06 ws08 lug mesh meth
TRANSCRIPT
WORKSHOP 8
VARIOUS METHODS OF SOLID MESHING
Problem Description Import a parasolid solid. Use the geometry to create the geometry
for use with either the IsoMesh or TetMesh. Create the geometry for use with the IsoMesh by breaking the original solid into a set of six faced blue parametric solids. The actions used to do this are 1) create breaking planes, 2) break the solid several times, 3) refit some of the white solids to be blue solids, and 4) mirror. Create geometry for use with the TetMesh by breaking the original solid two times. This is done only to create solid faces for use in creating pressure loading. The original solid could be TetMeshed as is. Four sets of solids are created. The various sets are meshed with hex8, hex20, tet4 or tet10 topologies. The four models are completed and analyzed using MSC.Nastran. Finally, the results for the models are viewed in MSC.Patran. A brief comparison is made of the results.
Suggested Exercise Steps1. Create a new database called lug.db.
2. Import a parasolid solid using the file lug.xmt.
3. Rename the default group, create a new group, and place a copy of the original solid in the new group. Groups will be used to separate the four models. This will make it easier to work with them.
4. Post(show) only the group for the hex8 element mesh.
5. Create three points to be used for creating a plane for breaking the solid.
6. Create two breaking planes.
7. Break the hex8 solid twice.
8. Create five points, these will be used in creating more breaking planes.
9. Create two more breaking planes.
10. Break the solid twice
11. Create a point and plane.
12. Break the solid.
13. Practice using Plot/Erase, and refit the solids to make all solids blue parametric solids.
14. Delete the unwanted solid(from first break; at top of model).
15. Mirror the five blue solids so that they appear where the deleted solid was.
Suggested Exercise Steps (Cont.)16. Create a group for the hex20 mesh model, copy the hex8 geometry into it
and post the group with the tet4 geometry.
17. Edit the tet4 geometry by breaking the solid twice.
18. Create a group for the tet10 mesh, copy the tet4 geometry into it, and post all the groups.
19. Create a cylindrical coordinate system at the center of the hole for the hex8 model.
20. Post just the hex8 group, IsoMesh with hex8 topology, then repeat for the hex20 group, using hex20 topology.
21. Post just the tet4 group, TetMesh with tet4 topology, then repeat for the tet10 group, using tet10 topology.
22. Post all four groups. Display the element free edges, equivalence, then display the free edges again.
23. Create pressure loads and constraints for all four models. First, create three more cylindrical coordinate systems for the other three models by translating the original coordinate frame for the hex8 model. Use the coordinate systems to create four fields. Each field corresponds to a unique model. The fields use the function sinr(‘T). Having created four fields, create four pressure loadings using a scalar factor of 1000.0, so the loading for each model is 1000*sinr(‘T). Each model is constrained on its back faces.
Suggested Exercise Steps (Cont.)24. Create material and element properties.
25. Check the default load case to see that all the pressure and constraints have been applied.
26. Perform the analysis of the four models using MSC.Nastran.
27. Post process the results. First, attach the XDB file. Display the deformed shape with and without the undeformed models and geometry. Add the von Mises stress fringe to the display. Create three more viewports . Post each group to the corresponding viewport. Display the deformed shape and stress fringe for each group in each viewport.
Step 1. Create New Database for 3D Lug
Create a new database called lug.db
and set the model preferences.
a. File / New.
b. Enter lug as the file name.
c. Click OK.
d. Set the Tolerance by clicking
on Based on Model.
e. Enter 10.0 for the Approximate
Model Dimension
f. Set the Analysis Code and
Analysis Type to MSC.Nastran
and Structural, respectively.
g. Click OK.
a
b ce
d
Step 2. Import the Parasolid.xmt File
Import the existing parasolid
and change views.
a. File / Import.
b. Select lug.xmt and click
Apply.
c. Click OK.
d. Select Iso 1 View icon.
a
b
c
d
Step 2. Import the Parasolid .xmt File (Cont.)
