Fatigue Life Prediction Of Wind Turbine Blade

The wind turbine is exposed to various harsh environment, the blade subjectedto alternating load may usually tend to fatigue failure, so the fatigue life prediction isespecially important. Load spectrum is the foundation of fatigue life prediction, atpresent, since it lacks of measured load spectrum of the wind turbine blade, to seek areasonable fatigue life estimation method for wind turbine blade is extremelynecessary.Combined with Jilin university scientific frontier and interdisciplinaryinnovation project funding (No:201103116) and on the basis of referencing thedomestic and foreign relevant research, fatigue life estimation method for windturbine blade have been researched in present paper, the main works and researchcontents are listed as follows:⑴The significance of long-term wind speed simulation for fatigue lifeestimation of wind turbine blade is analyzed, the theory of Markov chain andMCMC is detailed, and MCMC method is applied to establish the forecast model ofthe wind speed data. Based on1year wind speed data,10years wind speed data usedfor fatigue life estimation is simulated. The simulation results are analyzed, showingthat the MCMC method in terms of long-term wind speed simulation goes well.⑵The geometry model of1.5MW wind turbine rotor is established, numericalsimulation analysis of the rotor is conducted using ANSYS Workbench to obtaindangerous node and its stress value of each wind speed conditions. Then, theresponse function of wind speed and dangerous node stress is obtained. Combinedwith long-term wind speed simulation, the equivalent fatigue load spectrum isobtained, laying a foundation for the final blade fatigue life estimation.⑶The significance of the extreme load in the process of blade fatigue lifeestimation is analyzed, commonly used extreme extrapolation methods areintroduced, mainly the POT method and its basic steps, which is applied toextrapolate extreme load of the equivalent fatigue load spectrum. For the thresholddetermination problem, from the viewpoint of optimizing design, an optimizationmethod is put forward to determine the optimal threshold. The result indicates thatthis method is simple and effective. ⑷The linear fatigue damage theory and nonlinear fatigue damage theory areintroduced, the amplitude frequency distribution is obtained using rainflow countingmethod, the blade fiberglass material S-N curve is obtained selecting the powerfunction equation. Based on Miner linear fatigue cumulative damage theory, thefatigue life of1.5MW wind turbine blade is estimated through the stress-life method.The result is23years, meeting the requirements for wind turbine blade design life.The life estimation result shows that the fatigue life estimation method for windturbine blade presented in this paper is a feasible method.