Ws06_modalfrequency

8/6/2019 Ws06_modalfrequency

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WS6-1

WORKSHOP 6

MODAL FREQUENCY RESPONSEANALYSIS

NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation


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WS6-2NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation


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MODAL FREQUENCY RESPONSE

Problem Description Using the Modal Method, determine the frequency response of the

flat rectangular plate, created in Workshop 1a, excited by a 0.1 psi

pressure load over the total surface of the plate and a 1.0 lb. force

at a corner of the tip lagging 45r. Use a modal damping of \ =

0.03. Use a frequency step of 20 Hz between a range of 20 and

1000 Hz; in addition, specify five evenly spaced excitationfrequencies between the half power points of each resonant

frequency between the range of 20-1000 Hz.


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P

roblem Description (cont.) Below is a finite element representation of the flat plate. It also

contains the loads and boundary constraints.

1.0

0.1 psi. over the total surface


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Suggested Exercise Steps1. Import the model from Workshop 1a.2. Create a non-spatial field for the pressure load and the force load.

3. Create a time dependent load case.

4. Create the time dependent force load.

5. Create the time dependent pressure load.

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

7. Attach the .XDB results file.

8. Post Process results create X vs Y graph of displacements.


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CREATE NEW DATABASE

Create a new database calledws6.db.

a. File / New.

b. Enterws6 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. File / Import

Import the model from Workshop 1a.

a. File / Import.

b. Select MSC.Patran DB as theSource.

c. Select ws1a.db.

d. Click Apply.

e. Click OK when the PatranDatabase Import Summaryappears.

a

bc

d


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Step 2. Field: Create / Non Spatial / Tabular Input

Create a Non Spatial field forthe pressure load.

a. Field: Create / NonSpatial / TabularInput.

b. Enterpressure forthe Field Name.

c. Select Frequency (f)

as the ActiveIndependent Variable.

d. Click Input Data.

e. Enter the valuesshowed in the table.

f. Click OK.

g. Click Apply.

a

b

c

d

e

f

g


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Step 2. Field: Create / Non Spatial / Tabular Input (Cont.)

Create a Non Spatial field forthe force load.

a. Field: Create / NonSpatial / TabularInput.

b. Enterforce for theField Name.

c. Select Complex asthe Scalar Field Type.

d. Click Input Data.

e. Change the ComplexData Format toMagnitude-Phase

(degrees).

f. Enter the values

showed in the table.g. Click OK.

h. Click Apply.

a

bc

d

e

f

h

g


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Step 3. Load Cases: Create

Create a Time Dependent load case.

a. Load cases: Create

b. Entermodal_freq_response

for the Load Case Name.

c. Select Time Dependent asthe Load Case Type.

d. Click Assign/Prioritize

Loads/ BCs.

e. Click on the Displ_constraint

in the Select IndividualLoads/BCS field.

f. Click OK.

g. Click Apply. b

c

d

e

f

g

a


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Step 4. Loads/BCs: Create / Force / Element Uniform

Create the time dependentForce load.

a. Loads/BCs: Create /Force / Nodal.

b. EnterForce for the NewSet Name.

c. Click on the Input Data

button.

d. Enter for Force,and select force for theTime/Freq. DependentField.

e. Click OK.

f. Click on SelectApplication Region.

g. Change the Geometry

Filter to FEM.h. Select the node on the

bottom right corner.

i. Click Add, and click OK.

j. Click Apply.

a

b

c

d

e

f

g

h

j

i

i


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Step 5. Loads/BCs: Create / Pressure / Element Uniform

Create the time dependentPressure load.

a. Loads/BCs: Create /Pressure / ElementUniform.

b. Enterpressure for theNew Set Name.

c. Change the TargetElement Type to 2D.

d. Click on the Input Data

button.

e. Enter-0.1 for Top SurfPressure, and selectpressure for theTime/Freq. DependentField.

f. Click OK.g. Click on Select

Application Region.

h. Select all the elementsfor the application region.

i. Click Add, and click OK.

j. Click Apply.

a

b

c

d

e

f

g

h

i

j

i


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

Submit the model for analysis.

a. Analysis: Analyze / EntireModel / Full Run.

b. Click on Solution Type.

c. Select FrequencyResponse.

d. Change the Formulation toModal.

e. Click on SolutionParameterbutton.

f. Select Coupledfor MassCalculation.

g. Enter0.00259 for Wt-MassConversion.

h. Click OK.

i. Click OK.

a

b

c

d

e

f

h i

g


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

Submit the model for analysis(cont.).

a. Click on Subcases.

b. Selectmodal_freq_response

from the AvailableSubcases field.

c. Click on SubcaseParameters.

d. Click on DEFINE

FREQUEYNCIES

button.

e. Use the values in the

table.

f. Click OK.

a

b

c

d

e

f


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a. Change Modal Damping toCrit. Damping (CRIT).

b. Click on DEFINE MODALDAMPING.

c. Enter the values showed inthe Define Dampingwindow.

d. Click OK.

e. Click OK.

f. Click Apply (on theSubcase form).

g. Click Cancel.

a

b

c

d

e


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a. Click on SubcaseSelect.

b. Selectmodal_freq_response

and unselect Default.

c. Click OK.

d. Click Apply.

a

b

c

d


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

Attach the XDB result file.

a. Analysis: AccessResults / Attach XDB /Result Entities.

b. Click on Select ResultFile.

c. Select ws6.xdb

.d. Click OK.

e. Click Apply.

a

b

c

e

d


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Step 8. Results: Create / Graph / Y vs X

Create a X-Y graph ofdisplacement results.

a. Results: Create /Graph / Y vs X.

b. Click onSC1:MODAL_FREQ_

RESPONSE.

c. Select GlobalVariable as the FilterMethod.

d. Click Filter.

e. Click Apply.

f. Click Close.

a

b

c

d

e f


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Step 8. Results: Create / Graph / Y vs X (Cont.)

Create a X-Y graph ofdisplacement results (cont.).

a. Select Displacement,Translational for theSelect Y Result field.

b. Select Z Component asthe Quantity.

c. Click on the TargetEntities icon.

d. Change the TargetEntity Selection toNodes.

e. Select the node where

force is applied.

f. Click Apply.

b

a

c

d

e

f


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Create a X-Y graph ofdisplacement results (cont.).

a. Click on DisplayAttribute.

b. Change Y Axis Scalefrom Linear to Log.

c. Click on Plot Option.

d. Change the ComplexNo. as to Magnitude.

e. Click Apply.

b

ac

d

e


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Displacement Magnitudevs. Frequency Plot


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Create a X-Y graph of phase

results.

a. Change Complex No.as from Magnitude toPhase.

b. Change Y Axis Scalefrom Log to Linear.

c. Click Apply.

a

b

a

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Ws06_modalfrequency