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An approximate digital signal processing technique is presented which can assist in the early detection of local defects such as fatigue cracks in gears by enhancing the changes which these defects produce in the signal average of the vibration of the gear. The technique is demonstrated by the identification of an early fatigue crack in a helicopter gear. The importance of phase modulation in the detection of defects is indicated.
McFadden et al. (Tue,) studied this question.