compostie surface

WS2-1PAT302, Workshop 2, December 2004Copyright2004 MSC.Software Corporation

WORKSHOP 2

COMPOSITE SURFACES


Problem Description In this exercise a CAD(IGES) file for a plate structure is imported into

a database. However, the translation leads to gaps anddiscontinuities in the geometric model. In order to create a suitablemesh for analysis the geometry needs to be “cleaned up”. This iswhere the concept of composite surfaces is introduced.

Combine the disjoint(non-congruent) surfaces, which represent theplate structure, to create a set of composite surfaces. Mesh seedswill be created on the edges of the composite surfaces. Finally, thesurfaces will be meshed.


Suggested Exercise Steps1. Create a new database called composite_surfaces.db.2. Import the surface geometry from an IGES file.3. Check the model for geometric incongruencies.4. Formulate the procedure for creating the composite surfaces for the model.5. Change the picking preferences.6. Create the composite surface for the first quarter of the model.7. Create the second composite surface.8. Create a third composite surface.9. Change the picking preferences back to the original settings.10. Create the final composite surface.11. Determine where the internal surface free edges are.12. Create the mesh seeds.13. Mesh the composite surfaces.14. Connect elements by equivalencing.15. Change the lighting and display options.16. Display only the composite surfaces.


Step 1. Create a New Database

Create a new database calledcomposite_surfaces.db and set thenew model preferences.

a. Click on the File New icon.b. Enter composite_surfaces

for the file name and click OK.c. Select the Based on Model

toggle under Tolerance.d. Set the Approximate Maximum

Model Dimension to 10.0.e. Make sure that the Analysis

Code and Analysis Type areset to MSC.Nastran andStructural, respectively.

f. Click OK.

b

c

d

e

f

a


Step 2. Import the Surface Geometry

Import the IGES file callednon_cong_surfs.igs and changethe display and view to get a betterrepresentation of the model.

a. File : Import…b. Select non_cong_surfs.igs.c. Click on Apply.d. Click OK when IGES Report

Summary Appears.e. Click on the Iso 1 View icon.f. Click on the Smooth Shaded

icon.g. Click on the Fit View icon.

a

b

c

d

efg


Step 2. Import the Surface Geometry

Illustrated here is the imported surfacegeometry.


Step 3. Check the Model for Geometric Incongruencies

Check the model for geometricincongruencies by verifying thesurface boundaries.

a. Click on the Wireframe viewicon.

b. Geometry : Verify / Surface/ Boundary.

c. Make sure that theTopology toggle is setunder Verification Criteria.

d. Under Surface List, selectthe entire model.

e. Click Apply.

A warning message willappear in the historywindow stating that freeedges and/or non-manifold edges exist

a

b

c

d

e


Step 4. Formulate Procedure for Creating Composite Surfaces

Observations From the markers displayed on the interior of the model it can be

seen that there exists a non-congruency problem which will affect thecongruency of the meshes. That is, the meshes will not becompatible at adjacent boundary interfaces of the non-congruentsurfaces.

This problem can be dealt with by using composite surfaces inMSC.Patran. To do this a set of several surfaces is combined into anew simple or trimmed surface whose perimeter is identical to theoriginal set of surfaces. A plan has to be developed to usecomposite surfaces. The follow steps outline this plan.


Step 4. Formulate Procedure for Creating Composite Surfaces (Cont.)

Composite Surface Outline The model is to be divided into four quarters(labeled below). The

surfaces in each of the quarters are to be used to construct a singlecomposite surface for each quarter of the model. The four compositesurfaces are then to be meshed, and the elements connected byequivalencing, creating a single congruent mesh that can be used forperforming an analysis.

Also, because there are no surfaces edges interior to a compositesurface when the composite surface is meshed the created nodes donot have to follow interior edges or vertices.

12

4 3


Step 5. Change the Picking Preferences

Change the Picking Preferences.a. Preferences : Pickingb. Under Single Picking, make

sure that Entity is selected.c. Under Rectangle/Polygon

Picking, select Enclose entireentity.

d. Select Cycle picking formand Horizontal select menus.

e. Under Preselection Settings,select Entity Highlighting.

f. Click on Close.g. Click on the Front View icon.

a

b

c

d

e

f

g


Step 6. Create the first Composite Surface

Create the first composite surface.a. Geometry : Create /

Surface / Composite.b. Select the toggle for Delete

Constituent Surfaces.c. Under Surface List, select

the upper right quarter ofthe model (i.e section 1).

d. Under Vertex List, selectpoints (indicated by theblack squares) to define theoutside corners of thecomposite surface.

a

b

c

d


Step 6. Create the first Composite Surface (Cont.)

