Hypermesh几何清理的资料.doc

几何清理在进行有限元分析计算时，经常遇到的问题有以下几种： 1. 导入曲面数据时，有时存在缝隙、重叠、错位等缺陷，这会影响网格质量。 2. 因为生产的需要，CAD模型中通常会包含某些细微特征，例如曲面和边的倒圆、小孔，进行分析时如果要准确模拟这些特征，需要用到很多小单元，导致求解时间不必要的加长。 3. 边界错位经常引起网格扭曲，导致单元质量不高，求解精度差。 通过消除错位和小孔，压缩相邻曲面之间的边界，消除不必要的细节，就能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 在拓扑显示模式下（这是在geom cleanup面板中默认的显示模式），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定的。 1）红色的边表示单个曲面的自由边。自由边会导致网格的不连续，即自由边上分布的节点不会被相邻曲面上的单元所共享。 2）绿色的边称为共享边，表示这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型连接或者重复曲面。（不过关于黄线的问题，要分情况对待。如果是重复曲面，应该设法删除，对可能由此造成的缺面问题，采用补面的方式。如果是T形连接，则有可能是正常的。）4）深蓝色的短线段代表被压缩的边。自动网格生成器在划分网格时会忽略被压缩边，不会在上面布置节点。在压缩边上，两个相邻的曲面实际上被缝合到一起形成一个较大的曲面。几何清理常用面板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、节点或者点定义组成的有限区域，都可以定义一个曲面；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，还可以找到并去除表面和表面边界上的倒角。1、surface面板的spline/filler子面板用于从线、节点或固定点生成曲面来填充CAD模型中的孔，通过选择环绕某个区域的三个或更多的线、节点或点，可以创建一个曲面。另外，可以使用ruled(第一项) 或 spline/filler（第二项）进行补面。2、edge edit面板用来改变表面边界之间的连通性状态，有四种不同的工具：toggle, replace, (un)suppress 和equivalence。toggle toggle菜单可以通过在边界上单击鼠标左键将其从自由边变成共享边，或者从共享边变成压缩边。使用鼠标右键可以取消toggle操作，并将压缩边变为共享边，或将共享边变成自由边。要将一条自由边变成共享边，在这条自由边附近的容差范围内必须有一条对应的自由边。 replace replace菜单可以将一对自由边合并成共享边，但是合并后的共享边的位置是在设定的被保留的边上，而另一条边则被删除。这一功能实际上扩展了toggle的控制功能。任何与被删除的边相关连的几何特征被关连到被保留的边上。 (un)suppress (un)suppress菜单允许同时压缩或释放多条边。在这个菜单可以使用扩展的线条选择菜单，可以使用多种线条选择方式。如果需要消除在由对称方式生成曲面时产生的缝隙，该功能非常有用。equivalence equivalence菜单可以自动识别并合并多个自由边对。 3、defeature 面板pinholes功能用于查找和删除曲面内的孔。孔根据孔径来识别。一旦确定， 孔可以被删除。孔可以是任何形状。所给定的直径确定孔跨度的最大距离。duplicates菜单用于识别和删除重合曲面。surface fillets surface fillet用于消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，或者指定曲面和倒圆半径的范围来确定倒圆曲面。 edge fillets edge fillet用于删除曲面自由边上的任何倒圆。HyperMesh能确定给定圆角半径和最小圆弧角度范围内的倒圆。边的倒圆将被确定，标明那些投影出方角的切点。一旦确定，边的倒圆在被删除前可以被解除选择。4、Delete面板几何清理实例Step 1: Open and view the model fileStep 2: View the model in topology display toolbar and shaded mode to evaluate its integrity.Go to the autocleanup panel或 1、Note that the surface edges are now colored according to their topology status. This occurs because Geometry Color is set to auto (). 2、Click Visualization () 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.5、Note the locations where there are closed loops of free edges. These are locations that probably have missing surfaces.6、Select only the Non-manifold check 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 indicate incorrect connectivity. For this part, there are yellow edges completely surrounding two areas. This indicates that there are probably duplicate surfaces in these locations.8、Select all the check boxes.9、Click Shaded Geometry and Surface Edges ()The surfaces should 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 Surface2） 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.1、Access the surfaces panel.2、Access the spline/filler sub-panel.3、Clear the keep tangency check box.The keep 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.5、Verify the auto create (free edges) check box is selected.The auto create option 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.6、Pick one of the red lines bounding one of the gaps (missing surfaces).HyperMesh automatically creates a filler surface to close the hole. Step 5: Set the global geometry cleanup tolerance to .01.1、Press O to go to the options panel2、Go to the geometry sub-panel.3、In the cleanup tol = field, type 0.01 to stitch the surfaces with a gap less than 0.01.Step6: Combine multiple free edge pairs at one time with the equivalence tool.1、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 Edit2、Go to the equivalence sub-panel.3、Activate the equiv free edges only check box.4、Select surfs all.5、Verify that the cleanup tol= is set to 0.01, which is the global cleanup tolerance specified in the options panel.6、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 few remaining are caused by gaps larger than the cleanup tolerance.Step 7: Combine free edge pairs, one pair at a time, using the toggle.1、Go to the toggle sub-panel.2、In the cleanup tol = field, type 0.1.3、In the graphics area, click one of the free edges shown in the following image.4、Rotate and zoom into 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.Step 8: Combine the remaining free edge pair using replace.1、Go to the replace sub-panel.2、Click user views ().3、Click restore1 to bring back 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. 5、Select the rightmost red edge.6、In the cleanup tol = field, enter 0.17、Click replace.Once the line is selected, HyperMesh posts a message similar to:Gap = (.200018). Do you still wish to toggle?8、Click Yes to close the gap.Step 9: Find and delete all duplicate surfaces.You should still be in the geom cleanup panel.1、Access the Defeature panel in one of the fo