Design of near-periodic struts for helicopter gearbox vibration isolation using multicell optimization

Abstract

The structure-borne tones generated by the main gearbox are the primary components of helicopter interior noise. Recently, a kind of periodic strut has been designed to isolate the multispectral vibration from transmitting to the cabin, for their specific stop-band characteristics. Using multicell optimization, the disorders are designed into the strut to obtain better vibration and noise reduction effect. The dynamic model of the periodic strut is firstly established by combining the spectral element method and the transfer matrix method. On this basis, a multi-objective multivariable genetic algorithm is adopted to optimize the geometry by taking the maximum attenuation as the performance objective function. Then, a near-periodic structure is achieved. Compared with the perfect periodic strut, the optimal one has a much wider and deeper stop band, which is critical for a better vibration and noise attenuation effect. In addition, a method is presented to analyze the wave propagation to explore the increase of width and depth of the bandgaps more closely. Experimental investigations are then carried out on a pair of original and optimal struts to validate the improvements. It is shown that 26.22% more attenuation is achieved through this structural optimization.

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