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Buckling of a fixed-fixed beam

Posted Sep 6, 2010, 9:31 a.m. EDT Geometry, Studies & Solvers Version 4.4 7 Replies

Kasra Momeni
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I am trying to model the buckling of a fixed-fixed beam while one end has a specific displacement.
When I fix a boundary the COMSOL would not let me to define a fixed displacement for that boundary again.
I would appreciate any suggestion regarding this problem.
7 Replies Last Post Mar 3, 2015, 8:27 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Sep 7, 2010, 2:57 a.m. EDT
Hi

if yu fix a boundary, you say u=0 v=0 ... so you cannot then apply a prescribed displacement that is u=disx, v=disy ... if disx and disy are different from "0".

remove the fixed at the end you put only a prescribed displacement and it should solve correctly.

Basically "fixed means" prescribed displacement all = "0"

If you are afraid your prescribed displacement will overstress the items in certain directions, apply a moment, check the ST doc (3.5a) or have a look at the example in the Model Exhange

--
Good luck
Ivar
Hi if yu fix a boundary, you say u=0 v=0 ... so you cannot then apply a prescribed displacement that is u=disx, v=disy ... if disx and disy are different from "0". remove the fixed at the end you put only a prescribed displacement and it should solve correctly. Basically "fixed means" prescribed displacement all = "0" If you are afraid your prescribed displacement will overstress the items in certain directions, apply a moment, check the ST doc (3.5a) or have a look at the example in the Model Exhange -- Good luck Ivar
aboozar ghafari
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Posted: 1 decade ago Sep 7, 2010, 1:31 p.m. EDT
Dear Ms Momeni
may you explain more! you mean the boundary moves by applying the stress?
Dear Ms Momeni may you explain more! you mean the boundary moves by applying the stress?
Kasra Momeni
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Posted: 1 decade ago Sep 7, 2010, 1:56 p.m. EDT
Thanks for your response. It solved my problem.
Thanks for your response. It solved my problem.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Sep 8, 2010, 1:08 a.m. EDT
Hi

your question is slightly short, but if I got you right, yes, basically stress times strain is the Young modulus. In linear thory the Young modulus is generally considered as a constant so if you apply some stress you will get a displacement (for a fixed-free or free free object), just as if you imply a relative displacement on a fixed free object you will get a resulting stress, no ?

--
Good luck
Ivar
Hi your question is slightly short, but if I got you right, yes, basically stress times strain is the Young modulus. In linear thory the Young modulus is generally considered as a constant so if you apply some stress you will get a displacement (for a fixed-free or free free object), just as if you imply a relative displacement on a fixed free object you will get a resulting stress, no ? -- Good luck Ivar
Doni Wulandana
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Posted: 1 decade ago Mar 2, 2012, 9:02 a.m. EST
Hello,

I was wondering if you actually get the beam to buckle simply by applying the displacement.
Is the applied displacement prescribed in step-by-step mode from 0 ? How about from high displacement?

Doni
Hello, I was wondering if you actually get the beam to buckle simply by applying the displacement. Is the applied displacement prescribed in step-by-step mode from 0 ? How about from high displacement? Doni
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 2, 2012, 10:11 a.m. EST
Hi

for large displacements, turn on the (now since 4.2a in the solver node) geometrical non-linearitites

--
Good luck
Ivar
Hi for large displacements, turn on the (now since 4.2a in the solver node) geometrical non-linearitites -- Good luck Ivar
Sara Bucci
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Posted: 10 years ago Mar 3, 2015, 8:27 a.m. EST
Hello,
I am trying to include geometric nonlinearities in my model but when I go to the study setting I just get an empty windows.
Why I don't have the possibility of checking "include geometric nonlinearities"?

Thanks
Hello, I am trying to include geometric nonlinearities in my model but when I go to the study setting I just get an empty windows. Why I don't have the possibility of checking "include geometric nonlinearities"? Thanks

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