Dynamic Reliability Modeling For Wind Turbine Gearbox System

Wind turbine gearbox is the key component among the equipments of the wind turbine.It is critical for wind turbine system to make sure a long service life and high reliability.However,due to the uncertainty of wind speed,gearbox is one of the components with highest failure rate in wind turbine.Under the long-term effects of highly unstable loads,on the one hand,the fatigue damage of materials gradually increase,the strength of gears will decrease over time;On the other hand,the gearbox is a multi-state series system composed with a series of gears,there is a widespread failure-dependence in gear box.The reliability of gearbox system is between two situations,independence and complete dependence.Therefore,in this dissertation,both the strength degradation and failure-dependence are considered to investigate the dynamic reliability of gears,and a dynamic reliability model for wind turbine gearbox is established.The main results of this dissertation are as follows:(1)It is difficult to measure the degradation data that characterizes the strength degradation process(wear,crack,corrosion,etc.)directly,which brings difficulties to strength degradation modeling of components.In this case,the stress is derived from the statistical result of wind speed,then based on the linear fatigue cumulative damage theory and S-N curve,a strength degradation model of gear is established by using the Markov process.(2)Based on the stress calculation result and th e strength degradation model,combing the Stress Strength Interference(SSI)model,both the tooth surface contact fatigue and the tooth root bending fatigue are considered,a dynamic reliability model of the gear is established by using the Universal Generating Function(UGF)method.(3)Based on the dynamic reliability model of the gear,the dynamic reliability models of gearbox system under independent and complete dependence situations are established by using the UGF method.Finally,the dynamic reliability interval of wind turbine gearbox system is obtained.