Reliability Analysis Of Wind Turbine Gearbox Considering Strength Degradation And Failure-dependence

Wind turbine gearbox is the key component in the equipments of wind turbine, with the technical requirements of long life and high reliability, etc. However, due to the load of gear transmission system under the variation with wind speed shows a high degree of instability, leading gearbox is one of the components with highest failure rate of wind turbine. In the long-term effects of this highly unstable loads, on the one hand, the internal damage of materials continue to accumulate, the strength of parts in the gearbox shows a gradual degradation with the timetable; On the other hand, due to the gearbox is a system of motion and dynamic coupling, whether the same part between different failure modes, or between different parts in the gearbox system, there are widespread failure-dependence. Therefore, in this dissertation, we depend on the two aspects of strength degradation and failure-dependence to study the reliability of wind turbine gearbox and its components.The main research results include the following three aspects:(1) Due to the degradation data that characterizes degenerate state(wear, crack, corrosion, etc.) is often difficult to measure directly during strength degradation process of components, which is the typical missing data. In this case, it has obvious difficulties to analyze the strength degradation process of components. Therefore, in this dissertation, the Gamma process is used to describe the rule of strength degradation of components, and estimate the characteristic parameters of Gamma process by using P-S-N curve of material. Then a stochastic model of strength degradation based on P-S-N curve is established.(2) In order to analyze the failure-dependence existing in the wind turbine gearbox, in this dissertation, first of all, a mixed Copula function model is introduced to describe the correlation between different failure modes of each individual component in wind turbine gearbox. In this way, the failure-dependence model of each component contained in the wind turbine gearbox, that considering the correlation between different failure modes, can be constructed. Then, according to the principle of nested Copula function, the failure-dependence model of entire wind turbine gearbox system, that considering failure-dependence between different components is constructed.(3) In order to illustrate the effectiveness and the rationality of the proposed methods in this dissertation, taking a 2MW wind turbine gearbox as the research object, the theories and methods presented in this dissertation are verified.