Download - WS14 Rect Plate Modes
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WORKSHOP 14
NORMAL MODES OF ARECTANGULAR PLATE
NAS120, Workshop 14, January 2003 WS14-1
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WS14-2NAS120, Workshop 14, January 2003
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WS14-3NAS120, Workshop 14, January 2003
Problem Description
A rectangular plate is simply supported at all edges. Find the first 10normal modes for this plate.
E = 10 x 106 psi
=0.33
= 0.101 lb/in3
t = 0.125 in
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Workshop Objectives
Perform a normal modes analysis on a rectangular plate.
Evaluate the quality of the normal modes solution graphically.
Compare analysis results to theoretical results.
Evaluate the effect of varying mesh density.
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Suggested Exercise Steps
1. Create a new database and name it rectangular_plate1.db.
2. Create a rectangular surface.
3. Mesh the surface to create plate elements.
4. Create material properties. Dont forget to enter density.
5. Create physical properties.
6. Apply Loads and Boundary Conditions.
7. Perform a normal modes analysis to determine the first 10 modes for the plate.
8. Read the results into MSC.Patran.
9. Plot the mode shapes. Visually evaluate the quality of the mode shapes.
10. Compare the first natural frequency to theoretical results.
11. File / save a copy as rectangular_plate2.db.
12. Close the database and open the rectangular_plate2 database.
13. Delete the original results file.
14. Re-mesh the surface. Use a global edge length of 0.5 in.
15. Re-run the analysis.
16. Attach the new results file to the database.
17. Plot the mode shapes.
18. Compare the results from the finer mesh with the earlier results.
St 1 C t N D t b
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Step 1. Create New Database
a
b c
d
f
g
e
a
Create a new database called
rectangular_plate1.db
a. File / New.b. Enter rectangular_plate1 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.
St 2 C t R t l S f
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Step 2. Create a Rectangular Surface
Create a surface
a. Geometry: Create /
Surface / XYZ.
b. Enter for theVector Coordinates list.
c. Click Apply.
b
c
a
Step 3 Mesh the Surface
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Step 3. Mesh the Surface
Create a surface mesh
a. Elements: Create / Mesh
/ Surface.
b. Select the surface.
c. Enter 1.4 for the Global
Edge Length.
d. Click Apply.
a
b
c
d
Step 4 Create Material Properties
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Step 4. Create Material Properties
a
c
b
d
hg
e
f
Create an isotropic material
a. Materials: Create / Isotropic
/ Manual Input.
b. Enter plate_material for
the Material Name.
c. Click Input Properties.
d. Enter 10e6 for the Elastic
Modulus.
e. Enter 0.33 for the Poisson
Ratio.
f. Enter 0.101 for the Density.
g. Click OK.
h. Click Apply.
Step 5 Create Physical Properties
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Step 5. Create Physical Properties
a
b
c
f
d
e
Create physical properties
a. Properties: Create / 2D /
Shell.
b. Enter plate_prop as theProperty Set Name.
c. Click Input Properties.
d. Select plate_material as
the material.
e. Enter 0.125 for the
Thickness.f. Click OK.
Step 5 Create Physical Properties
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Step 5. Create Physical Properties
a
b
c
d
e
Apply the physical properties
a. Properties: Create / 2D
/ Shell.
b. Click in the SelectMembers box.
c. Rectangular pick the
entire plate as shown.
d. Click Add.
e. Click Apply.
Step 6 Apply Loads and Boundary Conditions
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Step 6. Apply Loads and Boundary Conditions
b
c
d
e
a
Create a boundary condition
a. Loads/BCs: Create /
Displacement / Nodal.
b. Enter simple_support as
the New Set Name.
c. Click Input Data.
d. Enter for
Translations
e. Click OK.
Step 6 Apply Loads and Boundary Conditions
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Step 6. Apply Loads and Boundary Conditions
Apply the boundary condition
a. Click Select
Application Region.
b. For the Geometry
Filter selectGeometry.
c. Set the Selection
Filter to Curve or
Edge and select an
edge.
d. Click Add.e. Repeat the procedure
until all four edges
have been added.
f. Click OK.
g. Click Apply.
af
g
d
b
c
Step 7. Run Normal Modes Analysis
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WS14-14NAS120, Workshop 14, January 2003
Step 7. Run Normal Modes Analysis
Analyze the model
a. Analysis: Analyze / Entire
Model / Full Run.
b. Click Solution Type.
c. Choose Normal Modes.
d. Click Solution Parameters.
e. Enter 0.00259 for Wt.-Mass
conversion.
f. Click OK.
g. Click OK.h. Click Apply.
f
e
a
h
b
c
g
d
Step 8. Read Results into MSC.Patran
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Step 8. Read Results into MSC.Patran
a
b
c
e
d
Attach the results file
a. Analysis: Access Results /
Attach XDB / Result
Entities.
b. Click Select Results File.
c. Choose the results file
Rectangular_plate1.xdb.
d. Click OK.
e. Click Apply.
Step 9. Plot Mode Shapes
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WS14-16NAS120, Workshop 14, January 2003
p p
a
c
b
Create a quick plot
a. Results: Create / Quick
Plot.
b. Select Eigenvectors,
Translational as theDeformation Result.
c. Click Apply.
First 10 modes:
1_________ 6_________
2_________ 7_________
3_________ 8_________
4_________ 9_________
5_________ 10________
Step 10. Compare to Theoretical Results
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p p
Theoretical results based on Formulas for Natural Frequency
and Mode Shape, 1984 edition, Table 11-4, case 16
)(2
=
112
tE
a2
f
3
2
21
1
a = 12, b = 8, a/b = 1.5
12 = 32.08
E = 10 x 106
t = 0.125
= 0.33
= 0.101/386.1 = 2.616 x 10-4
= . t = 3.270 x 10-5
f1 = 265 Hz
Step 11. Save a Copy
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p py
a
b c
Save a copy of the file
a. File: Save a Copy.b. Type rectangular_plate2
as the file name.
c. Click Save.
Step 12. Open the New Database
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a
b
c
d
Close the original file and open
the new file
a. File: Close.
b. File: Open.
c. Select the file:
rectangular_plate2.db .
d. Click OK.
Step 13. Delete Old Results File
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e
Delete XDB attachment
a. Analysis: Delete / XDB
Attachment.
b. Select the
rectangular_plate1.xdb attachment.
c. Click Apply.
d. ChooseYes to delete
the attachment.
e. Click on the front view
icon.
d
a
b
c
Step 14. Re-Mesh the Surface
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WS14-21NAS120, Workshop 14, January 2003
a
b
c
d
e
Create a finer mesh
a. Elements: Create / Mesh
/ Surface.
b. Select the entire surface.
c. Enter 0.5 for the Global
Edge Length.
d. Click Apply.
e. ChooseYes to delete
the existing mesh.
Step 15. Run Normal Modes Analysis
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Analyze the model
a. Analysis: Analyze /
Entire Model / Full
Run.
b. Change the jobname to:
rectangular_plate2.
c. Click Apply.
a
b
c
Step 16. Attach New Results File
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a
b
e
Attach the results file
a. Analysis: Access Results /
Attach XDB / Result
Entities.
b. Click Select Results File.c. Choose the results file
rectangular_plate2 .xdb.
d. Click OK.
e. Click Apply.
c
d
Step 17. Plot Mode Shapes
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Create a quick plot
a. Results: Create / Quick
Plot.
b. Select Eigenvectors,
Translational as theDeformation Result.
c. Click Apply.
First 10 modes:
1_________ 6_________
2_________ 7_________
3_________ 8_________
4_________ 9_________
5_________ 10________
a
c
b