Step 3. Rename, Create New Group, and Translate Geometry.
Rename the default group and create
a new group for the Tet4 geometry.
a. Group / Modify.
b. Click Rename.
c. Enter hex8 for new name and
click Apply.
d. Group / Create.
e. Enter tet4 under New Group
Name.
f. Select Make Current box.
g. Click Apply and Cancel.
a
b
c
d
ef
g
Step 3. Rename, Create New Group, and Translate Geometry (Cont.)
Copy the solid(Solid 1) into
the tet4 group.
a. Geometry :
Transform / Solid /
Translate.
b. Enter <0 -10 0>
under Translation
Vector.
c. Turn off Auto
Execute. Select the
solid by dragging the
mouse cursor over it.
d. Click Apply.
a
b
d
c
c
Step 4. Post Only the Hex8 Group.
Post only the group hex8.
a. Group / Post…
b. Unselect the tet4
group from the list of
group names.
c. Click Apply then
Cancel.
d. Click Fit View icon.
e. Reset graphics to
eliminate the orange
lines.
a
b
c
de
Step 5. Create Points for Plane Creation
Create the points that will be
used later to create several
breaking planes.
a. Geometry : Create / Point
/ Extract.
b. Make sure the
Parametric Position is
set to 0.5.
c. Turn Auto Execute off.
d. Shift-click three edges:
the two edges that make
up the outer radius of the
solid, and one of the back
edges.
e. Click Apply.
f. Increase Point size.
a
b
ce
d
f
c
Step 6. Create the First Two Planes
Create two planes that will be
used for breaking the solid.
a. Geometry : Create /
Plane / 3 Points.
b. Click under Point 1 List.
Select the first point for
the first plane. Then, select
the other two points. Note,
with Auto Execute on the
mouse focus changes to
the next line automatically.
c. Select next 3 points to
create the second
plane.
a
c
b
Step 7. Break Solid
Break the solid using the newly
created planes.
a. Geometry : Edit / Solid /
Break.
b. Option : Plane
c. Turn off Auto Execute.
Select the Lug for Solid
List(Solid 1)
and Plane 2 for Break
Plane List.
d. Click Apply.
e. Click Yes when message
pops up.
f. Select lower solid for Solid
List(Solid 4) and Plane 1
for Break Plane List.
g. Repeat steps d and e.
a
b
c
d
e
Plane 2
Plane 1
Step 8. Create More Points for Breaking Planes
Create 5 points that will be used
to create several planes.
a. Geometry : Create / Point
/ Extract.
b. Make sure Parametric
Position is set to 0.5.
c. Shift select 5 edges:
four edges that make
up the lower half of the
lug-hole, and an edge at
the base of the solid.
d. Click Apply.
a
b
d
c
c
Step 8. Create More Points (Cont.)
Create points at the center of
the hole of the Lug.
a. Geometry : Create / Point
/ ArcCenter
b. Turn Auto Execute off.
c. Shift click two edges that
make up the hole of the
lug.
d. Click Apply.
a
dc
b
b
Step 9. Create More Breaking Planes
Create two more planes that
will be used to break the
solids again.
a. Geometry : Create /
Plane / 3 Points.
b. Select three points that
define a plane and it
will automatically be
created.
c. Select the next three
points for the next
plane.
a
bb
c
Step 10. Break Solids Again
Break the solids again, this
time, using the newly created
planes.
a. Geometry : Edit / Solid /
Break.
b. Select bottom left
portion of solid(Solid 5)
and break along Plane 3.
c. Click Apply.
d. Click Yes when message
appears.
e. Select bottom right
portion of solid(Solid 6)
and break along Plane 4.
f. Repeat steps c and d.
a
b
c
d
eb
Step 11. Create Final Point and Plane.
