关于solid45和solid95单元对模态分析的影响！

SOLID95 比较精细点吧

一般来说带中节点的二次单元分析精度高，但为什么还要用不带中节点的线性单元呢，那是因为很多分析不适合用二次单元，比如，动态分析不要用带中节点的单元（因为动态分析中涉及波的传播，而二次单元质量分布不均匀），非线性分析尽量用线性单元（因为线性单元的积分点多），所以不要一味地追求高精度而使用二次单元。
具体可以参见帮助文件：Modeling and Meshing Guide/2.2. Choosing Between Linear and Higher Order Elements/2.2.2. Quadratic Elements (Midside Nodes)
For linear structural analyses with degenerate element shapes (that is, triangular 2-D elements and wedge or tetrahedral 3-D elements), the quadratic elements will usually yield better results at less expense than will the linear elements. However, in order to use these elements correctly, you need to be aware of a few peculiar traits that they exhibit:
In dynamic analyses where wave propagation is of interest, midside-node elements are not recommended because of the nonuniform mass distribution.
A quadratic element has no more integration points than a linear element. For this reason, linear elements will usually be preferred for nonlinear analyses.

一般来说带中节点的二次单元分析精度高，但为什么还要用不带中节点的线性单元呢，那是因为很多分析不适合用二次单元，比如，动态分析不要用带中节点的单元（因为动态分析中涉及波的传播，而二次单元质量分布不均匀），非线性分析尽量用线性单元（因为线性单元的积分点多），所以不要一味地追求高精度而使用二次单元。
具体可以参见帮助文件：Modeling and Meshing Guide/2.2. Choosing Between Linear and Higher Order Elements/2.2.2. Quadratic Elements (Midside Nodes)
For linear structural analyses with degenerate element shapes (that is, triangular 2-D elements and wedge or tetrahedral 3-D elements), the quadratic elements will usually yield better results at less expense than will the linear elements. However, in order to use these elements correctly, you need to be aware of a few peculiar traits that they exhibit:

• In dynamic analyses where wave propagation is of interest, midside-node elements are not recommended because of the nonuniform mass distribution.
• A quadratic element has no more integration points than a linear element. For this reason, linear elements will usually be preferred for nonlinear analyses.
  

solid95是高级单元，可能造成计算量很大，所以出错