R048ABAQUS资料BUCKW06QTubeCrush.docx

R048ABAQUS资料BUCKW06QTubeCrush.docx

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R048ABAQUS资料BUCKW06QTubeCrush

Note:

ThisworkshopprovidesinstructionsintermsoftheAbaqusGUIinterface.IfyouwishtousetheAbaqusKeywordsinterfaceinstead,pleaseseethe“Keywords”versionoftheseinstructions.

PleasecompleteeithertheKeywordsorInteractiveversionofthisworkshop.

Goals

∙Performaneigenvaluebucklinganalysis.

∙Understandtheeffectofperturbingameshbasedonthebucklingmodes.

∙Performanexplicitanalysistosimulatethecrushingofatube.

∙UsetheVisualizationmoduletoviewresultsfromeigenvalueandcontactanalyses.

Introduction

Inthisworkshopyouwillstudythecrushingofasquare,steelboxtubebetweentworigidplates.Thetubeisfreeatoneendandisattachedtoarigidplatewitha500kgmassatitsotherend.Boththetubeandtherigidplatewithmasshaveaninitialvelocityof8.9408m/s（20 m.p.h.）justbeforethetube’stopedgeimpactsthefixedrigidplate,asshowninFigureW6–1.Duringimpact,thetubedissipatesalargeamountofinitialkineticenergyintoplasticdeformation.Thegoalofthisanalysisistoevaluatethetube’sabilitytoabsorbkineticenergy.Thissimulationrunsforatotaltimeof5milliseconds.

E=207GPa

ν=0.3

ρ=7800kg/m3

σy=158.7MPa（initial）

shellthickness=1mm

FigureW6–1.Square,steelboxtubecrushedbetweentwoplates

FigureW6–2showsthedetailsofthemodel,includingthesetsusedinthemodel.

FigureW6–2.Modelgeometryandsets.

Preliminaries

1.Entertheworkingdirectoryforthisworkshop:

../buckling/interactive/tubecrush

2.Runthescriptws_advxpl_tubecrush.pyusingthefollowingcommand:

abaquscaestartup=ws_advxpl_tubecrush.py

TheabovecommandcreatesanAbaqus/CAEdatabasenamedCrush.caeinthecurrentdirectory.Thegeometry,materialandmeshdefinitionsforthetubeandtheplateareincludedinthemodelnamedBuckle.Thismodelwillfirstbeusedtoperformtheeigenvaluebucklinganalysisandwilllaterbeeditedtoperformthecrushinganalysis.

Eigenvaluebucklinganalysis

Beforeperformingthecrushinganalysis,youneedtoperformaneigenvaluebucklinganalysistodeterminethebucklingeigenmodesofthestructure.Thesebucklingeigenmodeswillbeusedtointroduceimperfectionsintothegeometryofthetubetoensureaphysicallycorrectdeformedshapeattheendofthecrushinganalysis.

Toensureaphysicallymeaningfulsimulation,thebucklinganalysismustbeperformedonamodelthatissimilartothecrushingmodel.Thetubemustbeloadedinamannersimilartotheactualloadingthatthetubewillexperienceduringcrushing.Thisloadingisachievedbyapplyingaconcentratedforceinthedirectionofthetubeaxis;thisloadisalreadydefinedinthemodel.Thebucklingmodelmustalsoincludetheeffectsofcontactbetweenthetubeandtheplates.Youwillhavetoeditthemodeltoincludetheseeffects,anddefinethejob.

Tocompletetheeigenvaluebucklingmodel,dothefollowing:

1.IntheModelTree,expandtheAssemblycontaineranddouble-clicktheSurfacescontainer.Createageometry-basedsurfaceonthetoprigidplatenamedTopSurf;inthepromptarea,selectthecolorofthesideoftheplatefacingthetube.Similarly,createasurfacenamedBotSurfthatcorrespondstothesideofthelowerplatethatwillcontactthetube.

2.Inthebucklinganalysisfrictionlesscontactisassumedtooccurbetweenthetubeandthetopplate.FrictionlesscontactisthedefaultcontactpropertyinAbaqus.IntheModelTree,double-clicktheInteractionPropertiescontainer;defineacontactpropertynamedNoFric,andacceptthedefaultpropertysettings.

3.Defineacontactinteractionbetweenthetopofthetubeandthetopplate.

a.IntheModelTree,double-clicktheInteractionscontainer.NametheinteractionTopSurf-TubeandchoosetheInitialstep.SelectSurface-to-surfacecontact（Standard）astheinteractiontype,TopSurfasthemastersurface,andTopastheslaveNodeRegion.

b.Bydefault,thecontactconditionsatthestartofalinearperturbationstep（suchasaneigenvaluebucklinganalysis）remainunchangedthroughoutthestep.Therefore,ifyouensurethatthetopnodesofthetubeareincontactwiththetoprigidsurfaceatthebeginningofthestep,thiscontactconstraintwillremainineffectthroughoutthebucklinganalysis.Thus,intheSlaveAdjustmentoptionsoftheEditInteractiondialogbox,specifyanadjustmentzonetoleranceof0.01mtoensureaninitiallyclosedcontactcondition.ClickOKtocompletethecontactinteractiondefinition.

4.Thelowerplatewillbe"glued"tothebottomofthetubeusingatieconstraintasindicatedbelow:

c.IntheModeTree,double-clickConstraints.

d.IntheCreateConstraintdialogboxthatappears,nametheconstraintBotSurf-Tube,selectTieasthetype,andclickContinue.

e.SelectBotSurfasthemastersurfaceandBotastheslaveNodeRegion.

f.ToggleoffTierotationalDOFsandacceptallotherdefaultsintheEditConstraintdialogbox.

