Research On Prestressing Of The Annular Gear In Interference Joint Effects On Tooth Root Flexural Fatigue Strength

In the large planetary transmission, in order to reduce cost and decrease processing difficulty, the annular gear is always interference jointed with the box. But, when the annular gear interference joints with the box, there is prestressing on the annular gear. The prestressing severely impacts the tooth root flexural fatigue strength of the annular gear. In the design of the annular gear which is interference jointed with the box, if we just according to the general design theory, it will lead to the low tooth root flexural fatigue strength, tooth breaking and substandard working life, then, it will increase maintenance cost of the planetary transmission. So, in the design of the annular gear that is in interference joint, the effects on the tooth root flexural fatigue strength of the annular gear that caused by the prestressing of interference joint must be considered.The following is the main research contents in this paper:(1) Based on the yaw and pitch gearbox of 5MW wind generator, when the annular gear interference joints with the box, the annular gear is equivalent to a thick wall cylinder. The prestressing distribution of the annular gear is derived in elastic range, and the theoretical curves of prestressing of the annular gear in interference joint are got. According to the interference joint prestressing formula which is calculated, five main factors those are magnitude of interference δ, pitch diameter of annular gear dd, diameter of joint surface df, external diameter of box d4 and contact length lf are chosen. The 5 factors and 4 levels orthogonal experiments are determined.(2) According to the data of the orthogonal experiments, the models those the annular gear interference joints with the box are built by Solid Works, and the models those the annular gear interference joints with the box are simulated by ABAQUS. Then, the simulation curves of prestressing of the annular gear in interference joint are got by finite element analysis.(3) The orthogonal experiments are conducted by X-ray diffraction method. The values of prestressing are got by experiments. The experimental curves of prestressing of the annular gear in interference joint are got. Finally, the formula correction coefficients of prestressing of the annular gear in interference joint are calculated by contrasting the theoretical curves, the simulation curves and the experimental curves.(4) According to the calculation process of the tooth root flexural fatigue strength, the meshing load and the load that effects on the dangerous section by prestressing of interference joint are compounded. Finally, the formula of the flexural fatigue strength in the annular gear root is corrected.(5) According to the correctional formula of the flexural fatigue strength in the annular gear root, a parameterized design software which is applied to designing the gear transmission that is in interference joint is developed by Microsoft Visual C++.