hypermesh单元质量参数说明Word格式文档下载.docx
《hypermesh单元质量参数说明Word格式文档下载.docx》由会员分享,可在线阅读,更多相关《hypermesh单元质量参数说明Word格式文档下载.docx(15页珍藏版)》请在冰豆网上搜索。
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:
Chorddev
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jacobian<
0,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)
Thismeasuresthedeviationofanelementfromitsidealor"
perfect"
shape,suchasatriangle’sdeviationfromequilateral.TheJacobianvaluerangesfrom0.0to1.0,where1.0representsaperfectlyshapedelement.
ThedeterminantoftheJacobianrelatesthelocalstretchingoftheparametricspacewhichisrequiredtofititontotheglobalcoordinatespace.
HyperMeshevaluatesthedeterminantoftheJacobianmatrixateachoftheelement’sintegrationpoints(alsocalledGausspoints)orattheelement’scornernodes,andreportstheratiobetweenthesmallestandthelargest.InthecaseofJacobianevaluationattheGausspoints,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);
referredtoas"
.
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.
HyperMeshthenfindsthesmallestratioofeachofthesetriangularareasto½
thequadelement’stotalarea(inthediagramabove,"
a"
issmallest).
Theresultingvalueissubtractedfrom1,andtheresultreportedastheelementtaper.Thismeansthatasthetaperapproaches0,theshapeapproachesarectangle.
Trianglesareassignedavalueof0,inordertopreventHyperMeshfrommistakingthemforhighly-taperedquadrilateralsandreportingthemas"
failed"
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
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。
Intheheighttoclosestnodemethod,HyperMeshcalculatestheclosest(perpendicular)distancestotheplanesformedbytheoppositefacesforeachcornernode.
Theresultingminimumlength/sizeistheminimumofallsuchmeasureddistances.
Tetracollapse
网格塌陷
理想值1;
网格塌陷时逼近0;
不小于0.5
四面体网格高度根据四个节点到对面的距离计算,除以面积平方根。
最小的值除以1.24。
网格塌陷,这个值逼近0。
理想的四面体该数值为1。
非四面体单元统一赋值为1,以免Hypermesh误以为质量差的四面体单元。
Theheightofthetetraelementismeasuredfromeachofthefournodestoitsoppositeface,andthendividedbythesquarerootoftheface’sarea.
Theminimumofthefourresultingvalues(onepernode)isthennormalizedbydividingitby1.24.
Asthetetracollapses,thevalueapproaches0.0,whileaperfecttetrahasavalueof1.0.
Non-tetrahedralelementsaregivenvaluesof1sothatHyperMeshwon’tmistakethemforbadtetraelements.
Vol.AspectRatio
体长宽比
取四面体网格最长边除以最短变长
HyperMeshevaluatesTetrahedralelementsbyfindingthelongestedgelengthanddividingitbytheshortestheight(measuredfromanodetoitsopposingface).
Other3-Delements,suchashexelements,areevaluatedbasedontheratiooftheirlongestedgetotheirshortestedge.
VolumeSkew
体扭曲度
0最优
1最差
仅检查四面体单元。
其他单元都被赋值为零。
体扭曲度等于四面体单元体积除以理想四面体体积。
Thischeckappliesonlytotetrahedralelements;
allothersareassignedvaluesofzero.VolumeSkewisdefinedas1-shapefactor,soaskewof0isperfectandaskewof1istheworstpossiblevalue.
Theshapefactorforatetrahedralelementisdeterminedbydividingtheelement’svolumebythevolumeofanideal(equilateral)tetrahedronofthesamecircumradius.
Inthecaseoftetrahedralelements,thecircumradiusistheradiusofaspherepassingthroughthefourverticesofthetetrahedron.
VolAR
高度与底面积比值