PATRAN中如何修补模型间隙

1、WORKSHOP 8 SURFACE MESHING FOR NONCONGRUENT SURFACES .2 Workshop 8 Surface Mesh For Noncongruent Surfaces .3 nObjectives uImport geometric surfaces from a MSC.Patran neutral file. uObserve the many gaps between adjacent surface edges. uMesh the surfaces with tria elements, then connect elements wher

2、e there are internal free element edges. uCreate a geometric surface from the tria mesh. uMesh the new surface. Workshop 8 Surface Mesh For Noncongruent Surfaces .4 nProblem Description uTo create a finite element model for several geometric components (for this case multiple surfaces; see below) it

3、 is necessary to connect adjacent elements (e.g. Equivalence) at geometric interfaces. When there are gaps (larger than the tolerance (*), or difference of vertices (*) at interfaces it is more difficult to connect the elements. One way to deal with this is to create a triangular (tria) element mesh

4、 for each of the geometric entities, “sew” (equivalence) the regions where there are no elements, then create a single geometric surface from all the tria elements. Finally, delete the tria element mesh, and create a 2-D mesh (e.g. Quad4) by meshing the single surface obtained from the tria element

5、mesh. * * Workshop 8 Surface Mesh For Noncongruent Surfaces .5 nSuggested Exercise Steps n Create a Database. n Import a MSC.Patran neutral file with surfaces. n Show the distance between two points. n Create 2-D mesh. n Close gaps between adjacent tria elements. n Look at element free edge boundari

6、es. n Delete original geometry and create new surface. 1. Mesh new surface. Workshop 8 Surface Mesh For Noncongruent Surfaces .6 Step 1. Create a Database Create a new database named shell. n File / New. n Enter shell as the file name. n Click OK. n Select Default under tolerance. n Select MSC.Nastr

7、an as Analysis Code. n Select Structural as Analysis Type. n Click OK. a b d c f e g .7 Step 2. Import a MSC.Patran Neutral File With Surfaces Import the neutral file called shell_prt.out.1. n File / Import. n Select Neutral as Source. n Locate the file named non_cong_surfs.out. n Click Apply. n Cli

8、ck Yes. n Click Yes. a b c d e f .8 This is what the imported surfaces should look like. Look at the gaps Step 2. Import an MSC.Patran Neutral File With Surfaces (Cont.) .9 Step 3. Show the Distance Between two Points Determine the distance between two adjacent points. This will help in the determin

9、ation of the value of the global edge length for subsequent Paver meshing. n Geometry: Show / Point / Distance. n Select Point 231 under First Point List. n Select Point 370 under Second Point List. a. Click Apply. a c c b b d .10 Step 4. Create 2-D Mesh Create 2-D mesh using Paver for set of surfac

10、es. Elements: Create / Mesh / Surface. Select Tria, Paver, and Tria3. Uncheck Automatic Calculation. Enter 2.0 as Global Edge Length. Select all surfaces for Surface List. Click Apply. a b c d e f .11 Step 5. Close Gaps Between Adjacent Tria Elements Close the gaps in the model by “sewing” the mesh

11、together.The “Sew” command is similar to Equivalence. Elements: Modify / Mesh / Sew. Enter 6.0 as Target Element Edge Length. Click on Tria Element List and select all elements. Click Apply. a b c d .12 Step 6. Look at Element Free Edge Boundaries Show where the element free edges are Elements: Veri

12、fy / Element / Boundaries Select Free Edges as Display Type. Click Apply. a b c .13 Step 7. Delete Original Geometry and Create New Surface Delete the original geometry for visual clarity, and create a surface from the existing 2-D tria mesh with a gap/hole. n Geometry: Delete / Surface. n Click on

13、Surface List and select all surfaces. n Click Apply. n Geometry: Create / Surface / Mesh. n Check Delete Original Elements. n Click on Elements List and select all elements. n Choose None for Inner Loop Options. n Choose Fast for Surface Creation Methods. a. Click Apply. a b c d e f g h i .14 This is what the new surface should look like. Step 7. Delete Original Geometry and Create New Surface (Cont.) .15 Step 8. Mesh New Surface Mesh the surface just created using Quad4 elements. Elements: Create / Mesh / Surface. Select Qua