含裂纹损伤叶片在切变来流下的应力耦合性分析

针对含裂纹损伤风力机在运行过程中产生的失效现象，将切变来流作为入口条件，基于流固耦合原理，分析含不同形式裂纹损伤的风力机叶片应力分布规律。通过无人机现场实验得知，裂纹主要集中于叶根（r/R=0.10截面）和叶中（r/R=0.50截面）后缘部位。单叶片在30°方位角时应力最大，额定风速下分布于叶根的裂纹受力最大，为33.34 MPa。强风风速下分布于叶中的裂纹受力最大，为44.31 MPa。重力载荷主要影响叶根部位的受力，气动载荷则主要作用于叶中，风速越大，叶中部位的裂纹越容易产生扩展。同时，沿弦向分布的裂纹，其扩展趋势最强。对于叶根处裂纹而言，若使叶片产生失效，裂纹长度需达到弦长的1/2、深度需达到叶片厚度的1/2；对于叶中处裂纹而言，若使叶片产生失效，裂纹长度需达到弦长的3/8、深度需达到叶片厚度的1/3。

STRESS COUPLING ANALYSIS OF BLADES WITH CRACK DAMAGE UNDER SHEAR FLOW

In view of the failure phenomenon of wind turbine with crack damage during operation, the shear flow was taken as the inlet condition, and the stress distribution law of wind turbine blade with different forms of crack damage was analyzed based on the principle of fluid-structure coupling. Through the field experiment of UAV （unmanned aerial vehicle）,it was found that the cracks were mainly concentrated in the blade root （r/R=0.10 section） and the trailing edge of the blade middle （r/R=0.50 section）. The stress of single blade reaches the maximum at 30° azimuth angle, and the crack stress at blade root reaches the maximum at rated wind speed, which is 33.34 MPa. Under strong wind speed, the crack force distributed in the blade is the maximum, which is 44.31 MPa. The gravity load mainly affects the force at the root of the blade, while the aerodynamic load mainly acts on the blade. The higher the wind speed is, the easier the crack in the middle part of the blade is to propagate. At the same time, the crack distributed along the chord has the strongest growth tendency. For the crack at the blade root, if the blade fails, the crack length shall be 1/2 of the chord length and the depth shall reach 1/2 of the blade thickness; for the crack at the middle of the blade, if the blade fails, the crack length shall reach 3/8 of the chord length and the depth shall reach 1/3 of the blade thickness.