hmintrosdayPPT学习教案

1、会计学1 hmintrosdayPPT课件课件 or the “interior” of a surface nSeparates surface edges from each other nForces a node to be placed at that location during meshing nSurface edge nLine associated with a surface nDefines a surfaces boundary nCannot be moved off the surface nHas a fixed point on both ends Surf

2、ace 第1页/共53页 Topology” is how surfaces connect to adjacent surfaces of a part Surface connectivity is controlled by the associated surface edges If a surface edge is associated with more than 1 surface, those surfaces are considered to be connected (“equivalenced”) Surface edges are categorized, nam

3、ed, and colored according to the number of associated surfaces: Free edge (red) Associated with only 1 surface Surfaces with a free edge between them are NOT equivalenced at that edge Shared edge (green) Associated with 2 surfaces Surfaces are equivalenced Suppressed edge (blue) Surfaces are treated

4、 as though combined into 1 surface T-junction edge (yellow) Associated with 3 or more surfaces Example: surfaces forming a T-connection Surfaces are equivalenced 第2页/共53页 AutoDefault (topology display in only default panels mentioned above) By CompAlways in component color mode By TopoAlways in topo

5、logy display mode By 2D TopoDisplays only 2D geometry in topology display mode By 3D TopoDisplays only 3D geometry in topology display mode MixedDisplays 2D and 3D geometry in topology display mode 第3页/共53页 第4页/共53页 n correcting connectivity errors between adjacent surfaces nPossible errors include:

6、 nUnconnected adjacent surfaces nDuplicate surfaces nMissing surfaces The Goal of Topology Repair: Restore the surface data to a perfectly clean representation of the part 第5页/共53页 Missing surface created Example: Free edge pair equivalenced Duplicate surface deleted 第6页/共53页 nPoint Edit Panel nRepl

7、ace (1 edge at a time) nRelease Combine pairs of free edges with gaps between them into a shared edges nDefeature Panel nDuplicates Identify and delete duplicate surfaces within a user specified tolerance nSurfaces Panel nSpline / filler Select lines / surface edges to recreate any missing surfaces

8、第7页/共53页 nFiller surf Select a line on a free surface edge to recreate any missing surfaces nDelete surf Same as delete panel (surfaces only) nReplace point Same as point edit panel; move/retain point nRelease point Same as point edit panel; must be associated with line 第8页/共53页 nCan change value mu

9、ltiple times for work on various areas of the model nUse topology display tools to decide what needs to be cleaned nUse equivalence to combine as many free edge pairs as possible nMake sure surfaces are not collapsed in undesirable manner nUse toggle to combine any remaining free edge pairs, 1 by 1

10、nuse replace function if more control is needed nUse find duplicates to check for any duplicate surfaces and delete them nUse filler surface to recreate any missing surfaces 第9页/共53页 For many FE analyses, parts are represented by shell elements Thickness is assigned mathematically, rather than geome

11、trically Mesh is usually placed on the midplane of the part CAD geometry usually comes as a solid part, or a series of surfaces defining a volume. Midsurfacing creates a layer of surfaces on the midplane which can be directly meshed 第10页/共53页 Midsurfaces can be created using midsurface panel on the

12、geom page Auto Midsurface Automatically extracts midsurfaces from surfaces that enclose a volume or a solid geometry Can sometimes work if there are missing surfaces The greater number of missing surfaces, the less reliable the result Surface Pair creates a midsurface between 2 selected surfaces 第11

13、页/共53页 Once a midsurface has been created, it can be modified using tools on the midsurface panel Quick Edit Repair a midsurface by correcting where the verticies of the surface were placed Assign Target An extension to quick edit, and functions in a similar fashion Replace Edge Fill in gaps and sli

14、vers by combining one surface edge with another same as in the edge edit panel Extend Surface Extends two surfaces (e.g., ribs) until they intersect View Thickness Review of the thickness of a midsurface using white lines (probes) extending from each vertex of the surface 第12页/共53页 1.Obtain a closed

