The Stress Characteristics Research Of The Wind-power Blades Impacted By Hail

As a kind of clean and renewable energy with large energy and broad prospects, wind power has aroused the attention and use of the countries all over the world. As the force source of wind turbine, blade is the part of the most prone to failure in the wind power system with quite complicated structure and force. Therefore, the material selection, design, health monitoring and testing of the blade is seen as the key to the wind power equipment performance and the safe operation.The impact stress analysis of the blade can explicitly reflect the resistance to impact ability of each region and the stress distribution of each region when impacted in the blade structure, which provides important reference basis for the structure design of blade and material layer design of each part of the blade. Moreover, it is more accurately to grasp the site of the health monitoring through the stress analysis, which provides important theoretical basis for sensor layout. In addition, the study on the impact features of blade containing the preliminary crack and the extension ways of cracks can offer important reference value for the detection of the blade and the repair of crack.Based on the existing basis theory on the Wind-driven generator blade design, the paper analyzed the composition of aerodynamic parameters and structure parameters of the wind power blade, and discussed the choice of the blade material and the form of structure, then studied the theory method of the blade preliminary structure design.On account of the materials of wind-power blades in the paper, the hail impact has been simulated, and the stress characteristics of the tablet when impacted by hail and the propagation characteristics of stress wave have been analyzed. The stress features which have nothing to do with the material have been obtained through the impact simulation contrast of different material. It is studied the main factors which impacted the stress in the process of impact using the control variable method.The paper used the initial structure design method of the blade to design the initial structure for blade, and established the three-dimensional model and finite element model of the blade. On the basis of the locations of different structures on the blade, it also preceded the hail impact simulation, and analyzed in detail the influence of the blade structure to the stress property, as well as the characteristics of the stress and the stress wave propagation on each region. At last, it compared the different of the stress characteristics and the resistance to impact strength represented in the difference structural locations.The thesis studied the cause and extension mechanism of the cracks, and set up the finite element model of the blade with preliminary crack, and analyzed and contrasted the difference in stress characteristic about the hail impact crack blade and nondestructive blade. On the other hand, it analyzed and contrasted the difference in stress characteristic when the hail impacts the position of different azimuth and different angles near the crack, and discussed in detail the expansion trend of the crack.