| Fatigue failure is the main reason of wind turbine blade failure.As the key component of wind turbine to capture wind energy,the wind turbine blade will be subjected to a variety of random variable amplitude loads during the work due to the harsh operating environment,resulting in different damages.Therefore,it is of great significance to identify and locate the damage of the blade and estimate the residual fatigue life of the damaged blade.The main work and conclusions of this paper are as follows:Firstly,the load on the operation process of wind power generation is introduced,and the concept and calculation formula of three main loads which affect the fatigue life of wind turbine blade are summarized,and the time under various wind speeds in Inner Mongolia Bayan Obo mining area is calculated by using Weibull distribution theory,and the wind speed distribution table is compiled.An experimental platform for modal testing of fan blades was built,and the self-cross spectral density method was used to identify the modal parameters of small blades before and after damage.The experimental results show that blade damage will lead to the decrease of natural frequency,and with the increase of the damage area,the decrease of natural frequency becomes larger.Therefore,the damage can be determined by the change of natural frequency.According to the change rate curve of axial mode mode difference,compared with other parts,the mode shapes of the area around the blade damage have more obvious changes,and the damage location is basically consistent with the peak position of the curve,which proves that the change rate of axial mode mode difference can effectively locate the damage location of the blade.Using ANSYS Workbench software,fluid-structure coupling analysis was carried out on the wind turbine under complete and different damage conditions to obtain the analysis results of wind pressure,deformation and strain on the blade.The simulation results show that the blade deformation at the tip is the largest under different wind speeds,and the blade deformation increases with the increase of wind speed.From blade tip to blade root,the amount of deformation decreases gradually,and the amount of deformation at blade root is basically 0.At different wind speeds,the maximum pressure of the blade all appears at the blade root,which is consistent with the actual engineering.As the wind speed increases,so does the stress.After the blade is damaged,the maximum stress increases significantly,with the maximum stress change in the direction of 30 degrees,and the stress change in the direction of 30 degrees and 60 degrees is significantly greater than that in the direction of 0 degrees and 90 degrees.Finally,the related theory of fatigue life analysis,the linear fatigue cumulative damage theory,is introduced,and the fatigue life estimation is performed for the intact and four damage condition blade models.The calculated results show that the fatigue life of the complete blade is 35.4 years,which meets the requirement that the design life of the fan blade is 20 years.Compared with the intact blade,the fatigue life of the blade is significantly reduced after damage,and the residual life of the blade in the 30 ° and 60 °directions is significantly lower than that in the vertical and horizontal directions. |
