基于应变模态的风机塔筒根部疲劳裂纹损伤检测研究

Study on Damage Detection of Fatigue Cracks at the Root of theWind Turbine Tower Based on Strain Mode

风力发电机塔筒根部所受弯矩大易产生疲劳裂纹,及早地检测发现裂纹有利于防止风机倒塌破坏。研究一种基于应变模态的塔筒根部疲劳裂纹损伤识别方法。首先建立塔筒的振动微分方程和应变模态;然后构建风机模型并进行模态分析,研究塔筒损伤前后固有频率、位移和应变模态振型的差异;最后建立应变模态变化率的疲劳裂纹识别指标,并基于最小二乘法拟合应变模态变化率与损伤程度的数学关系。结果表明:塔筒受损前后固有频率和位移模态振型无显著改变,无法进行损伤定位;应变模态振型在受损处出现峰值突变,且损伤程度越高突变越明显;应变模态变化率与损伤程度呈正相关,采用六次多项式可拟合出两者的关系。

The large bending moment at the root of the wind turbine tower can induce fatigue cracks easily,and the early detection of cracks is beneficial to prevent from the collapse and damage of the wind turbine.In this paper,a fatigue crack damage identification method at the tower root based on strain mode was studied.Firstly,the vibration differential equation and strain mode of the tower were established.Then,the wind turbine model was built and modal analysis was performed to study the differences of natural frequencies,displacement mode shapes and strain modal shapes before and after tower damage.Finally,the fatigue crack identification index of the strain modal change rate was established,and the mathematical relationship between the strain modal change rate and the damage degree was fitted based on the least squares method.The results show that there is no significant change in natural frequency and displacement mode shapes before and after tower damage,and they cannot be used for damage localization.The strain mode shape has a peak mutation at the damaged area,and the larger the degree of damage is,the more obvious the mutation is.There is a positive correlation between the strain modal change rate and the damage degree,and the relationship between the two is fitted by a sixth-order polynomial.