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AATAS Offline Analysis of Vibrations Software Components Core Module - Part 1 Core Module - Part 2 Traveling Wave LSMF Analysis Individual Blade FFT Analysis

Individual Blade FFT Analysis Individual Blade FFT is used for analyzing non-synchronous responses. The Individual Blade FFT assumes constant Frequency/Coherent phase vibrations over the time length of the FFT data set. Given the low sample rate of 1E, FFT time spans can be large which can challenge the assumptions of constant amplitude and phase. Typically, this analysis technique is only valid for steady state data sets with stable vibrational characteristics. Due to the narrow aliased window, the Individual blade FFT calculates Individual Mode Frequencies to a high accuracy. It is especially helpful when there is very little blade-blade coupling and Traveling wave analysis can not be used.

 

Vibration in Time

Vibration in Frequency



Time Domain

Frequency Domain

 

Individual Blade 3D FFT Waterfall Plot The main graphical display in the individual blade FFT analysis is the 3D FFT waterfall plot. There are, by default, 100 FFT slices spread evenly across the data range.  The x axis is the location in the analysis range. It can be revolution or rpm linear. The beginning of the analysis range is at the back of the plot. The y axis is the observed order. The z axis is the deflection amplitude.   Utilizing one of 3 order tracking methods to follow certain modes, calculations are made to obtain average blade amplitudes and mode frequencies over a pre-selected time period.
	Individual Blade Order Tracking The individual blade order tracking plot displays the results of the order tracking analysis performed in the individual blade FFT waterfall plot. The frequency found during a predictive order tracking is displayed on the upper left side of the graph and the maximum peak-peak amplitude is listed as well.
Amplitude, RPM, and Frequency Bar Charts Bar charts of the peak amplitude, rpm of the peak amplitude location, true frequency calculation at the peak amplitude location. Maximum, Minimum, Average, Maximum/Average Ratio and the Highlighted blade values are display
Campbell Plot Blade amplitude and frequency from the order tracking calculations are plotted on the Campbell.