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2003,ABAQUS软件公司北京办事处.ABAQUS/Standard基础教程ElementSelectionCriteriaAppendix12003,ABAQUS软件公司北京代表处.A1.2ABAQUS/Standard基础教程内容提要•ElementsinABAQUS•StructuralElements(ShellsandBeams)vs.ContinuumElements•ModelingBendingUsingContinuumElements用实体单元模拟弯曲•StressConcentrations应力集中•Contact接触•IncompressibleMaterials不可压缩材料•MeshGeneration网格生成•SolidElementSelectionSummary2003,ABAQUS软件公司北京办事处.ABAQUS/Standard基础教程ElementsinABAQUS2003,ABAQUS软件公司北京代表处.A1.4ABAQUS/Standard基础教程ElementsinABAQUS•ABAQUS单元库中提供广泛的单元类型，适应不同的结构和几何特征ThewiderangeofelementsintheABAQUSelementlibraryprovidesflexibilityinmodelingdifferentgeometriesandstructures.–Eachelementcanbecharacterizedbyconsideringthefollowing:单元特性：•Family单元类型•Numberofnodes节点数•Degreesoffreedom自由度数•Formulation公式•Integration积分2003,ABAQUS软件公司北京代表处.A1.5ABAQUS/Standard基础教程•单元类型（Family）–Afamilyoffiniteelementsisthebroadestcategoryusedtoclassifyelements.–同类型单元有很多相同的基本特。Elementsinthesamefamilysharemanybasicfeatures.–同种类单元又有很多变化：Therearemanyvariationswithinafamily.ElementsinABAQUSspecial-purposeelementslikesprings,dashpots,andmassescontinuum(solidelements)shellelementsbeamelementsrigidelementsmembraneelementstrusselementsinfiniteelements2003,ABAQUS软件公司北京代表处.A1.6ABAQUS/Standard基础教程ElementsinABAQUS•Numberofnodes节点数(interpolation)–Anelement’snumberofnodesdetermineshowthenodaldegreesoffreedomwillbeinterpolatedoverthedomainoftheelement.–ABAQUSincludeselementswithbothfirst-andsecond-orderinterpolation.插值函数阶数可以为一次或者两次First-orderinterpolationSecond-orderinterpolation2003,ABAQUS软件公司北京代表处.A1.7ABAQUS/Standard基础教程ElementsinABAQUS•自由度数目Degreesoffreedom–Theprimaryvariablesthatexistatthenodesofanelementarethedegreesoffreedominthefiniteelementanalysis.–Examplesofdegreesoffreedomare:•Displacements位移•Rotations转角•Temperature温度•Electricalpotential电势2003,ABAQUS软件公司北京代表处.A1.8ABAQUS/Standard基础教程•公式Formulation–Themathematicalformulationusedtodescribethebehaviorofanelementisanotherbroadcategorythatisusedtoclassifyelements.–Examplesofdifferentelementformulations:•Planestrain平面应变•Planestress平面应力•Hybridelements杂交单元•Incompatible-modeelements非协调元•Small-strainshells小应变壳元•Finite-strainshells有限应变壳元•Thickshells后壳•Thinshells薄壳ElementsinABAQUS2003,ABAQUS软件公司北京代表处.A1.9ABAQUS/Standard基础教程•积分Integration–单元的刚度和质量在单元内的采样点进行数值计算，这些采样点叫做“积分点”Thestiffnessandmassofanelementarecalculatednumericallyatsamplingpointscalled“integrationpoints”withintheelement.–数值积分的算法影响单元的行为Thenumericalalgorithmusedtointegratethesevariablesinfluenceshowanelementbehaves.–ABAQUS包括完全积分和减缩积分。ABAQUSincludeselementswithboth“full”and“reduced”integration.ElementsinABAQUS2003,ABAQUS软件公司北京代表处.A1.10ABAQUS/Standard基础教程•Fullintegration:完全积分•Theminimumintegrationorderrequiredforexactintegrationofthestrainenergyforanundistortedelementwithlinearmaterialproperties.•Reducedintegration:简缩积分•Theintegrationrulethatisoneorderlessthanthefullintegrationrule.ElementsinABAQUSFirst-orderinterpolationFullintegrationSecond-orderinterpolationReducedintegration2003,ABAQUS软件公司北京代表处.A1.11ABAQUS/Standard基础教程ElementsinABAQUS•Elementnamingconventions:examples单元命名约定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,Electrical2003,ABAQUS软件公司北京代表处.A1.12ABAQUS/Standard基础教程ElementsinABAQUS•ABAQUS/Standard和ABAQUS/Explicit单元库的对比–Bothprogramshaveessentiallythesameelementfamilies:continuum,shell,beam,etc.–ABAQUS/Standardincludeselementsformanyanalysistypesinadditiontostressanalysis:热传导,固化soilsconsolidation,声场acoustics,etc.•AcousticelementsarealsoavailableinABAQUS/Explicit.–ABAQUS/Standardincludesmanymorevariationswithineachelementfamily.–ABAQUS/Explicit包括的单元绝大多数都为一次单元。•例外:二次▲单元和四面体单元and二次beamelements–Manyofthesamegeneralelementselectionguidelinesapplytobothprograms.2003,ABAQUS软件公司北京办事处.ABAQUS/Standard基础教程StructuralElements(ShellsandBeams)vs.ContinuumElements2003,ABAQUS软件公司北京代表处.A1.14ABAQUS/Standard基础教程StructuralElements(ShellsandBeams)vs.ContinuumElements–实体单元建立有限元模型通常规模较大，尤其对于三维实体单元–如果选用适当的结构单元(shellsandbeams)会得到一个更经济的解决方案•模拟相同的问题，用结构体单元通常需要的单元数量比实体单元少很多–要由结构体单元得到合理的结果需要满足一定要求：theshellthicknessorthebeamcross-sectiondimensionsshouldbelessthan1/10ofatypicalglobalstructuraldimension,suchas:•Thedistancebetweensupportsorpointloads•Thedistancebetweengrosschangesincrosssection•Thewavelengthofthehighestvibrationmode2003,ABAQUS软件公司北京代表处.A1.15ABAQUS/Standard基础教程•Shellelements–Shellelementsapproximateathree-dimensionalcontinuumwithasurfacemodel.•高效率的模拟面内弯曲Modelbendingandin-planedeformationsefficiently.–Ifadetailedanalysisofaregionisneeded,alocalthree-dimensionalcontinuummodelcanbeincludedusingmulti-pointconstraintsorsubmodeling.–如果需要三维实体单元模拟细节可以使用子模型ShellmodelofahemisphericaldomesubjectedtoaprojectileimpactStructuralElements(ShellsandBeams)vs.ContinuumElements3-Dcontinuumsurfacemodel2003,ABAQUS软件公司北京代表处.A1.16ABAQUS/Standard基础教程StructuralElements(ShellsandBeams)vs.ContinuumElements•Be