关键词: 风电叶片, 疲劳寿命, 均值修正, 玻纤拉挤板, 分段线性, 复合材料

Abstract: With the expansion of wind turbines, fatigue strength design has become one of the most critical factors in the large wind turbine blades design. The current calculation method for the blade fatigue life is mainly based on the simplified approach, which has many simplifications and assumptions and cannot predict the actual fatigue damage of wind turbine blades. Therefore, a more reasonable approach of fatigue life is needed. This paper proposes a suitable method for the fatigue life prediction of large wind turbine blades based on Goodman linear mean stresses correction theory and combined with multiple known fatigue S-N curves, which according to the piecewise linear mean stresses correction method mentioned in IEC 61400-5. With the widely used glass fiber pultrusion plate as the analysis object, the comparative analysis between the linear mean stresses correction and the piecewise linear mean stresses correction has been preformed. Finally through the analysis of the actual fatigue test damage and the spar cap fatigue strength of the blades, the conclusions come as follows: ① The fatigue performance of glass fiber pultrusion plate is not linear, and the fatigue performance predicted by the linear method based on a single fatigue S-N curve has a significant discrepancy with the test results. The piecewise linear CLD model based on multiple fatigue S-N curves is more suitable for describing the change of fatigue performance of glass fiber pultrusion plate, and the fatigue life prediction method based on piecewise linear mean stresses correction can better predict the actual fatigue damage of blades test; ② In the blade design, more attention should be paid to the fatigue strength of PS side of spar cap. It is suggested to calculate the fatigue strength of large wind turbine blades by using the piecewise linear mean stresses correction method based on multiple fatigue S-N curves to improve the reliability of blade fatigue design.

Key words: wind turbine blade, fatigue life, mean stress correct, glass fiber pultrusion plate, piecewise linear, composites