoselectthingsthattheywanttooperateon,andthentheydontremembertoreselectallthenodesandelements.IfyouissueanNSELandgetsaythenodesonthetopofyourpartthatyouwanttoapplyaloadto.Ifyoujuststoptherethesolverwillgenerateerrorsbecausethosewillbetheonlyactivenodesinthemodel.

ALLSELfixesthis.Itsimplymakeseverythingactive.Itisagoodideatojuststickitattheendofyourscriptsifyoudoanyselecting.

11.CMCMSEL

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IfyouuseANSYSMechanicalyoushouldbeveryfamiliarwiththeconceptofNamedSelections.Thesearegroupsofentities(nodes,elements,surfaces,edges,vertices)thatyouhaveputintoagroupsoyoucanscopebasedonthemratherthanselectingeachtime.InANSYSMAPDLthesearecalledcomponentsandcommandsthatworkwiththemstartwithCM.

AnynamedselectionyoucreateforgeometryinANSYSMechanicalgetsturnedintoanodalcomponentallofthenodesthattouchthegeometryintheNamedSelectiongetthrownintothecomponent.YoucanalsocreateyourownnodeorelementNamedSelectionsandthosealsogetcreatedascomponentsinMAPDL.

YoucanuseCMtocreateyourowncomponentsinyourAPDLscripts.Yougiveitanameandoperateaway.YoucanalsoselectcomponentswiththeCMSELcommand.

12.*GET

ThisisthesinglemostawesomelyusefulcommandinAPDL.Itisawaytointerrogateyourmodeltofindoutallsortsofusefulinformation:numberofnodes,largestZvaluefornodeposition,ifanodeisselected,loadsonanode,resultinformation,etc

Checkoutthehelponthecommand.IfyoueverfindyourselfwritingascriptandgoingifIonlyknewblahdeblahblahaboutmymodelthenyouprobablyneedtouse*get.

13.CSYSLOCALRSYS

CoordinatesystemsareveryimportantinANSYSMechanicalandANSYSMAPDL.InmostcasesyoushouldcreateanycoordinatesystemsyouneedinANSYSMechanical.TheywillbeavailabletoyouinANSYSMAPDL,butbydefaultANSYSMechanicalassignsadefaultID.TouseacoordinatesysteminMAPDLyoushouldspecifythecoordinatesystemnumberinthedetailsforagivencoordinatesystembychangingCoordinateSystemfromProgramDefinedtoManualandthenspecifyinganumberforCoordinateSystemID

IfyouneedtomakeacoordinatesysteminyourAPDLscript,usetheLOCALcommand.

Whenyouwanttouseacoordinatesystem,useCSYStomakeagivencoordinatesystemactive.

Note:Coordinatesystem0istheglobalCartesiansystem.IfyouchangetheactivecoordinatesystemmakesureyousetitbacktotheglobalsystemwithCSYS,0

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RSYSislikeCSYSbutforresults.IfyouwanttoplotorlistresultinformationinacoordinatesystemotherthantheglobalCartesian,useRSYStomakethecoordinatesystemyouwantactive.

14:NROTATE

Onethingtobeveryawareofisthateachnodeinamodelhasarotationassociatedwithit.Bydefault,theUX,UY,andUZdegreesoffreedomareorientedwiththeglobalCartesiancoordinatesystem.InANSYSMechanical,whenyouspecifyaloadoraboundaryconditionasnormalortangenttoasurface,theprogramactuallyrotatesallofthosenodessoadegreeoffreedomisnormaltothatsurface.

IfyouneedtodothatyourselfbecauseyouwanttoapplyaloadorboundaryconditioninacertaindirectionbesidestheglobalCartesian,useNROTATE.Youbasicallyselectthenodesyouwanttorotate,specifytheactivecoordinatesystemwithCSYS,thenissueNROTATE,ALLtorotatethem.

Becarefulthough.YoudontwanttoscrewwithanyrotationsthatANSYSMechanicalspecified.

15.D

Themostcommonboundaryconditionisdisplacement,evenfortemperature.TospecifythoseinanANSYSMAPDLscript,usetheDcommand.Mostpeopleusenodalselectionorcomponentstoapplydisplacementstomultiplenodes.

Initssimplestformyouapplyasinglevaluefordisplacementtoonenodeinonedegreeoffreedom.Butyoucanspecifymultiplenodes,multipledegreesoffreedom,andmorepowerfully,thevaluefordeflectioncanbeatable.Learnabouttableshere.

16.F

TheFcommandisthesameastheDcommand,exceptitdefinesforcesinsteadofdisplacement.Know,it,useit.

17.SFSFE

Ifyouneedtoapplyapressureload,youuseeitherSFtoapplytonodesoreSFEtoapplytoelements.ItworksalotliketheDandFcommands.

18./OUTPUT

WhentheANSYSMAPDLsolverissolvingawayitwritesbitsandpiecesofinformationtoafilecalledjobename.out,wherejobnameisthenameofyoursolverjob.Sometimesyoumaywanttowriteoutspecificinformation,saylistthestressesforallthecurrentlyselectednodes,toafile.use/OUTPUT,filenametoredirectoutputtoafile.Whenyouaredonespecify/OUTPUTwithnooptionsanditwillgobacktothestandardoutput.

19./SHOW

ANSYSMAPDLhassomeverysophisticatedplottingcapabilities.Thereareatonofcommandandoptionsusedtosetupandcreateaplot,butthemostimportantis/SHOW,png.ThistellsANSYSMAPDLthatallplotsfromnowonwillbewritteninPNGformattoafile.Readallabouthowtousethiscommand,andhowtocontrolyourplots,here.

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20.ETABLE

TheANSYSMAPDLsolversolvesforalotofvalues.Themorecomplextheelementyouareusing,themorethenumberofvaluesyoucanstore.Buthowdoyougetaccesstothemoreobscureones?ETABLE.Issue38ofTheFocusfrom2005goesintosomeofthethingsyoucandowithETABLE.

WheretogoFromHere

Thisiscertainlynotthedefinitivelist.Ask20ANSYSMAPDLuserswhatAPDLcommandsallANSYSMechanicalusersshouldknow,andyoumightgetfiveorsixincommon.Butbasedonthesupportcallswegetandthescriptswewrite,this20arethemostcommonthatweuse.

Commandhelpisyourfriendhere.Useitalot.

TheotherthingyoushoulddoisopenupANSYSMAPDLinteractivelyandplaywiththesecommands.Seewhathappenswhenyouexecutethem.