ADINA Mesh Generation 网格划分 仿真软件.docx

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1、AutomaticFree-FormAll-BrickElementsinMeshesMeshingisanimportantcapabilityintheADINApre-processorthatweareconstantlyworkingtoimprove.Notlongago,wepresentedtheenhancementsmadetoourautomaticfree-formhexdominantmesherandmentionedthatanallbrickmeshcannotbeachievedforageneralbody.InthisNews,wedescribeanin

2、terestingcaseofanimportantclassofproblemswheretheADINAreshercangenerateanall-brickmesh.Whenageometricmodeldoesnothaveedges,itispossibletocreatea100%hexmesh.Often,inbiomedicalengineering,modelscomingfromComputerTomography(CT)orMagneticResonanceImaging(MRI)arestoredintheST1.format(alistoftrianglesdefi

3、ningthesurfaceofthemodel)andtheytypicallydonothavehardedgesduetothewaytheyaregenerated.Whenamodelhasnoedges(typically,abodywithasingleface),therearenotopologicalconstraintsonthehexmesherthatpreventthegenerationofameshconsistingofonlybrickelements.Ofcourse,anautomaticallygeneratedfree-formhexmeshisve

4、rydesirablebecauseforagivenrequiredaccuracyinresults,thenumberofelementsrequired(andhencenodesused)ismuchlessthanwhenusingatetmesh.ThemeshshownbelowwascreatedfromanST1.filedescribingahumantorso(courtesyofAIMSHAPEShapeRepository).Thetopologyofthemodelisonebodymadeupofasinglebodyface(whenloadingtheST1

5、.fileintotheADINAinterface,theridgedetectionanglewassetto180degrees).Themeshdensityfollowsthecurvatureofthemodel.Aboundarylayeriscreatedallaroundthemodelinordertomaximizethequalityoftheelementsontheboundary.Themeshhasabout177,000elementsandtheyareallbricks.Figure1MeshofhumantorsogeneratedfromST1.fil

6、eFigure2DetailofabovemeshshowingthevariationofmeshdensityFigure3Partialcross-sectionshowingtheall-brickmeshinsideBeingabletomeshtheseedgelessmodelswith100%bricksispowerfulnotonlybecausetheelementsareallhexahedrabutalsobecausethemeshescreatedhavefarfewerelementsthantetrahedralmeshesorevenmixedmesheso

7、fthesamedensity,asalreadymentionedabove.ThismethodologyisalsoavailableasanoptionformeshinggeneralADINA-Mbodies(theParasolidbasedADINAModeler),i.e.bodiesestablishedinCADprograms.Note,however,thereisthentheneedtouseafineenoughmeshtomatchthetopologyoftheCADmodel.Hence,greatercareneedstobeexercisedwhenu

8、singthiscapabilitywithADINA-Mbodies.ThisfeatureinADINAofautomaticfree-formmeshingofairbrickelementsisclearlyanimportantcapabilityinmanyareasofthree-dimensionalanalyses.KeyWords:Stereolithography1ST1.format,CT1MRI,CADimport,brickmeshAutomaticHexDominantMeshingFree-formhexdominantmeshinghasbeenavailab

9、leinADINAforseveralyears(sinceversion8.2).However,itisrestrictedtopartswithsomewhatlimitedcomplexityandthemeshsubdivisiononapartmustbeuniform.InADINA8.71thefree-formhexdominantmesherissignificantlyimprovedtohandlemorecomplexpartsandallownon-uniformmeshsubdivision.Inaddition,variousfeaturesthatareava

10、ilableinthefree-formtetmeshercannowbeusedforthehexdominantmesher,e.g.1CUrVatUebaSedrefinement,automaticgrading.Themesherwillalsoautomaticallyrefineareaswhereithasdifficultymeshing.Ideally,onewouldliketogenerateameshwithallhexahedralelements.However,thatisnotpossibleforageneralgeometry.Hence,hexdomin

11、antmeshingisusedinpracticetoobtainmesheswithamixofhexahedra,pyramidsandtetrahedra.Asthenameimplies,themeshertriestogenerateasmanyhexahedraaspossible.Complexmodelsremainchallengingtomeshwithmostlyhexahedrasoitisimportanttoremembertosimplifyasmuchaspossiblethepartspriortoapplyingthehexdominantmeshing.

