Research on time-varying reliability of wind power gearbox with failure correlation

In the process of reliability modeling and design of a wind power gearbox, the influence of failure correlation of system components and random dynamic loads can not be ignored. In this paper, taking the output power of each shaft of the gearbox as the starting point, distribution parameters of stress and strength for critical failed components (gear and bearing) of the gearbox are solved. After normalization of these parameters, and when there is a linear correlation between the loads of each component, finally, the time-varying reliability related to failure correlation is calculated based on a full probability differential method by using the stress strength interference theory at the system level, and the results are verified by the Monte-Carlo simulation method. It is found that the failure correlation caused by the external dynamic loads between components can significantly reduce reliability of the gearbox system. The stronger the correlation, the lower the reliability of the gearbox system. Meanwhile, the time-varying reliability conforms to characteristics of the “failure bathtub curve” of typical mechanical products. This paper can lay a foundation for the time-varying reliability optimization design and structural robustness design of the wind power gearbox.