Choose menu path Material> Exit to remove the Define Material Model Behavior dialog box

7.6.3.4. Define Nodes and Elements

1. Choose menu path Main Menu> Preprocessor> Modeling> Create> Nodes> In Active CS. The Create Nodes in Active Coordinate System dialog box appears.

2. Enter 1 for node number.

3. Click on Apply. Node location defaults to 0,0,0.

4. Enter 11 for node number.

5. Enter 0,100,0 for the X, Y, Z coordinates.

6. Click on OK. The two nodes appear in the ANSYS Graphics window.

Note — The triad, by default, hides the node number for node 1. To turn the triad off, choose menu path Utility Menu> PlotCtrls> Window Controls> Window Options and select the "Not Shown" option for Location of triad. Then click OK to close the dialog box.

7. Choose menu path Main Menu> Preprocessor> Modeling> Create> Nodes> Fill between Nds. The Fill between Nds picking menu appears.

8. Click on node 1, then 11, and click on OK. The Create Nodes Between 2 Nodes dialog box appears.

9. Click on OK to accept the settings (fill between nodes 1 and 11, and number of nodes to fill 9).

10. Choose menu path Main Menu> Preprocessor> Modeling> Create> Elements> Auto Numbered>

Thru Nodes. The Elements from Nodes picking menu appears.

11. Click on nodes 1 and 2, then click on OK.

12. Choose menu path Main Menu> Preprocessor> Modeling> Copy> Elements> Auto Numbered. The Copy Elems Auto-Num picking menu appears.

13. Click on Pick All. The Copy Elements (Automatically-Numbered) dialog box appears.

14. Enter 10 for total number of copies and enter 1 for node number increment.

15. Click on OK. The remaining elements appear in the ANSYS Graphics window.

7.6.3.5. Define the Boundary Conditions

1. Choose menu path Main Menu> Solution> Unabridged Menu> Analysis Type> New Analysis. The New Analysis dialog box appears.

2. Click OK to accept the default of "Static."

3. Choose menu path Main Menu> Solution> Analysis Type> Analysis Options. The Static or Steady-State Analysis dialog box appears.

4. In the scroll box for stress stiffness or prestress, scroll to "Prestress ON" to select it.

5. Click on OK.

6. Choose menu path Main Menu> Solution> Define Loads> Apply> Structural> Displacement> On Nodes. The Apply U,ROT on Nodes picking menu appears.

7. Click on node 1 in the ANSYS Graphics window, then click on OK in the picking menu. The Apply U,ROT on Nodes dialog box appears.

8. Click on "All DOF" to select it, and click on OK.

9. Choose menu path Main Menu> Solution> Define Loads> Apply> Structural> Force/Moment> On Nodes. The Apply F/M on Nodes picking menu appears.

10. Click on node 11, then click OK. The Apply F/M on Nodes dialog box appears.

11. In the scroll box for Direction of force/mom, scroll to "FY" to select it.

12. Enter -1 for the force/moment value, and click on OK. The force symbol appears in the ANSYS Graphics window.

7.6.3.6. Solve the Static Analysis

1. Choose menu path Main Menu> Solution> Solve> Current LS.

2. Carefully review the information in the status window, and click on Close.

3. Click on OK in the Solve Current Load Step dialog box to begin the solution.

4. Click on Close in the Information window when the solution is finished.

7.6.3.7. Solve the Buckling Analysis

1. Choose menu path Main Menu> Solution> Analysis Type> New Analysis.

Note — Click on Close in the Warning window if the following warning appears: Changing the analysis type is only valid within the first load step. Pressing OK will cause you to exit and reenter SOLUTION. This will reset the load step count to 1.

2. In the New Analysis dialog box, click the "Eigen Buckling" option on, then click on OK.

3. Choose menu path Main Menu> Solution> Analysis Type> Analysis Options. The Eigenvalue Buckling Options dialog box appears.

4. Click on the "Block Lanczos" option, and enter 1 for number of modes to extract.

5. Click on OK.

6. Choose menu path Main Menu> Solution> Load Step Opts> ExpansionPass> Expand Modes.

7. Enter 1 for number of modes to expand, and click on OK.

8. Choose menu path Main Menu> Solution> Solve> Current LS.

Section 7.6: Sample Buckling Analysis (GUI Method)

9. Carefully review the information in the status window, and click on Close.

10. Click on OK in the Solve Current Load Step dialog box to begin the solution.

11. Click on Close in the Information window when the solution is finished.

7.6.3.8. Review the Results

1. Choose menu path Main Menu> General Postproc> Read Results> First Set.

2. Choose menu path Main Menu> General Postproc> Plot Results> Deformed Shape. The Plot Deformed Shape dialog box appears.

3. Click the "Def + undeformed" option on. Click on OK. The deformed and undeformed shapes appear in the ANSYS graphics window.

7.6.3.9. Exit ANSYS

1. In the ANSYS Toolbar, click on Quit.

2. Choose the save option you want and click on OK.

7.7. Sample Buckling Analysis (Command or Batch Method)

You can perform the example buckling analysis of a bar with hinged ends using the ANSYS commands shown below instead of GUI choices. Items prefaced by an exclamation point (!) are comments.

/PREP7

/TITLE, BUCKLING OF A BAR WITH HINGED SOLVES ET,1,BEAM3 ! Beam element R,1,.25,52083E-7,.5 ! Area,IZZ, height

MP,EX,1,30E6 ! Define material properties N,1

N,11,,100 FILL E,1,2 EGEN,10,1,1 FINISH

/SOLU

ANTYPE,STATIC ! Static analysis

PSTRES,ON ! Calculate prestress effects D,1,ALL ! Fix symmetry ends

F,11,FY,-1 ! Unit load at free end SOLVE

FINISH

/SOLU

ANTYPE,BUCKLE ! Buckling analysis

BUCOPT,LANB,1 ! Use Block Lanczos solution method, extract 1 mode MXPAND,1 ! Expand 1 mode shape

SOLVE FINISH /POST1 SET,FIRST PLDISP,1 FINISH

7.8. Where to Find Other Examples

Several ANSYS publications, particularly the ANSYS Verification Manual, describe additional buckling analyses.

The ANSYS Verification Manual consists of test case analyses demonstrating the analysis capabilities of the ANSYS program. While these test cases demonstrate solutions to realistic analysis problems, the ANSYS Verification

Manual does not present them as step-by-step examples with lengthy data input instructions and printouts.

However, most ANSYS users who have at least limited finite element experience should be able to fill in the missing details by reviewing each test case's finite element model and input data with accompanying comments.

The ANSYS Verification Manual contains a variety of buckling analysis test cases:

VM17 - Snap-Through Buckling of a Hinged Shell

VM127 - Buckling of a Bar with Hinged Ends (Line Elements) VM128 - Buckling of a Bar with Hinged Ends (Area Elements)

Section 7.8: Where to Find Other Examples