This paper presents a general approach to predict the contact fatigue life of the gears in the drive-train system of a wind turbine under dynamic conditions. A simplified predictive pitting model that estimates service lives is presented and validated by comparisons with published experimental evidence. Finally, the predictive model is used to estimate the contact fatigue lives of the sun gear and planetary gears in the drive-train system of the National Renewable Energy Laboratory’s 750 kW land-based wind turbine based on time domain simulations. The occurrence frequencies of different wind speeds are described by the generalized gamma distribution. The time series of the torques in the main shaft are obtained from a global dynamic response analysis of the wind turbine. The time series of the gear contact forces is obtained from a dynamic analysis of the gearbox using multi-body simulation. The two-parameter Weibull distribution, the three-parameter Weibull distribution, and the generalized-gamma distribution are used to fit the long-term probabilistic distribution of the gear tooth contact pressures. The case study shows the validity of the approach presented in this paper.
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