Defining Frequency Steps

You can define a frequency step to perform eigenvalue extractions that calculate the natural frequencies and the corresponding mode shapes of a system.

See Also
About Frequency Steps
  1. From the Procedures section of the action bar, click Frequency Step .
  2. Optional: Enter a descriptive Name.
  3. Select the Solver type.
    OptionDescription
    Lanczos Provides the most general capabilities.
    AMS Faster than the Lanczos solver when a large number of eigenmodes is required for a model with many degrees of freedom.
  4. In the Number of modes field, enter the number of eigenvalues to be calculated.
  5. In the Minimum frequency field, enter the minimum eigenvalue frequency of interest.
  6. In the Maximum frequency field, enter the maximum eigenvalue frequency of interest.
  7. Optional: For Property evaluation, enter the frequency at which frequency-dependent properties for viscoelasticity, springs, and dashpots should be computed.

    If no value is provided, the simulation evaluates the stiffness associated with frequency-dependent springs and dashpots at 0 Hz and does not consider the stiffness contributions from frequency domain viscoelasticity.

  8. If you are using the Lanczos method, enter the Shift point in squared cycles per time (positive or negative).
  9. Optional: Select Damping projection to project the viscous and structural damping operators during the natural frequency extraction step for use in a subsequent steady-state dynamic step.

    If there is no damping defined in the model, the projection is not performed. This option is subject to licensing restrictions and is not available in all scenario apps (depending on the product or process licenses purchased).

  10. Optional: Select Residual modes to compute and include residual modes based on the loads specified in the immediately preceding static, linear perturbation step.

    This option is subject to licensing restrictions and is not available in all scenario apps (depending on the product or process licenses purchased).

  11. If you have defined an acoustic coupling for your model, specify how the app will account for the coupling during the frequency step by selecting one of the following from the Acoustic coupling options:
    OptionDescription
    Projection Account for structural-acoustic coupling during the frequency extraction.
    On Project structural-acoustic coupling operators onto the subspace of eigenvectors during the frequency extraction.
  12. Click OK.