ws-1 workshop define equivalent section plate properties nas121, workshop, may 6, 2002
TRANSCRIPT
WS-1
WORKSHOP
Define Equivalent Section Plate Properties
NAS121, Workshop , May 6, 2002
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.
WS-3NAS121, Workshop , May 6, 2002
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
120.10
120.050.05/2 0.50/20.052
12T
12TfTf/2 Tc/2Tf2
*3*12/T 3
32
3
32
WS-4NAS121, Workshop , May 6, 2002
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.
WS-5NAS121, Workshop , May 6, 2002
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
WS-6NAS121, Workshop , May 6, 2002
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
WS-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 enter 10
c. Click on the bottom edge of the plate to create a mesh seed
d. Then click on the right edge
a
c
d b
WS-8NAS121, Workshop , May 6, 2002
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
WS-9NAS121, Workshop , May 6, 2002
Step 4. Apply boundary conditions to the model
a
b
c
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g
In Loads/BCs
a. Select Create / Displacement / Nodal
b. For New Set Name enter “constraints”
c. In Input Data, enter <0,0,0> 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 four edges all around the surface
g. Click Add and OK
h. Click Apply
f
f
f
d
WS-10NAS121, Workshop , May 6, 2002
Step 5. Apply loads to the model
a. On the top menu
click Reset Graphics
b. Select Create / Pressure / Element Uniform
c. Enter “pressure” for New Set Name
d. At Target Element Type select 2D
e. In Input Data, Enter 15 for Top Surface Pressure, then OK
f. Click on Select Application Region
g. In the top menu click on the Surface or Face icon
h. click on Surface 1i. Click Add then OK
j. Click Apply
b
c
e
h
j
i
a
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d
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WS-11NAS121, Workshop , May 6, 2002
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 <tab> .3
d. Click OK
e. Click Apply
a
b
c
d
e
WS-12NAS121, Workshop , May 6, 2002
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
ef
i
h
c
g
k
j
WS-13NAS121, Workshop , May 6, 2002
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
WS-14NAS121, Workshop , May 6, 2002
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
WS-15NAS121, Workshop , May 6, 2002
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 Displacements Translational
e. Click Apply
b
c
d
e
a
WS-16NAS121, Workshop , May 6, 2002
Step 1. Display deformations using MSC.Patran
To display the model’s 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