Abaqus單元選擇、壓力、接觸和網(wǎng)格生成(abaqus軟件公司北京代表處)課件

ABAQUS/Standard基礎(chǔ)教程ElementSelectionCriteriaAppendix1ABAQUS/Standard基礎(chǔ)教程ElementSeABAQUS/Standard基礎(chǔ)教程內(nèi)容提要ElementsinABAQUSStructuralElements(ShellsandBeams)vs.ContinuumElementsModelingBendingUsingContinuumElements

用實體單元模擬彎曲StressConcentrations應(yīng)力集中Contact接觸IncompressibleMaterials不可壓縮材料MeshGeneration網(wǎng)格生成SolidElementSelectionSummaryABAQUS/Standard基礎(chǔ)教程內(nèi)容提要ElemenABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSABAQUS單元庫中提供廣泛的單元類型，適應(yīng)不同的結(jié)構(gòu)和幾何特征

ThewiderangeofelementsintheABAQUSelementlibraryprovidesflexibilityinmodelingdifferentgeometriesandstructures.Eachelementcanbecharacterizedbyconsideringthefollowing:

單元特性：Family單元類型Numberofnodes節(jié)點數(shù)Degreesoffreedom自由度數(shù)Formulation公式Integration積分ABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程單元類型（Family）Afamilyoffiniteelementsisthebroadestcategoryusedtoclassifyelements.同類型單元有很多相同的基本特。Elementsinthesamefamilysharemanybasicfeatures.同種類單元又有很多變化：Therearemanyvariationswithinafamily.ElementsinABAQUSspecial-purposeelementslikesprings,dashpots,andmassescontinuum(solidelements)shellelementsbeamelementsrigidelementsmembraneelementstrusselementsinfiniteelementsABAQUS/Standard基礎(chǔ)教程單元類型（FamilABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSNumberofnodes

節(jié)點數(shù)(interpolation)Anelement’snumberofnodesdetermineshowthenodaldegreesoffreedomwillbeinterpolatedoverthedomainoftheelement.ABAQUSincludeselementswithbothfirst-andsecond-orderinterpolation.

插值函數(shù)階數(shù)可以為一次或者兩次First-orderinterpolationSecond-orderinterpolationABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程ElementsinABAQUS自由度數(shù)目

DegreesoffreedomTheprimaryvariablesthatexistatthenodesofanelementarethedegreesoffreedominthefiniteelementanalysis.Examplesofdegreesoffreedomare:Displacements位移Rotations轉(zhuǎn)角Temperature溫度Electricalpotential電勢ABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程公式

FormulationThemathematicalformulationusedtodescribethebehaviorofanelementisanotherbroadcategorythatisusedtoclassifyelements.Examplesofdifferentelementformulations:Planestrain平面應(yīng)變Planestress平面應(yīng)力Hybridelements雜交單元Incompatible-modeelements非協(xié)調(diào)元Small-strainshells小應(yīng)變殼元Finite-strainshells有限應(yīng)變殼元Thickshells后殼Thinshells薄殼ElementsinABAQUSABAQUS/Standard基礎(chǔ)教程公式

FormulaABAQUS/Standard基礎(chǔ)教程積分Integration單元的剛度和質(zhì)量在單元內(nèi)的采樣點進行數(shù)值計算，這些采樣點叫做“積分點”

Thestiffnessandmassofanelementarecalculatednumericallyatsamplingpointscalled“integrationpoints”withintheelement.數(shù)值積分的算法影響單元的行為

Thenumericalalgorithmusedtointegratethesevariablesinfluenceshowanelementbehaves.ABAQUS包括完全積分和減縮積分。

ABAQUSincludeselementswithboth“full”and“reduced”integration.ElementsinABAQUSABAQUS/Standard基礎(chǔ)教程積分IntegratABAQUS/Standard基礎(chǔ)教程Fullintegration:

完全積分Theminimumintegrationorderrequiredforexactintegrationofthestrainenergyforanundistortedelementwithlinearmaterialproperties.Reducedintegration:

簡縮積分Theintegrationrulethatisoneorderlessthanthefullintegrationrule.ElementsinABAQUSFirst-

orderinterpolationFullintegration

Second-

order

interpolationReducedintegrationABAQUS/Standard基礎(chǔ)教程FullintegABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSElementnamingconventions:examples單元命名約定B21:Beam,2-D,

