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MEMS Piezoelectric (Voltage vs. Eigenfreq)

Posted Aug 19, 2010, 4:58 p.m. EDT MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Studies & Solvers 3 Replies

Albert Chen
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Hi,

I am changing the voltage across the piezoelectric beam actuator I've created. I expect to see a different set of eigenfrequency numbers when I change the voltage. However, the numbers remain the same.

Under solve parameters
Analysis Types: Piezo Solid (smpz3d) Eigenfrequency with Eigenfrequency Solver.

I'm reading the eigenfrequency numbers from
Point evaluation > Solution to use > eigenfrequency

Any ideas??

-Albert
3 Replies Last Post Apr 17, 2014, 12:39 p.m. EDT
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Hello Albert Chen

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Chris Menzel
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Posted: 1 decade ago Jan 6, 2011, 11:24 a.m. EST
Albert,
My understanding is that the eigenfrequency calculation is for unloaded model. I suppose that in this case the voltage would be considered a load rather than a BC.....

My guess would be that you can get around this by running a frequency response around the values that come out of the eigenvalue problem at the various voltages...
Albert, My understanding is that the eigenfrequency calculation is for unloaded model. I suppose that in this case the voltage would be considered a load rather than a BC..... My guess would be that you can get around this by running a frequency response around the values that come out of the eigenvalue problem at the various voltages...
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 7, 2011, 1:35 a.m. EST
Hi

Indeed what Physical phenomena should change the Eigenfrequency of a beam if you apply a voltage ?

f[Hz]= 1/2*pi*sqrt(K[N/m]/m[kg])

Probably you expected a stress stiffening via "K" or somewhat like that ?

then you must use Matlab and v3.5a or just COMSOL v4 (if possible 4.1 while 4.0 is rather limited and far more difficult to tweak in the solver section, it's was a too-early version)

for that
a) you apply your voltage in a stationary case to stress your beam,
b) you store the solution, and
c) you do an eigenfrequency analysis taking the stored solution as linearizion point

--
Good luck
Ivar
Hi Indeed what Physical phenomena should change the Eigenfrequency of a beam if you apply a voltage ? f[Hz]= 1/2*pi*sqrt(K[N/m]/m[kg]) Probably you expected a stress stiffening via "K" or somewhat like that ? then you must use Matlab and v3.5a or just COMSOL v4 (if possible 4.1 while 4.0 is rather limited and far more difficult to tweak in the solver section, it's was a too-early version) for that a) you apply your voltage in a stationary case to stress your beam, b) you store the solution, and c) you do an eigenfrequency analysis taking the stored solution as linearizion point -- Good luck Ivar
Cindy Nshuti
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Posted: 1 decade ago Apr 17, 2014, 12:39 p.m. EDT
Hello Ivar,

I've been trying to figure out how to get a voltage vs. freq, initially I performed a study for the eigenfrequencies but I can't seem to get results computing power vs. freq or voltage vs. freq

[A bit of context]
I am designing piezoelectric energy harvesters with different geometric dimensions, shapes and materials, but in order to compare their feasibility to other research I need values for their power or voltage versus frequencies of 60-120 Hz

[Method so far in COMSOL]
1. Pzd > Eigenfrequency > created geometry, mesh and selected materials > added Electric Potential and Ground > after computing it I then stop here , because even though I've seen tutorials on how to create plots, I'm not getting the desired results

2. Pzd > Stationary > created geometry, mesh and selected materials > added Electric Potential and Ground > stopped here as well.

Your advice would be very helpful.

Yours Sincerely,
Cindy
Hello Ivar, I've been trying to figure out how to get a voltage vs. freq, initially I performed a study for the eigenfrequencies but I can't seem to get results computing power vs. freq or voltage vs. freq [A bit of context] I am designing piezoelectric energy harvesters with different geometric dimensions, shapes and materials, but in order to compare their feasibility to other research I need values for their power or voltage versus frequencies of 60-120 Hz [Method so far in COMSOL] 1. Pzd > Eigenfrequency > created geometry, mesh and selected materials > added Electric Potential and Ground > after computing it I then stop here , because even though I've seen tutorials on how to create plots, I'm not getting the desired results 2. Pzd > Stationary > created geometry, mesh and selected materials > added Electric Potential and Ground > stopped here as well. Your advice would be very helpful. Yours Sincerely, Cindy

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