View the current perimeter of the set of surfaces, as seen by the composite surfaceapplication.

a. Click on the Preview Boundary button.b. Click No when the Question from application SGM appears.c. An informational message will appear in the history window describing the following colors

White free edges within the current surface selectionDark blue two coincident surface edgesLight blue more than two coincident surface edgesRed surface edges that are not part of the boundary due

to a gap

a

b

c



In this illustration, andthroughout the remainderof the exercise, the whitedots and white lines arerepresented in black.

The boundary definition(represented by blackand dark blue lines withsolid dots) needs to bemodified so it will includeonly the desired surfaceedges. For this problem,only the surface edgeson the outside (outerperimeter) of the set ofsurfaces in the SurfaceList are to be used. Thesurface edges coloredwhite with white dotsthat are interior to thesurfaces must beremoved from theboundary definition.



Remove the four interior edges fromthe desired composite surfaceperimeter.

a. Geometry : Create / Surface /Composite.

b. Click on the Remove toggle.c. Hold down shift and select the

four interior edges.d. Click on Apply.e. A message will appear indicating

that the boundary loop is notclosed at the red square(there isa gap). Click OK.

a

b

c

de

c



The red square indicates thearea where the boundary loopis not closed. To close theloop, a curve needs to becreated.



Zoom in on the red square and create acurve that closes the gap.

a. Click on the View corners icon.b. Zoom in on the corner with the red

square. (zooming may need to bedone a few times in order to get agood view)

c. Click on the Label Control iconand show click on Point.

d. Geometry : Create / Surface /Composite.

e. Change the Modify Boundarytoggle to Add.

f. Click on the Two Points icon.g. Under Edge List, select point 58

and 75.h. Click on the Fit view icon.i. Turn of the Label Control.

a

b d

eg

i c

f

h



The composite surface is now ready to be submitted.a. Geometry : Create / Surface / Composite.b. Click on Apply.c. Click Yes to message asking to change the view.d. Click on OK to message asking to increase the gap tolerance to 0.386.

a

b

c

d



Modify the Cleanup Tolerance and createthe composite surface.

a. Click on the Options… button.b. Enter 0.4 for both the Cleanup Tol.

and Gap Distance.c. Click on OK.d. Click on Apply.e. Click Yes when asked to delete the

original surfaces.f. Click on the Refresh graphics

icon.

a

b

c

de

f



Magenta linesindicate that thesurface hasmore than fouredges

First Composite Surface


Step 7. Create the Next Composite Surface

Select the boundary for the second compositesurface.

a. Geometry : Create / Surface / Composite.b. Under Surface List, select upper left

quarter (i.e section 2).c. Under Vertex List, select the 5 points

(indicated by the black squares).

a

b

b

c

c


Step 7. Create the Next Composite Surface (Cont.)

Set the Composite Options back to the default setting.a. Click on Options…b. Click on the Defaults button and both the Cleanup

Tol. and the Gap Distance should change back to0.005.

c. Click OK.d. Click on Preview Boundary.e. Click Yes when asked to change the tolerance.f. Click on Apply.

a

bc

d

ef


Step 7. Create the Next Composite Surface (Cont.)

Finish creating the second compositesurface.

a. Click Yes when asked tochange to optimal view.

b. Click on Yes when asked todelete the original surfaces.

c. Click on the Refresh graphicsicon.

a

c


Step 8. Create another Composite Surface

Create the composite surface for the lower rightquarter of the model.

a. Geometry : Create / Surface / Composite.b. Under Surface List, select the lower-right

quarter of the model (i.e, section 3).c. Under Vertex List, select the four points

(indicated by the black squares).

a

b

c

bc


Step 8. Create another Composite Surface (Cont.)

Set the Composite Options back to the default setting.a. Click on Options…b. Click on the Defaults button and both the Cleanup

Tol. and the Gap Distance should change back to0.005.

c. Click OK.d. Click on Preview Boundary.e. Click Yes when asked to change the tolerance.f. Click on the View corners icon and zoom in

on the lower-right quarter of the model.

a

bc

d

e

f



Change the picking preferences and remove the edges internal tothe desired composite surface.

a. Preferences : Pickingb. Change Rectangle/Polygon Picking toggle to Enclose any

portion of entity.c. Click on Close.d. Click on Remove under Modify Boundary.e. Under Edge List, hold

down shift and selectthe two internalsurfaces (as indicated)by dragging a boxaround the circle.

f. Click on Apply.

a

b

c

d

f

e



Finish creating the composite surface.a. Click on Yes when asked to change to a better view.b. Click on Yes when asked to delete the original surfaces.c. Click on the Refresh graphics icon.d. Click on the Fit View icon.

a

b

dc



Shown here is the model with threecompleted composite surfaces.


