Ws01a_normalmodes

8/6/2019 Ws01a_normalmodes

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WS1a-1

WORKSHOP 1A

NORMAL MODES ANALYSIS

NAS122, Workshop 1a, August 2005Copyright 2005 MSC.Software Corporation


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WS1a-2NAS122, Workshop 1a, August 2005Copyright 2005 MSC.Software Corporation


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Problem Description For this problem, we use the Lanczos method to find the first ten

natural frequencies and mode shapes of a flat rectangular plate.

Below is a finite element representation of the rectangular plate. It

also contains the geometric dimensions and the loads and

boundary constraints. Table 1 contains the necessary parameters

to construct the input file (see next page).


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Problem Description (cont.) Table1

en t (a) in

Hei t (b) in

T ic ness .1 in

ei t Densit . 8 lbs/in

ass/ ei t actor . 9E sec /in

Elastic o l s . E6 lbs/in

Poissons Ratio .


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Suggested xercise Steps1. Create a geometry surface using the given dimensions.

2. Mesh the surface with Quad elements using Global dge Length of

0.5.

3. Assign the boundary conditions to the model.

4. Create the appropriate material properties and call it mat_1.

5. Assign the appropriate element properties to the model and call itprop_1.

. Submit the model to MSC.Nastran for analysis.

7. Attach the .XDB results file.

. Post Process results create a quick plot for each of the 10 mode

shapes.


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WS1a-NAS122, Workshop 1a, August 2005Copyright 2005 MSC.Software Corporation

CREATE NEW DATABASE

Create a new database calledws1.db.

a. File New.

b. nter ws1a as the file name.

c. Click OK.

d. Choose Default Tolerance.

e. Select MSC.Nastran as theAnalysis Code.

f. Select Structural as theAnalysis Type.

g. Click OK.

a

b c

d

e

f

g


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Step 1. Geometry: Create / Surface / XYZ

Create a 5 x 2 surface.

a. Geometry: Create SurfaceXYZ.

b. nter as the VectorCoordinates List.

c. Turn offAuto Execute.

d. Click Apply.

a

d

c

b


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Step 2. Elements: Create / Mesh / Surface

Create the finite elements onthe surface.

a. lements: Create MeshSurface.

b. Select Quad for lemShape and IsoMesh forMesher.

c. Screen pick Surface 1

for the Surface List.

d. Uncheck the Automatic

Calculation option.

e. Change the Global dgeLength value to 0.5.

f. Click Apply.

a

b

c

d

e

f


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Step 3. Loads/BCs: Create / Displacement / Nodal

Assign the boundaryconstraints to the finiteelement model.

a. Loads BCs: CreateDisplacement Nodal

b. nter constraint forthe New Set Name.

c. Click Input Data.

d. Input the value for theTranslation and for the otation

e. Click OK.

f. Click on SelectApplication Region.

g. Change the GeometryFilter to FEM.

h. Select all the nodeson the left edge of theplate.

i. Click Add and OK.

j. Click Apply.

a

b

c

d

e

f

g

h

i

i

j


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Step 4. Materials: Create / Isotropic / Manual Input

Create the material properties.

a. Materials: Create IsotropicManual Input.

b. nter mat_1 for the Material

Name.

c. Click Input Properties.

d. nter 3e7 for the lastic

Modulus and 0.3 forPoissonatio.

e. nter 0.282 for the Density.

f. Click OK.

g. Click Apply.

a

b

c

d

e

fg


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Step 5. Properties: Create / 2D / Shell

Assign element properties to themodel.

a. Properties: Create 2D Shell.

b. nter prop_1 for the Material

Name.

c. Click Input Properties.

d. Click in the Material Name

icon, and select mat_1 fromthe Select Material box.

e. nter 0.1 for the Thickness.

f. Click OK.

g. Select Surface 1 in the SelectMembers box.

h. Click Add and click Apply.

a

b

c

e

fg

h

h

d


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Step 6. Analysis: Analyze / Entire Model / Full Run

Submit the model for analysis.

a. Analysis: Analyzentire Model Full un.

b. Click on Solution Type.

c. Select Normal Modes.

d. Click on Solution

Parameter.e. nter 0.00259 for Wt-

Mass Conversion.

f. Click OK.

g. Click OK.

a

b

c

d

e

fg


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Step 6. Analysis: Analyze / Entire Model / Full Run (Cont.)

Submit the model for analysis(cont.).

a. Click on Subcases.

b. Select Default inAvailable Subcases

c. Click on Subcase

Parameters.d. Select Lanczos

xtraction Method.

e. nter 10 as the Numberof Desired oots.

f. Select Mass forNormalization Method.

g. Click OK.

h. Click Apply.

i. Click Cancel.

j. Click Apply.

a

i

c

d

e

f

g

hj

b


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Step 7. Analysis: Access Results / Attach XDB / Result Entities

Attach the XDB result file.

a. Analysis: Accessesults Attach XDBesult ntities.

b. Click on Select ResultsFile.

c. Select ws1a.xdb.d. Click OK.

e. Click Apply.

a

b

c

d

e


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Step 8. Results: Create / Quick Plot

Create a Quick Plot of the firstmode shape.

a. esults: Create Quick Plot.

b. Click on A1:Mode1.

c. Select Eigenvector,Translational in both Fringe

and Deformation resultboxes.

d. Click Apply.

a

b

c

d

c


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Step 8. Results: Create / Quick Plot


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Summary

Summary of Frequencies and Modes for project _______________

Mode Freq

(Hz)

Description


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Documents

Ws01a_normalmodes