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1、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。This is the ratio of the longest edge of an element to either its shortest edge or the shortest distance from a corner node to the opposing edge (heigh
2、t to closest node). HyperMesh uses the same method used for length (min) described below. For 3-D elements, each face of the element is treated as a 2-D element and its aspect ratio determined. The largest aspect ratio among these faces is returned as the 3-D elements aspect ratio.Aspect ratios shou
3、ld rarely exceed 5:1Chord dev 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。Curved surfaces can be approximated by using many short lines instead of a true curve.Chordal deviation is the perpendicular distance between the actual curve and the approximating line segments.Interior Angles内角 检查三角形与四边形最大与最小角These ma
4、ximum and minimum values are evaluated independently for triangles and quadrilaterals.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 Jac
5、obian 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This measures the deviation of an element from its ideal or perfect shape, such as a triangles deviation from equilateral. The Jacobian value ranges from 0.0 to 1.0, where 1.0 represents a
6、perfectly shaped element. The determinant of the Jacobian relates the local stretching of the parametric space which is required to fit it onto the global coordinate space.HyperMesh evaluates the determinant of the Jacobian matrix at each of the elements integration points (also called Gauss points)
7、 or at the elements corner nodes, and reports the ratio between the smallest and the largest. In the case 体现面积的变化。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Jacobia
8、n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perfect shape;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）of Jacobian evaluation at the Gauss points, values of 0.7 and above are generally acceptable.
9、 You can select which method of evaluation to use (Gauss point or corner node) from the Check Element Settings window.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。Minimum element lengths are calculated using one of two methods: The shortest edge of the element. This method
10、 is used for non-tetrahedral 3-D elements.The shortest distance from a corner node to its opposing edge (or face, in the case of tetra elements); referred to as height to closest node.You can choose which method to use in the Check Element Settings window. Note that this setting also affects the cal
11、culation of Aspect Ratio.Minimum Length / 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。HyperMesh uses 2 methods to calculate the minimum element size: the shortest edge (in which the length of the shortest edge of each element is used) and the height to closest node (which is more accurate, but mo
12、re complex). Height to Closest Node (HCN) is calculated differently for different element types. For triangular elements:For each corner node (i) HyperMesh calculates the closest (perpendicular) distance to the ray including the opposite leg of the triangle, h(i). HCN = min(hi) * 2/sqrt(3.0). The sc
13、aling factor 2/sqrt(3.0) ensures that for equilateral triangles, the HCN is the length of the minimum side. For quadrilateral elements:For each corner node, HM calculates the closest (perpendicular) distances to the rays containing the legs of the quadrilateral that do not include this node. The fig
14、ure above depicts these lengths as red lines. Height to Closest Node is taken to be the minimum of all eight lines and the four edge lengths (thus, the minimum of 12 possible lengths).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Skew of triangular elements is calculated by finding the minimum
15、angle between the vector from each node to the opposing mid-side, and the vector between the two adjacent mid-sides at each node of the element. The minimum angle found is subtracted from ninety degrees and reported as the elements skew.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。Taper r
16、atio for the quadrilateral element is defined by first finding the area of the triangle formed at each corner grid point:These areas are then compared to one half of the area of the quadrilateral.HyperMesh then finds the smallest ratio of each of these triangular areas to the quad elements total area (in the diagram above, a is smallest). The resulting value is subtracted from 1, and the result reported as the element taper.
