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Geometric Nonlinearity problem

Posted Feb 2, 2012, 2:49 p.m. EST Studies & Solvers, Structural Mechanics Version 4.3 12 Replies

Julian Freed-Brown
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I have an odd problem. I am trying to recreate the Large Deformation Beam model (www.comsol.com/showroom/documentation/model/204/) before I start my own project to investigate buckling. I was following along with the model, but when I go to Study 1 > Step 1: Stationary and open Study Settings, I do not see any buttons that say "Include Geometric Nonlinearity". Indeed, I do not see any buttons at all.

When I download the support file for the Large Deformation Beam model, I do see this button.

However, if I delete the stationary solver and add a new one, I do not see the button any more.

It seems like I must be doing something dumb here, but I can't seem to figure out what. Any help would be appreciated.

Thanks,
-jfb
12 Replies Last Post Dec 16, 2013, 2:18 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 Feb 2, 2012, 4:10 p.m. EST
Hi

it could be a version issue, as these changes vere brought in in 4.2 or 4.2a (have forgotten which one exactly) and older versions put the non linear button in the linear elastic material subnode of solid. By the way I understand it as two non linearitites, the stress representations (with or without cross derivative terms) and the large geometrical deformations.

Be sure you have a newly patche 4.2a (mine is 166 today) and that you reconstruct the model from scratch (do not change an older version, I never trust that fully, at least not for pre 4.2a versions

--
Good luck
Ivar
Hi it could be a version issue, as these changes vere brought in in 4.2 or 4.2a (have forgotten which one exactly) and older versions put the non linear button in the linear elastic material subnode of solid. By the way I understand it as two non linearitites, the stress representations (with or without cross derivative terms) and the large geometrical deformations. Be sure you have a newly patche 4.2a (mine is 166 today) and that you reconstruct the model from scratch (do not change an older version, I never trust that fully, at least not for pre 4.2a versions -- Good luck Ivar
Julian Freed-Brown
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Posted: 1 decade ago Feb 3, 2012, 11:10 a.m. EST
Hi Ivar,

Thanks for the quick reply. Unfortunately, this did not solve my problem.

I am using version 4.2a and the most recent patch (166). However, I still do not see anything that says "Include Geometric Nonlinearity" under the "Stationary" subnode (even when I create a new model from scratch). I also checked the "Linear Elastic Material Model" subnode under the solid mechanics node, but didn't see anything there, either.

Please let me know if their are any more suggestions.

Thanks again,
-jfb
Hi Ivar, Thanks for the quick reply. Unfortunately, this did not solve my problem. I am using version 4.2a and the most recent patch (166). However, I still do not see anything that says "Include Geometric Nonlinearity" under the "Stationary" subnode (even when I create a new model from scratch). I also checked the "Linear Elastic Material Model" subnode under the solid mechanics node, but didn't see anything there, either. Please let me know if their are any more suggestions. Thanks again, -jfb
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 3, 2012, 11:13 a.m. EST
Hi

I do (if I select solid, it depends on the physics (also .166 on Win-7)

--
Good luck
Ivar
Hi I do (if I select solid, it depends on the physics (also .166 on Win-7) -- Good luck Ivar

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Julian Freed-Brown
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Posted: 1 decade ago Feb 3, 2012, 11:39 a.m. EST
Hi

I don't (even when I select solid, on a Mac)


-jfb
Hi I don't (even when I select solid, on a Mac) -jfb

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 3, 2012, 2:29 p.m. EST
Hi

that's funny, I would say send a mail to "support" and refer to the discussion here, they might have an explanation

--
Good luck
Ivar
Hi that's funny, I would say send a mail to "support" and refer to the discussion here, they might have an explanation -- Good luck Ivar
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Feb 3, 2012, 3:53 p.m. EST
Are you sure you have the Structural Mechanics module, or one of the other modules that support nonlinear structural analysis?

Nagi Elabbasi
Veryst Engineering
Are you sure you have the Structural Mechanics module, or one of the other modules that support nonlinear structural analysis? Nagi Elabbasi Veryst Engineering
Mohammad Khalili
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Posted: 1 decade ago Apr 9, 2013, 6:42 p.m. EDT
Hi,
I have the same problem when I use "beam" model. I am using 4.3a on win vista. There should be a way to select "geometric non-linearity" option when I am using beam model too.

I have to say that I don't have this problem when I use "solid mechanics" model, but when I use "beam" or "plate" models that option disappears!!!

Please help
Hi, I have the same problem when I use "beam" model. I am using 4.3a on win vista. There should be a way to select "geometric non-linearity" option when I am using beam model too. I have to say that I don't have this problem when I use "solid mechanics" model, but when I use "beam" or "plate" models that option disappears!!! Please help
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago Apr 10, 2013, 1:21 a.m. EDT
Hi Mohammad,

The Beam interface does not support geometric nonlinearity, so in a model with only a beam interface this option is not available. For the plate interface it should be there, though.

Regards,
Henrik
Hi Mohammad, The Beam interface does not support geometric nonlinearity, so in a model with only a beam interface this option is not available. For the plate interface it should be there, though. Regards, Henrik
Mohammad Khalili
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Posted: 1 decade ago Apr 10, 2013, 2:44 a.m. EDT

Hi Henric,

Now I am a little confused. I have a beam model that is under large deformation, so I need to use "geometry non linearity " to get correct results. How can I solve this problem? This is very basic I don't think COMSOL doesn't support something this basic!!!

Thanks for your answer
Hi Henric, Now I am a little confused. I have a beam model that is under large deformation, so I need to use "geometry non linearity " to get correct results. How can I solve this problem? This is very basic I don't think COMSOL doesn't support something this basic!!! Thanks for your answer
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago Apr 10, 2013, 9:57 a.m. EDT
Hi Mohammad,

Unfortunately geometric nonlinearity is not yet implemented for the Beam interface. We are planning to expand our beam capabilities in the future.

Regards,
Henrik
Hi Mohammad, Unfortunately geometric nonlinearity is not yet implemented for the Beam interface. We are planning to expand our beam capabilities in the future. Regards, Henrik
Saurabh Mittal
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Posted: 1 decade ago Dec 13, 2013, 1:44 a.m. EST
Geometric Nonlinearity in the electromechanics module cannot be unticked.
Does comsol 4.3 use geometric non linearity in this case?
The error returned always is:

Warning: Inverted mesh element near coordinates

What to do?
Geometric Nonlinearity in the electromechanics module cannot be unticked. Does comsol 4.3 use geometric non linearity in this case? The error returned always is: Warning: Inverted mesh element near coordinates What to do?
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago Dec 16, 2013, 2:18 a.m. EST
Hi,

Yes, Geometric nonlinearity is always on when using the Electromechanical physics interface.

The Inverted mesh element error could mean that you get excessive mesh distortions in the air domain. Look at the deformed mesh just before the solution fails, and try to figure out what is happening. Another initial mesh may then help. You could also try to apply the load in smaller steps.

Regards,
Henrik
Hi, Yes, Geometric nonlinearity is always on when using the Electromechanical physics interface. The Inverted mesh element error could mean that you get excessive mesh distortions in the air domain. Look at the deformed mesh just before the solution fails, and try to figure out what is happening. Another initial mesh may then help. You could also try to apply the load in smaller steps. Regards, Henrik

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