# Discussion Forum

## Piezoelectric device Physics

 Topics: 4.1
RSS feed   |   Turn on email notifications   |   2 Replies   Last post: March 30, 2012 2:23am UTC

Sankha Mukherjee

March 21, 2012 3:32pm UTC

Piezoelectric device Physics

Hello all,

I have been trying to calculate resonance frequencies of a PZT device and have been obtaining complex Eigen frequencies. I then modeled a single-crystal cantilever beam in the Piezoelectric device module and in the Solid mechanics module. In the piezoelectric module I get complex eigen frequencies but the real part of it matches with the estimates of solid mechanics module. Can anyone tell me as to why Piezoelectrc device module gives comlex frequencies. To me a silicon cantilever should not have a complex frequency! Can anyone explain?

Thanks,
Sankha

PS: In the piezoelectric device module I had turned of damping, dielectric losses, still got complex Eigen frequencies.

Ivar Kjelberg

March 21, 2012 6:01pm UTC in response to Sankha Mukherjee

Re: Piezoelectric device Physics

Hi

but whith wich phase angle ?, if you turn off all damping in PZT the imaginary part should be small, most probably in solid without damping the complex part is simply ignored, because it's easy to get complex eigenfrequencies in Solid with some damping

What's so wrong with imaginary eigenfrequencies ?, you can always take the norm and the phase value

--
Good luck
Ivar

Sankha Mukherjee

March 30, 2012 2:23am UTC in response to Ivar Kjelberg

Re: Piezoelectric device Physics

Hello,

I have been thinking and reading about piezoelectric device mode, and seems that to accommodate for energy losses , piezoelectric constants are expressed in complex form. This is why whatever material I use (be it single-crystal silicon) there is always some numerical residue left which appears as the complex component.

I was looking at the manual at found that Eigen frequency is equal to (-) Im(Eigen value)/ 2*pi.

I observed that if I calculate the Eigen value and follow the aforesaid expression I get real numbers all the time. Can you comment on as to why this behavior is observed.

I do not have problem with complex resonance frequencies, as long as I know for sure why complex frequencies are obtained!!!!!!!!!!

Thanks

Sankha

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