1st-orderinterpolationCAX8R:Continuum,AXisymmetric,8-node,ReducedintegrationDC3D4:Diffusion(heattransfer),Continuum,3-D,4-nodeS8RT:Shell,8-node,Reducedintegration,TemperatureCPE8PH:Continuum,Planestrain,8-node,Porepressure,HybridDC1D2E:Diffusion(heattransfer),Continuum,1-D,2-node,ElectricalABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSABAQUS/Standard和ABAQUS/Explicit單元庫的對比

Bothprogramshaveessentiallythesameelementfamilies:continuum,shell,beam,etc.ABAQUS/Standardincludeselementsformanyanalysistypesinadditiontostressanalysis:熱傳導(dǎo),固化soilsconsolidation,聲場acoustics,etc.AcousticelementsarealsoavailableinABAQUS/Explicit.ABAQUS/Standardincludesmanymorevariationswithineachelementfamily.ABAQUS/Explicit包括的單元絕大多數(shù)都為一次單元。例外:二次▲單元和四面體單元and二次beamelementsManyofthesamegeneralelementselectionguidelinesapplytobothprograms.ABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程StructuralElements(ShellsandBeams)vs.ContinuumElementsABAQUS/Standard基礎(chǔ)教程StructuralABAQUS/Standard基礎(chǔ)教程StructuralElements(ShellsandBeams)vs.ContinuumElements實體單元建立有限元模型通常規(guī)模較大，尤其對于三維實體單元如果選用適當?shù)慕Y(jié)構(gòu)單元(shellsandbeams)會得到一個更經(jīng)濟的解決方案模擬相同的問題，用結(jié)構(gòu)體單元通常需要的單元數(shù)量比實體單元少很多要由結(jié)構(gòu)體單元得到合理的結(jié)果需要滿足一定要求：theshellthicknessorthebeamcross-sectiondimensionsshouldbelessthan1/10ofatypicalglobalstructuraldimension,suchas:ThedistancebetweensupportsorpointloadsThedistancebetweengrosschangesincrosssectionThewavelengthofthehighestvibrationmodeABAQUS/Standard基礎(chǔ)教程StructuralABAQUS/Standard基礎(chǔ)教程ShellelementsShellelementsapproximateathree-dimensionalcontinuumwithasurfacemodel.高效率的模擬面內(nèi)彎曲

Modelbendingandin-planedeformationsefficiently.Ifadetailedanalysisofaregionisneeded,alocalthree-dimensionalcontinuummodelcanbeincludedusingmulti-pointconstraintsorsubmodeling.如果需要三維實體單元模擬細節(jié)可以使用子模型ShellmodelofahemisphericaldomesubjectedtoaprojectileimpactStructuralElements(ShellsandBeams)vs.ContinuumElements3-DcontinuumsurfacemodelABAQUS/Standard基礎(chǔ)教程ShellelemABAQUS/Standard基礎(chǔ)教程StructuralElements(ShellsandBeams)vs.ContinuumElementsBeamelements用線簡化三維實體。Beamelementsapproximateathree-dimensionalcontinuumwithalinemodel.高效率模擬彎曲，扭轉(zhuǎn)，軸向力。提供很多不同的截面形狀截面形狀可以通過工程常數(shù)定義linemodelframedstructuremodeledusingbeamelements3-DcontinuumABAQUS/Standard基礎(chǔ)教程StructuralABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsPhysicalcharacteristicsofpurebendingTheassumedbehaviorofthematerialthatfiniteelementsattempttomodelis:

