英语翻译.docx

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英语翻译

113

Lesson3NonlinearStaticBucklingAnalysis

Aftersuccessfulcompletionofthislesson,youwillbeable

Performanonlinearlarge-deformationbucklinganalysis

DefineControlsforanonlinearbucklinganalysisusingartlength

Control.

Compareresultsfromlinearbucklingandnonlinearstudies

Understandtheinfluenceofinitialdisturbancesonthebuckingof

symmetricstructres

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CaseStudy:

CylindricalShell

Inthislesson,wewillperformabucklinganalysisonacylindrical

shell.Symmetrywillbeutilizedtosimplifythecalculations.First,a

linearbucklinganalysiswillbeperformedanditslimitationswillbe

discussed.Alinearstaticanalysiswillthenbeperformedtoobtain

parametersforanonlinearstaticbucklinganalysis.Thearc-length

incrementalcontroltechniquewillbeutilizedtoovercomeinherent

instabilitiesinthenonlinearcalculations.Finally,theresultsfromthe

linearandnonlinearstudieswillbecomparedanddiscussed.

ProblemStatement

Ashallowcylindricalarcistobe

analyzedforbucklingwhenitis

subjectedtoacentralpointload.

Theshellissimplysupported

alongtwoparallelsideswiththe

othertwoedgesunrestrained.

Theparametersofthemodelare

asfollows:

Radius:

2540mm

thickness:

6.35mm

Width:

508mm

Thetasection:

20rad（11.46deg）

Material:

Aluminum1060Alloy

Referenceload:

1000Ncenterpointload

StagesintheProcess

Linearbucklinganalysis

Alinearbucklinganalysiswillprovideuswithpreliminaryresults

thatcanbecomparedwiththenonlinearanalysis.

Linearstaticanalysis

Toestimatesomeparameterstobeusedinthenonlinearanalysis;a

linearstaticanalysiswillbeperformed.

Nonlinearstaticbucklinganalysis

Anonlinearstaticanalysiswillbeusedtoobtainamoreaccurate,0

predictionofbuckling.

LinearSuckling

Toreviewlinearbucklinganalysis,pleaserefertoLesson3ofthe

SolidWorksSimulationProfessionaltrainingmanual.Inthislesson,we

willquicklyperformthelinearbucklinganalysistobeeotrx,

thenonlinearstudy.

Procsdure

Followtheprocedurebelow:

1Openthefile.

OpenthefileCylindricalShellfromtheLesson3folder

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2Changeconfiguration.

Becauseboththestructureandtheloadaresymmetrical,wewill

analyzeaquartermodelonly.IntheSolidWorks

ConfigurationManager,activateQuartermodelconfiguration

IntheViewmenu,selectAllAnnotationstoviewthecenterandedges

3Createastudy.

FromtheSimulationmenu,selectStudyEnterLinear

Buckling-QuarterastheNameandselectBucklingastheType.

4Excludesolidbody.

ThemodelWillbemeshedusingshellelements.Excludethesolidbody

thatislocatedintheCylindricalShellfolderoftheSimulate

tree.

Whentheconfigurationwassetup.thesolidbodywashiddenusingthe

FeatureManagerdesigntree.Thiswillinsurethatsurfaceenti

selectedwhenapplyingloadsandrestraints.

5Definethickness.

Right-clickSurfaoeBody1intheCylindricalSellfolderofthe

SimulationStudytreeandselectEditDefinition.

SpecifyaThinshellwithaShellthicknessof6.35mm

ClickOK.

6Applymaterial.

ApplyAluminum1060Alloyasthematerial.

7Createmesh.

Usethedefaultglobalmeshsizeand

Tolerance,11.14mmand0.557mm,

respectively.

ClickonAdvancedandmakesurethat

Draftelenutsaresepta

ClickonOKtoacceptandtocreatethe

mesh.

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8Createsimplysupportedfixture.

Right-clickFixturesandselectFixedGeometry

ApplyImmovable（Notranslation）boundaryconditiononthe

supportedstraightedge.

ClickOKtosavethisboundarycondition.

RenamethisboundaryconditiontoSimplysupportededge.

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9CreatefirstSymmetryRestraint.

Becauseonlyaquarteroftheshellis

modeled,wehavetoapplysymmetry

restraints.

Right-clickonFixturesandchoose

AdvancedFixtures.

UnderAdvancedselectUsereference

geometry.

ChoosethesymmetryStraightEdgeonthe

topsurface（asshowninthefigure）.

SelectRightPlaneasthereference

geometry.

IntheTranslationsdialog,setNormalto

planedirectiontranslationto0mm.

IntheRotationdialogsetbothAlongplane

Dir1andAlongplaneDir2rotationsto0

rad.

ClickOKtosavethisfirstsymmetryrestraint

Renamethisrestrainttosymmetryx-dir.

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10CreatesecondSymmetryrestraint

RIP-ht-clickonFixturesandchoose

AdvancedFixtures.

UnderAdvancedselectUsereference

geometry.

ChoosethesvmmetrvCurvedEdgeonthe

topsurface（asshowninthefigure）.

SelectFrontPlaneasthereference

geometry.

IntheTranslationsdialog.setNormalto

planedirectiontranslationto0mm.

IntheRotationdialogsetbothAlongplane

Dir1andAlongplaneDir2rotationsto0

rad.

ClickOKtosavethissendsymmetry

restraint.RenamethisrestrainttoSymmetryz-dir

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11CreateForce.

