2 Replies Latest reply on May 30, 2017 1:32 PM by Ryan Dark

    In frequency analysis or dynamic studies, mode shapes application?

    Win Lai

      In frequency analysis or dynamic studies, is the mode shapes carry meaningful information on where resonance really happen?

      Are there any other applications on the mode shape? Thank You.

        • Re: In frequency analysis or dynamic studies, mode shapes application?
          Bill McEachern

          I am not clear on what you are asking. In a linear dynamic study the modes are computed prior to the study and then the response of the structure is calculated at the points specified in addition to the response at the exact modal frequencies. Resonance occurs at the resonant frequencies - hence the name - which are the natural modes of the system. The response with zero damping is infinity at resonance in steady state. In reality damping attenuates the response to some finite value.

          • Re: In frequency analysis or dynamic studies, mode shapes application?
            Ryan Dark

            Hi Win,

            The mode shapes from a frequency do not correspond to a real life behavior of the model.  They are a representation of what a pure, undamped vibration would be at that particular natural frequency.  The plots of mode shapes are qualitative in nature only.

             

            If you need to know actual displacements, stresses, or strains, you would need to utilize a dynamic analysis of your model with a specific loading condition in mind.  For that loading condition the linear dynamic results would show where the actual deflections are occurring.