英语翻译.docx
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英语翻译.docx
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英语翻译
113
Lesson3NonlinearStaticBucklingAnalysis
Aftersuccessfulcompletionofthislesson,youwillbeable
Performanonlinearlarge-deformationbucklinganalysis
DefineControlsforanonlinearbucklinganalysisusingartlength
Control.
Compareresultsfromlinearbucklingandnonlinearstudies
Understandtheinfluenceofinitialdisturbancesonthebuckingof
symmetricstructres
115
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.
118
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.
122
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
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