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ISOLATION
OF HELICOPTER GEARBOX VIBRATION USING
PERIODIC SUPPORT STRUTS A new class of support struts called periodic struts is introduced as an isolator of the vibration transmitted from Helicopter gearbox to the fuselage and cabin. It has been presented the innovative use of unique characteristics of periodic struts in controlling the wave propagation both in the spectral and spatial domains. The emphasis is placed on studying the dynamics of one-dimensional periodic struts in their passive mode of operation in order to demonstrate their unique filtering capabilities. Both experimental and numerical results are presented to demonstrate the effect in attenuating the vibration transmitted from gearbox to the airframe. The numerical results predict the stop bands associated with any struts configuration (Figures (1) and (3)). Such predictions are found to be in close agreement with the experimental results as shown in Figures (2). Active periodic is also introduces in order to tune the spectral width and location of the pass and stop bands in response to the structural vibration. These struts are conventional periodic struts augmented with built-in sensing and actuation capabilities in order to stop and confine the propagation of undesirable disturbances. Such active struts are utilized to control vibration transmission from a helicopter gearbox to the fuselage. Figure (1) The experiment setup of gearbox with periodic struts with material discontinuity
Figure (2) Vibration transmission through a periodic gearbox strut
Its evident that periodic struts with material discontinuity can be vary effective in attenuating the vibration transmission over a broad frequency band. Increasing the length Lb of the material b insert (rubber) results in widening the spectral width of the stop bands.
Figure (3) The experiment setup of gearbox with periodic
struts with material and geometrical discontinuities
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Last modified: February 23, 2002 |
