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Structural Eigenfrequency Analysis, missing Mass Partcipation Factor calculations
Posted Jul 19, 2009, 3:57 p.m. EDT 1 Reply
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Hello everybody
I have noticed that COMSOL uses a different eigenfrequency normalisation scheme than i.e. Ansys or Nastran, therefore the "Mass Participtopn Factors" for the eigenmodes are not so easily derived.
Does anybody out there have a M file or a GUI to run on an eigenmode analysis (a complex analysis case, one having large sparse matrices when exporting to Matlab) such that one can get printed out these Participation Factors ?
And that these give similar results as the two mentionned "classical" FEM softwares tools ?
For me these items are essential, as I'm using COMSOL for calculations for clients normally used to the two other softwares and they have as "quality" check to always request these participation factors. So I have a severe non-compliance with my simulations, even if the rest is OK (for me).
Furthermore, I do not know any other way how to sort eigenmodes on complex systems so that you keep or concentrate on only those really having an effect along a particular Degree of Freedom. Anybody with another suggestions ?
I find COMSOL still somewhat weak on structural analysis, understand by that: the ease to set up complex postprocessing, define coordinates frames, to do detailed local analysis etc, but not for the results, which are OK and the expansion possibilities that are excptional.
Probably COMSOL developpers are concentrating on the other "multiphysics", this I understand well, but for me the multiphysics start with a structural analysis (with comparative results to the "clasical" FEM software) and then I can add the missing "multiphysics" for my actuators, sensors and control , and why not some fluidics ...
I have reported the lack of Eigenfrequency Participation Factors to COMSOL Support, and they are looking into how to implementd this (I beleive) for a future version, but in the mean time I'm somewhat stuck.
Any help in the large community out there ?
Thanks in advance
Ivar
I have noticed that COMSOL uses a different eigenfrequency normalisation scheme than i.e. Ansys or Nastran, therefore the "Mass Participtopn Factors" for the eigenmodes are not so easily derived.
Does anybody out there have a M file or a GUI to run on an eigenmode analysis (a complex analysis case, one having large sparse matrices when exporting to Matlab) such that one can get printed out these Participation Factors ?
And that these give similar results as the two mentionned "classical" FEM softwares tools ?
For me these items are essential, as I'm using COMSOL for calculations for clients normally used to the two other softwares and they have as "quality" check to always request these participation factors. So I have a severe non-compliance with my simulations, even if the rest is OK (for me).
Furthermore, I do not know any other way how to sort eigenmodes on complex systems so that you keep or concentrate on only those really having an effect along a particular Degree of Freedom. Anybody with another suggestions ?
I find COMSOL still somewhat weak on structural analysis, understand by that: the ease to set up complex postprocessing, define coordinates frames, to do detailed local analysis etc, but not for the results, which are OK and the expansion possibilities that are excptional.
Probably COMSOL developpers are concentrating on the other "multiphysics", this I understand well, but for me the multiphysics start with a structural analysis (with comparative results to the "clasical" FEM software) and then I can add the missing "multiphysics" for my actuators, sensors and control , and why not some fluidics ...
I have reported the lack of Eigenfrequency Participation Factors to COMSOL Support, and they are looking into how to implementd this (I beleive) for a future version, but in the mean time I'm somewhat stuck.
Any help in the large community out there ?
Thanks in advance
Ivar
1 Reply Last Post Aug 4, 2009, 5:27 a.m. EDT
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Posted:
1 decade ago
Hey,
are there really nobody out here using structural eigenmode mass participation factors (or equivalent masses). How dou you then reply to ESA or ESO's requests for mandatory FEM model validations ?
Perhaps you do not use COMSOL for this market segment, a pity as COMSOL can do more for you than several of the other tools.
Thanks for you comments
Ivar
If you need some good reading: (§4.5 on mass participation factors
"Vibration Dynamics and Control", by Gienacarlo GENTA, Springer, 2009, ISBN 978-0-387-79579-9
are there really nobody out here using structural eigenmode mass participation factors (or equivalent masses). How dou you then reply to ESA or ESO's requests for mandatory FEM model validations ?
Perhaps you do not use COMSOL for this market segment, a pity as COMSOL can do more for you than several of the other tools.
Thanks for you comments
Ivar
If you need some good reading: (§4.5 on mass participation factors
"Vibration Dynamics and Control", by Gienacarlo GENTA, Springer, 2009, ISBN 978-0-387-79579-9