Bolt Fatigue Strength for the Tower of Large-scale Horizontal Axis Wind Turbines

For achieve the anti-fatigue strength design of the tower flange’s bolts for the large-scale horizontal axis wind turbines, the checking method of fatigue strength was proposed based on the Schmidt-Neuper model. According to the stiffness distribution ratio of single sector flange system, the nonlinear relationship of internal force-external tension was established for the bolt. The sequential stresses of the bolts were derived through the linear interpolation of load, and the fatigue cumulative damage distribution of the whole bolt circle was obtained by using the rain flow counting and accumulated damage calculation. Furthermore the position of the maximum fatigue cumulative damage can be found. And on this basis, the effect of some parameters such as retightening force of bolts, number of bolts and thickness of flange to the maximum fatigue cumulative damage was analyzed. The results showed that the proposed method and procedure was feasible and effective in analyzing and checking the fatigue strength of the tower flange bolts.