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1、几何清理在进行有限元分析计算时，常常碰到的问题有以下几种：1. 导入曲面数据时，有时存在裂缝、重叠、错位等缺点，这会阻碍网格质 量。2. 因为生产的需要，CAD模型中通常会包括某些细微特点，例如曲面和边 的倒圆、小孔，进行分析时若是要准确模拟这些特点，需要用到很多小单元，致 使求解时刻没必要要的加长。3. 边界错位常常引发网格扭曲，致使单元质量不高，求解精度差。通过排除错位和小孔，紧缩相邻曲面之间的边界，排除没必要要的细节，就 能够够提高整个划分网格的速度和质量，提高计算精度。曲面边界的拓扑关系显示:唇饵U.U凸irnBy T op。5 BCji i|.下（这是在geom cleanup面板中
2、默许的显示By 2D T Dpo 一 Dy 3D TDpo 在拓扑显示模式比一心；T模式），曲面边界的颜色显示是由其与周围曲面边界的连接关系来确信的。1）红色的边表示单个曲面的自由边。自由边会致使网格的不持续，即自由 边上散布的节点可不能被相邻曲面上的单元所共享。2）绿色的边称为共享边，表示那个边被两个相邻曲面所共享，在共享边上 的节点同属于相邻的曲面。3）黄色的边称为非重合边。表示曲面的边界被三个或三个以上的曲面所共 享，这通常代表一种T型连接或重复曲面。（只是关于黄线的问题，要分情形对待。 若是是重复曲面，应该设法删除，对可能由此造成的缺面问题，采纳补面的方式。若是题 形连接，那么有可能是
3、正常的。）4）深蓝色的短线段代表被紧缩的边。自动网格生成器在划分网格时会忽略 被紧缩边，可不能在上面布置节点。在紧缩边上，两个相邻的曲面事实上被缝合 到一路形成一个较大的曲面。几何清理经常使用面板1）surface面板的spline/filler子面板用于填充曲面之间较大的间隙和空缺。 对任意由三个或更多的线、节点或点概念组成的有限区域，都能够概念一个曲面;2）edge edit和defeature面板用于划分网格前的曲面几何清理；3）edge edit用来改变表面边界之间的连通性状态；4）defeature面板用于修剪表面，找到并删除小孔，还能够找到并去除表面 和表面边界上的倒角。r rul
4、ed(* spline/filler L skin - drag/spin r from FE一、surface 面板的 spline/filler 子面板 r fillets用于从线、节点或固定点生成曲面来填充CAD模型中的孔，通过选择围绕 某个区域的三个或更多的线、节点或点，能够创建一个曲面。另外，能够利用ruled(第一项)或spline/filler (第二项)进行补面。鼻 toggle 广(un)suppress replnce 厂 equivalenceunplit一 , A,对M2、edge edit 面板 :-by fealu-e用来改变表面边界之间的连通性状态，有四种不同的工
5、具：toggle, replace, (un)suppress 和 equivalenceotoggletoggle菜单能够通过在边界上单击鼠标左键将其从自由边变成共享边，或从 共享边变成紧缩边。利用鼠标右键能够取消toggle操作，并将紧缩边变成共享边， 或将共享边变成自由边。要将一条自由边变成共享边，在这条自由边周围的容差 范围内必需有一条对应的自由边。replacereplace菜单能够将一对自由边归并成共享边，可是归并后的共享边的位置 是在设定的被保留的边上，而另一条边那么被删除。这一功能事实上扩展了 toggle的操纵功能。任何与被删除的边相关连的几何特点被关连到被保留的边 上。(u
6、n)suppress(un)suppress菜单许诺同时紧缩或释放多条边。在那个菜单能够利用扩展的 线条选择菜单，能够利用多种线条选择方式。若是需要排除在由对称方式生成曲 面时产生的裂缝，该功能超级有效。equivalenceequivalence菜单能够自动识别并归并多个自由边对。L pinholesL surf fillets- edge fillets(* duplicates3、defeature 面板 rpinholes功能用于查找和删除曲面内的孔。孔依照孔径来识别。一旦确信， 孔能够被删除。孔能够是任何形状。所给定的直径确信孔跨度的最大距离。duplicates菜单用于识别和删除重
7、合曲面。surface filletssurface fillet用于排除曲面倒圆或两个非共面曲面之间的过渡圆滑曲面。曲 面倒圆将被一个沿相邻曲面切向延伸的平面替代。通过选择倒圆的轮廓线，或指 定曲面和倒圆半径的范围来确信倒圆曲面。edge filletsedge fillet用于删除曲面自由边上的任何倒圆。HyperMesh能确信给定圆角 半径和最小圆弧角度范围内的倒圆。边的倒圆将被确信，标明那些投影出方角的 切点。一旦确信，边的倒圆在被删除前能够被解除选择。4、Delete 面板几何清理实例Step 1: Open and view the model fileStep 2: View t
8、he model in topology display toolbar and shaded mode to evaluate its integrity.s By CompBy2DTDPo新 Eiy 3D T 叩口Go to the autocleanup panel 或-r-一、Note that the surface edges are now colored according to their topology status. Thisiijtntoccurs because Geometry Color is set to auto ().W二、Click Visualizat
9、ion () and navigate to the Topology tab3、Clear all the check boxes except the Free check boxOnly the free edges should be displayed at this point.4、Observe the free edges and make note of where they areThe free (red) edges show where there is incorrect connectivity or gaps.五、Note the locations where
10、 there are closed loops of free edges. These are locations that probably have missing surfaces.六、Select only the Non-manifoldcheck box.7、Observe the non-manifold edges and make note of where they are.The non-manifold edges show where there are more than two surfaces sharing an edge, which might indi
11、cate incorrect connectivity. For this part, there are yellow edges completely surrounding two areas. This indicates that there are probably duplicate surfaces in these locations.八、Select all the check boxes. SuiTacf! iwerhsrigiiritj art edqe九、Click Shaded Geometry and Surface Edges (J)The surfaces s
12、hould now appear solid rather than having only their edges displayed.A surface that overhangs a round corner; A missing surfaceStep 3: Delete the surface that overhangs the round corner.1、Enter the Delete panel in one of the following ways:1) From the Geometry menu, point to Delete and click Surface
