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Resonant Frequency - Membrane
Posted 03.08.2010, 13:49 GMT-4 1 Reply
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Hi,
I am trying to model a circular membrane that is made up of 5 layers stacked one on top of the other. Oxide-nitride-Oxide-Chromium-Gold. The model was drawn in comsol by creating each division for the layer. The properties were defined for the respective subdomains and the boundary properties for the walls were defined as fixed. While the top and bottom surfaces were defined as free. In the subdomain the initial stress was defined in for each layer. The meshing applied was the fine using the swept mesh option. Once the simulation was run using the eigenfrequency solver the results obtained were completely away from the desired experimental value.
Can some one please help me in analysing the resonant frequency for this membrane
Thanks
Karthik
I am trying to model a circular membrane that is made up of 5 layers stacked one on top of the other. Oxide-nitride-Oxide-Chromium-Gold. The model was drawn in comsol by creating each division for the layer. The properties were defined for the respective subdomains and the boundary properties for the walls were defined as fixed. While the top and bottom surfaces were defined as free. In the subdomain the initial stress was defined in for each layer. The meshing applied was the fine using the swept mesh option. Once the simulation was run using the eigenfrequency solver the results obtained were completely away from the desired experimental value.
Can some one please help me in analysing the resonant frequency for this membrane
Thanks
Karthik
1 Reply Last Post 04.08.2010, 01:40 GMT-4
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Posted:
1 decade ago
Hi
There are several issues to check, such as
1) which COMSOL version 3.5 or 4 ? 4 has improved response for setting up prestress analysis, in 3.5 I believe youmust pass via matlab
2) how many elements do you have in the thickness for each layer, I would say 3 is an absolute minimum, 10 would be better, but then the shape of the elements migh become very assymetric, and the DOF runs off ...
3) have you run a static case to scheck that your initial stress is there correctly, and you have some (probably) deflection from this initial stress ?
4) the eigenmode analysis is a linear analysis, and you need to define the linearisation point (after the static case when you are shure your initial stress is correct), as else the stress levels are ignored
5) sometimes shell elements are easier to use for thin layers, BUT you are far more limited in prestress and eigenmode analysis
6) if nothing works, you are left with setting up your own physics based on theory of multilayer shells with stress, and you use then COMSOl as a pure math tool & solver
--
Good luck
Ivar
There are several issues to check, such as
1) which COMSOL version 3.5 or 4 ? 4 has improved response for setting up prestress analysis, in 3.5 I believe youmust pass via matlab
2) how many elements do you have in the thickness for each layer, I would say 3 is an absolute minimum, 10 would be better, but then the shape of the elements migh become very assymetric, and the DOF runs off ...
3) have you run a static case to scheck that your initial stress is there correctly, and you have some (probably) deflection from this initial stress ?
4) the eigenmode analysis is a linear analysis, and you need to define the linearisation point (after the static case when you are shure your initial stress is correct), as else the stress levels are ignored
5) sometimes shell elements are easier to use for thin layers, BUT you are far more limited in prestress and eigenmode analysis
6) if nothing works, you are left with setting up your own physics based on theory of multilayer shells with stress, and you use then COMSOl as a pure math tool & solver
--
Good luck
Ivar