12、Below,weshowsomemeshesobtainedwiththefree-formhexdominantmesherinADINA8.7.Clickonanimagetoseethedetail.ADINAXXADINAWerecognizethatmeshingisaveryimportantpartofperformingafiniteelementanalysisanditisourgoaltocontinuouslyimprovethemeshingcapabilitiesoftheADINASystem.Keywords:Free-formmesh,hexahedralel

13、ement,brickelement,meshrefinement,automaticmeshgradingEffectiveMeshesusingtheSizeFunctionOptionInmanyproblems,itisveryimportanttobeabletomeshdenselyincertainareasandmorecoarselyinotherareaslikeintheanalysisofthehelmetabove,wherethecontactarearequiresafinemesh.ADINA8.4haspowerfulcapabilitiestoachieve

14、meshgradation,inparticularwhenADlNA-Misused.HerewefeaturethenewSizeFunctionoptionthatgivesgreatflexibilityindefiningmeshdensities.Theoptionisparticularlyusefulwhenthedensitieshavetobeappliedinspecificareasofthemodel.Thereareanumberofsizefunctiontypesavailable: nearapointinspace, nearanaxis(straightl

15、ine), nearaplane, inandnearahexahedronofanyshapez inandnearaboundingbox,and anycombinationoftheabove.Thehexahedronsizefunctiontypeisparticularlyeffectiveforthree-dimensionalcontactproblemswherethecontactareaisexpectedtobeinsideahexahedron.Theanalysisofthehelmetaboveinvolvescontactmodelingandmakesuse

16、ofthehexahedronsizefunction.Thesetupofthemodelisshowninthenextfigure.Theanvil(green)isassumedtohitthehelmetwithinthevolumedefinedbytheyellowhexahedron(sizefunction),andthisiswhereafinermeshisdesired.Thetetrahedralmeshobtainedisthemeshshownatthetopofthiswebpage.Thenextfigureisacloseuptoshowthe(automa

17、tic)smoothmeshsizegradationfromveryfinetocoarse.MeshgenerationcapabilitiesinADINAinclude: meshingforIDelementssuchastruss,beam,andpipeelements, 2Dsurfacemeshingforshells,plates,and2Dplanarelements,and general3DmeshingforsolidsandfluidsThissectiononmeshgenerationmostlydescribeour3Dmeshingcapabilities

18、whichinclude: mappedmeshingthatgeneratesbrick,wedge,ortetrahedralelements,and free-formmeshingthatgeneratestetrahedralelements. mixedfree-formmeshingthatgenerateshexahedraalongwithpyramids(ifdesired)andtetrahedraPleaseclickonthelinksbelowfortheexplanationandillustrationofthefeaturesinourmeshgenerati

19、oncapabilities.AnisotropicTriangularSurfaceMeshingMeshingM.粉QuadSurfaceMeshingAUtOmatiC净Grading_TetrahedralMeshingCurvature-basedMeshing：MappedMeshingMeshAdaptation-RepairSomeotherfeaturesAUtomatiCFree-FormAll-BriCkEIementSinMeSheSAUtomatiCHeXDOminantMeShinqEffeCtiVeMeSheSIISingtheSiZeFUnCtiOrOCtiOn

20、TheBOdVDefeatUreTOOlTheBOdVCleanUDTOOlTheBODYC1.EANUPToolGeometrybodiesoftenhavefaceswithverysmallareascomparedtothemodeldimensions.Ifleftuntouched,theseundesirablebodyfacesleadtothecreationofpoorlyshapedsurfacetrianglesorquadrilaterals.Inturn,theseleadtothecreationofpoorlyshapedthree-dimensionalele

21、ments.TheBODYC1.EANUPtool,whichwillbeavailableinADINA8.3zcanbeusedsimplytoremovebodyedgesandfaceswithdimensionsbelowauser-specifiedlength.Theusercanalsohavemorecontrolbyspecifyingalistofedges/facesnottobemodifiedaswellasalistofedges/facestoberemoved.Afterusingthistooltoremoveundesirableandunnecessar

22、yfaces,anytypeofmeshing(e.g.zmappedmeshing,triangularorquadrilateralfacemeshing,tetrahedralormixedmeshing)canbeperformedonthecleaned-upbody.BelowzweshowtwoexamplesoftheuseoftheBODYC1.EANUPtool.Ineachexample,themodelisshownzandadetailofthemesh.Ifyoumoveyourmouseontooneofthemeshesthatfollow,youwillsee

23、themeshafterthetoolhasbeenapplied.Movingyourmouseawayfromthemeshrestorestheimagewithoutcleanupzsoyoucanseetheareaswherethemeshhasbeenimproved.Example1:OilscreenADINATIME1OOOBodyfacestobecleanedupareshowninblue.Example2:PropellerBodyfacestobecleanedupareshowninblue.TheBODYDEFEATUREToolTheBODYC1.EANUP

24、toolpresentedintheIaStNeWSisusedtoremovesmallfacesandedgesfromthegeometrybodybeforemeshing.Itworksdirectlyonthegeometrybodyandallmeshingoptionscanbeused.Toremovelargerfeatures,includingprotrusionsandholes,whicharenotrelevanttotheanalysis,theBODYDEFEATUREtoolcanbeusedtoobtainamoreeffectivemeshforanal

25、ysis.TheBODYDEFEATUREtool,availableinADINA8.3,worksontheboundarydiscreterepresentation(surfacetriangularmesh)onabody.Typically,thefeaturestoberemovedaregivenasalistoffacesintheinput.Forexample,toremoveacylindricalhole,thetwofacesoftheholearespecified.Theusercanalsospecifyaminimumlengthwhereanysurfac

26、etrianglebelowthelengthwillberemoved,exceptforfaceswhichareidentifiedtobeexcludedfrommodification.Below,weshowthreeexamplesoftheuseoftheBODYDEFEATUREtool.Example1:EngineblockInthefollowingboundarydiscreterepresentation,theholestoberemovedareshowninyellow.Movingyourmouseontothemeshwilldisplaythemesha

27、ftertheBODYDEFEATUREtoolhasbeenapplied.Movingyourmouseawayfromthemeshrestorestheoriginalmesh.ADINABeforedefeaturingZAXTheBODYDEFEATUREtoolisalsousedtoremovetrianglesinthesurfacemeshthatarebelowaspecifiedminimumlength(showninyellowbelow).Ifyoumoveyourmouseontothemesh,youwillseetheeffectoftheBODYDEFEA

28、TUREtool.Example2:KeyboardThemeshplotofakeyboardisshownbelow.Thefeaturestoberemovedarecoloredyellowthearrowkeysandthechannelsurroundingthemanufacturerslabel.Followingisadetailofthemesharoundthearrowkeys.Thefeaturestoberemovedareshowninyellow.IfyoumoveyourmouseontothemeshzyouwillseetheeffectoftheBODY

29、DEFEATUREtool.BeforedefeaturingAdetailofthemesharoundthemanufacturerslabelareaisshownbelow.Thefeaturetoberemoved-thechannelaroundthelabel-isshowninyellow.Asbefore,moveyourmouseontothemeshtoseetheeffectoftheBODYDEFEATUREtoolonthemesh,andmoveitawaytorestoretheoriginalmesh.BeforedefeaturingExample3:ScrewdriverThefeaturestoberemovedareshowninyellow.MoveyourmouseontothemeshtoseetheeffectoftheBODYDEFEATUREtool.TIME100oZx、YAfterdefeaturing