BEAM188单元中文说明

Release10.0DocumentationforANSYSBEAM1883-DLinearFiniteStrainBeam三维线性有限应变梁单元BEAM188ElementDescriptionBEAM188单元描述BEAM188issuitableforanalyzingslendertomoderatelystubby/thickbeamstructures.ThiselementisbasedonTimoshenkobeamtheory.Sheardeformationeffectsareincluded.Beam188单元适合于分析从细长到中等粗短的梁结构，该单元基于铁木辛哥梁结构理论，并考虑了剪切变形的影响。BEAM188isalinear(2-node)oraquadraticbeamelementin3-D.BEAM188hassixorsevendegreesoffreedomateachnode,withthenumberofdegreesoffreedomdependingonthevalueofKEYOPT(1).WhenKEYOPT(1)=0(thedefault),sixdegreesoffreedomoccurateachnode.Theseincludetranslationsinthex,y,andzdirectionsandrotationsaboutthex,y,andzdirections.WhenKEYOPT(1)=1,aseventhdegreeoffreedom(warpingmagnitude)isalsoconsidered.Thiselementiswell-suitedforlinear,largerotation,and/orlargestrainnonlinearapplications.Beam188是三维线性（2节点）或者二次梁单元。每个节点有六个或者七个自由度，自由度的个数取决于KEYOPT(1)的值。当KEYOPT(1)＝0（缺省）时，每个节点有六个自由度；包括节点坐标系的x、y、z方向的平动和绕x、y、z轴的转动。当KEYOPT(1)=1时，每个节点有七个自由度，这时引入了第七个自由度（横截面的翘曲）。这个单元非常适合线性、大角度转动以及大应变等非线性问题。BEAM188includesstressstiffnessterms,bydefault,inanyanalysiswithNLGEOM,ON.Theprovidedstressstiffnesstermsenabletheelementstoanalyzeflexural,lateral,andtorsionalstabilityproblems(usingeigenvaluebucklingorcollapsestudieswitharclengthmethods).当NLGEOM选项打开的时候，beam188的应力刚化，在任何分析中都是缺省项。应力刚化选项使本单元能分析弯曲、横向及扭转稳定问题（用弧长法分析特征值屈曲和塌陷）。BEAM188canbeusedwithanybeamcross-sectiondefinedviaSECTYPE,SECDATA,SECOFFSET,SECWRITE,andSECREAD.Thecross-sectionassociatedwiththebeammaybelinearlytapered.Elasticity,creep,andplasticitymodelsaresupported(irrespectiveofcross-sectionsubtype).Across-sectionassociatedwiththiselementtypecanbeabuilt-upsectionreferencingmorethanonematerial.Beam188可以采用sectype、secdata、secoffset、secwrite及secread命令定义横截面。本单元支持弹性、蠕变及塑性模型（不考虑横截面子模型）。这种单元类型的截面可以由不同材料组成。BEAM188ignoresanyrealconstantdatabeginningwithRelease6.0.SeetheSECCONTROLScommandfordefiningthetransverseshearstiffness,andaddedmass.Beam188从6.0版本开始忽略任何实常数，参考seccontrols命令来定义横向剪切刚度和附加质量。ForBEAM188,theelementcoordinatesystem(/PSYMB,ESYS)isnotrelevant.单元坐标系统（/psymb，esys）与beam188单元无关。Figure188.1:BEAM188Geometry图188.1：Beam188单元几何示意图BEAM188InputDataBEAM188输入数据Thegeometry,nodelocations,andcoordinatesystemforthiselementareshowninFigure188.1:BEAM188Geometry.BEAM188isdefinedbynodesIandJintheglobalcoordinatesystem.该单元的几何形状、节点位置、坐标体系如图188.1“Beam188单元几何示意图”所示，beam188由整体坐标系的节点I和J定义。NodeKisapreferredwaytodefinetheorientationoftheelement.Forinformationaboutorientationnodesandbeammeshing,seeGeneratingaBeamMeshWithOrientationNodesintheANSYSModelingandMeshingGuide.SeetheLMESHandLATTcommanddescriptionsfordetailsongeneratingtheKnodeautomatically.