The main effort of this work is on acquiring the Campbell diagram of a helicopter main rotor by processing the signals measured for the bending and torsional structural moments of its blade. These moments are gathered by some sets of strain gauges while increasing the blade rotational speed. Because of the non-stationary nature of these signals, the Short Time Fourier Transform (STFT) is chosen as the relevant processing method and applied to the moment signals. The result is the moment's spectral content variation versus time. Combining the measured rotational speed signal with the results of time-frequency transform, moment spectral content variation versus rotational speed is acquired. By determining the local maxima of this diagram, it is possible to determine the resonance frequencies which are in fact the natural frequencies. Natural frequencies of the rotor under the test have been calculated using computational Holtzer-Myklestad method which then used to find the assignment of some of natural frequencies to corresponding natural modes.
Hadian Jazi, S., & Ghadamyari, E. (2015). Use of short-time Fourier transform in vibration analysis of helicopter main rotor. Journal of Solid and Fluid Mechanics, 4(4), 101-112. doi: 10.22044/jsfm.2015.396
MLA
Shahram Hadian Jazi; E. Ghadamyari. "Use of short-time Fourier transform in vibration analysis of helicopter main rotor". Journal of Solid and Fluid Mechanics, 4, 4, 2015, 101-112. doi: 10.22044/jsfm.2015.396
HARVARD
Hadian Jazi, S., Ghadamyari, E. (2015). 'Use of short-time Fourier transform in vibration analysis of helicopter main rotor', Journal of Solid and Fluid Mechanics, 4(4), pp. 101-112. doi: 10.22044/jsfm.2015.396
VANCOUVER
Hadian Jazi, S., Ghadamyari, E. Use of short-time Fourier transform in vibration analysis of helicopter main rotor. Journal of Solid and Fluid Mechanics, 2015; 4(4): 101-112. doi: 10.22044/jsfm.2015.396
)