| The blade is the key component of the wind turbine for receiving wind energy. Its strength and stability take great roles in wind turbine's reliability. Cyclic load which the blade undergoes in its major life time is possible to lead fatigue failure. This thesis presents an improved fatigue life estimate method for GFRP blade which adapted for engineering application. This method was used to fatigue life prediction of a 1.5MW wind turbine blade. The thesis has three parts.In part one, a 3D finite element model of a typical blade of 1.5MW wind turbine was established. Details of the model, e.g. element type, material property .et al were presented. The way of how to transform the resultant internal force on cross section of blade into external distributed force on 3D FE model has been advanced. With this method, two kinds of fatigue loads, named static-equivalent load and different wind speed load, were calculated.In part two, troditional theory of fatigue life estimation of composite blade were introduced. It includes contents, e.g. S-N curve, equivalent of load spectrum and Palmgren-Miner linear fatigue damage accumulation rule. An improved fatigue life evaluation method for composite blade convenient for engineering application was presented. The key theory in it, like Puck fracture criterion and Goodman curve, were introduced.In part three, Fatigue life of one typical 1.5MW wind turbine blade under two kinds of cyclic loads were estimated, separately. By computing results analysis, the structure design and fatigue life of the blade has been evaluated. |
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