Multiaxial Fatigue Life Prediction Of Large Wind Turbine Blade

The wind turbine blade is the core component of wind turbine.Its working environment is poor and it suffers complex load conditions.With the increasing of wind turbines power,the size of wind turbine blade has been increasing rapidly,which easily leads to the fatigue damage.Therefore,the research about the fatigue performance of the wind turbine blade has great significance.In view of the fact that most of fatigue life analyses of wind turbine blade are based on the uniaxial model,as the starting point,this thesis takes the multi-axial theory of composite material to study the multiaxial fatigue life of the 1.5MW wind turbine blade.The main contents and results of this thesis are as follows:(1)Selection of multiaxial failure models for wind turbine blade.Based on the prediction of the fatigue life of wind turbine blades,the f ailure criterion of composite materials under multiaxial stress is contrasted.Considering the engineering value,the multi-axial fatigue failure model is concluded,which can calculate the life of wind turbine blades.(2)Load calculation and acquisition of dangerous section stress for wind turbine blade.The different loads of wind turbine blades are analyzed.Based on the result s,the wind power industry specialized software-GH bladed is used to calculate the load under different wind speeds.The corresponding airfoil data of wind turbine blade are extracted.The coordinate data of the three-dimensional space are calculated and the geometric model of wind turbine blade is established by using the three-dimensional computer software.Then,the finite element method is used to set material properties and lay-up of the wind turbine blade.The corresponding load values are loaded to calculate the stress of the dangerous cross-section of wind turbine blade.(3)Calculation and analysis of multiaxial fatigue life of wind turbine blade.Based on the S-N curve of the wind turbine blade material,the fatigue life of the wind turbine blade is calculated by using the multiaxial model.The results of multiaxial fatigue life model and the uniaxial one are compared.The results show that the uniaxial fatigue life model ignores the longitudinal and transversal fatigue damage of wind turbine blades,which leads to the result is too high,so the method of multi-axial fatigue life calculation is more accurate.Therefore,the method proposed in this thesis can obtain more accurate fatigue life results,which will be more conducive to guide the design of wind turbine blade structure and apply in practice engineering.