Now create the last point that will
be used to create one more plane.
a. Geometry : Create / Point /
Project.
b. Select the point at the
bottom end of the sloped
edge where it intersects
with the base, under Point
List.
c. Select edge normal to the
hole.
e. Geometry : Create / Plane /
3 Points.
f. Select two points along the
base of the solid and point
from projection.
a
b
c
d
e
g
f
b
c
f
Step 12. Break Solid
Break a solid one final time
using the recently created plane.
a. Geometry : Edit / Solid /
Break.
b. Option : Plane
c. Select solid at bottom-right
for Solid List(Solid 9).
d. Select Plane 5 for Break
Plane List.
e. Click Apply.
f. Click Yes when
message appears.
a
b
c
d
e
f
Step 13. Erase all Geometry, Plot Desired Solids, and Refit
Erase all of the geometry from the screen, then
plot only the desired five solids. Then, refit the
five solids so that they become parametric
(blue) solids.
a. Click the Plot/Erase icon.
b. Shift-click the 5 solids at the bottom
of the geometry, under Selected
Entities.
c. Click the Erase button under Geometry.
d. Click the Plot button under Selected
Entities and click OK.
e. Geometry : Edit / Solid / Refit.
f. Option : To TriCubicNet
g. Enter 1 for all of the Refit Parameters.
h. Select Delete Original Solids.
i. Select all five solids by dragging a
box around them.
j. Click Yes when first message
appears and Yes for All when second
message appears.
a
b
c
d
e
f
g
h
i
Step 14. Replot and Delete Unwanted Geometry
Replot all of the geometry and
delete all the unwanted sections
of the model, namely, the top
solid and the planes.
a. Click on the Plot/Erase
icon.
b. Click Plot under
Geometry and click OK.
c. Geometry : Delete / Solid.
d. Select top solid and click
Apply.
e. Geometry : Delete / Plane
f. Select all five planes by
dragging a box around the
entire solid.
g. Click Apply.
b
c
d
e
fg
a
Step 15. Complete the Geometry for the Hex Mesh
Finish creating all the geometry
by mirroring the five parametric
solids, producing a complete
parametric model.
a. Geometry : Transform /
Solid / Mirror.
b. Select the 3 Points for
Plane icon under Define
Mirror Plane Normal.
c. Select any 3 points that
lie in the plane in figure
d. Make sure the Reverse
Solid box is checked
e. Select all the solids, and
click Apply.
a
b
d
e
b
Select any 3 points that lie within this plane. This plane will serve as the mirror plane.
c
Step 16. Create Group, Copy Geometry, and Post only Tet4 Group
Create the Hex20 group and
translate the geometry.
a. Group : Create
b. Enter hex20 for New
Group Name.
c. Click Apply and Cancel.
d. Geometry : Transform /
Solid / Translate.
e. Enter <15 0 0> for Trans-
lation Vector.
f. Select all ten solids and
click Apply.
g. Group : Post.
h. Select group tet4.
i. Click Apply, then Cancel.
j. Click Fit View icon.
a
b
c
d
e
f
g
h
i
j
Step 17. Edit Solid for TetMesh
Edit the parasolid solid in group tet4
by creating three points, exactly as
the first three points were created for
the hex8 model.
a. Geometry : Create / Point
/ Extract.
b. Make sure the
Parametric Position is
set to 0.5.
c. Shift-click three edges:
the two edges that make
up the outer radius of the
solid, and one of the back
edges.
d. Click Apply.
a
b
c
d
c
Step 17. Edit Solid for TetMesh (Cont.)
Continue editing the solid by
creating two planes.
a. Geometry : Create /
Plane / 3 Points.
b. Select 3 points to create
the first plane.
c. Click Apply.
d. Next, select 3 points to
create the second
plane.
e. Click Apply.
a
b
c
The planes being created in this step have the same relative location as the planes for the hex8 group.
bd
b
Step 17. Edit Solid for TetMesh (Cont.)
