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The local mean decomposition (LMD), a new adaptive time-frequency analysis method, is the research focus in the fault diagnosis field in recent years. In this paper, the LMD’s characteristics are obtained by processing multi-component frequency and amplitude modulation signal, which are usually used to describe the gear pitting corrosion fault signals. Base on the simulation analysis, LMD is presented to deal with the vibration signals of gear pitting corrosion fault, comparing with traditional method. The results show that the gear pitting corrosion defect can be diagnosed by LMD effectively, and LMD can eliminate the false composition effect, thus improving the accuracy of gear fault diagnosis.

This document concentrates on the relationship between critical speeds and geometrical dimensions such as length, outer diameter, thickness, support stiffness and so on. An effective method was summarized for helicopter tail drive shaft system rotor dynamic design. A tail drive shaft system designed by this method was mounted in a helicopter and performed its first flight-test successfully. According to the feedback of tests in the air or on test bench, the vibration level of this shaft system was very low and rightly met the design requirements.