Ws04_modaltransient

8/6/2019 Ws04_modaltransient

http://slidepdf.com/reader/full/ws04modaltransient 1/20

WS4-1

WORKSHOP 4

MODAL TRANSIENT ANALYSIS

NAS122, Workshop 4, August 2005Copyright¥ 2005 MSC.Software Corporation



WS4-2NAS122, Workshop 4, August 2005Copyright¥ 2005 MSC.Software Corporation




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

flat rectangular plate, created in Workshop 3, subject to time-

varying excitation. This example structure is excited by a 1 psi

pressure load over the total surface of the plate varying at 250 Hz.

In addition, a 25 lb force is applied at a corner of the tip also

varying at 250 Hz, but starting 0.004 seconds after the pressureload begins. Both time-dependent dynamic loads are applied for

the duration of 0.008 seconds only. Use a modal damping of z =

0.03 for all modes. Carry out the analysis for 0.04 seconds.

MODAL TRANSIENT RESPONSE




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

contains the loads and boundary constraints.


X

Y

Z

12345

25.0

12345

12345

12345

12345

1.0 psi o ver the total surface

X

Y

Z





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.




CREATE NEW DATABASE

Create a new database calledws4.db.

a. File / New.

b. Enter ws4 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.

bc

a

d




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

Create a Non Spatial field for the pressure load.

a. Field: Create / NonSpatial / Tabular Input.

b. Enter pressure for the Field Name.

c. Select Time (t) as the Active IndependentVariable.

d. Click Input Data.

e. Click Map Function

to Table.

f. Type in the function,sind(250*360*¶t) and

values shown.g. Click Apply.

h. Click OK on the table.

i. Click Apply.

a

b

c

d

e

f

gh

i




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

Create a Non Spatial field for the force load.

a. Enter force for theField Name.

b. Select Time (t) as the Active IndependentVariable.

c. Click Input Data.

d. Click Map Function

to Table.

e. Type in the function,sind(250*360*(¶t-

0.004)) and values

shown.

f. Click Apply.

g. Click OK on the table.

h. Click Apply.

a

b

c

d

e

f

g

h

Note the required Delay has been

defined by putting in a start time of 0.004 and term (µt-0.004)




Step 3. Load Cases: Create

Create a Time Dependent load case.

a. Load Cases: Create

b. Enter modal_transient for theLoad 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.

a

b

c

e

f g

d




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

Create the time dependentForce load.

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

b. Enter force for theNew Set Name.

c. Click on the Input

Data button.

d. Enter <0 0 25> for Force, and selectForce for theTime/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 the application region.

i. Click Add, and clickOK.

j. Click Apply.

a

b

c

d

e

f

g

h

i

j

i




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

Create the time dependentPressure load.

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

b. Enter pressure for the New Set Name.

c. Change the TargetElement Type to 2D.

d. Click on the Input

Data button.

e. Enter -1 for Top Surf Pressure, and selectPressure for theTime/Freq.Dependent Field.

f. Click OK.g. Click on Select

Application Region.

h. Select all theelements for theapplication region.

i. Click Add, and clickOK.

j. Click Apply.

a

b

c

d

e

f

g

h

i

j

i




Step 6. 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 Transient

Response.

d. Change the Formulationto Modal.

e. Click on Solution

Parameter button.

f. Enter 0.00259 for Wt-Mass Conversion.

g. Click OK.

h. Click OK.

a

b

c

d

e

f

g

h




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

Submit the model for analysis(cont.).

a. Click on Subcases.

b. Select modal_transient

from the AvailableSubcases field.

c. Click on Sub

caseParameters.

d. Click on DEFINE TIME

STEPS button.

e. Change Delta-T to0.0004. Click Enter.

f. Click OK.

a

b

c

d

e

f






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

b. Click on DEFINE MODAL

DAMPING.

c. Enter the values showed inthe Define Dampingwindow.

d. Click OK.

e. Click OK.

f. Click Apply (on theSubcases form).

g. Click Cancel.

a

b

c

d

e






a. Click on Subcase

Select.

b. Select modal_transient

and unselect Default.

c. Click OK.d. Click Apply.

a

b

c d




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 Result

File.

c. Select ws4.xdb

.d. Click OK.

e. Click Apply.

a

b

c

d

e




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

Create a X-Y graph of displacement results.

a. Results: Create / Graph / Yvs X.

b. Click onSC1:MODAL_TRANSIENT.

c. SelectGlobal Variable

asthe Filter Method.

d. Click Filter .

e. Click Apply.

f. Click Close.

a

b

c

d

e f




Step 8. 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 upper right

node. Also choose thenode at the center of the

free edge.f. Click Apply.

b

a

c

d

e

f




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

Documents

Ws04_modaltransient