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how to limit deflection to a particular value in comsol

Posted 04.12.2011, 06:55 GMT-5 Low-Frequency Electromagnetics, MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Structural Mechanics Version 4.1, Version 4.2a 1 Reply

Deepak Khushalani
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Respected Sir,

I have understood the coupling of mutipysics and have been able to get some results respect to deformation of my cantilever

Now the problem is how to limit the deformation to a particular value in z domain. As the beam in my model is crossing the bottom electrode(RF line) with which I have to study the contact deformations.


The gap between the beam and the RF line is 1.5 microns so I need to limit my deflection to that value to study contact analysis and see the current transmission for which I need to decide the physics to be used.

Hope you can help me out. Attaching my model along with the mail.


Yours sincerely
Deepak khushalani
RCOEM
Nagpur

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1 Reply Last Post 11.12.2011, 06:58 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 11.12.2011, 06:58 GMT-5
Hi

I have had a quick look on your model, and I believe I can come with a few suggestions

you should better sort the physics used w.r.t the domains required, for me the ALE is mainly for the air, in v4 even you can us the spatial and material frame approach (see the doc).

Then you should drive the ale deformation with the solid u,v,w and not block it to =0.

One of the difficulties you will encounter, for your contact region is the change of topology, if you leave "air" in between the air film will go to "0" as well as your air mesh and the solver will fail before having finished. one way around is to remove the air domain from the contact region and solve it only in solid.

Then your two contact plates, if hey are fixed at the bottom, thin as they are they will not deform much you could even consider them as just a top "surface"

The simpler you make your model, at least to start with the simpler and quicker you will get some first results, later you might complexify to take into account 2d order effects etc

Personally I mostly start in 2D, then only I go the 3D, and then to a "full" 3D model, if required

--
Good luck
Ivar
Hi I have had a quick look on your model, and I believe I can come with a few suggestions you should better sort the physics used w.r.t the domains required, for me the ALE is mainly for the air, in v4 even you can us the spatial and material frame approach (see the doc). Then you should drive the ale deformation with the solid u,v,w and not block it to =0. One of the difficulties you will encounter, for your contact region is the change of topology, if you leave "air" in between the air film will go to "0" as well as your air mesh and the solver will fail before having finished. one way around is to remove the air domain from the contact region and solve it only in solid. Then your two contact plates, if hey are fixed at the bottom, thin as they are they will not deform much you could even consider them as just a top "surface" The simpler you make your model, at least to start with the simpler and quicker you will get some first results, later you might complexify to take into account 2d order effects etc Personally I mostly start in 2D, then only I go the 3D, and then to a "full" 3D model, if required -- Good luck Ivar

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