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Coupling B/W two solid stress-strain modules
Posted 9 apr 2013, 01:00 GMT-4 Structural Mechanics Version 4.2 5 Replies
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I am trying to model a 3D structural mechanics problem with two separate solid stress-strain modules coupled together at the interfacial boundary through equal displacement boundary condition (i.e. Rx, Ry and Rz for one module is equal to u, v and w of other module) where Ri represents applied displacements in x, y and z directions while u, v and w represents the displacements (the solid stress-strain module always solves for u,v and w in each domain along with the stresses and strains). I think the constraint on the interfacing boundary in this way means that at the interface the displacements must be same. However I cannot acheive convergence at all and the simulations always diverges. I am using default solver settings and unstructured tetrahedral elements mesh. Can some one guide me what should I do.
Regards
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Why 2 structural ?, cant you use only 1 ? then it should converge better. The default conversion in "union" mode is to set all common boundaries to "continuity" you do not need to care more, if you need specail cases, you can use assembly mode, but then group by "unioN" the geoemtry that can be treated as one common continuos domain, this will reduce the number of identiy pairs you need to handle manually
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Good luck
Ivar
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Can u please tell me how to work with union mode in structural mechanics module of comsol 3.5(a). Is it the usual union of the domains that can be created with bolean algebra of geometries (like the typical "union" option available in comsol) or is it something else?, because there is no continuity b.c in structural mechanics module as far as I know and I think one has to implement it on the common boundaries.
Kind regards
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by default in union "geometry" finish/geomanalyze mode your geometry is simplified and you have entities with common boundaries and continuity of flux over the boundaries.
The finsh union is like making a "big union" of all geometrical objects, and then analyse them and reduce any double overlappoing points, edges boundaries or domains, or split up in smaller parts any overalling but not fully mathcning entities
This hasnt changed from 3.5 times. But in V4 you can now use union mode an have automatically several of the "thin boundary physics implemented without having to manually define assembly mode and identitiy pairs
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Good luck
Ivar
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Can you please guide me how can I use geometry union mode in V4.2? I must have continuity boundary condition on a common boundary in my model. I have noticed that if I create a geometry and click "form union (fin)" button I still have to define pairs if I select the continuity condition, however u mentioned that if I use union mode in 4.2 automatically I can define continuity without defining pairs. Kindly let me know how to select geometry union mode in 4.2.
Kind regards
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the default approach of COMSOL is that you use "Union Finish mode" which sets continuity for all common boundaries between domains of a given physics.
But if you have different physics in different domain, it's up to your to ensure that you get the desired continuity along common borders
In structural, apart for some contact problems, I never use "assembly" mode
Check the doc
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Good luck
Ivar