hypermesh单元质量参数说明

Hypermesh单元质量参数说明网格质量中文名推荐取值物理意义Help原文2D单元质量参数Aspect(ratio)长宽比必须小于5:1单元最长边与最短边（或最短对角节点距离）之比。3D单元的每个面被看做一个2D单元并且计算长宽比。最大的长宽比作为3D单元的长宽比。Thisistheratioofthelongestedgeofanelementtoeitheritsshortestedgeortheshortestdistancefromacornernodetotheopposingedge(heighttoclosestnode).HyperMeshusesthesamemethodusedforlength(min)describedbelow.For3-Delements,eachfaceoftheelementistreatedasa2-Delementanditsaspectratiodetermined.Thelargestaspectratioamongthesefacesisreturnedasthe3-Delement’saspectratio.Aspectratiosshouldrarelyexceed5:1Chorddev弦长偏差—圆弧可以大量短直线模拟，弦长偏差是圆弧与直线的垂直距离。Curvedsurfacescanbeapproximatedbyusingmanyshortlinesinsteadofatruecurve.Chordaldeviationistheperpendiculardistancebetweentheactualcurveandtheapproximatinglinesegments.InteriorAngles内角—检查三角形与四边形最大与最小角Thesemaximumandminimumvaluesareevaluatedindependentlyfortrianglesandquadrilaterals.Jacobian雅克比理想值1大于0.7可接受，质量较好，小于0.5，准确性不能保证jacobian值是衡量网格质量好坏的一个重要指标。数学上Jacobian是进行坐标变换的Jacob矩阵的行列式|J|，它的取值可以在[-∞,+∞]变化。Abs(|J|)1说明面积扩大，abs(|J|)1说明面积缩小。|J|0说明组成微元的两个向量所称的角的sin值发生了符号变化(比如从锐角变成钝角)。HM中所谓的Jacobian并不是上面讲的数学意义上的Jacobian，而是在自然坐标(s,t)中的微元向量dS,dT(在自然坐标中成90度)，对应在全局坐标中的向量dS’,dT’所成角度的sin值。它只体现了’变形’，而没有体现面积Thismeasuresthedeviationofanelementfromitsidealorperfectshape,suchasatriangle’sdeviationfromequilateral.TheJacobianvaluerangesfrom0.0to1.0,where1.0representsaperfectlyshapedelement.ThedeterminantoftheJacobianrelatesthelocalstretchingoftheparametricspacewhichisrequiredtofititontotheglobalcoordinatespace.HyperMeshevaluatesthedeterminantoftheJacobianmatrixateachoftheelement’sintegrationpoints(alsocalledGausspoints)orattheelement’scornernodes,andreportstheratiobetweenthesmallestandthelargest.Inthecase的变化。而实际上单纯面积/体积的变化，对于单元的形状/质量是没有影响的，所以HM用这个sin值来评价单元的质量是有道理的。这个值应该可以在[-1,1]变化，但是由于负值表示单元发生了’反转’或者’穿透’(比如TETRA中一个节点运动到了另外三个节点组成三角形的另一侧)，HW认为此时的单元是完全不可用于有限元计算的，所以默认的取值范围是[0,1]。虽然HM中的’Jacobian’取值在单元内部各点可能是不同的，但是可以直观地理解为:以QUAD单元为例,如果jacobian=1,说明该单元的四个角都是直角，单元质量是最好的，也就是所谓的’perfectshape’;如果jacobian=0,说明该单元发生了严重的变形，某个内角变为0度或者180度；如果jacobian0,说明该单元发生了非常严重的变形，某个内角变为负值(反转)或者大于180度。（此段摘自网贴）ofJacobianevaluationattheGausspoints,valuesof0.7andabovearegenerallyacceptable.Youcanselectwhichmethodofevaluationtouse(Gausspointorcornernode)fromtheCheckElementSettingswindow.Length(min)最小长度—最小长度，计算使用以下两种方式：（1）单元最短变长，对于非四面体网格；（2）从节点到对角边（或面）的最短距离。Minimumelementlengthsarecalculatedusingoneoftwomethods:•Theshortestedgeoftheelement.Thismethodisusedfornon-tetrahedral3-Delements.•Theshortestdistancefromacornernodetoitsopposingedge(orface,inthecaseoftetraelements);referredtoasheighttoclosestnode.YoucanchoosewhichmethodtouseintheCheckElementSettingswindow.NotethatthissettingalsoaffectsthecalculationofAspectRatio.MinimumLength/Size最小单元长度—使用两种方法计算最小单元长度：（1）最短边长；（2）节点到对边的高度。HyperMeshuses2methodstocalculatetheminimumelementsize:theshortestedge(inwhichthelengthoftheshortestedgeofeachelementisused)andtheheighttoclosestnode(whichismoreaccurate,butmorecomplex).HeighttoClosestNode(HCN)iscalculateddifferentlyfordifferentelementtypes.Fortriangularelements:Foreachcornernode(i)HyperMeshcalculatestheclosest(perpendicular)distancetotherayincludingtheoppositelegofthetriangle,h(i).HCN=min(hi)*2/sqrt(3.0).Thescalingfactor2/sqrt(3.0)ensuresthatforequilateraltriangles,theHCNisthelengthoftheminimumside.Forquadrilateralelements:Foreachcornernode,HMcalculatestheclosest(perpendicular)distancestotherayscontainingthelegsofthequadrilateralthatdonotincludethisnode.Thefigureabovedepictstheselengthsasredlines.HeighttoClosestNodeistakentobetheminimumofalleightlinesandthefouredgelengths(thus,theminimumof12possiblelengths).skew面扭曲三角单元的扭曲度计算方式如下：从每个节点到对边中点的矢量以及两相邻边中点矢量的最小夹角Skewoftriangularelementsiscalculatedbyfindingtheminimumanglebetweenthevectorfromeachnodetotheopposingmid-side,andthevectorbetweenthetwoadjacentmid-sidesateachnodeoftheelement.Theminimumanglefoundissubtractedfromninetydegreesandreportedastheelement’sskew.Taper锥度—四边形对角节点连线分割成两个三角形。锥度等于1减去最小三角形面积除以四边形一半面积的比值。Taperratioforthequadrilateralelementisdefinedbyfirstfindingtheareaofthetriangleformedateachcornergridpoint:Theseareasarethencomparedtoonehalfoftheareaofthequadrilateral.HyperMeshthenfindsthesmallestratioofeachofthesetriangularareasto½thequadelement’stotalarea(inthediagramabove,aissmallest).Theresultingvalueissubtractedfrom1,andtheresultreportedastheelementtaper.Thismeansthatasthetaperapproaches0,theshapeapproachesarectangle.Trianglesareassignedavalueof0,inordertopreventHyperMeshfrommistakingthemforhighly-taperedquadrilateralsandreportingthemasfailed.Warpage翘曲度小于5度依次沿对角线将四边形分为两个三角形，寻找这两个三角形所在面构成夹角的最大夹角，该角即为WarpAngle。Thisistheamountbywhichanelement(orinthecaseofsolidelements,anelementface)deviatesfrombeingplanar.Sincethreepointsdefineaplane,thischeckonlyappliestoquads.Thequadisdividedintotwotriasalongitsdiagonal,andtheanglebetweenthetrias’normalsismeasured.Warpageofuptofivedegreesisgenerallyacceptable.3D网格质量检查补充参数MinimumLength/Size最短边长使用两种方法计算：（1）最短变长（2）节点到对面最短距离。HyperMeshuses2methodstocalculatetheminimumelementsize:theshortestedge(inwhichthelengthoftheshortestedgeofeach