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Resonance frequency of a piezoelectric cube

Posted Jan 25, 2011, 11:45 a.m. EST MEMS & Nanotechnology, Piezoelectric Devices, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.2a 6 Replies

Jean-Michel Poirier
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Hello,

I am trying to find the resonance frequency of a piezoelectric cube, using the Piezoelectric Devices physics of COMSOL 4.0.

The edge of the cube is 500e-9m long, and its material is Zync Oxide.

I mean to do so by two studies:

1- Frequency Domain study.

I put a voltage of 40mV on a face of the cube, the opposed face being the ground. This potential induces a deformation in the cube.
I do the study from 1e9 to 10e9 Hz with a 10e6Hz step.

I don't really know how to see the resonance... So I guess the best solution must be to plot the displacement of a corner depending on the frequency ( disp=f(freq) )?
I see something looking like a resonance frequency around 3.4GHz, but I see several other maximums at higher frequencies (8.1GHz, 8.3GHz....) , that I can't explain.

Could you tell me if it can be because of some wrong or missing parameters? or else they would be normal..

2- Eigenfrequency

I try to find eigenfrequencies around the 3.4GHz seen before (6 values by def.) , but the software seems to give me random values around this 3.4GHz frequency.
Even stranger, I will get eigenfrequencies for any eigen value I put (like 5 or 6 GHz).

Finally, sometimes I get unexplainable Complex eigenfrequencies... Do you know why?

Thanks for your time,
Regards

Michel
6 Replies Last Post Sep 11, 2012, 11:25 p.m. EDT
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Hello Jean-Michel Poirier

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User COMSOL
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Posted: 1 decade ago Mar 16, 2011, 9:40 a.m. EDT
The best way is to plot the impedance of the piezo cube and check the resonances
--
User COMSOL
The best way is to plot the impedance of the piezo cube and check the resonances -- User COMSOL
Sahar Simyari
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Posted: 1 decade ago Mar 27, 2012, 5:46 p.m. EDT
Hi,
can you explain me how i can plot impedance?my project consist a zinc that some Al electrodes are on that,i apply 10v to one of electrodes and i want to get resonsnce frequency and admittance value(matrix) but i cant.
Hi, can you explain me how i can plot impedance?my project consist a zinc that some Al electrodes are on that,i apply 10v to one of electrodes and i want to get resonsnce frequency and admittance value(matrix) but i cant.
Anurag
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Posted: 1 decade ago Aug 21, 2012, 5:26 a.m. EDT
Hi there,

I did a similar analysis using version 4.2a. Instead of applying an electrical potential, apply a terminal constraint of voltage type. Then after the frequecy domain analysis if you plot -- abs(1/imag(pzd.Y11)); you will get the required impedance trace. Looking at the impedance trace, you can find the resonance and anti-resonance frequencies of the model.

Hope it helps.

Anurag Dhutti
Hi there, I did a similar analysis using version 4.2a. Instead of applying an electrical potential, apply a terminal constraint of voltage type. Then after the frequecy domain analysis if you plot -- abs(1/imag(pzd.Y11)); you will get the required impedance trace. Looking at the impedance trace, you can find the resonance and anti-resonance frequencies of the model. Hope it helps. Anurag Dhutti
Jingwen Yang
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Posted: 1 decade ago Sep 8, 2012, 10:02 a.m. EDT
Hello Anurag：

I began to study comsol lately, could you tell me how to plot the connection of impedance and frequency. when I try your suggestion why the software tell me： failed to value the expresion imag(pzd.Y11) and abs(1/imag(pzd.Y11)). look forward to your reply.

thank you,

yang
Hello Anurag： I began to study comsol lately, could you tell me how to plot the connection of impedance and frequency. when I try your suggestion why the software tell me： failed to value the expresion imag(pzd.Y11) and abs(1/imag(pzd.Y11)). look forward to your reply. thank you, yang
Anurag
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Posted: 1 decade ago Sep 11, 2012, 5:42 a.m. EDT
Hi Yang,

The only reason I can think of is that you might have assigned an electrical constraint of 'Electric Potential' instead of 'Terminal'. Assign Terminal constraint type on the desired surface of your geometry and then in the properties window, you can choose the terminal to be a 'Voltage Type' of the desired voltage.

This worked for me so hope it does for you, but if it doesn't, I'll be happy to look at your model to get a better understanding of the problem.

Best Regards,
Anurag Dhutti
Hi Yang, The only reason I can think of is that you might have assigned an electrical constraint of 'Electric Potential' instead of 'Terminal'. Assign Terminal constraint type on the desired surface of your geometry and then in the properties window, you can choose the terminal to be a 'Voltage Type' of the desired voltage. This worked for me so hope it does for you, but if it doesn't, I'll be happy to look at your model to get a better understanding of the problem. Best Regards, Anurag Dhutti
Jingwen Yang
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Posted: 1 decade ago Sep 11, 2012, 11:25 p.m. EDT
Hi Anurag,

Thanks for your reply. Yes you were right, I use the wrong electrical constraint. Now I have done the impedance analysis. But I want to know that whether "abs(1/imag(pzd.Y11))" is the image part of the impedance?
If I want to konw the real part of impedance, am I right to use the function "abs(1/real(pzd.Y11))"? But in my model, the curve "abs(1/real(pzd.Y11)) vs frequency" is nothing. it is so strange, I don't know why, could you help me?

Besides, my model is a very simple one(just for try): a pzt film, one surface is ground, the other surface is terminal with voltage. frequency domain 150000:1000:750000.

Thanks for your time

Yang
Hi Anurag, Thanks for your reply. Yes you were right, I use the wrong electrical constraint. Now I have done the impedance analysis. But I want to know that whether "abs(1/imag(pzd.Y11))" is the image part of the impedance? If I want to konw the real part of impedance, am I right to use the function "abs(1/real(pzd.Y11))"? But in my model, the curve "abs(1/real(pzd.Y11)) vs frequency" is nothing. it is so strange, I don't know why, could you help me? Besides, my model is a very simple one(just for try): a pzt film, one surface is ground, the other surface is terminal with voltage. frequency domain 150000:1000:750000. Thanks for your time Yang

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