Failure Analysis Of Aero-Engine Accessory Gearbox

The aviation industry is a national strategic high-tech industry, which is the material basis of national defense air force and air transportation. As the key component of aero-engine, the performance of the accessory gearbox system has a direct impact on the normal operation of the aircraft. In the long-term practical engineering, it is found that a series of problems caused by gear failure seriously affect the performance of the aero-engine, which restricts the development of national aero-engine technology to a certain extent. The research scholars at home and abroad have carried out research on the mechanism of gear failure, theoretical analysis and experimental technology for solving above problems. Based on the internal abnormal problem of one kind of aero-engine accessory gearbox, this paper analyzes the failure form of gear surface through macroscopical and microcosmic methods. And combined with relevant theories and experiments, the influences of the modification coefficient, the machining precision and the heat treatments on gear scuffing failure are studied. The research of related contents have important theoretical significance and technical reference value for the realization of high reliability and durability of accessory gearbox system and the development of the aviation industry.Major contents of the thesis are summarized as follows:(1) The working condition and technical background of the aero-engine accessory gearbox system are analyzed. The failure mode of these accessory gears are determined and analyzed through macroscopical method, micro-3D morphology and metallographic structure analysis technology, combined with the characteristics of the main failure forms of gears.(2) The sliding ratio curve and the maximum values of each gear pair of the accessory gearbox are analyzed. Based on the principle that the sliding ratio is minimum and the maximum sliding ratio of each gear is equal, the mathematical model is established and the modification coefficient is optimized by sequential quadratic programming algorithm. Before and after optimization, the relative sliding ratio, anti-scuffing bearing capability of all those gears are calculated and comparatively analyzed, in order to study the influence of the modification coefficient on gear scuffing failure.(3) According to the application requirements of aero-engine accessory transmission gears, the impact of manufacturing errors on gear meshing is studied by combining errors evaluation, measurement and analysis technique. Based on the adhesion-furrows theory of friction, the influence of surface roughness on tribology properties and gear scuffing bearing capability is discussed by carrying out the reciprocating friction test.(4) On the basis of carburization and carbonitriding heat treatments, the influence of these two heat treatments on gear scuffing bearing capability is studied by carrying out the ball-disk friction test under the normal temperature and high temperature atmosphere respectively, and the comparative experiment of anti-scuffing bearing capability under the complex working condition.