Right-clickExternalLoadsandchooseForce.

Selectthevertexattheshellsymmetrypoint.

SelectTopPlaneasareference.

SettheUnitstoSIandspecifyaForceof250Nin

theNormaltoplanedirection.（Makesurethe

forceisorienteddownward）.

ClickOKtosavethisforcedefinition.

RenamethisloadconditiontoCenterforce.

Thetotalforceonthemodelisactually1000N,we

use250Nduetooursymmetryconditions.

12Runthebucklinganalysis.

Theanalysiswillcompletesuccessfully.

13PlotDisplacementresults.

DefineURES:

ResultantDisplacementplotforthefirstbuckling

mode.

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Theactualquantityplottedistheresultantdisplacement.Theabsolute

valuesofthesenumbersaremeaninglessastheydonotrepresentreal

displacements;theyonlyshowtherelativedisplacements（shape）

relevanttothefirstbucklingmode.

14Animatethefirstmodeshape.

IntheSimulationmenu,selectResultTools,Animate.

YoucanalsosavethemovieasanAV1file.

15ListBucklingloadfactor.

Right-clicktheResultsfolderandselectListBucklingLoadFactors

fromthemenu.

ReviewthebucklingfactorsandclickonClose.

WeobservealinearbucklingfactorofapproximatelyXI.linear-27.9.

Thisimpliesthattheshellwouldcollapse（duetobuckling）underthe

loadof1000x.27.9=27900N.

Linearbuckling:

assumptionsand

limitations

Linearbucklingassumesthatthestructuredoesnotexhibitsignificant

changesinshapepriortotheonsetofbuckling（definedbylimiting

snap-throughpointontheequilibriumpath）.Therefore,theresults

mustalwaysbetakenwithcaution.Furthermore,theanalysisdosenot

allowustostudythepost-bucklingbehaviorthatmaybeofsignificant

importanceinsomeapplications.

Wewillthereforesolvetheproblemasanonlinearstudyandcompare

theresultsfrombothstudies.

Linearstaticstudy

Beforeproceedingtothenonlinearbucklinganalysis,weperforma

linearstaticstudyonthismodeltogetanestimateofthemaximum

displacementthatweexpect.

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Procedure

Followtheprocedurebelow:

1Createastaticstudy.

Createastaticstudyandcopythefollowingfeaturesfromthebuckling

study:

CylindricalShell,Fixtures,ExternalLoads,andMesh.

Makesurethatthesolidbodyisexcludedandtheshe11thicknessis

defined.

2Runthestudy.

Runthestaticstudyandplotthedisplacements.Noticethatthe

maximumdisplacementislessthan0.5mm.

Nonlinear

Symmetrical

Buckling

Toaccountfortheshapechangeduringthedeformation,anonlinear

analysiswillbeperformed.Thiswillallowustostudythepost-

bucklingbehaviorofthestructurethatmaybeofimportanceinsome

designs.Thistypeofstudyshouldalsogiveusamoreaccurate

predictionofthebucklingloadfactor.

Procedure

Followtheprocedurebelow:

1Createastudy.

FromtheSimulationmenu,selectStudy.Enter

Nonlinear-QuarterastheNameandselectNonlinearasthe

Type.

2CopydefinitionofMaterials,Fixtures,Loads,andmeshfrom

Linearbuckling-quarterstudytoNonlinear-quarter

Drag-and-droptheCylindricalShell,externalloads,fixtures,

andMeshfoldersfromtheLinearBuckling-quarterstudyfolder

ontotheNonlinear-Quarterstudy.folder.

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3Checkstudyproperties.

Right-clicktheNonlinear-quarterstudynameandselectProperties.

MakesuretheInitialtimeincrementis0.01,minstepis1e-008,Max

stepis0.1andNo.ofadjustmentsis5.

Startandendtimeswillnotbeusedforthisanalysis（seethefollowing

discussion）.

MakesurethatUselargedisplacementformulationisselected.

UnderSolver,selectDirectSparse.

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4Settheadvancedoptions.

SelecttheAdvancedOptionsbutton.

UndertheMethoddialog,setControltoArcLength,andmakesure

IterativeisNR（Newton-Raphson）.

SetMaximumdisplacement（fortranslationDOF）to30mm（seethe

followingdiscussion.

KeepMaximumload-patternmultiplieratitsdefaultvalueof1e8and

setMaximumnumberofarcstepsto100.

TheoptionsMaximumloadpatternmultiplierandMaximum

numberofarcstepsindicatehowfarwewishtotracethesolution

alongtheequilibriumpath.

Keepallotheroptionsattheirdefaultvalue.

Clickok

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AmLength:

Parameters

WhenArcLengthcontrolmethod'sused,wedonotneedtospecify

anytimecurve（neithertheloadsnorthestructuralresponseare

controlled）.Therefore,whensettingthepropertiesofanonlinearstudy,

theEndtimeoptionisnotconsidered.TheStarttimeisalwayssetto

0.

OptionsInitialtimeincrementandMaxtimeincrementsarerelatedto

the"length"ofthearc.Exactlyhowtheyrelatetooneanotherispot

immediatelyapparent.ItisthereforerecommendedtokeepInitialtime

incrementat0.01andMaxequalto0.1.Whentheequilibriumpathis

plottedafterthesolutionhasbeenobtained（orpartialpath,ifthe

analysisfailed）,wecanobservewhetherornottomodl,

parametersbasedonthedistributionofthepoints.

Consider