Ws05_directfrequency

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WS5-1

WORKSHOP 5

DIRECT FREQUENCY RESPONSEANALYSIS

NAS122, Workshop 5, August 2005Copyright¥ 2005 MSC.Software Corporation



WS5-2NAS122, Workshop 5, August 2005Copyright¥ 2005 MSC.Software Corporation




DIRECT FREQUENCY RESPONSE ANALYSIS

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

flat rectangular plate, created in Workshop 1a, subject to time-

varying excitation. This example structure is excited by a unit load

at a corner of the tip. Use a frequency step of 20 Hz between a

range of 20 and 1000 Hz. Use structural damping of g = 0.06.

Below is a finite element representation of the flat plate. It also

contains the loads and boundary constraints.

1.00




DIRECT FREQUENCY RESPONSE ANALYSIS

Suggested Exercise Steps1. Import the model from Workshop 1.

2. Create a non-spatial field for the pressure load.

3. Create a time dependent load case.

4. Create the time dependent force load.

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

6. Attach the .XDB results file.7. Post Process results ± create X vs Y graph of displacements.




CREATE NEW DATABASE

Create a new database calledws5.db.

a. File / New.

b. Enter ws5 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.

a

b c

d

e

f

g




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




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

Create a Non Spatial field for thepressure load.

a. Fields: Create / NonSpatial / Tabular Input.

b. Enter frequency_depend_load

for the Field Name.

c. Select Frequency (f) asthe Active IndependentVariable.

d. Click Input Data.

e. Enter the values shown inthe table.

f. Click OK.

g. Click Apply.

a

b

c

d

e

f

g




Step 3. Load Cases: Create

Create a Time Dependent load case.

a. Load Cases: Create

b. Enter direct_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




Step 4. Loads/BCs: Create / Force / Nodal

Create the time dependentForce load.

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

b. Enter unit_load for theNew Set Name.

c. Click on the Input Data

button.

d. Enter <0 0 1> for Force, and selectfrequency_depend_

load for the Time/Freq.Dependent Field.

e. Click OK.

f. Click on Select

Application Region.

g. Change the GeometryFilter to FEM.

h. Select the bottom right

corner node for theapplication region.

i. Click Add, and clickOK.

j. Click Apply.

a

b

c

d

e

f

g

h

i

j

i




Step 5. Analysis: Analyze / Entire Model / Full Run

Submit the model for analysis.

a. Analysis: Analyze /Entire Model / Full Run.

b. Click on Solution Type.

c. Select Frequency

Response.

d. Change the Formulationto Direct.

e. Click on Solution

Parameter button.

f. Enter 0.00259 for Wt-Mass Conversion.

g. Enter 0.06 for Struct.Damping Coeff.

h. Click OK.

i. Click OK.

a

b

c

d

e

f

g

hi




Step 5. Analysis: Analyze / Entire Model / Full Run (Cont.)

Submit the model for analysis(cont.).

a. Click on Subcases.

b. Selectdirect_freq_response

from the AvailableSubcases field.

c. Click on Subcase

Parameters.

d. Click on DEFINE

FREQUENCIES«

button.

e. Enter the data according

to the table.

f. Click OK.

g. Click OK.

h. Click Apply.

i. Click Cancel.

a

b

c

f

d

g

h i

e




Step 5. Analysis: Analyze / Entire Model / Full Run (Cont.)

Submit the model for analysis(cont.).

a. Click on Subcase

Select.

b. Selectdirect_freq_response

and unselect Default.

c. Click OK.

d. Click Apply.

a

b

c

d




Step 6. Analysis: Access Results / Attach XDB / Result Entities

Attach the XDB result file.

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

b. Click on Select Results

File.

c. Select ws5.xdb.d. Click OK.

e. Click Apply.

a

b

c

d

e




Step 7. Results: Create / Graph / Y vs X

Create a X-Y graph of displacement results.

a. Results: Create / Graph / Yvs X.

b. Click onSC1:DIRECT_FREQ_RESP

ONSE.

c. Select Global Variable asthe Filter Method.

d. Click Filter .

e. Click Apply.

f. Click Close.

a

b

c

d

e f




Step 7. Results: Create / Graph / Y vs X (Cont.)

Create a X-Y graph of displacement results (cont.).

a. Select Displacement,

Translational for theSelect Y Result field.

b. Select Z Component asthe Quantity.

c. Click on the Target

Entities icon.

d. Change the TargetEntity Selection toNodes.

e. Select the node where

force is applied.

f. Click Apply.

b

a

c

d

e

f





Create a X-Y graph of displacement results (cont.).

a. Click on Display

Attribute.

b. Change Y Axis Scalefrom Linear to Log.

c. Click on Plot Option.d. Change the Complex

No. as to Magnitude.

e. Click Apply.

b

ac

d

e








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Ws05_directfrequency