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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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WS6-3NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-4NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
MODAL FREQUENCY RESPONSE
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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WS6-5NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
MODAL FREQUENCY RESPONSE
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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WS6-6NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-7NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-8NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-9NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-10NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-11NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-12NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-13NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-14NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-15NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
Step 6. Analysis: Analyze / Entire Model / Full Run (Cont.)
Submit the model for analysis(cont.).
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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WS6-16NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
Step 6. Analysis: Analyze / Entire Model / Full Run (Cont.)
Submit the model for analysis(cont.).
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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WS6-17NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-18NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-19NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
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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WS6-20NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
Step 8. Results: Create / Graph / Y vs X (Cont.)
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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WS6-21NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
Step 8. Results: Create / Graph / Y vs X (Cont.)
Displacement Magnitudevs. Frequency Plot
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WS6-22NAS122, Workshop 6, August 2005Copyright 2005 MSC.Software Corporation
Step 8. Results: Create / Graph / Y vs X (Cont.)
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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