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

MSC.Nastran 120 Exercise Workbook 3-7

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

MSC.Nastran 120 Exercise Workbook 3-9

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

MSC.Nastran 120 Exercise Workbook 3-11

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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