WORKSHOP 14
BUCKLING OF A SUBMARINE PRESSURE HULL
WS14-2NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
WS14-3NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Workshop ObjectivesCreate groups based on property sets.
Run a linear buckling analysis.
WS14-4NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Problem DescriptionA submarine pressure hull is modeled by plate and bar elements. Check the pressure hull for buckling at an operating depth of 1000 ft which is equivalent to an external pressure of 445 psi.
WS14-5NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Suggested Exercise Steps1. Create a new database and name it submarine.db. 2. Import the MSC.Nastran input file pressure_hull.bdf.3. Create groups based on property sets.4. Post only the center pressure shell section.5. Apply boundary conditions.6. Post the entire pressure shell.7. Apply an external pressure of 445 psi to the pressure shell.8. Run a linear buckling analysis. Request the first 5 roots (buckled
modes).9. Read the xdb file into MSC.Patran.10. Post all the groups.11. Plot the buckled mode shapes and identify which part of the pressure
hull is buckling for each mode.
WS14-6NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
b c
d
f
g
Step 1. Create New Database
Create a new database called submarine.db
a. File / New.b. Enter submarine 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
e
WS14-7NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 2. Import File
a
b
c
Import the Nastran Filea. File: Import.b. Set the object to model and
the source to MSC.NastranInput.
c. Select pressure_hull.bdf.d. Click Apply.e. Click OK to Summary Input
File
d
WS14-8NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 3. Create Groups
Create a new groupa. Group: Create. b. Select Property Set as
the method.c. Select Multiple Groups.d. Click Apply.
a
b
c
d
WS14-9NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 4. Post Entire Pressure Shell
Post two groupsa. Group: Post. b. Shift click to select
pshell.1 and pshell.2.
c. Click Apply.d. Click OK to change
the Current Group.
a
d
b
c
WS14-10NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 5. Apply Boundary Conditions
Create a boundary conditiona. Loads/BCs: Create /
Displacement / Nodal.b. Enter xyzconstraint as the
New Set Name.c. Click Input Data.d. Enter <0 0 0> for
Translations and Rotations.e. Click OK.
d
e
b
c
a
WS14-11NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Apply the boundary conditiona. Click Select
Application Region.b. For the Geometry
Filter select FEM.c. Select the node at the
tip of the shell as shown.
d. Click Add.e. Click OK. f. Click Apply.
e
d
b
c
Step 5. Apply Boundary Conditions
a
f
WS14-12NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 7. Apply Pressure Load
Create a pressure loada. Loads/BCs: Create /
Pressure / Element Uniform.
b. Enter pressure_load as the New Set Name.
c. Set the Target Element Type to 2D.
d. Click Input Data.e. Enter 445 for the Bottom
Surface Pressure.f. Click OK.
e
f
b
a
c
d
WS14-13NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Apply the boundary conditiona. Click Select
Application Region.b. For the Geometry
Filter select FEM.c. Select the entire shell.d. Click Add.e. Click OK. f. Click Apply.
e
d
b
Step 7. Apply Pressure Load
c
a
f
WS14-14NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 8. Run Linear Buckling Analysis
Analyze the modela. Analysis: Analyze /
Entire Model / Full Run.
b. Enter submarineas the job name.
c. Click Solution Type.
d. Choose Buckling.e. Click Solution
Parameters.f. Verify that the Plate
Rz Stiffness Factor is 100.0
g. Click EigenvalueExtraction.
h. For the Number of Desired Roots, enter 5.
i. Click OK.j. Click OK.k. Click OK. l. Click Apply.
a
c
d
eg
h
i
j
k
l
f
b
WS14-15NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 9. Read Results into MSC.Patran
Attach the results filea. Analysis: Access Results /
Attach XDB / Result Entities.
b. Click Select Results File.c. Choose the results file
submarine.xdb.d. Click OK. e. Click Apply.
a
b
c
e
d
WS14-16NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 10. Post All Groups
Post the default groupa. Group:Post.b. Select default_group.c. Click Apply.d. Click on the Reset Graphics
Icon.
a
b
c
d
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Step 11. Plot Mode Shapes
Create a quick plota. Results: Create / Quick
Plot.b. Select a Mode.c. Select Eigenvectors,
Translational as the Deformation Result.
d. Click Apply.e. Repeat for other modes.
a
d
c
b
WS14-18NAS120, Workshop 14, May 2006Copyright© 2005 MSC.Software Corporation
Step 11. Plot Mode Shapes
Record Data in the following table:
Mode No: Buckling Load Factor: Region of Buckling:
1 _________________ ______________________________
2 _________________ ______________________________
3 _________________ ______________________________
4 _________________ ______________________________
5 _________________ ______________________________