| In the wind power transmission gearbox, the uneven bearing of the planetary transmission system will cause a large load of single transmission component, resulting in system vibration and noise or reducing the safety and reliability of the system. In order to ensure the load of planetary transmission system balanced, the flexible planetary wheel pin junction structures(hereinafter referred to as "flexible pin") are widely used as the support of planet wheel while the assembly space is limited. As the transmission requirements, the structures are often assembled in interference fit. However, the cyclical fluctuation to bending load of flexible pin is caused by the meshing impact of the transmission gear. The alternating stress will lead to the slight deformation on the interference fit surface and result in fretting fatigue. Fretting fatigue will make the fatigue crack initiating and extending or leading to premature failure of flexible pin, thereby significantly reduce the service life of wind turbine gearbox. Therefore, the influence of fretting fatigue damage must be taken in to consideration in the design of flexible pin. This paper studies fretting fatigue life and damage mechanism of flexible pins and makes it as design guide of flexible pin in order to weaken fretting fatigue damage and prolong its service life. The followings are the main research contents in this paper:(1) Following thick-walled cylinder theory and Lame formula to calculate stress-stain, interference amount of the flexible pin and the maximum bending load of the structure. Regarding to the limitations of experimental conditions, the flexible pin shrinkage ratio model are designed, and the rationality of the model is verified by comparing the size and load parameters with the full-size model. Based on the influence of various factors on the fretting fatigue damage of the flexible pin, studying the bending load, the amount of interference and the carburize layer factors. Then three factors and three levels orthogonal test program are identified.(2) The flexible three-dimensional model of the flexible pin is established by SolidWorks software and referred to the actual service conditions to analyze the finite element of flexible pin under the interference coupling. Simulating interference connection of the flexible pin shaft in bending loading process to extracting data of different bending load, the amount of interference and the carburizes layer under the stress-stain, the value graphs of junction surface contact stress, friction, and slip amplitude, and analyze the rule of each factor causing fretting fatigue damage can be gotten. Through the relevant data collection, the fretting fatigue life and the location of the crack based on SWT can be predicted.(3) According to orthogonal experiment, 11 interference coupling in flexible pin ratio test-pieces are trial-manufactured, and the S~N curve by microscopic observing fatigue damage under different factors can be gotten, comparing with stimulation result, the rule of different factors influencing flexible pin fretting fatigue life and fatigue damage are studied.(4) Based on the research conclusion of fretting fatigue, gradient amount of interference are set, and the optimized matching mode is designed while the stress-stain value of fit surface are lowered. By analyzing stimulation results, the variant expression of the amount of interference, and amended stress-stain formulas of flexible pin are obtained. |
PDF Full Text Request