Fracture analysis and improvement of the main shaft of wind turbine based on finite element method

For the main shaft of wind turbine of certain type, shaft fracture occurs at the variable section of the shaft during early stage of operation. In order to validate the failure analysis, finite element analysis of the main shaft was performed. The analysis results demonstrate that there is a severe stress concentration that leads to the formation of initial cracks at variable inner diameters of the main shaft. Also, the stress in the variable part mainly resulted in the pressure of the bulging joining sleeve applied on the main shaft via the gearbox planet carrier shaft. According to the above analysis, local structure improvements were carried out through increasing the action area between the bulging joining sleeve and the main shaft. The finite element simulation results show that the stress concentration in the variable section of the improved shaft decreases significantly. The improvement of shaft strength decreases the possibility of crack formation and its growth, thus enhancing the reliability of the main shaft. This analysis process and the results of this study can provide a reference in shaft fracture analysis and also technical support for improvement in the design of wind turbine main shafts.