节点K是定义单元方向的首选方式，有关方向节点和梁的网格划分的信息可以参见ANSYSModelingandMeshingGuide中的GeneratingaBeamMeshWithOrientationNodes。参考LMESH和LATT命令描述可以得到k节点自动生成的详细资料。BEAM188mayalsobedefinedwithouttheorientationnode.Inthiscase,theelementx-axisisorientedfromnodeI(end1)towardnodeJ(end2).Forthetwo-nodeoption,thedefaultorientationoftheelementy-axisisautomaticallycalculatedtobeparalleltotheglobalX-Yplane.ForthecasewheretheelementisparalleltotheglobalZ-axis(orwithina0.01percentslopeofit),theelementy-axisisorientedparalleltotheglobalY-axis(asshown).Forusercontroloftheelementorientationabouttheelementx-axis,usethethirdnodeoption.Ifbotharedefined,thethirdnodeoptiontakesprecedence.Thethirdnode(K),ifused,definesaplane(withIandJ)containingtheelementxandz-axes(asshown).Ifthiselementisusedinalargedeflectionanalysis,itshouldbenotedthatthelocationofthethirdnode(K)isusedonlytoinitiallyorienttheelement.Beam188也以在没有方向节点的情况下被定义。在这种情况下，单元的x轴方向为I节点指向J节点。对于两节点的情况，默认的y轴方向按平行x－y平面自动计算。对于单元平行与z轴的情况（或者斜度在0.01％以内），单元的y轴的方向平行与整体坐标的y轴（如图188.1）。用第三个节点的选项，用户可以定义单元的x轴方向。如果两者都定义了，那么第三节点的选项优先考虑。第三个节点（K）如果采用的话，将和I、J节点一起定义包含单元x轴和z轴的平面(如图188.1)。如果该单元采用大变形分析，需要注意这个第三号节点仅仅在定义初始单元方向的时候有效。Thebeamelementsareone-dimensionallineelementsinspace.Thecross-sectiondetailsareprovidedseparatelyusingtheSECTYPEandSECDATAcommands(seeBeamAnalysisandCrossSectionsintheANSYSStructuralAnalysisGuidefordetails).AsectionisassociatedwiththebeamelementsbyspecifyingthesectionIDnumber(SECNUM).Asectionnumberisanindependentelementattribute.Inadditiontoaconstantcross-section,youcanalsodefineataperedcross-sectionbyusingtheTAPERoptionontheSECTYPEcommand(seeDefiningaTaperedBeam).梁单元是一维空间线单元。横截面资料用sectype和secdata命令分别提供，参见ANSYSStructuralAnalysisGuide的BeamAnalysisandCrossSections看详细资料。截面与单元用截面ID号（SECNUM）来关联，截面号是独立的单元属性。除了等截面，还可以用sectype命令中的锥形选项来定义楔形截面（参考DefiningaTaperedBeam）。ThebeamelementsarebasedonTimoshenkobeamtheory,whichisafirstordersheardeformationtheory:transverseshearstrainisconstantthroughthecross-section;thatis,cross-sectionsremainplaneandundistortedafterdeformation.BEAM188isafirstorderTimoshenkobeamelementwhichusesonepointofintegrationalongthelengthwithdefaultKEYOPT(3)setting.Therefore,whenSMISCquantitiesarerequestedatnodesIandJ,thecentroidalvaluesarereportedforbothendnodes.WithKEYOPT(3)setto2,twopointsofintegrationareusedresultinginlinearvariationalongthelength.单元基于铁木辛哥梁理论，这个理论是一阶剪切变形理论；横向剪切应力在横截面是不变的，也就是说变形后横截面保持平面不发生扭曲。Beam188是一阶铁木辛哥梁单元，沿着长度用了一个积分点，用默认的KEYOPT(3)设置。