純彎狀態(tài)：Planecross-sectionsremainplanethroughoutthedeformation.保持平面Theaxialstrainxxvarieslinearlythroughthethickness.Thestraininthethicknessdirectionyyiszeroif=0.Nomembraneshearstrain.Impliesthatlinesparalleltothebeamaxislieonacirculararc.xxABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsModelingbendingusingsecond-ordersolidelements(CPE8,C3D20R,…)二次單元模擬Second-orderfull-andreduced-integrationsolidelementsmodelbendingaccurately:Theaxialstrainequalsthechangeinlengthoftheinitiallyhorizontallines.Thethicknessstrainiszero.Theshearstrainiszero.Linesthatareinitiallyverticaldonotchangelength(impliesyy=0).Becausetheelementedgescanassumeacurvedshape,theanglebetweenthedeformedisoparametriclinesremainsequalto90o(impliesxy=0).isoparametriclinesABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsModelingbendingusingfirst-orderfullyintegratedsolidelements(CPS4,CPE4,C3D8)Theseelementsdetectshearstrainsattheintegrationpoints.Nonphysical;presentsolelybecauseoftheelementformulationused.Overlystiffbehaviorresultsfromenergygoingintoshearingtheelementratherthanbendingit(called“shearlocking”).Becausetheelementedgesmustremainstraight,theanglebetweenthedeformedisoparametriclinesisnotequalto90o(implies).IntegrationpointDonotusetheseelementsinregionsdominatedbybending!ABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsModelingbendingusingfirst-orderreduced-integrationelements(CPE4R,…)Theseelementseliminateshearlocking.However,hourglassingisaconcernwhenusingtheseelements.Onlyoneintegrationpointatthecentroid.Asingleelementthroughthethicknessdoesnotdetectstraininbending.Deformationisazero-energymode(有應(yīng)變形但是沒有應(yīng)變能的現(xiàn)象called“hourglassing”).Changeinlengthiszero(impliesnostrainisdetectedattheintegrationpoint).Bendingbehaviorforasinglefirst-orderreduced-integrationelement.ABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsHourglassingisnotaproblemifyouusemultipleelements—atleastfourthroughthethickness.Eachelementcaptureseithercompressiveortensileaxialstrains,butnotboth.Theaxialstrainsaremeasuredcorrectly.Thethicknessandshearstrainsarezero.Cheapandeffectiveelements.Hourglassingcanpropagateeasilythroughameshoffirst-orderreduced-integrationelements,causingunreliableresults.FourelementsthroughthethicknessNohourglassingABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsDetectingandcontrollinghourglassingHourglassingcanusuallybeseenindeformedshapeplots.Example:Coarseandmediummeshesofasimplysupportedbeamwithacenterpointload.ABAQUShasbuilt-inhourglasscontrolsthatlimittheproblemscausedbyhourglassing.Verifythattheartificialenergyusedtocontrolhourglassingissmall(<1%)relativetotheinternalenergy.Sameloadanddisplacementmagnification(1000×)ABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsUsetheX–YplottingcapabilityinABAQUS/Viewertocomparetheenergiesgraphically.InternalenergyArtificialenergyArtificialenergyInternalenergyTwoelementsthroughthethickness:Ratioofartificialtointernalenergyis2%.Fourelementsthroughthethickness:Ratioofartificialtointernalenergyis0.1%.ABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsModelingbendingusingincompatiblemodeelements(CPS4I,…)Perhapsthemostcost-effectivesolidcontinuumelementsforbending-dominatedproblems.Compromiseincostbetweenthefirst-andsecond-orderreduced-integrationelements,withmanyoftheadvantagesofboth.Modelshearbehaviorcorrectly—noshearstrainsinpurebending.Modelbendingwithonlyoneelementthroughthethickness.Nohourglassmodesandworkwellinplasticityandcontactproblems.Theadvantagesoverreduced-integrationfirst-orderelementsarereducediftheelementsareseverelydistorted;however,allelementsperformlessaccuratelyifseverelydistorted.ABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ModelingBendingUsingContinuumElementsExample:CantileverbeamwithdistortedelementsParalleldistortionTrapezoidaldistortionABAQUS/Standard基礎(chǔ)教程ModelingBABAQUS/Standard基礎(chǔ)教程ElementtypexxyyxyNotesPhysicalbehavior000Second-order000OKFirst-order,fullintegration000ShearlockingFirst-order,reducedintegration000Hourglassingiftoofewelementsthroughthickness000OKifenoughelementsthroughthethicknessIncompatiblemode000OKifnotoverlydistortedModelingBendingUsingContinuumElementsSummaryABAQUS/Standard基礎(chǔ)教程ElementtyABAQUS/Standard基礎(chǔ)教程StressConcentrationsABAQUS/Standard基礎(chǔ)教程StressConABAQUS/Standard基礎(chǔ)教程StressConcentrations二次單元處理應(yīng)力集中問題，明顯優(yōu)于一次單元

Second-orderelementsclearlyoutperformfirst-orderelementsinproblemswithstressconcentrationsandareideallysuitedfortheanalysisof(stationary)cracks.W無論是完全積分還是減縮積分都可以很好的反映應(yīng)力集中

Bothfullyintegratedandreduced-integrationelementsworkwell.減縮積分效率更高，而且計算結(jié)果往往優(yōu)于完全積分。

