基于分段线性均值修正的风电叶片疲劳寿命计算方法

Fatigue life calculation method of wind turbine blade based on piecewise linear mean stresses correction

随着风电机组的大型化,疲劳强度设计成为大型风电叶片设计中的最为关键因素之一。目前风电叶片疲劳寿命的计算方法主要采用传统的简化算法,该方法存在诸多的简化与假设,并不能很好地预测风电叶片实际的疲劳损伤,所以需要一种更为合理的疲劳寿命计算方式。本文根据IEC 61400-5中提出的分段线性均值修正的方法,基于Goodman线性均值修正理论,结合多条已知的疲劳S-N曲线,提出了一种适合大型风电叶片疲劳寿命的计算方法。以目前应用较为广泛的玻纤拉挤板作为分析对象,对比分析了线性均值修正与分段线性均值修正两种方法的差异,最后通过对风电叶片实际疲劳试验损伤的分析以及大型风电叶片主梁疲劳强度的分析,得出如下结论:(1)玻纤拉挤板的疲劳性能并不是线性变化,基于单一S-N曲线的线性预测结果与测试结果存在较大误差,玻纤拉挤板更适合采用基于多条S-N曲线的分段线性CLD模型来描述其疲劳性能的变化,且分段线性均值修正疲劳寿命计算方法能更好地预测试验叶片实际疲劳损伤;(2)叶片设计中更应该关注PS侧主梁的疲劳强度,建议采用基于多条疲劳S-N曲线的分段线性均值修正疲劳寿命计算方法对大型风电叶片的疲劳强度进行计算,提高叶片疲劳设计的可靠性。

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:①The 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;②In 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.