Break the solid into four parts along the planes, then delete the planes.
a. Geometry : Edit / Solid / Break.b. Option : Planec. Select Solid 2 for Solid
List and Plane 2 for Break Plane List.
d. Click Apply.e. Click Yes when message pops up. f. Shift-click both halves of the solid for Solid List and select Plane 1 for Break Plane List.g. Repeat steps d and e.h. Geometry : Delete / Plane. i. Select all planes and click Apply.
a
b
c
d
e
c
f
Step 18. Create Group, Translate Geometry, and Post All
Create a final group, tet10, and
Translate(copy) the newly created
solids. Then post all four models.
a. Group : Create
b. Enter tet10 under New Group
Name.
c. Click Apply, then Cancel.
d. Geometry : Transform / Solid /
Translate.
e. Enter <15 0 0> for
Translation Vector.
f. Select all four solids in group
tet4 and click
Apply.
g. Group : Post.
h. Click Select All button.
i. Click Apply, then Cancel.
a
b
c
d
h
g
f
e
i
Step 18. Create Group, Translate Geometry, and Post All (Cont.)
Step 19. Create a Coordinate System
Create a cylindrical coordinate
system for the hex8 model. This
coordinate frame will later be used to
apply a radial pressure. It is not
necessary to create coordinate
frames for the other models, because
this frame will later be translated to
the other three models.
a. Geometry : Create / Coord /
3Point.
b. Type : Cylindrical.
c. Select 3 points (as indicated).
Point on Plane 1-3
Origin
Point on Axis 3
This is what the coordinate system should look like for the hex8 model.
a
b
c
Step 20. IsoMesh the Hex8 and Hex20 Groups
Mesh solids for the hex8 and hex 20
groups using the IsoMesher.
a. Group : Post
b. Select the hex8 group.
c. Click Apply, then Cancel.
d. Elements : Create / Mesh / Solid.
e. Select Hex, IsoMesh, and Hex8.
f. Remove check on Automatic
Calculation and enter 0.5 for
Global Edge Length.
g. Select the hex8 geometry and
click Apply.
h. Repeat steps a through g, posting
the hex20 group, selecting
Hex20 instead of Hex8 for the
Topology and applying it to the
hex20 geometry.
Note the difference between the hex8 and hex20 meshes, namely the midsize nodes.
It may be necessary click the Refresh Graphics and the Fit View icons when switching from group to group.
a
d
e
f
g
h
Step 21. TetMesh the Tet4 and Tet10 Groups
Now, create the final two meshes for the remaining models. This time, the TetMesh-er will be utilized.
a. Group : Postb. Select the tet4 group.c. Click Apply, then Cancel.d. Elements : Create / Mesh / Solid.e. Select Tet, TetMesh, and Tet4.
f. Select the tet4 geometry, Solid 35:38, for the Input List.
g. Remove check on Automatic Calculation and enter 0.5 for Global Edge Length.
h. Click on Assembly Parameters… and and click on Match Parasolid Faces. i. Select tet4 solids again.
j. Click Close. k. Click Apply.
l. Repeat steps a through k, posting the tet10 group, selecting Tet10 for the Topology instead of Tet4, and applying it to the tet10 geometry.
Note the absence or presence of midside nodes.
d
e
g
f
i
h
k
h
j
Step 22. Observe Element Free Edges of Meshed Solids
Post all four groups and observe the
element free edges.
a. Group : Post.
b. Select all four groups.
c. Click Apply, then Cancel.
d. Elements : Verify /
Element / Boundaries.
e. Click Apply (Observe the free
element edges of meshes.
This can be easily remedied by
equivalencing the meshes),
f. Elements : Equivalence
/ All / Tolerance Cube.
g. Click Apply.
h. Elements : Verify /
Element / Boundaries.
i. Click Apply.
The yellow lines indicate the element free edges. Here, the elements are not connected.
After equivalencing, the elements are connected and the only yellow lines are for the desired free edges.It is not necessary to post each
group and equivalence each model. The equivalence “All” action is applied to all 4 models.
d
e
f
g
Step 23. Create Loads and Boundary Conditions
In order to create the loads and
boundary conditions, the
cylindrical coordinate system for
the hex8 model must be
translated to the remaining
models.
a. Geometry : Transform /
Coord / Translate.
b. Enter <15 0 0> for Trans-
lation Vector.
c. Select Coord 1 for
Coordinate Frame List.
d. Repeat steps a through c
for creating Coords 3 and
4 using <0 -10 0> for the
Translation Vector, and
selecting both coordinate
frames Coord 1 and Coord 2
for the Coordinate Frame
List.
a
b
c
Step 23. Create Loads and Boundary Conditions (Cont.)
