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To find out the effect of eccentricity of a gear wheel on inherent characteristics of a gear-rotor system, this paper establishes a pair of general transverse-rotational-axial-swinging multi degrees of freedom coupling helical gear meshing dynamic model based on the finite element method (FEM). Considering the influence of the azimuth, the meshing angle, the helix angle and the rotation direction of driving shaft on mesh stiffness matrix, it analyzes the effect of mesh stiffness and mesh damping on the inherent characteristics and the transient response of the system. It obtains the displacement response curve and the dynamic meshing force curve of all nodes responding to the incentives of static transmission error and unbalance while considering mesh damping. It concludes that the effects of gear coupling and eccentricity of gear wheel should be taken into account in a multi-parallel-shaft gear meshing rotor system.

Time-dependenT reliabiliTy of spur gear sysTem based on gradually wear process Zależna od cZasu nieZawodność układu prZekładni ZębaTej jako funkcja procesu sTopniowego Zużycia

The cause of fatigue fracture in gearbox housing of coal mining machine cutting part (CPGH) is analyzed in this paper. Considering the effects of low-frequency external excitation caused by coal cutting and high-frequency internal excitation caused by gear meshing, systematic studies of force analysis and local resonance analysis are employed. Force analysis is proposed to obtain the region of stress concentration and stress values are calculated by finite element analysis. Field testing and modal analysis are employed to get the resonance frequencies and main vibration modes under internal excitation. Further investigation including the influence of key design parameters on stress amplitude and natural frequencies of CPGH is proposed for avoiding the resonance frequencies and reduce stress concentration. The results indicate that fatigue failure is caused by internal and external excitations. Internal vibrations excite the 15th, 23rd and 27th resonance modes, and the superposition of these vibration modes causes beat phenomenon and results in excessive stress and increases the likelihood of exceeding fatigue limits in the failure region which is induced by external excitation. Fatigue fracture failure of CPGH was caused by both stress concentration and local resonance. The influence of some design parameters on stress amplitude and natural frequencies is analyzed, and some advices for reducing stress concentration and avoiding local resonance are provided.