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Rigid Boundary Condition on a vibrating membrane

Posted Jul 11, 2012, 5:59 a.m. EDT Acoustics & Vibrations Version 4.3 1 Reply

Elisa Benedetti
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Hi all,

I am working with a elastic circular membrane (acoustic-shell interaction): I would like to set a little "slice" of my membrane to be rigid. this means that, when the membrane vibrates, this slice can move "up and down" with the membrane, but it cannot bend. In other words, I want the slice to be completely stiff in the radial direction. I also attach an image that should clarify what my aim is.
Does anyone have any idea about how could I implement that with comsol (4.3)?

Any help is greatly appreciated!

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1 Reply Last Post Aug 13, 2012, 7:22 a.m. EDT
COMSOL Moderator

Hello Elisa Benedetti

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

JoeJohns
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Posted: 1 decade ago Aug 13, 2012, 7:22 a.m. EDT
Hi Elisa,

I am also a beginner in using COMSOL, but have some tips that can get you started in the right direction, until an expert takes the time to give a detailed solution. Or perhaps you discover it on your own.

You could try to make the membrane consist of two joined surface areas, the bulk, and the rigid segment.
Next you try the following options.

1) Use the Change Thickness feature to increase the thickness of the rigid segment only.
A sufficient thickness supposed to make the segment behave as a quite rigid object. If the consequent increase of its mass is not desirable then make a custom material from the original one, and lower its density - use it only for the rigid segment.

2) You could define an artificial solid material having properties that would make it extremely hard to deform. Assign this material to the segment.

The combination of the two would work perhaps even better.

Regards,
Joe
Hi Elisa, I am also a beginner in using COMSOL, but have some tips that can get you started in the right direction, until an expert takes the time to give a detailed solution. Or perhaps you discover it on your own. You could try to make the membrane consist of two joined surface areas, the bulk, and the rigid segment. Next you try the following options. 1) Use the Change Thickness feature to increase the thickness of the rigid segment only. A sufficient thickness supposed to make the segment behave as a quite rigid object. If the consequent increase of its mass is not desirable then make a custom material from the original one, and lower its density - use it only for the rigid segment. 2) You could define an artificial solid material having properties that would make it extremely hard to deform. Assign this material to the segment. The combination of the two would work perhaps even better. Regards, Joe

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