考虑平均应力影响的风力机叶片寿命估算

FATIGUE LIFE PREDICTION OF WIND TURBINE BLADE CONSIDERING EFFECT OF MEAN STRESS

考虑平均应力影响效应,建立一个适用于描述叶片材料疲劳寿命规律的应力寿命关系。分析风力发电机叶片的应力特征,指出叶片应力由工作载荷引发的低频应力和气动弹性振动引发的高频应力叠加而成,是具有平均应力的循环应力。通过对叶片材料疲劳特性分析发现,金属材料的疲劳极限线图不适合描述叶片材料。通过对叶片根部应变历程的测量获得相应的Von Mises应力历程,应用雨流计数法进行统计处理,获得应力幅和平均应力的累积分布。使用Palmgren-Miner线性损伤累积法则,给出叶片的疲劳损伤计算公式。以1.5 MW变速恒频风力发电机叶片为例,进行疲劳损伤分析和疲劳寿命估算。计算结果表明,该文提出的方法是合理可行的。

Considering the effect of mean stress, the general stress - fatigue life relationship for describing the fatigue life characteristics of blade materials was presented. The stress characteristics of wind turbine blades were analyzed, it was found that the total blade stress was superposed by the low frequency stress caused by working load and the high frequency stress caused by aero-elastic libration, which was a kind of cycle stress with mean stress. The fatigue property analysis of blade materials shows that the fatigue limit diagrams for metallic materials are not suitable to the blade materials of wind turbine. Von Mises stress process is acquired by means of measuring strain process of blade foot, and rain-flow counting method was used to dispose stress cycles statistically, and the cumulative distribution of stress amplitude and mean established by using wind turbine blade is stress were obtained. The fatigue damage calculation expression of wind turbine Palmgren-Miner linear cumulative damage rule. The 1.5 MW variable speed constan as an example to carry out the fatigue damage analysis and fatigue life prediction. The resuhs show that this method is reasonable and feasible.