5.Youneedtospecifythatadditionaldatabewrittentotheresults（.fil）fileusingtheKeywordsEditor.Youwillwritethenormalizednodaldisplacementscorrespondingtoeachlinearbucklingmode;thesewillbeusedtointroduceimperfectionsinthecrushinganalysis.

g.IntheModelTree,clickmousebutton3onthemodelnamedBuckleandselectEditKeywordsfromthemenuthatappears.

TheEditKeywordsdialogboxappearscontainingtheinputfilethathasbeengeneratedforyourmodel.

h.Onlytextblockswithawhitebackgroundcanbeedited.Usethescrollbarontherightsideofthedialogboxtofindthetextblockwherethe*RESTARToptionislocated（towardthebottomofthefile）.Selectthe*RESTARTblock,andclickAddAftertoaddanemptytextblock.

i.Inthenewtextblock,enterthefollowingdatatospecifythatdisplacementshouldbewrittentotheresultsfile:

*NodeFile

U,

j.ClickOKtosaveyourchangesandtoexittheKeywordsEditor.

6.CreateajobforthebucklinganalysisnamedTubeBucklewiththefollowingdescription:

Tubecrush--bucklinganalysis（intheModelTree,double-clickJobs）.

7.Saveyourmodeldatabasefile,andsubmitthejobforanalysis（intheModelTree,clickmousebutton3onthejobnameandselectSubmitfromthemenuthatappears）.Fromthesamemenu,youcanselectMonitortomonitorthejob’sprogress.

Postprocessingthebucklinganalysis

Whentheanalysisiscomplete,usethefollowingproceduretoviewtheeigenmodesfromthisbucklinganalysisintheVisualizationmodule:

1.IntheModelTree,clickmousebutton3onthejobTubeBuckleandselectResultsfromthemenuthatappearstoopenthefileTubeBuckle.odbintheVisualizationmodule.

2.Fromthemainmenubar,selectTools→DisplayGroup→Create.

3.Inthedialogboxthatappears,selectthepartinstancenamedTUBE-1andclickReplace.

4.ClickDismisstoclosetheCreateDisplayGroupdialogbox.

Observethatthetubealoneisnowdisplayedintheviewport.

5.Plotthedeformedmodelshape.

Thedeformedshapeforthefirsteigenmodewillbedisplayedintheviewport.Adjustyourview,ifnecessary,toseethedeformedconfigurationmoreclearly.

6.Viewthedeformedshapesoftheotherbucklingmodesusingtheframeselector（Result→Step/Frame）ortheframecontrolbuttonsinthecontextbarabovetheviewport.

FigureW6–3showsthefirstandsecondeigenmodesofthesteeltube.

FigureW6–3.Eigenmode1（left）andEigenmode2（right）

Crushinganalysis

Youwillnowmodifythebucklinganalysismodeltocreatethecrushinganalysismodel.Themodelforthecrushinganalysiswillincludegeneralcontactandtheinitialvelocityforthetubethatcausesittoimpactwiththetoprigidsurface.Inaddition,youwillusetheKeywordsEditortospecifythatthemodesfromthebucklinganalysisshouldbeusedtoseedtheimperfectionforthecrushinganalysis.

Beforeyoubeginthemodificationsrequiredforthecrushinganalysis,makeacopyofbucklinganalysismodelasfollows:

intheModelTree,clickmousebutton3onthemodelnamedBuckleandselectCopyModelfromthemenuthatappears.NamethenewmodelCrush.Inthecrushinganalysismodel,deletethekeywordsedit,concentratedload,andcontactinteractionusedintheoriginalbucklinganalysismodel.

Stepdefinition

Theexplicitdynamicsanalysisprocedurewillbeusedinsteadofthelineareigenvaluebucklingone.Thus,replacetheeigenvaluebucklingstepwithanexplicitdynamicsstep:

1.IntheModelTree,clickmousebutton3onthestepnamedTubeBuckleandselectReplacefromthemenuthatappears.Replacethelinearperturbationbucklestepwithageneralexplicitdynamicstep.Givethestepthefollowingdescription:

Impactofsquaretubewithfreedeceleration;andspecifyatimeperiodof0.03seconds.

2.RenamethestepTubeCrush.

Contact

Asthetubecrushes,itbucklesrepeatedly;thus,manyregionsontheinsideandtheoutsideofthetubecontacteachother.Sinceitisdifficulttoestablishbeforehandwhichregionswillbeincontactwithoneanother,wemustallowcontacttooccurinaverygeneralmannersothatanyregionmaycomeintocontact,bothontheinsideandontheoutsideofthetube.Thistypeofcontactcanbeachievedusinggeneralcontact.Theself-contactofthetubehasafrictioncoefficientof0.1;thecontactbetweenthetubeandplateisfrictionless.

1.Createadouble-sidedsurfacenamedTubecorrespondingtothefoursidesofthetube.

2.CreateanewcontactinteractionpropertynamedFric.UsethePenaltyfrictionformulation,andspecifyafrictioncoefficientof0.1.

3.CreateaGeneralcontactinteraction.ChooseFricastheglobalcontactproperty.EdittheindividualpropertyassignmentstoassignNoFricasalocalpropertytotheinteractionb