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Customer Training Material

or s op

Post Bucklin Anal sis

Structural Nonlinearities

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ANSYS Mechanical Structural Nonlinearities

Customer Training MaterialWorkshop 8B: Post Buckling

Goal

Use Nonlinear Stabilization tools together with restart technology

to simulate post buckling behavior.

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ANSYS Mechanical Structural Nonlinearities

Customer Training MaterialWorkshop 8B: Post Buckling

Model Description

L shaped frame represented with 3D Line Bodies

Meshed with 3D Beam elements

Linear Elastic Material

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Model Description (contd)

Horizontal beam fixed at far end.

Vertical column simply supported at bottom.

All nodes are constrained from movement in Z

direction.

500 lb compressive load applied 10 inches off

cen er o ver ca co umn.

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Steps to Follow:

Restore Archive browse for file W8b_buckling.wbpz

Save as

File name: W8b_buckling

*

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

The project Schematic should look like the

picture to the right.

From this Schematic, you can see that the

already been defined (green check marks). It remains to set up and run the FE model in

Mechanical

Open the Engineering Data Cell (highlight and

double click OR Right Mouse Button (RMB)>Edit)

To see relevant dialog boxes, it might be

necessary to go to Utility Menu > View..

Click on Properties and Outline

Verify that the units are in US Eng units (lb, in,)system. If not, fix this by clicking on

Utility Menu > Units > US Engineering(lb,

in

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Return to Project Schematic

Utility Menu > Return to Project

Double click on the Model Cell to open the FE Model (Mechanical

ess on or =>

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Once inside the Mechanical application, verify the working unit system

Unit > US English (lb,in,,,)

The frame model is already set up with the displacement boundary

.

Highlight the BCs and Load to confirm that the model is properly supportedand loaded.

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Note the Analysis Settings Specifications:

Auto Time Stepping = ON

Initial Substeps = 20 (min=20,max=1000)

,

Weak Springs = OFF Stabilization = OFF

Run the Solution

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

After a few bisections, the model fails to converge at about 91% of the

total load

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Review the results from last successfully converged substep

At the point of convergence failure, the structure is beginning to collapse

onto itself and loosing its stability

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

Highlight Analysis Settings and set up for

a manual restart and utilizing Stabilization

Restart specifications:

Restart Point = Load Step 1, Substep 20 Stabilization specifications:

Constant

Damping

Damping Factor = 0.05

Activation = On Nonconvergence

Execute the restart

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ANSYS Mechanical Structural Nonlinearities

Customer Training Material Workshop 8B: Post Buckling

With Stabilization

activated, the solution now

converges successfully.

displacement and otherresults at end time.

Animate results

- Over results set

- Highlight the last 10% of

displacement

- Slow down the animation

get a better view of the

snap thru behavior

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