Saturday, December 23, 2006

 

Buckling Analysis with ABAQUS

In searching for helps with ABAQUS, I found this documentation page informational, although I am not sure if we are using Version 6.5.

The particular question I have at the moment is about a static buckling analysis. I found in Section 6.2 a good introduction to linear eigenvalue buckling predcition (6.2.3) and nonlinear post-buckling analysis (6.2.4).

The first step in buckling analysis is to find the critical load, which should be related to the lowest eigenvalue. However, to relate the output eigenvalues to the critical load, one must clarify the following:

(1) What is the base state? The buckling loads are calculated relative to the base state. This could be the initial condition or the current state of the model at the end of the last analysis step. Geometric nonlinearity may be included in the general analysis steps prior to the eigenvalue buckling analysis (a linear perturbation to the current state).

(2) Does the base state have a preload? It is not clear to me what this preload means and how it is specified in ABAQUS.

(3) What is the perturbation load pattern? This must be specified as applied load, which could be nodal forces, distributed pressure, or thermal load. The amplitude of the applied load is not important, becasue it will be scaled by the eigenvalues.

For example, to analyse buckling due to thermal stress, the critical temperature can be obtained by multiplying the lowest eigenvalue with the applied temperature, assuming a base state with zero preload.

Comments:
The latest version we can use in LRC server is Version 6.6, and the html form of ABAQUS 6.6 Documentation can be reached by the link:
146.6.104.58:2180/v6.6/index.html
 
Yaoyu:

Thanks for the info. I have two questions.

(1) What is the ABAQUS version in our own server, mechanica?

(2) The link in your comment does not work. Can you fix it?

Rui
 
sorry. Our server name should be mechano instead of mechanica.
 
Dr. Huang,
(1) The ABAQUS version in our server is 6.6 for Linux. I am not quite sure about the difference from the Windows version, should not be that much.

(2) The link does not work for me too, I think that could be the server's problem. I just got one alternative link for 6.6 Documentation online:
http://lcadm.rrzn.uni-hannover.de:2080/v6.6/
 
I tried the LRC link at office today and it worked. So I believe this online help can only be reached inside UT network system as internal learning resource.

Actually, ABAQUS Documentation is not free and need to be purchased individually as part of the software bundle. It is just lucky we googled some accessible online documentations which are installed on others machines.
 
I am studying the buckling analysis these days, and i found the theroy given by ABAQUS for is different from our text book, and also the Result Table given by ABAQUS for Buckling ANalysis of a Beam can not calculated by the equation they gave? Do anybody have any idea about that?
 
Online version of Abaqus Documentaion 6.7
http://americanengineeringgroup.blogspot.com/2010/01/online-version-of-abaqus-documentaion.html
 
Hello Dr. Huang

I am using Abaqus for buckling simulation using linear perturbation to estimate the initial buckling critical load. I get the values of Eigen values but I do not get the expected results of simulations by multiplying the initial load to the Eigen value. Can you help me out on this?
 
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