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Current density and resistance in piezoelectric device

Posted 04.02.2013, 05:42 GMT-5 MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 4.3a 7 Replies

Stanley van den Heever
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I am trying to simulate the current density in a piezoelectric device.
The geometry is a simple rod with a fixed boundary (also ground boundary) and a surface load on the opposite boundary. I can easily get the displacement and voltage, due to the applied force.

If I plot the current density (normal or in any direction) the result is simply zero... due to the polarisation of the structure (due to the applied force) the current cannot be zero?

Secondly, I want to add resistance to the material properties, how can I do this? It is not a required parameter to solve the equations, I guess I have to alter the equations and add the resistance on that level?
7 Replies Last Post 24.07.2013, 09:14 GMT-4
Stanley van den Heever
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Posted: 1 decade ago 05.02.2013, 04:43 GMT-5
I added the electric currents (ec) physics to my problem. I do the piezoelectric study first and then the electric currents. I made the piezoelectric material a current source, but still no current is flowing...
What am I missing?
I added the electric currents (ec) physics to my problem. I do the piezoelectric study first and then the electric currents. I made the piezoelectric material a current source, but still no current is flowing... What am I missing?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 05.02.2013, 05:28 GMT-5
Hi

but normally PZT solves already for V arnt you doubling up your dependent variables ?
Normally you will only get current flow if you have a closed circuit with non zero conductivity, so I suspect that you have missed something in your model build-up

--
Good luck
Ivar
Hi but normally PZT solves already for V arnt you doubling up your dependent variables ? Normally you will only get current flow if you have a closed circuit with non zero conductivity, so I suspect that you have missed something in your model build-up -- Good luck Ivar
Stanley van den Heever
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Posted: 1 decade ago 05.02.2013, 05:55 GMT-5
I use the solved V, from PZT, for the second study (ec).

The PZT model doesn't use the conductivity as part of the model?
I use the solved V, from PZT, for the second study (ec). The PZT model doesn't use the conductivity as part of the model?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 05.02.2013, 07:53 GMT-5
Hi

that's it, because PZD solves for _u_ and V, there is nothing more by adding in EC and solving again for V2. So normally you can get everything via PZD physics

If you have defined a GND and a Terminal You should get a Voltage out, for a given impedance you have the bulk current too, and the complex impedance, and voltage gives you indications on phase lag

--
Good luck
Ivar
Hi that's it, because PZD solves for _u_ and V, there is nothing more by adding in EC and solving again for V2. So normally you can get everything via PZD physics If you have defined a GND and a Terminal You should get a Voltage out, for a given impedance you have the bulk current too, and the complex impedance, and voltage gives you indications on phase lag -- Good luck Ivar
Stanley van den Heever
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Posted: 1 decade ago 05.02.2013, 08:34 GMT-5
Thanks, think I am getting to where I want to be!
Thanks, think I am getting to where I want to be!
Naveet Kaur
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Posted: 1 decade ago 24.07.2013, 09:07 GMT-4
Hi Stanley,

How did you find the current / impedance?

Regards,
Naveet
Hi Stanley, How did you find the current / impedance? Regards, Naveet
Stanley van den Heever
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Posted: 1 decade ago 24.07.2013, 09:14 GMT-4
Hi Naveet,

The solution I came up with is using the AC/DC module, not sure if you have it?
I add the second physics (the AC/DC). In the piezoelectric physics I specify the top end of my piezoelectric device (where the maximum voltage is) as a Terminal.
In the AC/DC module I can then use that Terminal as a voltage source, close the loop with a resistor and a current is measured.

The problem with this solution is that the current is a constant. There is no variation with resistance within the device.

Please let me know if this helps and if you maybe find a better solution.
Hi Naveet, The solution I came up with is using the AC/DC module, not sure if you have it? I add the second physics (the AC/DC). In the piezoelectric physics I specify the top end of my piezoelectric device (where the maximum voltage is) as a Terminal. In the AC/DC module I can then use that Terminal as a voltage source, close the loop with a resistor and a current is measured. The problem with this solution is that the current is a constant. There is no variation with resistance within the device. Please let me know if this helps and if you maybe find a better solution.

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