*Article* **Stress Coupling Analysis and Failure Damage Evaluation of Wind Turbine Blades during Strong Winds**

**Kangqi Tian 1, Li Song 1,2,3,\*, Yongyan Chen 1,2,3, Xiaofeng Jiao 4, Rui Feng <sup>5</sup> and Rui Tian 1,2,3**


**Abstract:** Blades in strong wind conditions are prone to various failures and damage that is due to the action of random variable amplitude loads. In this study, we analyze the failure of 1.5 MW horizontal axis wind turbine blades. The computational fluid dynamics unsteady calculation method is used to simulate the aerodynamic load distribution on the blade. Fluid–structure coupling methods are applied to calculate the blade stress. The results show that the equivalent stress of the blade is the largest when the azimuth angle is 30◦, and the maximum equivalent stress is 20.60 MPa. There are obvious stress peaks in six sections, such as *r/R* = 0.10 (the span length of blade/the full length of the blade = 0.10). The frequency of damage that is caused by the stress in each area of the blade is determined based on the blade damage. The frequency of gel coat cracking in the blade tips and leaves is 77.78% and 22.22%, respectively, and the frequency of crack occurrence is 87.75%, 10.20% and 2.05%, respectively. By combining the stress concentration area and the damage results, the cause of blade damage is determined, which can replace the traditional inspection methods and improve the inspection efficiency.

**Keywords:** wind turbine blade; fluid–solid coupling; azimuth; stress concentration; failure location; failure damage evaluation