Create a field for each pressure loading.
a. Click on the Smooth Shaded icon.b. Fields : Create / Spatial / PCL Function.c. Enter sin_pressure_hex8 for Field Name.d. Select Coord 1 for Coordinate System.e. Enter sinr(‘T) for Scalar Function and click Apply. f. Create 3 more fields by following steps c through e. Refer to the table below for the corresponding field names and coordinate frames.
Field Name Coordinate System
sin_pressure_hex8 Coord 1
sin_pressure_hex20 Coord 2
sin_pressure_tet4 Coord 3
sin_pressure_tet10 Coord 4
There should be four different fields, and each field name should reference a corresponding coordinate frame (i.e., there should be one field per model.) When creating the fields it is not necessary to post each group separately.
b
c
d
e
a
Step 23. Create Loads and Boundary Conditions (Cont.)
Create four pressures, one for each
model, using the created fields.
a. Loads/BCs : Create :
Pressure / Element Uniform.
b. Enter hex8 for New Set
Name.
c. Click on Input Data…
d. Enter 1000 under Load/BC
Set Scale Factor.
e. Under Pressure, select
sin_pressure_hex8 from
Spatial Fields.
f. Click OK.
a
b
c
d
e
f
Step 23. Create Loads and Boundary Conditions (Cont.)
Set the application region for the pressure.
a. Click on the
Select
Application
Region.
b. Shift-click the four
faces (as
indicated) and
click Add.
c. Click OK.
d. Click Apply
a
b
c
d
Select these four faces for the application region for the hex8 pressure.
b
Step 23. Create Loads and Boundary Conditions (Cont.)
Pressure Name Spatial Field
hex8 sin_pressure_hex8
hex20 sin_pressure_hex20
tet4 sin_pressure_tet4
tet10 sin_pressure_tet10
These are two typical faces where the pressures for the tet4 and tet10 groups should be applied.
Repeat the previous steps for the remaining three pressures, zooming in on each model as needed. After all four pressures are created, click the Fit view icon to show all the models. The viewport should match the illustration below. Included is a table of the pressure names and the corresponding spatial fields.
These are four typical faces where the pressures for the hex8 and hex20 groups should be applied.
Step 23. Create Loads and Boundary Conditions (Cont.)
Create constraints on each model
with just one constraint set.
a. Loads/BCs : Create /
Displacement / Nodal.
b. Enter constraint for
New Set Name.
c. Click Input Data…
d. Enter <0 0 0> for
Translations only.
e. Click OK.
f. Click Select Application
Region…
g. Click the Surface or Face
icon.
h. Shift-click the back faces of all
the models(see next page)
and click Add, then OK.
i. Click Apply.
a
b
c
d
e
f
g
h
i
g
Step 23. Create Loads and Boundary Conditions (Cont.)
Step 24. Create Material and Element Properties
Create the material properties for
the models.
a. Materials : Create / Isotropic
/ Manual Input.
b. Enter Aluminum for
Material Name.
c. Click Input Properties…
d. Enter 10E6 and 0.3 for the
Elastic Modulus and
Poisson Ratio, respectively.
e. Click OK.
f. Click Apply.
a
b
c
d
e
f
Step 24. Create Material and Element Properties (Cont.)
Create the element properties using one
property set.
a. Properties : Create / 3D / Solid.
b. Enter Solid for Property
Set Name.
c. Click Input Properties…
d. Click on Mat Prop Name icon and select aluminum.
e. Click OK.
f. For Application Region, select all
solids, and click Add.
g. Click Apply.
a
b
c
d
e
f
g
Step 25. Check the Load Case
Check the load case Default to ensure that all the pressure loads and the constraint have been included.
a. Load Cases : Modify.
b. Click on load case name
Default.
c. Make sure all the loads and
constraint are listed, and click
Cancel.
