ws14 rect plate modes

8/6/2019 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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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


4/24WS14-4NAS120, Workshop 14, January 2003

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.



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



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



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



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



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



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



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



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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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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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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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.



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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

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