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Nonlinear bending of an isotropic plate

Posted Feb 19, 2012, 2:44 p.m. EST Structural Mechanics 5 Replies

Iftah Nudel
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Hello,

I m trying to simulate a very known benchmark problem which also apears on Reddy and Arciniega's article, ''Tensor-based finite element formulation for geometrically nonlinear analysis of shell structures''.

The problem consists of a plate with width=12 and height=1 (as defined in Comsol), E (module Young) = 1.2*10^6,
poisson ratio is 0 and the thickness of the plate is 0.1. The boundary conditions are fixed constraint at one edge and moment at the opposite edge. (the moment is defined in the Local Edge System and not in the Global Coordinate System).

While in the article Reddy and Arciniega are able to to reach fully circular rotation, using comsol i only can reach much lower rotations when the applied moment is 42. applying moments higher then 42 makes the solution false.

When applying moments lower then 42 , i get rotations that are accurate when comparing to analytical results, but i still wonder why i cant fully replicate what Reddy and Rrciniega did.

thx a lot
Iftah Nudel
5 Replies Last Post Feb 23, 2012, 7:39 a.m. EST
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Feb 19, 2012, 5:13 p.m. EST
If you post your model maybe someone on the Forum can help. Also, COMSOL support can help with such problems.
If you post your model maybe someone on the Forum can help. Also, COMSOL support can help with such problems.
Iftah Nudel
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Posted: 1 decade ago Feb 20, 2012, 5:24 a.m. EST
Hi,

I m attaching the model.

thx a lot
Hi, I m attaching the model. thx a lot
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 20, 2012, 11:44 a.m. EST
Hi

first of all define the material, or remove it and use the "User Definition fileds" (but all of them)

Then turn on the plot while solving (solver node) and use a parameter and a continuation parameter to ramp up your load from typically Param=0..1 * -45 (define Parameter Param = 0, select the stationary solver node, go the the Extensions tab and select "continuation" add (+) the Param and set a range such as " range(0,0.1,1)"

Still I'm not sure the shell physics accept such large deformations, one would need to go down and dig into the doc first


by the way check if you cannot update to latest version, there are a few improvement in the latest patch

you could also try with a 2D solid first

--
Good luck
Ivar
Hi first of all define the material, or remove it and use the "User Definition fileds" (but all of them) Then turn on the plot while solving (solver node) and use a parameter and a continuation parameter to ramp up your load from typically Param=0..1 * -45 (define Parameter Param = 0, select the stationary solver node, go the the Extensions tab and select "continuation" add (+) the Param and set a range such as " range(0,0.1,1)" Still I'm not sure the shell physics accept such large deformations, one would need to go down and dig into the doc first by the way check if you cannot update to latest version, there are a few improvement in the latest patch you could also try with a 2D solid first -- Good luck Ivar
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Feb 22, 2012, 10:49 a.m. EST
Use the parametric feature that Ivar mentioned and also put a symmetry condition on Line 3. Right now after some deformation the plate switches to another deformation mode. It’s a valid mode but that’s not the one you want. Adding the symmetry condition gives you the benchmark solution you’re expecting.

Nagi Elabbasi
Veryst Engineering
Use the parametric feature that Ivar mentioned and also put a symmetry condition on Line 3. Right now after some deformation the plate switches to another deformation mode. It’s a valid mode but that’s not the one you want. Adding the symmetry condition gives you the benchmark solution you’re expecting. Nagi Elabbasi Veryst Engineering
Iftah Nudel
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Posted: 1 decade ago Feb 23, 2012, 7:39 a.m. EST
Thx a lot! it's working.
Thx a lot! it's working.

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