Reduced-integrationelementstendtobesomewhatmoreefficient—resultsareoftenasgoodorbetterthanfullintegrationatlowercomputationalcost.ABAQUS/Standard基礎(chǔ)教程StressConABAQUS/Standard基礎(chǔ)教程PhysicalmodelModelwithfirst-orderelements—elementfacesarestraightlinesegmentsModelwithsecond-orderelements—

elementfacesarequadraticcurvesStressConcentrations二次單元可以以更少的單元更好的反應(yīng)結(jié)構(gòu)的幾何特征

Second-orderelementscapturegeometricfeatures,suchascurvededges,withfewerelementsthanfirst-orderelements.ABAQUS/Standard基礎(chǔ)教程PhysicalmABAQUS/Standard基礎(chǔ)教程StressConcentrationsBothfirst-andsecond-orderquadsandbricksbecomelessaccuratewhentheirinitialshapeisdistorted.First-orderelementsareknowntobelesssensitivetodistortionthansecond-orderelementsand,thus,areabetterchoiceinproblemswheresignificantmeshdistortionisexpected.Second-ordertrianglesandtetrahedraarelesssensitivetoinitialelementshapethanmostotherelements;however,well-shapedelementsprovidebetterresults.idealokaybaddistortedundistortedABAQUS/Standard基礎(chǔ)教程StressConABAQUS/Standard基礎(chǔ)教程ellipticalshapeStressConcentrationsAtypicalstressconcentrationproblem,aNAFEMSbenchmarkproblem,isshownatright.Theanalysisresultsobtainedwithdifferentelementtypesfollow.PABAQUS/Standard基礎(chǔ)教程ellipticalABAQUS/Standard基礎(chǔ)教程StressConcentrationsFirst-orderelements(includingincompatiblemodeelements)arerelativelypoorinthestudyofstressconcentrationproblems.Second-orderelementssuchasCPS6,CPS8,andCPS8Rgivemuchbetterresults.CoarsemeshFinemeshCPS355.0676.87CPS471.9891.2CPS4I63.4584.37CPS4R43.6760.6CPS696.12101.4CPS891.2100.12CPS8R92.5697.16syyatD(Target=100.0)ElementtypeABAQUS/Standard基礎(chǔ)教程StressConABAQUS/Standard基礎(chǔ)教程StressConcentrationsWell-shaped,second-order,reduced-integrationquadrilateralsandhexahedracanprovidehighaccuracyinstressconcentrationregions.Distortedelementsreducetheaccuracyintheseregions.ABAQUS/Standard基礎(chǔ)教程StressConABAQUS/Standard基礎(chǔ)教程ContactABAQUS/Standard基礎(chǔ)教程ContactABAQUS/Standard基礎(chǔ)教程ContactAlmostallelementtypesareformulatedtoworkwellincontactproblems,withthefollowingexceptions:Second-orderquad/hex

elements“Regular”second-order

tri/tetelements(asopposed

to“modified”tri/tetelements

whosenamesendwiththe

letter“M”)Thedirectionsofthe

consistentnodalforces

resultingfromapressure

loadarenotuniform.ABAQUS/Standard基礎(chǔ)教程ContactAlmABAQUS/Standard基礎(chǔ)教程IncompressibleMaterialsABAQUS/Standard基礎(chǔ)教程IncompressABAQUS/Standard基礎(chǔ)教程IncompressibleMaterialsManynonlinearproblemsinvolveincompressiblematerials

