Abstract: Load is the most direct factor to cause failure and affect product reliability. The load history that a wind turbine experienced has some special characteristic. Owing to the special service mode, the every wind turbines in a wind farm will experience different load histories. The probabilistic property of wind turbine load history is described in two aspects as the every turbine’s service location and service time. Based on such description, fatigue reliability analysis and modeling of wind turbine gearbox and its components are performed by means of the total probability principle. As the essential issues to develop fatigue reliability model and perform reliability evaluation, the way to characterize load history uncertainty, the methods to accumulate the fatigue damage under variable amplitude load history and calculate the equivalent stress amplitude, the way to develop fatigue reliability model based on stress distribution and life distribution condition to stress, as well as the technique to obtain fatigue life distribution parameters through multi-level small sample fatigue life experiment are introduced.

Key words: reliability;complex load history;cumulative fatigue damage;life distribution parameter estimation;wind turbine