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Solid Mechanics: Estimating change in out-of-plane thickness in 2D model

Posted Dec 8, 2011, 3:08 p.m. EST Geometry, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers, Structural Mechanics Version 4.2 4 Replies

Clinton Canaday
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Hello. I am trying to approximate an abrupt change in thickness in an otherwise planar part. The local increase in thickness is due to a reinforcement. I have really only found one approach, which involves modifying the modulus proportionally to the thickness, such that a region with twice the thickness would have a doubled modulus. Unfortunately, this does not work on a few initial trials, whether applied as a discontinuous change, i.e. two domains with different modulus but otherwise identical properties, or as a varying smooth transition.

I understand that a discontinuous modulus results in discontinuous displacement, etc. which is why it wouldn't solve, but are there other ways to do this since, in reality, the displacement is obviously not discontinuous, albeit gradients may be rather sharp.

I would like to avoid 3D modeling for a number of reasons, so please keep suggestions to the 2D domain.
4 Replies Last Post Dec 10, 2011, 3:53 a.m. EST
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Dec 8, 2011, 10:02 p.m. EST
The approach you suggested should work. When the Young’s Modulus changes even abruptly the displacements should still be continuous.

Nagi Elabbasi
Veryst Engineering
The approach you suggested should work. When the Young’s Modulus changes even abruptly the displacements should still be continuous. Nagi Elabbasi Veryst Engineering
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 9, 2011, 12:48 a.m. EST
Hi

normally you have a sub node "Domain Change thickness". If you are in HT you must turn on "out of plane heat transfer" to activate thickness changes (this is also valid for 1D HT) and if you do not define any "out of plane heat flux it remains isolated.

In this way there is no reason to adapt the physical parameters, its cleaner and less error prone, but basically should give the same results

--
Good luck
Ivar
Hi normally you have a sub node "Domain Change thickness". If you are in HT you must turn on "out of plane heat transfer" to activate thickness changes (this is also valid for 1D HT) and if you do not define any "out of plane heat flux it remains isolated. In this way there is no reason to adapt the physical parameters, its cleaner and less error prone, but basically should give the same results -- Good luck Ivar
Clinton Canaday
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Posted: 1 decade ago Dec 9, 2011, 3:34 p.m. EST
Thanks for the help. I meant to say discontinuous derivative, but now I'm insecure and have been reviewing FEM theory. That tends to get lost in "modelling".
Thanks for the help. I meant to say discontinuous derivative, but now I'm insecure and have been reviewing FEM theory. That tends to get lost in "modelling".
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 10, 2011, 3:53 a.m. EST
Hi

in gneral discontinous derivatives should be avoided, either by using "smoothing transitional function (step, pulse etc in v4 whixh include already the discreate Heaviside from v3. Or y sometimes using math with the weak form

--
Good luck
Ivar
Hi in gneral discontinous derivatives should be avoided, either by using "smoothing transitional function (step, pulse etc in v4 whixh include already the discreate Heaviside from v3. Or y sometimes using math with the weak form -- Good luck Ivar

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