(=0.5)andnearlyincompressiblematerials(>0.475).RubberMetalsatlargeplastic

strainsConventionalfiniteelement

meshesoftenexhibitoverly

stiffbehaviorduetovolumetric

locking,whichismostsevere

whenthesematerialsare

highlyconfined.overlystiffbehaviorofanelastic-plasticmaterialwithvolumetriclockingcorrectbehaviorofanelastic-plasticmaterialExampleoftheeffectofvolumetriclockingABAQUS/Standard基礎(chǔ)教程IncompressABAQUS/Standard基礎(chǔ)教程IncompressibleMaterialsThecauseofvolumetriclockingisthateachintegrationpoint’svolumemustremainalmostconstant,overconstrainingthekinematicallyadmissibledisplacementfield.Forexample,inarefinedthree-dimensionalmeshof8-nodehexahedra,thereis—onaverage—1nodewith3degreesoffreedomperelement.每個單元平均只有1個有三個自由度的節(jié)點Thevolumeateachintegrationpointmustremainfixed.Fullyintegratedhexahedrause8integrationpointsperelement;thus,inthisexamplewehaveasmanyas8constraintsperelement,butonly3degreesoffreedomareavailabletosatisfytheseconstraints.每個單元有8個約束，以至于產(chǎn)生體積鎖死。Themeshisoverconstrained—it“l(fā)ocks.”Volumetriclockingismostpronouncedinfullyintegratedelements.Reduced-integrationelementshavefewervolumetricconstraints.Reducedintegrationeffectivelyeliminatesvolumetriclockinginmanyproblemswithnearlyincompressiblematerial.ABAQUS/Standard基礎(chǔ)教程IncompressABAQUS/Standard基礎(chǔ)教程IncompressibleMaterialsFullyincompressiblematerialsmodeledwithsolidelementsmustusethe“hybrid”formulation(elementswhosenamesendwiththeletter

“H”).Inthisformulationthepressurestressistreatedasanindependentlyinterpolatedbasicsolutionvariable,coupledtothedisplacementsolutionthroughtheconstitutivetheory.Hybridelementsintroducemorevariablesintotheproblemtoalleviatethevolumetriclockingproblem.Theextravariablesalsomakethemmoreexpensive.TheABAQUSelementlibraryincludeshybridversionsofallcontinuumelements(exceptplanestresselements,wheretheyarenotneeded).ABAQUS/Standard基礎(chǔ)教程IncompressABAQUS/Standard基礎(chǔ)教程Hybridelementsareonlynecessaryfor:以不可壓縮材料為主的網(wǎng)格，如橡膠材料。Allmesheswithstrictlyincompressiblematerials,suchasrubber.精密的網(wǎng)格，使用減縮積分仍然有l(wèi)ocking的網(wǎng)格，比如彈塑性材料完全進入塑性階段

Refinedmeshesofreduced-integrationelementsthatstillshowvolumetriclockingproblems.Suchproblemsarepossiblewithelastic-plasticmaterialsstrainedfarintotheplasticrange.即使使用了hybrid單元一次三角形或者四面體單元仍然有過度約束。因此建議這類單元使用的比例要小，可以作為六面體單元的“填充物”使用。Evenwithhybridelementsameshoffirst-ordertrianglesandtetrahedraisoverconstrainedwhenmodelingfullyincompressiblematerials.Hence,theseelementsarerecommendedonlyforuseas“fillers”inquadrilateralorbrick-typemesheswithsuchmaterial.IncompressibleMaterialsABAQUS/Standard基礎(chǔ)教程HybrideleABAQUS/Standard基礎(chǔ)教程MeshGenerationABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程MeshGenerationQuad/Hexvs.Tri/TetElementsOfparticularimportancewhengeneratingameshisthedecisionregardingwhethertousequad/hexortri/tetelements.Quad/hexelementsshouldbeusedwhereverpossible.Theygivethebestresultsfortheminimumcost.Whenmodelingcomplexgeometries,however,theanalystoftenhaslittlechoicebuttomeshwithtriangularandtetrahedralelements.TurbinebladewithplatformmodeledwithtetrahedralelementsABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程MeshGenerationFirst-ordertri/tetelements(CPE3,CPS3,CAX3,C3D4,C3D6)arepoorelements;theyhavethefollowingproblems:Poorconvergencerate.Theytypicallyrequireveryfinemeshestoproducegoodresults.Volumetriclockingwithincompressibleornearlyincompressiblematerials,evenusingthe“hybrid”formulation.Theseelementsshouldbeusedonlyasfillersinregionsfarfromanyareaswhereaccurateresultsareneeded.ABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程Equivalentnodalforcescreatedbyuniformpressureonthefaceofaregularsecond-ordertetrahedralelementMeshGeneration“Regular”second-ordertri/tetelements(CPE6,CPS6,CAX6,C3D10)cannotbeusedtomodelcontact.Underuniformpressurethecontactforcesaresignificantlydifferentatthecornerandmidsidenodes.Forsmall-displacementproblemswithoutcontacttheseelementsprovidereasonableresults.ABAQUS/Standard基礎(chǔ)教程EquivalentABAQUS/Standard基礎(chǔ)教程MeshGenerationModifiedsecond-ordertri/tetelements(C3D10M,etc.)alleviatetheproblemsofothertri/tetelements.Goodconvergencerate—closetoconvergencerateofsecond-orderquad/hexelements.Minimalshearorvolumetriclocking.Canbeusedtomodelincompressibleornearlyincompressiblematerialsinthehybridformulation(C3D10MH).Theseelementsarerobustduringfinitedeformation.Uniformcontactpressureallowstheseelementstomodelcontactaccurately.Usethem!ABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程MeshGenerationMeshrefinementandconvergenceUseasufficientlyrefinedmeshtoensurethattheresultsfromyourABAQUSsimulationareadequate.Coarsemeshestendtoyieldinaccurateresults.Thecomputerresourcesrequiredtorunyourjobincreasewiththelevelofmeshrefinement.Itisrarelynecessarytouseauniformlyrefinedmeshthroughoutthestructurebeinganalyzed.Useafinemeshonlyinareasofhighgradientsandacoarsermeshinareasoflowgradients.Youcanoftenpredictregionsofhighgradientsbeforegeneratingthemesh.Usehandcalculations,experience,etc.Alternatively,youcanusecoarsemeshresultstoidentifyhighgradientregions.ABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程MeshGenerationSomerecommendations:Minimizemeshdistortionasmuchaspossible.Aminimumoffourquadraticelementsper90oshouldbeusedaroundacircularhole.Aminimumoffourelementsshouldbeusedthroughthethicknessofastructureiffirst-order,reduced-integrationsolidelementsareusedtomodelbending.Otherguidelinescanbedevelopedbasedonexperiencewithagivenclassofproblem.ABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程MeshGenerationItisgoodpracticetoperformameshconvergencestudy.Simulatetheproblemusingprogressivelyfinermeshes,andcomparetheresults.ThemeshdensitycanbechangedveryeasilyusingABAQUS/CAEsincethedefinitionoftheanalysismodelisbasedonthegeometryofthestructure.Thiswillbediscussedfurtherinthenextlecture.Whentwomeshesyieldnearlyidenticalresults,theresultsaresaidtohave“converged.”Thisprovidesincreasedconfidenceinyourresults.ABAQUS/Standard基礎(chǔ)教程MeshGenerABAQUS/Standard基礎(chǔ)教程SolidElement

