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Hi Mina,

What do you mean with frequency response? Do you want to know the resonance modes or you want to know the frequency response due to the application of an external force?

I am also working on a mechanical structure, does anyone knows how to simulate an AC voltage and view its consequence in the electrostatic force (hence in the displacement of the mechanical structure)? I have simulated my model in static (fixed DC voltage) and I have seen the displacement due to the electrostatic force. But now I want to see the frequency response if this voltage is AC.

Thanks for your answers.

Hi jordi....
By frequency response i mean that I want to plot the maximum displacement of my structure VS. the frequency of the applied external force!!!
I'm really new to COMSOL and i would use any help

THNX

Hi again mina,

So we are in the same situation. I would really appreciate some help.

By the way, I'm using COMSOL v4

Hi

I have been working on this too. I have gotten a frequency response to work in 4.0. My understanding is that if you apply a constant force (face load, domain load, edge load etc...), and then you go to the frequency response study and apply a single frequency that will multiply that constant load by a sine or cosine function with an angular frequency of 2 pi times the oscillation frequency.

To get a range of frequencies you take advantage of the fact that in COMSOL you can type any function or variable where a numerical input is required, among which are numbers. One function has following syntax:

range(x1,R,x2)

will give a list of all the numbers x1 x1+R x1+2R x1+3R ... x2.
Another way is to type numbers directly

x1 x2 x3 x4

and so forth however many numbers you want (with only spaces in between, no commas or anything)

The way I found out is, when I was playing with a 2D Solid Mechanics model, I applied an Edge Load to a side, and then right clicking on that you can add a phase. I Added that and went to the documentation for that by clicking on the little laptop icon in the settings section for phase. It talks about the equations involved.

I don't know how to get maximum displacement, but others have been talking about something similar on the forum if I remember correctly.

Hi

the frequency response is a harmonic development, typically the force is multiplied by an harmonic function ("*s" for the control guys working with Laplace). you define the domain wit a range or a series of values or a range (start, step,stop).

Note that once you have created a sequence in V4 and you change your frequency range in the Study Frequency Domain node it is not automatically updated in the solver sequence parametric field.

Another caveat is that the amplitudes are arbitrary, and will depend strongly on the damping you define, but as mostly one forget the damping the peaks are oftern very narrow, and you have convergence problems if you try to resolve them too nicely (its better in V4.0a)

have fun Comsoling
Ivar

Hi everybody,

I attach the file that Ivar uploaded but with some modifications (COMSOL v4 file). Now it has two physics (Solid Mechanics and Electrostatics).

I am trying to simulate the response of the system when the parameter Vin is and AC voltage. I tried using a Frequency Domain analysis but it does not seem to work. Vin is not becoming an AC voltatge and, therefore, the force "Fes" either.

Can somebody give me a hand with that?

Thanks & have fun!

Any chance you can send it in V3.5a ?

Amit

Hi

the frequency response is a harmonic development, typically the force is multiplied by an harmonic function ("*s" for the control guys working with Laplace). you define the domain wit a range or a series of values or a range (start, step,stop).

Note that once you have created a sequence in V4 and you change your frequency range in the Study Frequency Domain node it is not automatically updated in the solver sequence parametric field.

Another caveat is that the amplitudes are arbitrary, and will depend strongly on the damping you define, but as mostly one forget the damping the peaks are oftern very narrow, and you have convergence problems if you try to resolve them too nicely (its better in V4.0a)

have fun Comsoling
Ivar