13、2) Press F22、In the graphics area, select the overhanging surface shown in the previous figure.3、Click delete entity and click return.Step 4: Create surfaces to fill large gaps in the model.一、Access the surfaces panel.二、Access the spline/filler sub-panel.3、Clear the keep tangency check box.The keep
14、tangency option examines surfaces attached to the selected edges and tries to create a surface tangent to them. This helps to form a smooth transition to the surrounding surfaces.4、Verify the entity type is set to lines.五、Verify the auto create (free edges) check box is selected.The auto create opti
15、on simplifies the selection of the lines bounding the missing surface. Once a line is selected, HyperMesh automatically selects the remaining free edges that form a closed loop, and then create the filler surface.Ml样的六、Pick one of the red lines bounding one of the gaps (missing surfaces).HyperMesh a
16、utomatically creates a filler surface to close the hole.Step 5: Set the global geometry cleanup tolerance to .01.一、Press O to go to the options panel二、Go to the geometry sub-panel.3、In the cleanup tol = field, type to stitch the surfaces with a gap less than .Step6: Combine multiple free edge pairs
17、at one time with the equivalence tool.一、Enter the edge edit panel in one of the following ways:From the Menu Bar, select Geometry, then Edit, then edgeFrom the main menu, select Geom Page, then choose Edge Edit二、Go to the equivalence sub-panel.3、Activate the equiv free edges only check box.4、Select
18、surfs all.五、Verify that the cleanup tol= is set to , which is the global cleanup tolerance specified in the options panel.六、Click the green equivalence button to combine any free edge pairs within the specified cleanup tolerance.Most of the red free edges are combined into green shared edges. The fe
19、w remaining are caused by gaps larger than the cleanup tolerance.Step 7: Combine free edge pairs, one pair at a time, using the toggle.一、Go to the toggle sub-panel.二、In the cleanup tol = field, type .3、In the graphics area, click one of the free edges shown in the following image.4、Rotate and zoom i
20、nto the area if needed. When the edge is selected, it will change from red to green, indicating that the free edge pair has been equivalenced.Free !he toggleclStep 8: Combine the remaining free edge pair using replace.一、Go to the replace sub-panel.二、Click user views ().3、Click restorel to bring back
21、 the saved view.4、With the selector under moved edge: active, click the leftmost free edge in the graphics area.Verify that the selector under retained edge: is now active.五、Select the rightmost red edge.六、In the cleanup tol = field, enter7、Click replace.Once the line is selected, HyperMesh posts a
22、message similar to:“Gap = (.200018). Do you still wish to toggle?八、Click Yes to close the gap.Edges to retain and rerftove for replacementStep 9: Find and delete all duplicate surfaces.You should still be in the geom cleanup panel.一、Access the Defeature panel in one of the following ways:From the Me
23、nu Bar, choose Geometry, then DefeatureFrom the main menu, choose Geom Page, then Defeature、Go to the duplicates sub-panel.3、Select surfaces displayed.4、In the cleanup tol = field, type .五、Click find.The status bar displays the following message, 2 surfaces are duplicated六、Click delete to remove any
24、 duplicate surfacesStep 10: Observe the model again to identify any remaining free edges, or missing or duplicate surfaces.Use the topology display and shaded modes to perform this task. All of the edges in the model should be displayed as green shared edges, indicating that we have a completely enclosed thin solid part.Step 11 (Optional): Save your work.
