mesh 178.docx

mesh 178.docx

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mesh178

17.1 UnderstandingtheroleoftheMeshmodule

TheMeshmoduleallowsyoutogeneratemeshesonpartsandassembliescreatedwithinAbaqus/CAE.Variouslevelsofautomationandcontrolareavailablesothatyoucancreateameshthatmeetstheneedsofyouranalysis.Aswithcreatingpartsandassemblies,theprocessofassigningmeshattributestothemodel—suchasseeds,meshtechniques,andelementtypes—isfeaturebased.Asaresultyoucanmodifytheparametersthatdefineapartoranassembly,andthemeshattributesthatyouspecifiedwithintheMeshmoduleareregeneratedautomatically.

TheMeshmoduleprovidesthefollowingfeatures:

∙Toolsforprescribingmeshdensityatlocalandgloballevels.

∙Modelcoloringthatindicatesthemeshingtechniqueassignedtoeachregioninthemodel.

∙Avarietyofmeshcontrols,suchas:

∙Elementshape

∙Meshingtechnique

∙Meshingalgorithm

∙Adaptiveremeshingrule

∙AtoolforassigningAbaqus/StandardandAbaqus/Explicitelementtypestomeshelements.Theelementscanbelongeithertoamodelthatyoucreatedortoanorphanmesh.

∙Atoolforverifyingmeshquality.

∙Toolsforrefiningthemeshandforimprovingthemeshquality.

∙Atoolforsavingthemeshedassemblyorselectedpartinstancesasanorphanmeshpart

17.2 EnteringandexitingtheMeshmodule

YoucanentertheMeshmoduleatanytimeduringanAbaqus/CAEsessionbyclickingMeshintheModulelistlocatedinthecontextbar.UponenteringtheMeshmodule,theAbaqus/CAEinterfacechangesinthefollowingways:

∙TheSeed,Mesh,Feature,andToolsmenusappearonthemainmenubar.

TheObjectfieldthatappearsinthecontextbarallowsyoutodisplayeitherapartortheassembly.17.3.1 Themeshingprocess

Tocreateanacceptablemesh,youusethefollowingprocess:

Assignmeshattributesandsetmeshcontrols

TheMeshmoduleprovidesavarietyoftoolsthatallowyoutospecifydifferentmeshcharacteristics,suchasmeshdensity,elementshape,andelementtype.

Generatethemesh

TheMeshmoduleusesavarietyoftechniquestogeneratemeshes.Thedifferentmeshtechniquesprovideyouwithdifferentlevelsofcontroloverthemesh.

Refinethemesh

TheMeshmoduleprovidesavarietyoftoolsthatallowyoutorefinethemesh:

∙Theseedingtoolsallowyoutoadjustthemeshdensityinselectedregions.

∙ThePartitiontoolsetallowsyoutopartitioncomplexmodelsintosimplersubregions.

∙TheVirtualTopologytoolsetallowsyoutosimplifyyourmodelbycombiningsmallfacesandedgeswithadjacentfacesandedges.

∙TheEditMeshtoolsetallowsyoutomakeminoradjustmentstoyourmesh.

Optimizethemesh

Youcanassignremeshingrulestoregionsofyourmodel.Remeshingrulesenablesuccessiverefinementofyourmeshwhereeachrefinementisbasedontheresultsofananalysis.

Verifythemesh

Theverificationtoolsprovideyouwithinformationconcerningthequalityoftheelementsusedinamesh.

17.3.2 Meshattributesandcontrols

Abaqus/CAEprovidesyouwithavarietyoftoolsforcontrollingmeshcharacteristics:

∙Youcanspecifythedensityofameshbycreatingseedsalongtheedgesofthemodeltoindicatewherethecornernodesoftheelementsshouldbelocated.Forexample,Figure17–1displaysamodelwithbiasedseedingalongthetopandleftedges.

Figure17–1Amodelwithbiasedseeding.

Formoreinformation,see“Understandingseeding,”Section17.4.

∙Youcanselecttheshapeofthemeshelements.Forexample,Figure17–2showsamodelthathasbeenmeshedfirstwithquadrilateralelementsandthenwithtriangularelements.

Figure17–2Twomesheswithdifferentelementshapes.

Formoreinformation,see“AssigningAbaquselementtypes,”Section17.5.

∙Youcanchoosethemeshingtechnique—free,structured,orswept—and,whereapplicable,youcanchoosethemeshingalgorithm—medialaxisoradvancingfront.Formoreinformation,see“Meshgeneration,”Section17.3.3.

∙Youcanselecttheelementtypethatisassignedtothemeshbychoosingtheelementfamily,geometricorder,andshapealongwithspecificelementcontrols,suchashourglassing.Formoreinformation,see“Understandingmeshgeneration,”Section17.7.

Forinformationonrelatedtopics,clickanyofthefollowingitems:

∙“Understandingseeding,”Section17.4

∙“AssigningAbaquselementtypes,”Section17.5

∙“Verifyingandimprovingmeshes,”Section17.6

17.3.3 Meshgeneration

Abaqus/CAEcanuseavarietyofmeshingtechniquestomeshmodelsofdifferenttopologies.Insomecasesyoucanchoosethetechniqueusedtomeshamodelormodelregion.Inothercasesonlyonetechniqueisvalid.Thedifferentmeshingtechniquesprovidevaryinglevelsofautomationandusercontrol.TherearetwomeshingmethodologiesavailableinAbaqus/CAE:

top-downandbottom-up.

