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FRF of duffing oscillator attached to beam

Posted May 1, 2023, 4:17 a.m. EDT Modeling Tools & Definitions, Structural Mechanics, Structural Dynamics Version 6.0 3 Replies

Arghya Mondal AEROSPACE
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I need an FRF study of duffing oscillator attached to a beam. Can anyone please help me out to model this system?

3 Replies Last Post May 8, 2023, 2:57 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 12 months ago May 2, 2023, 5:25 a.m. EDT

Since it is a nonlinear problem, it is diffcult. Ordinary frequency domain analysis is not applicable.

There are two possible approaches:

  • Run a time dependent solution to steady state for each excitation frequency. This is time consuming.
  • Implement a harmonic balance method. This assume quite some familiarity with the software.
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Henrik Sönnerlind
COMSOL
Since it is a nonlinear problem, it is diffcult. Ordinary frequency domain analysis is not applicable. There are two possible approaches: * Run a time dependent solution to steady state for each excitation frequency. This is time consuming. * Implement a harmonic balance method. This assume quite some familiarity with the software.
Arghya Mondal AEROSPACE
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Posted: 12 months ago May 5, 2023, 2:51 p.m. EDT

Can you please explain little bit about the implementation of harmonic balance method in comsol for the above problem?

Can you please explain little bit about the implementation of harmonic balance method in comsol for the above problem?
Henrik Sönnerlind COMSOL Employee

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Posted: 12 months ago May 8, 2023, 2:57 a.m. EDT

I don't have an example of an implementation of the harmonic balance method, but I know it has been done in COMSOL for electrical simulations.

A short introduction to the method can be found in https://en.wikipedia.org/wiki/Harmonic_balance

I think the easiest (but maybe not very elegant) approach is to add one physics interface per harmonic, each operating at its own frequency. Then, coupling terms need to be inserted for the transfer of energy between the frequencies which is an effect of the nonlinearity.

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Henrik Sönnerlind
COMSOL
I don't have an example of an implementation of the harmonic balance method, but I know it has been done in COMSOL for electrical simulations. A short introduction to the method can be found in I think the easiest (but maybe not very elegant) approach is to add one physics interface per harmonic, each operating at its own frequency. Then, coupling terms need to be inserted for the transfer of energy between the frequencies which is an effect of the nonlinearity.

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