3-D Meshing (Hypermesh 3D网格划分经验_英语原文+汉语注释)

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7.1 When to Use 3-D Elements

100 ~ 200 ~ 50 3-D elements should be used when all dimensions are comparable.

x ~ y ~ z Element shape – Tetra, penta, hex, pyramid Additional data from user – Nothing Element type – Solid Practical applications : Gear box, engine block, crankshaft, etc.VII

3-D Meshing This chapter includes material from the book “Practical Finite Element Analysis”. It also has been reviewed and has additional material added by Matthias Goelke.何时采用3D 网格x,y,z 三个方向的尺寸相差不太大

单元形状——四面体、楔形、六面体、金字塔形

不需要用户提供其他数据（1D 单元需要截面形状，2D 单元需要厚度）

网格类型——实体

实际应用——齿轮箱、发动机缸体、曲轴等

196 6 cylinder crankcase brick mesh Crank Shaft Tetra Meshing (Image Source : Altair Calendar 2006, Courtesy : Bharat Forge Ltd. )3-D Element types :Tetra Penta or Wedge Hex or Brick Pyramid

Linear

Tetra 4Linear Penta 6

Linear Hex 8Tetra 10

Linear Pyram 5 Not supported by

all software

3-D Elements

7.2 DOFs For Solid Elements 2-D thin shell and 1-D beam element supports 6 dofs, but all solid elements have only 3 translational

dofs (no rotational dof) i.e. a 10 noded tetra element has total of 10 x 3 = 30 dofs

Why does a solid element have only 3 translational and no rotational dofs (Physical

interpretation)?

Consider a piece of paper (2-D geometry) or long steel scale (1-D geometry). It could be easily bent and

twisted (rotational dof). But now consider a solid object like a duster or a paper weight. It could not

实体单元的自由度

1D 、2D 单元都具有6个自由度，但是3D 实体单元只有3个移动自由度（没有转动自由度）设想一张纸（2D 几何体）或长钢尺（1D 几何体），很容易弯曲和扭转。但是对于像黑板擦或者镇纸这样的

3D 几何体，通常不会承受太大的弯曲或扭转，因此实体单元只具有3个移动自由度而没有转动自由度。

with 3 translational dofs and no rotational dofs.

7.3 Tetra Meshing Techniques

There are two methods of tetra meshing.

1) Automatic mesh: This approach is limited to simple geometries and the pre-requisite is an error

free CAD model. The user just has to select the volume and the software automatically carries out the

meshing as per the speci ed element length, quality criteria, etc.

Advantage: Very quick, no meshing e orts

Disadvantage: Results in a very high number of nodes and elements. There is no control over the

mesh ow and the speci c mesh pattern requirement (like bolted, welded joints or contact surface

simulation).

2) 2-D (Tria) to 3-D (Tetra): This is the most commonly used method. Quad or tria meshing is carried

out on all the outer surfaces of the geometry. During the tetra meshing the quads are automatically

split into trias which then serve as the “basis” of the tetra elements.

Steps for 2-D (Tria) to 3-D (Tetra) mesh generation :

Steps 1) Study the geometry

Step 2) Separate (isolate) the surfaces and split the job among engineers (if there is time constraint)

四面体网格划分

四面体划分有两种方法

自动划分：适用于简单的、没有错误的几何体，软件自动划分。

优势：非常快、简单

缺点：节点和单元数量很多，无法对网格划分过程进行控制，也不能对特定区域

（如螺栓、焊接或接触）的网格进行细化

2D网格到3D四面体：这是最常用的方法。先在几何体表面划分四

边形或三角形网格，然后软件以表面的网格为基础，自动在几何

体内部生成四面体网格。在网格生成过程中，表面的四边形会自

动分割成三角形。

1、研究几何模型

2、将几何模型的表面分成几个部分，分配给几个工程师去划分网格（如果有时间限制的话）

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