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Pre stressed frequency domain analysis - How to: Values of Dependent variables
Posted 17 giu 2013, 08:45 GMT-4 Studies & Solvers, Structural Mechanics Version 4.3b 3 Replies
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Hello,
I am trying to use the solution of the static deformation as the initial conditions for my frequency response analysis.
First, I have prepared two solutions, the static deformation is calculated in a stationary step. The frequency response is calculated in the frequency domain. And under the frequency domain solver, the Values of Dependent variables were taken from the static solution, at least I think I am doing it so.
When the solver finishes calculating, the results indicate no sings of the static solution as if the frequency domain was calculated independently from the static solution.
Secondly I tried using the Preset Studies: "Pre-stressed Analysis: Frequency Domain" with no success.
From the documentation it seems so straight forward to implement this and I feel that I am missing something fundamental.
Can somebody comment on the attached file? Or which example do you recommend for me to examine?
Thanks in advance,
Onur
I am trying to use the solution of the static deformation as the initial conditions for my frequency response analysis.
First, I have prepared two solutions, the static deformation is calculated in a stationary step. The frequency response is calculated in the frequency domain. And under the frequency domain solver, the Values of Dependent variables were taken from the static solution, at least I think I am doing it so.
When the solver finishes calculating, the results indicate no sings of the static solution as if the frequency domain was calculated independently from the static solution.
Secondly I tried using the Preset Studies: "Pre-stressed Analysis: Frequency Domain" with no success.
From the documentation it seems so straight forward to implement this and I feel that I am missing something fundamental.
Can somebody comment on the attached file? Or which example do you recommend for me to examine?
Thanks in advance,
Onur
Attachments:
3 Replies Last Post 4 mag 2016, 14:52 GMT-4
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Posted:
1 decade ago
Hi,
The Model Library example bracket_frequency ("Bracket - Frequency-Response Analysis") shows how to do a prestressed frequency domain analysis.
Please also read the forum posting from 'May 23, 2013 10:23am CEST' in the thread www.comsol.com/community/forums/general/thread/35454 where the difference between adding a 'Pre-stressed Analysis: Frequency Domain' study and adding the study steps manually is highlighted.
In your model there is a specific problem in that you want to use a Prescribed Acceleration. 'Prescribed Acceleration' does not have an option to add 'Harmonic Perturbation'. You can however create the same effect manually by writing 'linper(1)' instead of '1' as input for the acceleration.
As an alternative, you can use Prescribed Displacement, and add a 'Harmonic Perturbation' subnode where you set the displacement to 1/(solid.omega)^2. This means that instead of your current sequence (Fixed[5], Prescribed Displacement[2,13], Prescribed Acceleration[2,5,13]) you would use (Prescribed Displacement[5] , Prescribed Displacement[2,13]). Now there is no need to disable any features in the study step, since the pre-stress data is entered in the Prescribed Displacement node, and the perturbation data is entered in its Harmonic Perturbation subnode.
Using the latter approach also ensures consistency in the sense that a boundary which has a prescribed value (displacement or acceleration) in the frequency domain study should also have it already in the stationary prestress analysis.
Regards,
Henrik
The Model Library example bracket_frequency ("Bracket - Frequency-Response Analysis") shows how to do a prestressed frequency domain analysis.
Please also read the forum posting from 'May 23, 2013 10:23am CEST' in the thread www.comsol.com/community/forums/general/thread/35454 where the difference between adding a 'Pre-stressed Analysis: Frequency Domain' study and adding the study steps manually is highlighted.
In your model there is a specific problem in that you want to use a Prescribed Acceleration. 'Prescribed Acceleration' does not have an option to add 'Harmonic Perturbation'. You can however create the same effect manually by writing 'linper(1)' instead of '1' as input for the acceleration.
As an alternative, you can use Prescribed Displacement, and add a 'Harmonic Perturbation' subnode where you set the displacement to 1/(solid.omega)^2. This means that instead of your current sequence (Fixed[5], Prescribed Displacement[2,13], Prescribed Acceleration[2,5,13]) you would use (Prescribed Displacement[5] , Prescribed Displacement[2,13]). Now there is no need to disable any features in the study step, since the pre-stress data is entered in the Prescribed Displacement node, and the perturbation data is entered in its Harmonic Perturbation subnode.
Using the latter approach also ensures consistency in the sense that a boundary which has a prescribed value (displacement or acceleration) in the frequency domain study should also have it already in the stationary prestress analysis.
Regards,
Henrik
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Posted:
1 decade ago
Hello,
Thank you for your comprehensive and fulfilling response. You have been very helpful.
Regards,
Onur
Thank you for your comprehensive and fulfilling response. You have been very helpful.
Regards,
Onur
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Posted:
9 years ago
Hi
I'm a student and one of COMSOL 5.1 users.
I am trying to impose a displacement (static one) of a rigid circle in the center of a clambed elastic membrane , in order to vary the volume of a cavity. I applied a static displacement; the membrane deformes so a new volume is supposed to be created. I tryed to perform a frequency analysis study using the resulted displacement, to see the influence of the volume changing on the acoustic perfrmance of my membrane+cavity system but it seems that the change of volume in the cavity wasn't taken into account?
Do you have an idea of what I miss in my modeling?
Thanks for help.
best regards;
Izem
I'm a student and one of COMSOL 5.1 users.
I am trying to impose a displacement (static one) of a rigid circle in the center of a clambed elastic membrane , in order to vary the volume of a cavity. I applied a static displacement; the membrane deformes so a new volume is supposed to be created. I tryed to perform a frequency analysis study using the resulted displacement, to see the influence of the volume changing on the acoustic perfrmance of my membrane+cavity system but it seems that the change of volume in the cavity wasn't taken into account?
Do you have an idea of what I miss in my modeling?
Thanks for help.
best regards;
Izem