Failure Analysis And Finite Element Analysis Of Wind Turbine Main Shaft

As a core component of wind turbine drive,the main shaft is subjected to a variety of loads during service and has high requirements for mechanical properties.In recent years,failure caused by the fracture of main shaft is frequent.Once the main shaft fails,it will affect key components such as blades,gearboxes,and towers,and even cause the entire wind turbine to be scrapped,resulting in huge economic losses.The failure analysis and finite element analysis of the main shaft can further analyze the failure cause and provide guidance for the design improvement of the wind turbine.The main shaft of a wind turbine broke after about 5 years of service.The material and failure mode were analyzed by means of testing,the failure reasons were comprehensively analyzed combined with finite element analysis,and the fatigue life was estimated.The main research contents are summarized as follows:(1)By means of macroscopic observation,fracture analysis,metallography observation and mechanical property test,the microstructure and failure reason of the main shaft were analyzed.The fracture surface presents a typical characteristic of shell line,and there are fatigue strips in the micro,which shows that the failure mode of the main shaft is fatigue fracture.Fretting wear occurs between shaft and shaft sleeve,resulting in damage of surface,which is conducive to the formation of a fatigue source.The material factors affecting the fatigue cracking are related to the low hardness of surface,which is easy to produce surface damage.The center of the shaft is different from the surface in microstructure and strength,indicating that the hardenability of the main shaft needs to be improved.(2)Statics and modal analysis of the main shaft were carried out by using finite element software ABAQUS.Under the same boundary conditions,the ideal strength and the actual strength with a difference along the radial direction are given to calculate the stress distribution.In both cases,the maximum stress position of the main shaft appears on the contact surface between the main shaft and shaft sleeve.In the case of actual strength,the stress level is higher,indicating that the inhomogeneity of microstructure and strength leads to the reduction of the stiffness under the same load condition,and the deformation is larger,resulting in greater stress on the main shaft.The modal analysis of the main shaft was done,focusing on the first six vibration modes and natural frequencies.The comparison between the natural frequency of the main shaft and the impeller frequency showed that the main shaft would not resonate with the impeller.(3)The fatigue life of the main shaft was calculated by the fatigue analysis software FE-SAFE.The equivalent fatigue load spectrum is compiled based on the fatigue load sequence calculated by the wind turbine design software GH bladed.The S-N curve of the material was modified according to specification,and the fatigue life of the main shaft was calculated to be 4.9 years,which is consistent with the current situation.