Meshing Tutorials(网格划分教程)
HM-3120:2D Mshing in Curved Surfaces(2D在曲面中進行網格劃分)
弦偏差(Chordal deviation)是一種網格劃分算法，它允許HyperMesh沿著曲面邊緣自動改變節點密度和偏差，以獲得更準確的網格表面表示。(Chordal deviation is a meshing algorithm that allows HyperMesh to automatically vary node densities and biasing along curved surface edges to gain a more accurate representation of the surface being meshed.)
本節的學習內容
1.在本教程中，您將學習如何創建一個基于元素大小的網格。(In this tutorial you will learn how to Create a mesh based only on element size)
2.使用最大偏差參數對一組曲面進行網格劃分。(Mesh a set of surfaces using the maximum deviation parameter)
3.減小最大角度周長。(Reduce the maximum angle perimeter)
4.增加最大元素大小參數。（Increase the maximum element size parameter）。
Step 1. Open the Model File
In this step you will open the model file, chordal_dev.hm.
Step 2. Set the Mesh Parameters（設置網格參數）
In this step you will set the mesh parameters and create the mesh.（這一步你將設置網格參數并創建網格）
Step 3. Set the Chordal Deviation Parameters（設置弦偏差參數）
補充內容什么是弦偏差啊？
解答 ：（在點云內任意取3個點,過此三點必然可以作一個圓弧,連接此圓弧的2端點形成一直線,過此圓弧的中點作直線的垂線.此垂線的長度既為弦.則,以某點云的點為基準,必然可以在其它的點云里的點里找到上述的很多點,這些點形成一個區域.在此區域內的點云全部被過濾掉.）
In this step you will set the chordal deviation parameters and create the mesh.（在這一步中，您將設置弦偏差參數并創建網格）。
Note: To cycle through the parameter settings, press the Tab key after typing in a value.（注:輸入數值后按Tab鍵循環參數設置。）
The mesh is created.
Step 4. Set the Chordal Deviation Parameters, Part 2(步驟4。設置弦偏差參數，第2部分)
In this step you will set the chordal deviation parameters and create the mesh.
You will use the same chordal deviation settings from the previous step, but reducethe maximum angle parameter to compare the effects.（您將使用與上一步相同的弦偏差設置，但減少最大角度參數來比較效果。）
The mesh is created on the surfaces.
Step 5. Set the Chordal Deviation Parameters, Part 3
In this step you will set the chordal deviation parameters and create the mesh.You will use the same chordal deviation parameters from the previous step except for the maximum element size parameter. The maximum element size parameter is increased to allow the algorithm to create larger and fewer elements along planer and less curved surface edges.（在這一步中，您將設置弦偏差參數并創建網格。除了最大單元尺寸參數外，您將使用與上一步相同的弦偏差參數。增加了最大元素尺寸參數，以允許算法沿著平面和更少的曲面邊緣創建更大和更少的元素。）
補充
Hypermesh使用最小邊界偏差（edge deviation）命令提高曲線處網格劃分精度
有曲線邊界的面在劃分網格之后，網格和原來的邊界通常具有明顯的偏差。當幾何體在一條線上有很大的曲率時，這個偏差尤其明顯。造成這種偏差的原因是所有的單元邊界都是直線的。因此，只有畫出更細密的單元才能使網格的邊界和原有的幾何邊界更加貼合。
HyperMesh提供了一種處理這類問題的方法。用戶可以通過控制沿著曲面邊界的單元的生成方式來，減少邊界上的偏差。此功能可以通過automesh中的edge deviation子面板來實現。
edge deviation中的控制參數主要有以下幾個：
Min elem size: HyperMesh 創建的最小單元；
Max elem size: HyperMesh 創建的最大單元；
Max deviation : 指定網格和曲面邊界的最大偏差值，HyperMesh 會自動編輯節點和單元來滿足指定的條件；
Max angle: 指定相鄰兩個單元件的最大夾角值，HyperMesh會自動編輯節點和單元來滿足設定的條件。
上述問題也可以手動在邊界上添加點，通過控制這些點的數量來控制網格非常接近原有的邊界。要創建這些點，點擊Geom>point edit>add 選擇 on edge 并輸入想要創建的點的數目，或者創建網格時手動調整邊上所創建節點的數量。創建點的數目越多，網格和曲面的貼合程度就更高。
對于曲面也可以使用Surface Deviation來提高網格與曲面的貼合度，關于Hypermesh中Surface Deviation命令的使用方法可參考文章《hypermesh二維面網格局部加密細化》
HM-3130: QI Mesh Creation
HyperMesh has a set of features designed to help you achieve good element quality more efficiently.(HyperMesh有一組功能，旨在幫助您更有效地實現良好的元素質量。)
These features use settings from the Quality index panel to generate or modify a mesh This allows HyperMesh to give results that account you’re your preferences for which element quality checks are more or less important than others. The quality index (Q.I.) optimization features are found in the Auto mesh, Smooth, and Quality index panels. You can use these functions separately or in unison.(這些特性使用Quality索引面板的設置來生成或修改網格。這使得HyperMesh能夠根據你的喜好給出結果，對于哪些元素質量檢查比其他元素更重要或更不重要。質量指數(q.i)優化特征可以在Auto網格、Smooth和quality指數面板中找到。這些功能可以單獨使用，也可以同時使用。)
In this tutorial you will learn how to create and optimize a 2D mesh based on user-defined quality criteria.(在本教程中，您將學習如何創建和優化基于用戶定義的質量標準的2D網格。)
Step 1. Open the Model File
In this step you will open the model file, planar.hm.
