3D单元质量检查

icefox163

想请问一下，在单元质量检查时，

在3D中的warpage，aspect, jacobian等待和2D单元中相同命令的含义是什么？

warpage，aspect, jacobian不是只有2D单元都有的吗？

是不是用来检查体单元各个面的质量?谢谢

icefox163

我在划完2D单元后，检查最小jacobian是0.06

然后划3D单元，划完后隐藏2D单元，检查3D单元的jacobian最小是-1

这是为什么?

sunny0o0

完全有可能啊！2D与3D的雅克比不是一个意思。你这还不算小，昨天我做的2D的还好，3D的最差的是负一百多，最后全把它们删了，估计影响不大。

icefox163

那里晓得3D单元中，jacobian是什么意思吗？我英文看不大懂

sunny0o0

就是雅克比矩阵，就是x、y、z分别对3个形函数自变量偏导的雅克比行列式。具体从单元内角可以反映出雅克比值的大小。雅克比值不能为0，因此不允许单元中存在负的角度。

phoebetv

This measures the deviation of an element from its ideal or "perfect" shape, such as a triangle’s deviation from equilateral. The Jacobian value ranges from 0.0 to 1.0, where 1.0 represents a 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 element’s integration points (also called Gauss points) or at the element’s corner nodes, and reports the ratio between the smallest and the largest. In the case of Jacobian evaluation at the Gauss points, values of 0.7 and above are generally acceptable. You can select which method of evaluation to use (Gauss point or corner node) from the Check Element Settings window.

likui0708

雅各比主要反映单元偏离其理想形状的程度，一般大于0.7最好