Use the Harmonic Analysis Parameters (FRF) dialog to specify parameters for the analysis of harmonic vibrations in the frequency domain (FRF) for a load case defined for a structure.
To open the dialog:
- click the New button in the Analysis Types dialog, select the Harmonic in the frequency domain (FRF) option and click OK in the New Case Definition dialog
- select the Harmonic in the frequency domain (FRF) option and click OK in the Change of analysis type (modal) dialog, or highlight the FRF analysis case and click the Parameters button in the Analysis Types dialog.
Note: To define harmonic and harmonic in the frequency domain (FRF) analysis types, you need to define modal analysis first. Otherwise, these analysis types are not available.
You can specify the following parameters in the above dialog:
- Frequency - initial - the start of the interval of the frequency domain
- Frequency - final - the end of the interval of the frequency domain
- Division - a number of steps that the interval of the frequency domain is divided to; at each step the harmonic analysis is performed and results are saved
- Consider eigenfrequencies from the specified range in calculations - if selected, during analysis, the software takes account of points at which eigenvibration frequencies occur, apart from points that result from dividing the frequency interval.
In the lower part of the dialog box you can specify damping parameters for the harmonic analysis: you can ignore damping in the analysis, or define damping as:
- constant
- Rayleigh - calculated during calculations based on eigenvalues and material damping; click the Define button available for this option to open an additional dialog
- varying for each mode - if selected, the Define button becomes available; click it to open a dialog to define values of damping for each mode.
Take note, that if you ignore damping in the analysis, calculations at points at which eigenvibration frequencies occur, yield indeterminate results, that result from resonance.
See also: