Modalanalyse: How does the calculation work?

Alexander Buffler
Alexander Buffler Altair Community Member
edited September 2 in Community Q&A

Is the frequency increased step by step and examined for resonances?

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Answers

  • rdominguez
    rdominguez
    Altair Employee
    edited September 2

    Hi Alexander!

    How are you doing?

    In SimSolid, modal analysis does not work by incrementally increasing the frequency to search for resonances. Instead, it directly computes the natural frequencies and corresponding mode shapes of the model. For modal analysis, SimSolid solves an eigenvalue problem derived from the system's mass and stiffness matrices. The solution to this problem shows the natural frequencies (eigenvalues) and the corresponding mode shapes (eigenvectors) of the model.

    The analysis first identifies any rigid body modes, which are modes with very low or zero frequencies, indicating motion without deformation. These modes are typically found in under-constrained or unconstrained models.

    After detecting any rigid body modes, SimSolid calculates the natural (flexible) modes. These are the frequencies at which the model would naturally vibrate if it were disturbed.

    In the most recent versions of SimSolid, you can specify the number of modes to calculate or set a frequency span (upper limit) to determine how many natural frequencies should be found within that range. SimSolid will list the modes in ascending order, starting with any rigid body modes followed by the fundamental frequency and higher natural frequencies.

    I hope this helps!

    Best,

    R.

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