Step 2. Work with Node and Element Optimization(步驟2。與節點和元素優化工作**)
Within the quality index panel, there are tools you can use to select individual nodes or elements, and then alter the position or shape of the node/element to optimize the element quality for the surrounding elements. The element qualities are optimized according to the settings in the quality index panel. These features are very useful for improving element qualities in local areas of the mesh.(在質量索引面板中，有一些工具可以用來選擇單獨的節點或元素，然后改變節點/元素的位置或形狀，以優化周圍元素的元素質量。根據質量指標面板中的設置優化元素質量。這些特征對于改善網格局部區域的單元質量非常有用。)
Open the quality index panel by clicking Mesh > Check > Elements > Quality Index from the menu bar, or by selecting quality index from the 2D page.
On the right-hand side of the panel, note the value for comp. Q.I.=. It should read 85.09.
Note: Keep this number in mind so that you can judge how much progress you make in improving the element quality.
Click cleanup tools.
Open the quality index panel by clicking Mesh > Check > Elements > Quality Index from the menu bar, **or by selecting quality index from the 2D page. **
option | Description---------------------|------------------------------------------------------------------radial (徑向) | Use this option to alter the radius of a hole (and, optionally, the washer)To alter the radius of the hole, click and drag a node in the graphics area. The element orientation remains constant, but the hole may become larger or smaller based on the input. There are additionalcontrols to enable or disable automatic remeshing when altering the hole dimensions.(使用此選項可以改變孔的半徑(以及，可選的墊圈)。若要改變孔的半徑，請在圖形區單擊并拖動節點。元件的方向保持不變，但是孔可能會根據輸入的大小而變大或變小。當改變孔尺寸時，還有額外的控制來啟用或禁用自動重網格。)
Note: Keep this number in mind so that you can judge how much progress you make in improving the element quality.（記住這個數字，這樣您就可以判斷您在改進元素質量方面取得了多大的進展。）
The QI criteria is replaced by a series of yellow buttons, each representing a tool for element cleanup.
HM-3140: Batch Meshing (批處理劃分網格)
BatchMesher is a tool that can perform geometry cleanup and automeshing (in batch mode) for given CAD files. BatchMesher performs a variety of geometry cleanup operations to improve the quality of the mesh created for the selected element size and type. Cleanup operations include: equivalencing of “red” free edges, fixing small surfaces (relative to the element size), and detecting features.（BatchMesher是一個工具，可以執行幾何清理和自動化給定的CAD文件(批處理模式)。BatchMesher執行各種幾何清理操作，以提高為所選元素大小和類型創建的網格的質量。清理操作包括:等效“紅色”自由邊，固定小表面(相對于元素大小)，和檢測特征）
BatchMesher also performs specified surface editing/defeaturing operations such as: removal of pinholes (less than specified size), removal of edge fillets, and addition of a layer of washer elements around holes.（BatchMesher還執行指定的表面編輯/變形操作，如:去除針孔(小于指定尺寸)，去除邊緣圓角，并在孔周圍添加一層墊圈元素。）
All user-defined criteria determines the quality index (QI) of a model. The QI value is used to assess the potential of each geometry cleanup and meshing tool, and apply them accordingly. QI optimized meshing and node placement optimization are performed to obtain the best quality meshing. Final results are stored in a HyperMesh database file.（所有用戶定義的標準都決定模型的質量指數(QI)。QI值用于評估每種幾何清理和網格劃分工具的潛力，并相應地應用它們。通過QI優化網格劃分和節點布局優化，獲得最佳網格劃分質量。最終結果存儲在HyperMesh數據庫文件中。）
In this tutorial you will learn how to:
1.Define a configuration for the batch mesh（定義批處理網格的配置）
2.Edit the criteria and parameter files（編輯標準和參數文件）
3.Set up a simple user procedure for a post-batch mesh run（建立一個簡單的用戶程序后批量網格運行）
This exercise uses the following files found in the hm.zip file. Copy the files from this directory to your working directory.
- part1.hm
- part2.hm
- bm_housing.hm
- bm_housing.criteria
- bm_housing.param
- bm_housing.tc
Step 1Start BatchMesher
In this step you will start BatchMesher.
on Windows, click on the Start menu All Programs > Altair HyperWorks > BatchMesher, or type hw_batchmesh with the full path, ~altairhome\hm\batchmesh\hw_batchmesh.
on Unix, type the hw_batchmesh command to invoke the user interface or hw_batchmesh - noqui… to perform the batch mesh without a user interface.
In the Input model directory field, click and navigate to your working directory.
Note: In this exercise you will use files located in the hm.zip file.
In the Output directory, click and navigate to the appropriate directory if different from the Input model directory.
Optional: Move all of the .hm output files to the corresponding directory of the input model by selecting the Relocate .hm files to input model directory checkbox.
5 On the right-hand side of BatchMesher, click .
The Select Model Files dialog appears.
6.From the Type of Geometry list, select the appropriate CAD data type. For this tutorial, use the geometry already loaded in HyperMesh, therefore select HyperMesh.
==Note: ==A filter will help select applicable HyperMesh models for batch meshing.
7.Select the following model files: part1.hm, part2.hm, and bm_housing.hm.
Note: Select multiple files by pressing Ctrl while selecting files.
Click Select.
總結
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