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beam buckling analysis

Posted Mar 18, 2014, 12:52 a.m. EDT Structural Mechanics Version 4.4 3 Replies

Leon Pan
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Hi,
I am trying to analysis a beam buckling under gravity with different boundary conditions.
It can be fixed-free or fixed-fixed but slided in one direction.
Can anyone give some suggestions about buckling?
I studied the truss tower example and it seems that the beam has to been under unit load for buckling analysis.
Is this right?
thanks for anything.
3 Replies Last Post Mar 18, 2014, 9:53 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 18, 2014, 2:39 a.m. EDT
Hi

If you use the "linear buckling analysis" study, it is based on a prestressed eigenfrequency analysis, so the output is a "security factor" with respect to the initial stress from the given load.
So if you give a "unit" load you have a security factor w.r.t. this unit load,
if you however define a nominal load, then your security factor is w.r.t. the nominal load value

For more, see Henrik's intersting blog on buckling :

www.comsol.eu/blogs/buckling-structures-suddenly-collapse/

--
Have fun COMSOLing
Ivar
Hi If you use the "linear buckling analysis" study, it is based on a prestressed eigenfrequency analysis, so the output is a "security factor" with respect to the initial stress from the given load. So if you give a "unit" load you have a security factor w.r.t. this unit load, if you however define a nominal load, then your security factor is w.r.t. the nominal load value For more, see Henrik's intersting blog on buckling : http://www.comsol.eu/blogs/buckling-structures-suddenly-collapse/ -- Have fun COMSOLing Ivar
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago Mar 18, 2014, 3:03 a.m. EDT
Hi,

Please note that the Linear Buckling study type is not available for the Beam interface. It can currently only be used with the Solid Mechanics, Shell and Truss interfaces.

Regards,
Henrik
Hi, Please note that the Linear Buckling study type is not available for the Beam interface. It can currently only be used with the Solid Mechanics, Shell and Truss interfaces. Regards, Henrik
Leon Pan
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Posted: 1 decade ago Mar 18, 2014, 9:53 a.m. EDT
Thank you very much for all help.
Yes I did use the solid mechanics model to do my study. I want to analysis the buckling of a drill string which should look like a hollow tube (or shell?). But I start with solid mechanics because it is easier. I have many difficulties with it. First one: can you tell me how to set up two boundary conditions? One end is fixed at the bottom and I used fixed contraint. I think this one is ok. Another end should be fixed at x and y direction and the top face of the beam could not rotate. But in z-axis, it is free to slide. I am not sure if I explain it clearly. I tried to use prescribed displacement but the top face is rotated.
Thanks again.
Thank you very much for all help. Yes I did use the solid mechanics model to do my study. I want to analysis the buckling of a drill string which should look like a hollow tube (or shell?). But I start with solid mechanics because it is easier. I have many difficulties with it. First one: can you tell me how to set up two boundary conditions? One end is fixed at the bottom and I used fixed contraint. I think this one is ok. Another end should be fixed at x and y direction and the top face of the beam could not rotate. But in z-axis, it is free to slide. I am not sure if I explain it clearly. I tried to use prescribed displacement but the top face is rotated. Thanks again.

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