Even though there are four disjoint(unrelated) models in this database, MSC.Patran views them as one model. MSC.Nastran will solve the models as one model as long is each model is correctly defined.
a
b
c
Step 26. Run Analysis
Run the analysis by submitting
the model to MSC.Nastran.
a. Analysis : Analyze / Entire
Model / Full Run.
b. Click Translation
Parameters…
c. Make sure XDB and Print
is selected for Data
Output and click OK.
d. Click on Solution Type…
e. Make sure Linear Static
is selected and click OK.
f. Click Apply.
a
b
c
d
e
f
Step 27. Read and Display Analysis Results
Read and compare the results for
the four models. First, attach the
XDB file.
a. Analysis : Access Results / Attach XDB / Result Entities.
b. Click Select Results File…
c. Select lug.xdb and
click OK.
d. Click Apply.
a
b
c
d
Step 27. Read and Display Analysis Results (Cont.)
Create a deformation plot of all four
models. It will be difficult to see the
deformation with the undeformed
shape and geometry posted. So,
unpost both.
a. Results : Create / Deformation.
b. Select Displacements,
Transitional and click Apply.
c. Click on the Display Attibutes
icon.
d. Remove check from Show
Undeformed and Show Title
and click Apply.
e. Click on Plot/Erase icon.
f. Click Erase under Geometry,
and click OK.
a
b
f
e
c
d
Step 27. Read and Display Analysis Results (Cont.)
Step 27. Read and Display Analysis Results (Cont.)
Plot the von Mises
stress for each of the
models.
a. Results : Create /
Fringe.
b. Select Stress,
Tensor and von
Mises.
c. Click Apply.
a
b
c
Step 27. Read and Display Analysis Results (Cont.)
Here is the deformed shape plotted with the von Mises stress. Note that it is somewhat difficult making a comparison between each of the models because each model is referenced to the same color chart. Throughout the next series of steps, each model will be assigned to an individual view port. This will allow for much easier comparisons between each model.
Step 27. Read and Display Analysis Results (Cont.)
Modify the current viewport and
create three others.
a. Viewport : Modify.
b. Click Rename…
c. Enter hex8 under Rename
As.
d. Click Apply, then Cancel.
e. Viewport : Create.
f. Enter hex20 and click Apply.
g. Repeat step for creating
viewports tet4 and tet10.
h. Click Cancel.
i. Viewport : Tile.
There should now be four separate viewports. The next step will involve posting only one unique group per viewport.
a
b c
f
h
d
Step 27. Read and Display Analysis Results (Cont.)
Unpost the Coordinate frames and post each modelwith its corresponding viewport.
a. Click on Display: Coord. Frames…
b. Select Unpost All and click OK.c. Select the hex8 viewport by clicking on it.d. Group : Post.e. Select the hex8 group and click Apply.f. Click on the Fit view icon.g. Follow steps d through g for the remaining viewports, selecting each one and posting the corresponding group. h. Cancel from the group dialogue.
b
d
e
h
f
a
Step 27. Read and Display Analysis Results (Cont.)
Create the deformation and the fringe of the von Mises Stressfor the model in each viewport.
a. Make the viewport hex8 current by clicking in it.b. Results : Create / Deformation.c. Select Displacements, Transitional and click Apply.d. Results : Create / Fringe.e. Select Stress Tensor and von Mises. f. Click Apply.g. Repeat steps a through f for the remaining viewports.
b
c
c
d
Here is an illustration of the four tiled viewports with the corresponding model and results, each having a maximum stress value indicated. Note the similarity between results for the hex meshes and the tet10 mesh. The tet4 mesh model is very inaccurate. The TetMesh is a very convenient approach because it is not necessary to break up the solid into many parts, unlike the IsoMesh technique.
Step 27. Read and Display Analysis Results (Cont.)