Selecting Eigenmodes for Mode-Based Procedures

You can select a subset of eigenmodes computed from the preceding frequency step to use for a mode-based procedure, which can reduce the computational expense of your simulation. Selecting a subset of eigenmodes might affect the accuracy of your simulation.

The methods available for selecting the eigenmodes depend on the type of mode-based procedure. All of the mode-based procedures except substructure generation support selecting all eigenmodes, and all support selecting eigenmodes by specifying frequency ranges. These are the preferred methods for eigenmode selection.

This task shows you how to:

Before you begin: Define at least one mode-based procedure.
See Also
Defining Harmonic Response Steps
Defining Modal Dynamic Steps

Select All Eigenmodes

  1. From the Procedures section of the action bar, click Harmonic Response Step or Modal Dynamic Step .
  2. Expand the Eigenmodes section, and select All modes from the Retained eigenmodes options.

The step you created uses all eigenmodes computed in the preceding frequency step, including residual modes if activated.

Select Eigenmodes by Specifying Frequency Ranges

  1. From the Procedures section of the action bar, click Harmonic Response Step or Modal Dynamic Step .
  2. Expand the Eigenmodes section, and select Frequency range from the Retained eigenmodes options.
  3. In the table, enter values for Low Frequency and High Frequency, which are the lower and upper boundaries of the frequency range (in cycles/time).

    You can define mulitple frequency ranges in the table.

The step you created uses only the eigenmodes from the frequency ranges you specified, including boundaries.