| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 104 === In this thesis, the failure modes such as buckling and material failure and ways for improving the load carrying capability of wind blades are studied via both theoretical and experimental approaches. First of all, we separately tested two kinds of blades with different layer designs (Designs A and B) under static loads to detect the failure modes of the blades. In the tests, the strains at different locations on the blade skin and the blade tip displacement were measured. The finite element code ANSYS is then used to analyze the linear and nonlinear deformations of the blades. It has been shown that the nonlinear finite element method can produce more accurate results that the linear one when compared with the experimental results. In particular, it has been shown that the theoretical and experimental strains are in good agreement with errors less that 10% for both blade designs. The difference between the theoretical and experimental buckling loads of the blade with Design B is less than 1.3kilograms. The nonlinear finite element together with appropriate failure criteria is then used to design the wind blade of Design A under for enhancing the failure wind load of the blade. The wind load distributed on the blade is calculated based on the blade element theory. With the consideration of only one failure mode, it has been found that debounding occurs at wind speed of 40m/s, skin buckling at 42m/s, and first-ply failure at 47m/s. After an appropriate reinforcement of the blade structure by adding webs, the blade buckling wind speed becomes 85m/s without debounding, and first-ply failure occurs at 87m/s. Furthermore, we build a wireless strain measuring system to measure strains in the blade under wind load to verify the correctness of the method for stress analysis.
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