WORKSHOP 14 BUCKLING OF A SUBMARINE PRESSURE HULL

WS14-2 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation

WS14-3 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation l Workshop Objectives l Create groups based on property sets. l Run a linear buckling analysis.

WS14-4 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation l Problem Description l A submarine pressure hull is modeled by plate and bar elements. l Check the pressure hull for buckling at an operating depth of 1000 ft which is equivalent to an external pressure of 445 psi.

WS14-5 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation l 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.

WS14-6 NAS120, Workshop 14, May 2006 Copyright 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

WS14-7 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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 Input File d

WS14-8 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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

WS14-9 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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

WS14-10 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation Step 5. Apply Boundary Conditions Create a boundary condition a.Loads/BCs: Create / Displacement / Nodal. b.Enter xyzconstraint as the New Set Name. c.Click Input Data. d.Enter for Translations and Rotations. e.Click OK. d e b c a

WS14-11 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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 a f

WS14-12 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation Step 7. Apply Pressure Load Create a pressure load a.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

WS14-13 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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

WS14-14 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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 g.Click Eigenvalue Extraction. h.For the Number of Desired Roots, enter 5. i.Click OK. j.Click OK. k.Click OK. l.Click Apply. a c d e g h i j k l f b

WS14-15 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation 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

WS14-16 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation Step 10. Post All Groups Post the default group a.Group:Post. b.Select default_group. c.Click Apply. d.Click on the Reset Graphics Icon. a b c d

WS14-17 NAS120, Workshop 14, May 2006 Copyright 2005 MSC.Software Corporation Step 11. Plot Mode Shapes 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

WS14-18 NAS120, Workshop 14, May 2006 Copyright 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_________________ ______________________________