Top-downmeshinggeneratesameshbyworkingdownfromthegeometryofapartorregiontotheindividualmeshnodesandelements.Youcanusetop-downmeshingtechniquestomeshone-,two-,orthree-dimensionalgeometryusinganyavailableelementtype.Theresultingmeshexactlyconformstotheoriginalgeometry.Therigidconformancetogeometrymakestop-downmeshingpredominantlyanautomatedprocessbutmaymakeitdifficulttoproduceahigh-qualitymeshonregionswithcomplexshapes.

Bottom-upmeshinggeneratesameshbyworkingupfromtwo-dimensionalentities（geometricfaces,elementfaces,ortwo-dimensionalelements）tocreateathree-dimensionalmesh.Youcanusebottom-upmeshingtechniquestomeshonlysolidthree-dimensionalgeometryusingall—ornearlyall—hexahedralelements.Generatingameshusingthebottom-upmeshingtechniqueisamanualprocess,andtheresultingmeshmayvarysignificantlyfromtheoriginalgeometry.However,allowingthemeshtovaryfromgeometrymayallowyoutoproduceahighqualityhexahedralmeshonregionswithcomplexshapes.

Forinformationonrelatedtopics,clickanyofthefollowingitems:

∙“Top-downmeshing,”Section17.3.4

∙“Bottom-upmeshing,”Section17.3.5

∙

∙Abaqus/CAEmaychangethecolorofthepartinstancesintheassemblydisplayedintheviewport.Thesecolorcuesdescribethemeshabilityanddependenceofeachinstance.Independentinstancesappearinacolorthatdescribestheirmeshability,whiledependentintancesappearblueintheAssemblycontextandwhiteinthePartcontext.See“Meshingindependentanddependentpartinstances,”Section17.3.10.

Note:

 PartinstancesarecolorcodedaccordingtotheirmeshabilityanddependenceonlywhentheMeshdefaultscolormappingisselected.Ifyoudisplayedthedefaultcolormappinginadifferentmodule,Abaqus/CAEappliestheMeshdefaultscolormappingautomaticallyuponyourentrytotheMeshmodule.Ifyouselectedanon-defaultcolormappingsuchasMaterialsinadifferentmodule,Abaqus/CAEcontinuescolorcodingaccordingtothatcolormapping（inthiscase,bymaterialtype）whenyouentertheMeshmodule.

ToexittheMeshmodule,selectanyothermodulefromtheModulelist.Youneednotsaveyourmeshbeforeexitingthemodule;itwillbesavedautomaticallywhenyousavetheentiremodelbyselectingFile

SaveorFile

SaveAsfromthemainmenubar.

17.3.4 Top-downmeshing

Top-downmeshingreliesonthegeometryofaparttodefinetheouterboundsofthemesh.Thetop-downmeshmatchesthegeometry;youmayneedtosimplifyand/orpartitioncomplexgeometrysothatAbaqus/CAErecognizesbasicshapesthatitcanusetogenerateahigh-qualitymesh.Insomecasestop-downmethodsmaynotallowyoutomeshportionsofacomplexpartwiththedesiredtypeofelements.Thetop-downtechniques—structured,swept,andfreemeshing—andtheirgeometryrequirementsarewell-defined,andloadsandboundaryconditionsappliedtoapartareassociatedautomaticallywiththeresultingmesh.

Structuredmeshing

Structuredmeshingisthetop-downtechniquethatgivesyouthemostcontroloveryourmeshbecauseitappliespreestablishedmeshpatternstoparticularmodeltopologies.Mostunpartitionedsolidmodelsaretoocomplextobemeshedusingpreestablishedmeshpatterns.However,youcanoftenpartitioncomplexmodelsintosimpleregionswithtopologiesforwhichstructuredmeshingpatternsexist.Figure17–3showsanexampleofastructuredmesh.Formoreinformation,see“Structuredmeshingandmappedmeshing,”Section17.8.

Figure17–3Astructuredmesh.

Sweptmeshing

Abaqus/CAEcreatessweptmeshesbyinternallygeneratingthemeshonanedgeorfaceandthensweepingthatmeshalongasweeppath.Theresultcanbeeitheratwo-dimensionalmeshcreatedfromanedgeorathree-dimensionalmeshcreatedfromaface.Likestructuredmeshing,sweptmeshingisatop-downtechniquelimitedtomodelswithspecifictopologiesandgeometries.Figure17–4showsanexampleofasweptmesh.Formoreinformation,see“Sweptmeshing,”Section17.9.

Figure17–4Asweptmesh.

Freemeshing

Thefreemeshingtechniqueisthemostflexibletop-downmeshingtechnique.Itusesnopreestablishedmeshpatternsandcanbeappliedtoalmostanymodelshape.However,freemeshingprovidesyouwiththeleastcontroloverthemeshsincethereisnowaytopredictthemeshpattern.Figure17–5showsanexampleofafreemesh.Formoreinformation,see“Freemeshing,”Section17.10.

Figure17–5Afreemeshgeneratedwithtetrahedralelements.

Forinformationonrelatedtopics,clickanyofthefollowingitems:

∙“Bottom-upmeshing,”Section17.3.5

∙“Understandingmeshgeneration,”Section17.7

∙“AssigningAbaquselementtypes,”Section17.5

∙“Verifyingandimprovingmeshes,”Section17.6

17.3.5 Bottom-upmeshing

Bottom-upmeshingusesthepartgeometryasaguidelinefortheouterboundsofthemesh,but