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Effective stiffness in the Modal Nalysis

Posted Dec 18, 2009, 2:02 p.m. EST 2 Replies

Sadegh Hajhashemi
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Hi every one,

As you know, Resonance frequency is equal to the square root of effective stiffness divided by effective mass. My question is:
How can I find the effective mass and stiffness for a specific mode in the modal analysis.

Regards,
Sadegh
2 Replies Last Post Dec 19, 2009, 4:05 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 19, 2009, 3:54 p.m. EST
Hi

I assume you are referring to modal "mass partcipation factors", or "effective masses" that you get from most FEM tools in structural modal analysis.
These are extracted from the modal eigenvectors through a particular normalisation, that COMSOL is not using.
So there is no easy way from my knowledge to get them in COMSOL (I have alread complained a couple of time about this, pls forward your need to "support") in very simple cases you might export the matrices to matlab and renormalise them, but most models have so large sparse matrices that this is useless

Ivar
Hi I assume you are referring to modal "mass partcipation factors", or "effective masses" that you get from most FEM tools in structural modal analysis. These are extracted from the modal eigenvectors through a particular normalisation, that COMSOL is not using. So there is no easy way from my knowledge to get them in COMSOL (I have alread complained a couple of time about this, pls forward your need to "support") in very simple cases you might export the matrices to matlab and renormalise them, but most models have so large sparse matrices that this is useless Ivar
Sadegh Hajhashemi
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Posted: 1 decade ago Dec 19, 2009, 4:05 p.m. EST
Hi Ivar,

Thank you so much for your response, It was very helpful.

Regards,
Sadegh
Hi Ivar, Thank you so much for your response, It was very helpful. Regards, Sadegh

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