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MSC.Nastran 120 Exercise Workbook 3-1
WORKSHOP 3
Meshing and Property Assignment
Objectives:■ Apply a Refined Mesh near a critical location of the model.
■ Use a coarse Global Mesh for the rest of the model.
■ Define Material and Element properties, and apply them to the model.
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WORKSHOP 3 Meshing and Property Assignment
MSC.Nastran 120 Exercise Workbook 3-3
Model Description:Define a Finite Element Mesh for the Clevis Model developedearlier. Use Mesh Seed to create a Refined Mesh with a higher Meshdensity near a critical area.
After the Mesh is created, define Material and Element propertiesfor the model.
Figure 3.1
L1
L2
Mesh Parameters6 elements per edgeL2/L1 = 0.5Global Edge Length = 0.5
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Suggested Exercise Steps:
■ Start MSC.Patran and open the database clevis.db.
■ Starting with an isometric view of the model, zoom in on the lower half of the clevis hole. Save this view as a named view. Use the name zoom_in.
■ To further simplify the rendering of the clevis model, turn off the display lines so only the model boundaries are shown.
■ Apply the mesh seeds to increase the mesh density in a critical area.
■ Create a finite element mesh.
■ Define material properties.
■ Define element properties.
WORKSHOP 3 Meshing and Property Assignment
MSC.Nastran 120 Exercise Workbook 3-5
Exercise Procedure:
1. Start MSC.Patran and open the database clevis.db.
NOTE: Whenever possible, toggle off the ❑ Auto Execute option byleft clicking the check box.
1a. Use the Viewing/Select Corners option to zoom in on the clevismodel. Figure 3.2 shows which part of the model to focus on.
Or, use the View Corners icon:
Figure 3.2
Save this view by creating a named view of the current model view.
File/Open...
Existing Database Name: clevis.db
OK
Viewing/ Select Corners
Viewing/ Named View Options...
View Corners
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2. To simplify the model view, turn off the display lines.
Or, use the Display lines icon:
3. Create mesh seeds to increase the mesh density in the critical area.
In the Curve List box, choose the Curves as shown in Figure 3.3.
Create View...
Create New View: zoom_in
Apply
Close
Display/Geometry...
Number of Display Lines: 0
Apply
Cancel
◆ Finite Elements
Action: Create
Object: Mesh Seed
Type: One Way Bias
◆ Num and Elems and L2/L1
Number: 6
L2/L1: 2
Display lines
WORKSHOP 3 Meshing and Property Assignment
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Figure 3.3.
In the Curve List box, choose the curves as shown in Figure 3.4.
Figure 3.4
Apply
Number: 6
L2/L1: 0.5
Apply
1
R
T
Z
X
Y
Z
Curves formesh seeding.
1
R
T
Z
X
Y
Z
Curves foradditionalmesh seeds.
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Zoom out to see the entire model.
Or, use the Fit View icon:
4. Create a finite element mesh.
The complete mesh should resemble Figure 3.5.
Figure 3.5
5. Check the model for Free Edges using the verify action in the FiniteElements menu.
Viewing/Fit view
◆ Finite Elements
Action: Create
Object: Mesh
Type: Solid
Global Edge Length: 0.5
Solid List: Solid 1:22
Apply
◆ Finite Elements
Action: Verify
Object: Element
Fit view
1R
T
Z
X
Y
Z
WORKSHOP 3 Meshing and Property Assignment
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6. The Free Edge plot is shown in Figure 3.6. Since the model has“cracks” or free edges, use the Equivalence tool to connect themesh.
Figure 3.6
7. Re-check for free edges in the model,
Type: Boundaries
◆ Free Edges
Apply
◆ Finite Elements
Action: Equivalence
Object: All
Type: Tolerance Cube
Apply
◆ Finite Elements
Action: Verify
Object: Element
Type: Boundaries
◆ Free Edges
Apply
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Figure 3.7 shows a free edge plot of the complete mesh withoutdisconnected regions, or “cracks”.
Figure 3.7
8. Define material properties.
9. Define element properties.
◆ Materials
Action: Create
Object: Isotropic
Method: Manual Input
Material Name: steel
Input Properties...
Constitutive Model: Linear Elastic
Elastic Modulus = 30E6
Poisson Ratio = 0.3
OK
Apply
◆ Properties
Action: Create
Object: 3D
Type: Solid
WORKSHOP 3 Meshing and Property Assignment
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Quit MSC.Patran after finishing this exercise.
Property Set Name: solid_elements_steel
Input Properties...
Material Name: m:steel
OK
Select Members: Solid 1:22
Add
Apply
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