15、 volume of surfaces or solids Midsurface : auto midsurface requires an enclosed volume Use topology repair techniques if needed 2.For complex parts, try defeaturing the surface defining the volume This simplifies the part and may give better results with create : solid 3.Generate the midsurface usin

16、g midsurface : auto midsurface Use surface pair for areas that need more control Use midsurface : editing tools for midsurfaces that need fine tuning 4.View the midsurface and correct errors using the midsurface editing functionalities Can generally use quick edit 第13页/共53页 Depending on the analysis

17、, certain details in the geometry may be ignored. This may depend on: Importance of the part in the overall assembly Location of the feature relative to the area of interest in the analysis Size of the feature vs. the average size of the mesh being used Defeaturing is the removal of details in the g

18、eometry in order to make the shape of the part simpler Surface fillet Pinhole s Edge fillets 第14页/共53页 Defeature panel on Geom page Pinholes:Searches for closed loops of free edges (holes) within a surface Fills in the holes Leaves fixed point at the center Surf Fillets: Searches for surfaces that a

19、ct as fillet between other surfaces Tangentially extends them to form a sharp corner Edge fillets: Searches for rounded corners on a surface Squares off the corner Duplicate s: Finds and deletes duplicate surfaces Symmetry : Finds symmetric surfaces within a single component Deletes or organizes the

20、 surfaces into different components 第15页/共53页 “Topology refinement” is modifying topology in order to obtain a quality mesh Unlike defeaturing, this generally does not change the shape of the part CAD geometry has topology details that interfere with mesh quality Edges are created where ever there i

21、s a change in surface curvature Even smooth areas can be split into several faces The automesher will be forced to place nodes along the edges and fixed points This may cause small element lengths, angles, aspect ratios, etc. depending on the shape of the model CAD geometry can also have surfaces wi

22、th a complex outline Highly complex shapes can make it hard to get a quality mesh Adding in edges splits the surfaces into smaller and simpler regions which can be meshed easier Fixed points can be added in to force a node to be placed at that location, giving more control 第16页/共53页 Suppressin g edg

23、es Adding edges Removing fixed points Adding fixed points Replacing fixed points AfterBefore 第17页/共53页 nSuppress Removes unwanted fixed points nReplace Combines 2 fixed points together at a single location nProject Projects fixed points onto a nearby edge nUseful for aligning mesh between 2 edges nS

24、urface edit All functions add edges by cutting surfaces nAdding edges can be useful for controlling mesh patterns in large areas nTrim with nodes Uses node locations to cut surfaces nTrim with lines Uses lines to cut surfaces nTrim with surfs/plane uses other surfaces or a defined plane to cut surfa

25、ces 第18页/共53页 第19页/共53页 nProject point Same as edge edit panel 第20页/共53页 Mesh the part Visually scan the part to look for poor mesh patterns Use element checks in order to find areas of poor element quality Check elems panel, QI Panel, etc. Suppress edges with edge edit :(un)suppress Use various set

26、tings for break angle to suppress many edges at once Sometimes suppressing all edges and then unsuppressing desired edges can be a good method. Suppress all the fixed points before add more in Gets rid of as many fixed points as possible, leaving ones that are required Experiment! There is no set pr

27、ocess, so experience is a key factor in refining topology 第21页/共53页 nTetra meshing (3D : tetramesh : volume tetra sub-panel) nEspecially helpful when dividing a part into multiple volumes nA part can be divided into multiple, connected solids nThe connection between adjacent solids (topology) can maintain the connectivity of mesh nAids visualization when dividing a part into simple, mappable regions (used in hexa meshing) 第22页/共53页 Fixed Points Selectable as points Lie at the ends of edges Solid faces Selectable as surfaces Bounding Faces Green Belong to 1 solid Partition Faces