Spectral Map

A spectral map is a 2D map composed of slices. Each slice is the result of an FFT applied to a source signal. Each FFT is processed over a restricted time range. The time ranges of FFTs are contiguous and can overlap:

Figure 14: Moving FFT window

Spectral maps are commonly used for analyzing vibrating effects on rotating machines during a velocity transient (usually called run up, when the rotation speed increases or run down, when it decreases).

The spectral map computation is directly applied to a 1D curve. For this reason, the Spectral Map facility is available in the Analysis menu of the Simcenter Amesim plot.

Note

You should carefully read the FFT section before starting this section.

Figure 15: Spectral Map menu item

Selecting this menu will create a specific cursor. Clicking on the plot area containing the analyzed signal will produce the following dialog box.

Figure 16: Spectral Map setup

Signal segmentation

• Number of FFTs Number of FFTs : indicates the number of slices of the spectral map

• Overlap Overlap : overlap of each FFT window

• FFT Range FFT Range : size of the FFT window (see FFT range scaling for more information)

FFT

• Window type: See Data windowing for explanations on data windowing.

• Remove trend: See Removing a trend for explanations on detrending data.

• Correction factor: Use the check box to toggle the correction factor off and on.

Temporal constraints

Spectral map analysis can be limited to a range smaller than the whole simulation time. Select the check box to enable temporal constraints:

• Min: start point of the analysis

• Max: end point of the analysis.

You can use the sliders, or the spin boxes to adjust temporal constraints.

Frequency constraint

Select the check box to enable the frequency constraint.

Creation

This area defines how the new spectral map curve will be drawn:

• Location

  New graph: the curve will be placed in a new graph to the right of the current graph.
  
  
  New page: a new page (tab) is created to contain the spectral map.
  
  
  New plot: a new plot is created to contain the spectral map.
  

• View type

  2D view: a 2D spectral map will be created
  
  
  3D view: a 3D spectral map will be created
  

You can use the Restore button to reset the dialog box to the default parameters