Step 9. Change the Picking Preferences

Change the Picking Preferencesback to the previous setting.

a. Preferences : Pickingb. Under Single Picking, make

sure that Entity is selected.c. Under Rectangle/Polygon

Picking, select Enclose entireentity.

d. Select Cycle picking formand Horizontal selectmenus.

e. Under Preselection Settings,select Entity Highlighting.

f. Click on Close.

a

b

c

d

e

f


Step 10. Create the Final Composite Surface

Select the surface boundary forthe fourth composite surface.

a. Geometry : Create / Surface /Composite.

b. Under Surface List, select thelower-left section (i.e section4) bydragging a box around it.

c. Under Vertex List, select the fourpoints (indicated by the blacksquares).

a

b

b

c

c


Step 10. Create the Final Composite Surface (Cont.)

Set the Composite Options to the default.a. Click on the Options… button.b. Click on the Defaults button and

both the Cleanup Tol and GapDistance should change to 0.005.

c. Click on OK.d. Click on Preview Boundary.e. Click on Yes when asked to change

tolerance.f. Click on Apply.

a

bc

d

ef


Step 10. Create the Final Composite Surface (Cont.)

Finish creating the compositesurface.

a. Click on Yes when asked todelete original surfaces.

b. Click on the Refresh graphicsicon.

c. Change the view by clicking onIso 2 view icon.

d. Click on the Fit view icon.

a

cdb


Step 11. Check the Model

Check the model once again toverify that there are no geometricincongruencies.

a. Geometry : Verify / Surface /Boundary.

b. Select Topology underVerification Criteria.

c. Under Surface List, selectthe entire model.

d. Click Apply.e. Click on the Update

Graphics button.f. Click on the Erase Markers

button.g. Click on OK.h. Click on the Front view icon.

a

b

cd

e

f

g

h


Step 12. Create Mesh Seeds

Create mesh seeds for the model.a. Elements : Create / Mesh

Seed / Uniform.b. Select the toggle for

Number of Elements.c. Enter 10 under Number.d. Under Curve List,Shift-select

the 7 curves (indicated by thered arrows).

e. Click Apply.

a

bc

d

e


Step 12. Create Mesh Seeds (Cont.)

Continue to create mesh seeds forthe rest of the model.

a. Elements : Create / MeshSeed / Uniform.

b. Select the toggle forNumber of Elements.

c. Enter 4 under Number.d. Shift-select the 3 curves

(indicated by the red arrows).e. Click Apply.

a

bc

d

e


Step 13. Create a Surface Mesh

Create the mesh for the model.a. Elements : Create /

Mesh / Surface.b. Select Quad, Paver,

and Quad4 for theElem. Shape, Mesher,and Topology.

c. Under Surface List,select the top twosurfaces (i.e sections1 and 2).

d. Remove the check forAutomatic Calculation and enter 5.0 for the Global EdgeLength.

e. Click on the Paver Parameters… button.f. Select Used Desired Edge Lengths toggle.g. Enter 4.8 and 5.2 for the Min Edge and Max Edge Length,

respectively.h. Click OK.i. Click on Apply.

a

b

c

d

e

f

g

h


Step 13. Create a Surface Mesh (Cont.)

Mesh the remaining compositeSurfaces, this time using theIsomesher.

a. Elements: Create / Mesh /Surface.

b. Select Quad, IsoMesh, andQuad4 for the Elem. Shape,Mesher, and Topology.

c. Under Surface List, select thebottom two surfaces (i.esections 3 and 4).

d. Remove the check forAutomatic Calculation andenter 5.0 for the Global EdgeLength.

e. Click on Apply.

a

b

c

d


Step 13. Create a Surface Mesh (Cont.)

Here is the model with the completed mesh.


Step 14. Equivalence the Mesh

Equivalence the model.a. Elements: Equivalence / All /

Tolerance Cube.b. Change the Equivalencing

Tolerance to 0.05.c. Click Apply.

a

bc


Step 15. Change the Display and Lighting for the Model

Modify certain display parameters toget a better view of the model.

a. Click on the Smooth shadedicon.

b. Click on the Plot/Erase icon.c. Click on Erase under

Geometry.d. Click on OK.e. Viewing : Angles…f. Enter -10 -30 -20 for the

angles.g. Click on the Fit view icon.h. Click on Apply, then Cancel.

c

d

e

f

h

bag


Step 15. Change the Display and Lighting for the Model (Cont.)

Modify the lighting sources.a. Display : Light Sources…b. Under Post/Unpost Sources, select

ambient, directional_1, directional_2,and directional_3.

c. Click on Apply.d. Click on Cancel.

a

b

c d


Step 16. Display the Composite Surfaces.

Plot only the composite surfaces.a. Click on the Plot/Erase icon.b. Under FEM, click Erase.c. Under Geometry, click Plot.d. Click on OK.

e. Close the database and quitMSC.Patran after finishing theexercise.

bc

d

a

compostie surface

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