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I have a MDOF FEM model in which I perform a modal transient analysis based on the modal eigenfrequencies extracted in a prior step. I wish to excite only the first natural frequency of the system via a half sine impulse of 10G. I do not want to see contributions from other modes.

Is this possible? I'm not sure how to define the time abscissa value which correlates to the first natural mode. Any suggestions will be appreciated.

Best Regards

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  • $\begingroup$ Either I don't understand the question, or possibly you don't understand what you are trying to do (or didn't explain it very well) but if you have a modal model you already know the first natural frequency, so just throw away everything else and run the 1DOF model with your half sine wave excitation. (I have no idea what "I'm not sure how to define the time abscissa value which correlates to the first natural mode" means). $\endgroup$
    – alephzero
    Commented Mar 17, 2020 at 22:38
  • $\begingroup$ Its clear if the model has only the first mode that the mode contribution will 100%. I thought one can select which mode to be excited via the half sine equation. Ie depending on the duration of impulse? $\endgroup$
    – shoggananna
    Commented Mar 24, 2020 at 20:17

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