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WS-1

WORKSHOP

Define Equivalent Section PlateProperties

NAS121, Workshop , May 6, 2002


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WS-2NAS121, Workshop , May 6, 2002

Problem Description

A 20 in. x 20 in. sandwich plate is

loaded with 15 psi pressure and is

simply supported around the

edges.

The facesheets are 0.05 in. thick

aluminum and the core is 0.5 in.

thick.


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Hand calculations

a. The T field on the PSHELL is set to the sum of the facesheet thicknesses

T=(2*Tf)=0.10 .

b. The 12/T**3 field on the PSHELL is set to the ratio of the actual sandwich moment

of inertia to the moment of inertia calculated from T on the PSHELL. In this case

the core moment of inertia is ignored:

c. An approximation for the effective shear thickness is TS/T=(5/6)*(Tc+2Tf)/T= 5.0

0.91

12

0.10

12

0.050.05/20.50/20.052

12

T

12

TfTf/2Tc/2Tf2

*3*12/T3

32

3

32


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Suggested Exercise Steps1. Create a geometry model.

2. Use mesh seeds to define the mesh density.

3. Create a finite element mesh.

4. Apply boundary conditions to the model.

5. Apply loads to the model.

6. Define aluminum material properties.

7. Define equivalent section properties.

8. Submit the model to MSC.Nastran for analysis.

9. Attach xdb Results File.

10. Display stresses using MSC.Patran.

11. Display deformations using MSC.Patran.


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CREATE NEW DATABASE

Create a new database called

equivalent1.db:

a. In File select New

b. Enter equivalent1 as the file

name

c. Click OK

d. Choose Default Tolerance

e. Select MSC.Nastran as the

Analysis Code

f. Select Structural as the

Analysis Type

g. Click OK

a

b c

d

e

f

g


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Step 1. Create a geometry model

In Geometry create the first

curve.

a. Select Create / Surface /

Vertex

b. On the Surface Vertex n

Lists enter[0 0 0], [20 0 0],[20 20 0], [0 20 0]

c. Click Apply

a

b

c


7/16WS-7NAS121, Workshop , May 6, 2002

Step 2. Use mesh seeds to define the mesh density

In Elements, create mesh seeds.

a. Select Create / Mesh Seed /

Uniform

b. At Number enter10

c. Click on the bottom edgeof the

plate to create a mesh seedd. Then click on the right edge

a

c

d b

S C f



Step 3. Create a finite element mesh

In the Elements menu create

surface mesh based on the

mesh seeds.

a. Select Create / Mesh /

Surface

b. Select Quad as the

Elem Shape

c. Click on surface 1

d. Click Apply

a

b

c

d

St 4 A l b d diti t th d l



Step 4. Apply boundary conditions to the model

a

b

c

e

f

h

g

In Loads/BCs

a. Select Create /

Displacement /

Nodal

b. For New Set Name

enter constraints

c. In Input Data, enter

for

Translations, then

OK

d. Click on Select

Application Region

e. On the top menu

click on the Curve or

Edge icon

f. Shift click on the fouredges all around the

surface

g. Click Add and OK

h. Click Apply

f

f

f

d



Step 5. Apply loads to the model

a. On the top menuclick ResetGraphics

b. Select Create /Pressure /Element Uniform

c. Enter pressurefor New Set Name

d. At Target ElementType select 2D

e. In Input Data,Enter15 for TopSurface Pressure,then OK

f. Click on SelectApplicationRegion

g. In the top menuclick on theSurface or Faceicon

h. click on Surface 1

i. Click Add then OK

j. Click Apply

b

c

e

h

j

i

a

g

d

f

St 6 D fi l i t i l ti



Step 6. Define aluminum material properties

Go to Material menu

a. Select Create / Isotropic /

Manual Input

b. For Material Name enter

aluminum

c. Click Input Properties, enter

10e6 .3

d. Click OK

e. Click Apply

a

b

c

d

e

St 7 D fi i l t ti ti



Step 7. Define equivalent section properties

Go to Properties:

a. Select Create / 2D / Shell

b. Enter Equivalent at

Property Set Name

c. At Options select

Equivalent Section

d. In Input Properties click on

Aluminum for Membrane,Bending, and Shear

Materials

e. Enter 0.1 for thickness,

f. 91 for Bending Stiffness

g. 5 for Thickness Ratio

h. .3 and -.3 for Fiber Dist. 1

and 2

i. Click OK

j. Click Application Region

select box and click on

Surface 1 then Add

k. Click Apply

a

b

d

e

f

i

h

c

g

k

j

St 8 S b it th d l t MSC N t f l i



Step 8. Submit the model to MSC.Nastran for analysis

Go to Analysis:

a. Select Analyze / Entire Model / Full Run

b. Click Apply

a

b

Step 9 Attach xdb Results File



Step 9. Attach xdb Results File

Go to Analysis:a. Select Attach XDB

/ Result Entities /

Local

b. Click Select

Results File

c. Use the Select File

tool to find your xdb

file in your local

Patran directory and

click it, in this case,

equivalent1.xdb

d. Click OK

e. Click Apply

a

b

c

d

e

Step 10 Display stresses using MSC Patran



Step 10. Display stresses using MSC.Patran

To display the Von

Mises stress at stress

recovery position Z2:

go to the Results

menu:

a. First turn off the

geometry in

Plot/Erase

Geometry

Erase

b. Select Create /

Quick Plot

c. Click Stress

Tensor

d. Click

DisplacementsTranslational

e. Click Apply

b

c

d

e

a

Step 1 Display deformations using MSC Patran


16/16WS-16NAS121 Workshop May 6 2002

Step 1. Display deformations using MSC.Patran

To display the models

deformations:

go to the Results menu:

a. In the top menu, click on

Reset Graphics

b. Select Create /

Deformation

c. Click Displacements,

Translational

d. Click Apply

c

d

b

The bending deflection should be 91 times less than a plate made with 0.1 in.

aluminum.

The equivalent section can also be modeled as a composite material for more complex

facesheets or more accurate results.

a

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