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Application of different modal damping constants

Posted May 29, 2013, 7:36 a.m. EDT Structural Mechanics 4 Replies

Umut Tabak
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Dear all,

I have experimentally determined modal damping coefficients. Is that possible to use these modal damping coefficients directly in COMSOL for a frequency response function analysis?

Apparently, COMSOl gives me the chance to use a uniform loss factor for all the modes, I guess.

Can someone point me in the right direction whether this is possible or not?

Best,
Umut
4 Replies Last Post May 30, 2013, 9:39 a.m. EDT
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago May 29, 2013, 6:19 p.m. EDT
You can use modal damping coefficients in a frequency analysis if it is a modal frequency analysis. In that case you directly input the damping ratios in the Modal Solver settings.

Nagi Elabbasi
Veryst Engineering
You can use modal damping coefficients in a frequency analysis if it is a modal frequency analysis. In that case you directly input the damping ratios in the Modal Solver settings. Nagi Elabbasi Veryst Engineering
Umut Tabak
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Posted: 1 decade ago May 30, 2013, 5:38 a.m. EDT

You can use modal damping coefficients in a frequency analysis if it is a modal frequency analysis. In that case you directly input the damping ratios in the Modal Solver settings.

Nagi Elabbasi
Veryst Engineering


Dear Nagi,

Thanks for this response.

Modal frequency analysis is the frequency analysis that uses the modal superposition principle but not the direct solver option(where a different linear system is solved at each frequency to end up with the frequency response function), is this correct?

Thanks,
Umut
[QUOTE] You can use modal damping coefficients in a frequency analysis if it is a modal frequency analysis. In that case you directly input the damping ratios in the Modal Solver settings. Nagi Elabbasi Veryst Engineering [/QUOTE] Dear Nagi, Thanks for this response. Modal frequency analysis is the frequency analysis that uses the modal superposition principle but not the direct solver option(where a different linear system is solved at each frequency to end up with the frequency response function), is this correct? Thanks, Umut
Umut Tabak
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Posted: 1 decade ago May 30, 2013, 7:20 a.m. EDT

You can use modal damping coefficients in a frequency analysis if it is a modal frequency analysis. In that case you directly input the damping ratios in the Modal Solver settings.

Nagi Elabbasi
Veryst Engineering


Dear Nagi,

Do you have a simple example for a modal frequency analysis where damping ratios are specified?

BR,
Umut
[QUOTE] You can use modal damping coefficients in a frequency analysis if it is a modal frequency analysis. In that case you directly input the damping ratios in the Modal Solver settings. Nagi Elabbasi Veryst Engineering [/QUOTE] Dear Nagi, Do you have a simple example for a modal frequency analysis where damping ratios are specified? BR, Umut
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago May 30, 2013, 9:39 a.m. EDT
Dear Umut,

Yes, modal frequency analysis is based on modal superposition. There is an example file called elbow_bracket in the COMSOL models that shows how to setup a model frequency analysis. By default it does not use modal damping ratios (therefore they are set to zero). However, you can change that easily in the Modal Solver settings window.

Nagi Elabbasi
Veryst Engineering
Dear Umut, Yes, modal frequency analysis is based on modal superposition. There is an example file called elbow_bracket in the COMSOL models that shows how to setup a model frequency analysis. By default it does not use modal damping ratios (therefore they are set to zero). However, you can change that easily in the Modal Solver settings window. Nagi Elabbasi Veryst Engineering

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