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September 7, 2010 12:35pm UTC

Precision of the eigenfrequency analysis (structural mechanics)

Hi,

This problem is not very realistic, but I would like to use Comsol for some demonstration purposes.

I would like to visualize the first, second, third etc. mode of vibrations of a few, i.e. n (identical) cantilever beams hanging out from a common piece of solid.

When I start the eigenfrequency analysis in Comsol it calculates n nearly the same frequencies. The difference is at the second or third place after a comma, depending on the solver type and its settings.

How can I make the solver to "merge" these n eigenmodes into one, as these four beams were connected using an invisible and infinitely stiff connectors? I have thought about limiting the resolution of the solver that it does not distinguish between these closely spaced eigenmodes, but I suppose it is rather not feasible without changing the Comsol solver code.

Have any of you had a similar problem? Any clues for solving it?

Thank you in advance!

Kind regards
Stanislaw Kalicinski

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September 8, 2010 7:54am UTC in response to Ivar Kjelberg

Re: Precision of the eigenfrequency analysis (structural mechanics)

Hi Ivar,

Thank you for your answer.

Is then currently any way to display more than one eigenmode at a time in Comsol (preferably combined using logical OR)?

At first sight this may seem a useless feature, but it may be interesting in some cases when two or more eigenmodes are located very close to each other (e.g. in quartz resonators). Such visualization would help in understanding the influence of the spurous modes in this type of devices.

Regards
Stanislaw

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