Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.
Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Quality factor Vs. pressure for a cantilever.
Posted Apr 24, 2015, 4:29 p.m. EDT MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 4.4 1 Reply
Please login with a confirmed email address before reporting spam
Our system is a cantilever. One of its extremes is fix and, under the other extreme that is free, there is an electrode for the excitation of the cantilever. This system is immersed in an air box. Tests are made using “emi”.
Objectives/query:
1) We need to find the factor quality of the system, Q, in function of the box pressure containing our cantilever, from atmospheric pressure to very high vacuum. Which “physics” and “study” I can use to find it?
2) To obtain the response in frequency using the application “Frequency-Domain, Perturbation” it is necessary to consider an excitation voltage Vin = Vdc + Vac. Where Vac is a sine perturbation and Vdc a DC voltage. It is possible perform a study of response in frequency using only a Vac excitation?
Background:
I performed simulations of “Eigenfrequency” and “Frequency-Domain, Perturbation”. In the study of “Frequency-Domain, Perturbation” I used Rayleigh damping, where the parameters “alpha” and “beta” are calculated using equations of the “Frequency Response of a Biased Resonator - 3D” model (from the comsol library), assuming a value for Q. However, I need to find the value of Q changing the pressure of the box containing the cantilever/structure (vacuum chamber). Do you know how to do it?
Objectives/query:
1) We need to find the factor quality of the system, Q, in function of the box pressure containing our cantilever, from atmospheric pressure to very high vacuum. Which “physics” and “study” I can use to find it?
2) To obtain the response in frequency using the application “Frequency-Domain, Perturbation” it is necessary to consider an excitation voltage Vin = Vdc + Vac. Where Vac is a sine perturbation and Vdc a DC voltage. It is possible perform a study of response in frequency using only a Vac excitation?
Background:
I performed simulations of “Eigenfrequency” and “Frequency-Domain, Perturbation”. In the study of “Frequency-Domain, Perturbation” I used Rayleigh damping, where the parameters “alpha” and “beta” are calculated using equations of the “Frequency Response of a Biased Resonator - 3D” model (from the comsol library), assuming a value for Q. However, I need to find the value of Q changing the pressure of the box containing the cantilever/structure (vacuum chamber). Do you know how to do it?
1 Reply Last Post Apr 24, 2015, 5:06 p.m. EDT
Please login with a confirmed email address before reporting spam
Posted:
10 years ago
Pardon my ignorance, but in traditional linear systems damping comes from a damping force which is proportional to velocity. But wind resistance is generally proportional to the square of velocity. That implies a non-linear damping, for example more at higher amplitudes than at lower amplitudes. Would a linear analysis thus be able to model this?