WORKSHOP 13 NORMAL MODES OF A RECTANGULAR PLATE

WS13-2 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation

WS13-3 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation l Workshop Objectives l Perform a normal modes analysis on a rectangular plate. l Compare analysis results to theoretical results. l Evaluate the effect of varying mesh density.

WS13-4 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation l Problem Description l A rectangular plate is simply supported at all edges. Find the first 10 normal modes for this plate. l E = 10 x 10 6 psi =0.33 = lb/in 3 l t = in

WS13-5 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation l Suggested Exercise Steps 1. Create a new database and name it rectangular_plate1.db. 2. Create a rectangular surface. 3. Mesh the surface to create plate elements. 4. Create material properties. Dont forget to enter density. 5. Create physical properties. 6. Apply Loads and Boundary Conditions. 7. Perform a normal modes analysis to determine the first 10 modes for the plate. 8. Read the results into MSC.Patran. 9. Plot the mode shapes. Visually evaluate the quality of the mode shapes. 10. Compare the first natural frequency to theoretical results. 11. File / save a copy as rectangular_plate2.db. 12. Close the database and open the rectangular_plate2 database. 13. Delete the original results file. 14. Re-mesh the surface. Use a global edge length of 0.5 in. 15. Re-run the analysis. 16. Attach the new results file to the database. 17. Plot the mode shapes and compare the results from the finer mesh with the earlier results.

WS13-6 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation b c d f g Step 1. Create New Database Create a new database called rectangular_plate1. db a.File / New. b.Enter rectangular_plate1 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

WS13-7 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 2. Create a Rectangular Surface Create a surface a.Geometry: Create / Surface / XYZ. b.Enter for the Vector Coordinates list. c.Click Apply. b c a

WS13-8 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 3. Mesh the Surface Create a surface mesh a.Elements: Create / Mesh / Surface. b.Select the surface. c.Enter 1.4 for the Global Edge Length. d.Click Apply. a b c d

WS13-9 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 4. Create Material Properties Create an isotropic material a.Materials: Create / Isotropic / Manual Input. b.Enter plate_material for the Material Name. c.Click Input Properties. d.Enter 10e6 for the Elastic Modulus. e.Enter 0.33 for the Poisson Ratio. f.Enter for the Density. g.Click OK. h.Click Apply. d g e f a c b h

WS13-10 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 5. Create Physical Properties Create physical properties a.Properties: Create / 2D / Shell. b.Enter plate_prop as the Property Set Name. c.Click Input Properties. d.Click on the Select Material Icon. e.Select plate_material as the material. f.Enter for the Thickness. g.Click OK. g d f e a b c

WS13-11 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Apply the physical properties a.Click in the Select Members box. b.Screen pick the plate as shown. c.Click Add. d.Click Apply. b Step 5. Create Physical Properties a c d

WS13-12 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 6. Apply Loads and Boundary Conditions Create a boundary condition a.Loads/BCs: Create / Displacement / Nodal. b.Enter simple_support as the New Set Name. c.Click Input Data. d.Enter for Translations e.Click OK. d e b c a

WS13-13 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Apply the boundary condition a.Click Select Application Region. b.For the Geometry Filter select Geometry. c.Set the Selection Filter to Curve or Edge and select an edge. d.Click Add. e.Repeat the procedure until all four edges have been added. f.Click OK. g.Click Apply. f d b Step 6. Apply Loads and Boundary Conditions c a g

WS13-14 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 7. Run Normal Modes Analysis Analyze the model a.Analysis: Analyze / Entire Model / Full Run. b.Click Solution Type. c.Choose Normal Modes. d.Click Solution Parameters. e.Enter for Wt.-Mass conversion. f.Click OK. g.Click OK. h.Click Apply. c g f e d a h b

WS13-15 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 8. 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 rectangular_plate1.xdb. d.Click OK. e.Click Apply. a b c e d

WS13-16 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 9. Plot Mode Shapes Create a quick plot a.Select iso 3 view b.Results: Create / Quick Plot. c.Select a mode to plot. d.Select Eigenvectors, Translational as the Deformation Result. e.Click Apply. First 10 modes: 1_________ 6_________ 2_________ 7_________ 3_________ 8_________ 4_________ 9_________ 5_________ 10________ b e d a c

WS13-17 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 10. Compare to Theoretical Results l Theoretical results based on Formulas for Natural Frequency and Mode Shape, 1984 edition, Table 11-4, case 16 a = 12, b = 8, a/b = = E = 10 x 10 6 t = = 0.33 = 0.101/386.1 = x = t = x f 1 = 265 Hz

WS13-18 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 11. Save a Copy Save a copy of the file a.File: Save a Copy. b.Type rectangular_plate2 as the file name. c.Click Save. a bc

WS13-19 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 12. Open the New Database Close the original file and open the new file a.File: Close. b.File: Open. c.Select the file: rectangular_plate2.db. d.Click OK. a b c d

WS13-20 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 13. Delete Old Results File Delete XDB attachment a.Analysis: Delete / XDB Attachment. b.Select the rectangular_plate1. xdb attachment. c.Click Apply. d.Choose Yes to delete the attachment. e.Click on the front view icon. a b c e d

WS13-21 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 14. Re-Mesh the Surface Create a finer mesh a.Elements: Create / Mesh / Surface. b.Select the entire surface. c.Enter 0.5 for the Global Edge Length. d.Click Apply. e.Choose Yes to delete the existing mesh. e a b c d

WS13-22 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 15. Run Normal Modes Analysis Analyze the model a.Analysis: Analyze / Entire Model / Full Run. b.Change the job name to: rectangular_plate2. c.Click Apply. a b c

WS13-23 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 16. Attach New Results File Attach the results file a.Analysis: Access Results / Attach XDB / Result Entities. b.Click Select Results File. c.Choose the results file rectangular_plate2.xdb. d.Click OK. e.Click Apply. a b c e d

WS13-24 NAS120, Workshop 13, May 2006 Copyright 2005 MSC.Software Corporation Step 17. Plot Mode Shapes Create a quick plot a.Results: Create / Quick Plot. b.Select Default, A1: Mode 10 as the Select Result Case. c.Select Eigenvectors, Translational as the Deformation Result. d.Click Apply. e.Click on Iso 3 view icon First 10 modes: 1_________ 6_________ 2_________ 7_________ 3_________ 8_________ 4_________ 9_________ 5_________ 10________ a d c e b