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Deformation issue in electrostatic actuation of thin membrane
Posted May 3, 2010, 4:53 a.m. EDT 4 Replies
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Hello,
New try, hopefully I'll get an answer this time ;-)
The issue is the following: a thin membrane in 2D fixed on both sides, electrostatically actuated so that it defoms vertically (see file attached).
For that specific case the theory predicts an instability around 1.13µm (max displacement) and a pull-in voltage around 15V.
In the Model, with Large Deformation ON, I observe a much larger displacement and pull-in voltage, whereas with Large Deformation OFF, I retrieve the theoretical values.
Question: if the deformation is indeed small why are the two models giving such a difference?
Thank you
Elodie
4 Replies Last Post May 16, 2010, 4:38 p.m. EDT
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Posted:
1 decade ago
Sorry,
the file didn't get attached.
Here it is!
the file didn't get attached.
Here it is!
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Posted:
1 decade ago
Last try to upload the file
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Posted:
1 decade ago
Hi
if you have trouble uploading it could be because the file is too big, try to zip it first, or to do a "reset model" to leave us mother redo the analysis. If you do a reset model, be sure COMSOL is not saving the geometry as a separate file, in which case you must submit BOTH for us to rebuild it.
So without a model, my only guess is that your case is sufficient non-linear that the "large deformation" is better tracking reality, and that your analytical calculations are based on linear theory. But this is just a guess, you could also be unlucky with some values entered, and the results are somewhat wrong.
Hope this helps on the way
Have fun Comsoling
Ivar
if you have trouble uploading it could be because the file is too big, try to zip it first, or to do a "reset model" to leave us mother redo the analysis. If you do a reset model, be sure COMSOL is not saving the geometry as a separate file, in which case you must submit BOTH for us to rebuild it.
So without a model, my only guess is that your case is sufficient non-linear that the "large deformation" is better tracking reality, and that your analytical calculations are based on linear theory. But this is just a guess, you could also be unlucky with some values entered, and the results are somewhat wrong.
Hope this helps on the way
Have fun Comsoling
Ivar
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Posted:
1 decade ago
Looks like it's going to work this time! Firewall issue.
Yes the analytical calculation is based on linear theory of pull-in voltage for thin membranes. The main assumption being that the deformation is very small compared with the length of the membrane....
Anyway, if someone wants to have a look at it, I'm still interested in any comments or advice (I'm failrly new to Comsol and to mechanics!)
Thank you
Elodie
Yes the analytical calculation is based on linear theory of pull-in voltage for thin membranes. The main assumption being that the deformation is very small compared with the length of the membrane....
Anyway, if someone wants to have a look at it, I'm still interested in any comments or advice (I'm failrly new to Comsol and to mechanics!)
Thank you
Elodie
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