SelectionSummaryABAQUS/Standard基礎(chǔ)教程SolidElemABAQUS/Standard基礎(chǔ)教程SolidElementSelectionSummaryClassofproblemBestelementchoiceAvoidusingGeneralcontactbetweendeformablebodiesFirst-orderquad/hexSecond-orderquad/hexContactwithbendingIncompatiblemodeFirst-orderfullyintegratedquad/hexorsecond-orderquad/hexBending(nocontact)Second-orderquad/hexFirst-orderfullyintegratedquad/hex StressconcentrationSecond-orderFirst-orderNearlyincompressible(n>0.475orlargestrainplasticityepl>10%)First-orderelementsorsecond-orderreduced-integrationelementsSecond-orderfullyintegratedABAQUS/Standard基礎(chǔ)教程SolidElemABAQUS/Standard基礎(chǔ)教程SolidElementSelectionSummaryClassofproblemBestelementchoiceAvoidusingCompletelyincompressible(rubbern=0.5)Hybridquad/hex,first-orderiflargedeformationsareanticipatedBulkmetalforming(highmeshdistortion)First-orderreduced-integrationquad/hexSecond-orderquad/hexComplicatedmodelgeometry(linearmaterial,nocontact)Second-orderquad/hexifpossible(ifnotoverlydistorted)orsecond-ordertet/tri(becauseofmeshingdifficulties)Complicatedmodelgeometry(nonlinearproblemorcontact)First-orderquad/hexifpossible(ifnotoverlydistorted)ormodifiedsecond-ordertet/tri(becauseofmeshingdifficulties)Naturalfrequency(lineardynamics)Second-orderNonlineardynamic(impact)First-orderSecond-orderABAQUS/Standard基礎(chǔ)教程SolidElem演講完畢，謝謝觀看！演講完畢，謝謝觀看！ABAQUS/Standard基礎(chǔ)教程ElementSelectionCriteriaAppendix1ABAQUS/Standard基礎(chǔ)教程ElementSeABAQUS/Standard基礎(chǔ)教程內(nèi)容提要ElementsinABAQUSStructuralElements(ShellsandBeams)vs.ContinuumElementsModelingBendingUsingContinuumElements

