nas120 ws13 submarine buckling

8/10/2019 NAS120 WS13 Submarine Buckling

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WORKSHOP 14

BUCKLING OF A SUBMARINEPRESSURE HULL


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NAS120, Workshop 14, May 2006

Copyright 2005 MSC.Software Corporation


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Workshop Objectives

Create groups based on property sets.

Run a linear buckling analysis.


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Problem Description

A submarine pressure hull is modeled by plate and barelements.

Check the pressure hull for buckling at an operating depth of1000 ft which is equivalent to an external pressure of 445 psi.


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Suggested Exercise Steps

1. 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.


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Step 2. Import File

a

b

c

Import the Nastran File

a. File: Import.b. Set the object to model and

the source to MSC.Nastran

Input.

c. Select pressure_hull.bdf.

d. Click Apply.

e. Click OK to Summary InputFile

d

Step 3 Create Groups


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Step 3. Create Groups

Create a new group

a. Group: Create.

b. Select Property Set as

the method.

c. Select Multiple Groups.

d. Click Apply.

a

b

c

d

Step 4 Post Entire Pressure Shell


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Step 4. Post Entire Pressure Shell

Post two groups

a. 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

Step 5 Apply Boundary Conditions


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Step 5. Apply Boundary Conditions

Create a boundary condition

a. Loads/BCs: Create /

Displacement / Nodal.

b. Enterxyzconstraint as the

New Set Name.

c. Click Input Data.

d. Enter for

Translations and Rotations.

e. Click OK.

d

e

b

c

a

Step 5 Apply Boundary Conditions


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Apply the boundary condition

a. 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

af

Step 7 Apply Pressure Load


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Step 7. Apply Pressure Load

Create a pressure load

a. Loads/BCs: Create /

Pressure / Element

Uniform.

b. Enterpressure_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

Step 7 Apply Pressure Load


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Apply the boundary condition

a. 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

Step 8. Run Linear Buckling Analysis


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Step 8. Run Linear Buckling Analysis

Analyze the model

a. Analysis: Analyze /

Entire Model / Full

Run.

b. Enter submarine

as 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 Eigenvalue

Extraction.

h. For the Number ofDesired 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

Step 9. Read Results into MSC.Patran


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Step 9. Read Results into MSC.Patran

Attach the results file

a. 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

Step 10. Post All Groups


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p p

Post the default groupa. Group:Post.

b. Select default_group.

c. Click Apply.

d. Click on the Reset Graphics

Icon.

a

b

c

d

Step 11. Plot Mode Shapes


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p p

Create a quick plot

a. 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

Step 11. Plot Mode Shapes


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p p

Record Data in the following table:

Mode No: Buckling Load Factor: Region of Buckling:

1 _________________ ______________________________

2 _________________ ______________________________

3 _________________ ______________________________

4 _________________ ______________________________

5 _________________ ______________________________

nas120 ws13 submarine buckling

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