Harmonic (FRF) Analysis Parameters

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.

Access

1. Ensure that a modal analysis has already been defined.
2. Click Analysis Analysis Types New.
3. Select Harmonic in the frequency domain (FRF) in the Analysis Type dialog, and then click OK.

Note: You can also access this dialog by changing the type of an existing dynamic analysis to Harmonic in the frequency domain (FRF).

Dialog elements

Case

The name of the load case.

Frequency

Select a type of frequency:

• Initial: The first interval of the frequency domain.
• Final: The last interval of the frequency domain.
• Division: The number of steps that the interval is divided into. The harmonic analysis is performed at each step and the results are saved.
• Consider eigenfrequencies from the specified range in calculations: Considers points at which eigenvibration frequencies occur as well as the points which result from the division of the frequency interval.

Mass matrix

Select a type of mass matrix:

• Consistent: complete matrix - always with regard to rotational degrees of freedom.
• Lumped with rotations: diagonal matrix - with regard to rotational degrees of freedom.
• Lumped without rotations: diagonal matrix without rotational degrees of freedom.

Damping

Specify the damping parameters for the harmonic analysis:

• Without damping: Ignores damping during the analysis.
  Note: For calculations which consider eigenvibration frequencies in the structure, ignoring damping can lead to indeterminate results caused by resonance.
• Constant.
• Rayleigh: Uses the eigenvalues and material damping to calculate the results. Click Define to set up the Rayleigh Damping parameters.
• Varying for each mode: Uses predefined damping values for each mode. Click Define to specify the damping values for each mode.