用實體單元模擬彎曲StressConcentrations應(yīng)力集中Contact接觸IncompressibleMaterials不可壓縮材料MeshGeneration網(wǎng)格生成SolidElementSelectionSummaryABAQUS/Standard基礎(chǔ)教程內(nèi)容提要ElemenABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSABAQUS單元庫中提供廣泛的單元類型，適應(yīng)不同的結(jié)構(gòu)和幾何特征

ThewiderangeofelementsintheABAQUSelementlibraryprovidesflexibilityinmodelingdifferentgeometriesandstructures.Eachelementcanbecharacterizedbyconsideringthefollowing:

單元特性：Family單元類型Numberofnodes節(jié)點數(shù)Degreesoffreedom自由度數(shù)Formulation公式Integration積分ABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程單元類型（Family）Afamilyoffiniteelementsisthebroadestcategoryusedtoclassifyelements.同類型單元有很多相同的基本特。Elementsinthesamefamilysharemanybasicfeatures.同種類單元又有很多變化：Therearemanyvariationswithinafamily.ElementsinABAQUSspecial-purposeelementslikesprings,dashpots,andmassescontinuum(solidelements)shellelementsbeamelementsrigidelementsmembraneelementstrusselementsinfiniteelementsABAQUS/Standard基礎(chǔ)教程單元類型（FamilABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSNumberofnodes

節(jié)點數(shù)(interpolation)Anelement’snumberofnodesdetermineshowthenodaldegreesoffreedomwillbeinterpolatedoverthedomainoftheelement.ABAQUSincludeselementswithbothfirst-andsecond-orderinterpolation.

插值函數(shù)階數(shù)可以為一次或者兩次First-orderinterpolationSecond-orderinterpolationABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程ElementsinABAQUS自由度數(shù)目

DegreesoffreedomTheprimaryvariablesthatexistatthenodesofanelementarethedegreesoffreedominthefiniteelementanalysis.Examplesofdegreesoffreedomare:Displacements位移Rotations轉(zhuǎn)角Temperature溫度Electricalpotential電勢ABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程公式

FormulationThemathematicalformulationusedtodescribethebehaviorofanelementisanotherbroadcategorythatisusedtoclassifyelements.Examplesofdifferentelementformulations:Planestrain平面應(yīng)變Planestress平面應(yīng)力Hybridelements雜交單元Incompatible-modeelements非協(xié)調(diào)元Small-strainshells小應(yīng)變殼元Finite-strainshells有限應(yīng)變殼元Thickshells后殼Thinshells薄殼ElementsinABAQUSABAQUS/Standard基礎(chǔ)教程公式

FormulaABAQUS/Standard基礎(chǔ)教程積分Integration單元的剛度和質(zhì)量在單元內(nèi)的采樣點進行數(shù)值計算，這些采樣點叫做“積分點”

Thestiffnessandmassofanelementarecalculatednumericallyatsamplingpointscalled“integrationpoints”withintheelement.數(shù)值積分的算法影響單元的行為

Thenumericalalgorithmusedtointegratethesevariablesinfluenceshowanelementbehaves.ABAQUS包括完全積分和減縮積分。

ABAQUSincludeselementswithboth“full”and“reduced”integration.ElementsinABAQUSABAQUS/Standard基礎(chǔ)教程積分IntegratABAQUS/Standard基礎(chǔ)教程Fullintegration:

完全積分Theminimumintegrationorderrequiredforexactintegrationofthestrainenergyforanundistortedelementwithlinearmaterialproperties.Reducedintegration:

簡縮積分Theintegrationrulethatisoneorderlessthanthefullintegrationrule.ElementsinABAQUSFirst-

orderinterpolationFullintegration

Second-

order

interpolationReducedintegrationABAQUS/Standard基礎(chǔ)教程FullintegABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSElementnamingconventions:examples單元命名約定B21:Beam,2-D,

1st-orderinterpolationCAX8R:Continuum,AXisymmetric,8-node,ReducedintegrationDC3D4:Diffusion(heattransfer),Continuum,3-D,4-nodeS8RT:Shell,8-node,Reducedintegration,TemperatureCPE8PH:Continuum,Planestrain,8-node,Porepressure,HybridDC1D2E:Diffusion(heattransfer),Continuum,1-D,2-node,ElectricalABAQUS/Standard基礎(chǔ)教程ElementsiABAQUS/Standard基礎(chǔ)教程ElementsinABAQUSABAQUS/Standard和ABAQUS/Explicit單元庫的對比

Bothprogramshaveessen