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Damped Eigen frequency Analysis

Posted 5 mar 2015, 15:57 GMT-5 MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Studies & Solvers, Structural Mechanics Version 5.0 1 Reply

Saleha Quadssia
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Hei,

I am working on calculating Q factor from eigenfrequecny analysis using structural mechanics. I know that Q factor= abs(imag)/2*abs(real) but my problem is when I add damping in the form of isotropic loss factor, it would increase the real part too (which is frequency of the system) that should decrease with the increase in damping. Since both the real and imaginary part are increasing simultaneously, there is a little difference in the values of Q factor with or without damping.
I know that adding damping to eigenfrequency gives imaginary frequencies, but I am not sure how to deal with it.
Please give me some suggestions on how to proceed.
Any help would be appreciated.
Regards,
Saleha
1 Reply Last Post 22 mar 2017, 03:04 GMT-4
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Hello Saleha Quadssia

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宇鹏 傅
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Posted: 8 years ago 22 mar 2017, 03:04 GMT-4

Hei,

I am working on calculating Q factor from eigenfrequecny analysis using structural mechanics. I know that Q factor= abs(imag)/2*abs(real) but my problem is when I add damping in the form of isotropic loss factor, it would increase the real part too (which is frequency of the system) that should decrease with the increase in damping. Since both the real and imaginary part are increasing simultaneously, there is a little difference in the values of Q factor with or without damping.
I know that adding damping to eigenfrequency gives imaginary frequencies, but I am not sure how to deal with it.
Please give me some suggestions on how to proceed.
Any help would be appreciated.
Regards,
Saleha


Hi, Saleha
Have u tried the frequency domain? U can use it to verify the eigenfrequency result.
I have also confused about the damping set in the COMSOL. I used the Rayleigh damping factor to add the damping to the model, but the frequency sweeping result showed that at the eigenfrequency the amplitude is zero which is obviously wrong. I think the damping factor I give is wrong? I'd appreciate it if u can give me any advice.
Regards,
Yupeng.
[QUOTE] Hei, I am working on calculating Q factor from eigenfrequecny analysis using structural mechanics. I know that Q factor= abs(imag)/2*abs(real) but my problem is when I add damping in the form of isotropic loss factor, it would increase the real part too (which is frequency of the system) that should decrease with the increase in damping. Since both the real and imaginary part are increasing simultaneously, there is a little difference in the values of Q factor with or without damping. I know that adding damping to eigenfrequency gives imaginary frequencies, but I am not sure how to deal with it. Please give me some suggestions on how to proceed. Any help would be appreciated. Regards, Saleha [/QUOTE] Hi, Saleha Have u tried the frequency domain? U can use it to verify the eigenfrequency result. I have also confused about the damping set in the COMSOL. I used the Rayleigh damping factor to add the damping to the model, but the frequency sweeping result showed that at the eigenfrequency the amplitude is zero which is obviously wrong. I think the damping factor I give is wrong? I'd appreciate it if u can give me any advice. Regards, Yupeng.

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