海上风机支撑结构的时域和频域疲劳对比研究

Time-domain and frequency-domain fatigue analysisof offshore wind turbine support structure

对海上风机支撑结构进行动力响应分析,求出结构危险节点的载荷谱和功率谱密度函数,结合疲劳损伤模型和Dirlik概率模型,分别在时域和频域内对支撑结构进行疲劳寿命分析。由于时域法计算疲劳寿命需进行应力循环计数,这一过程需处理的数据庞大,耗时长。频域法省去应力循环计数,代之以概率密度函数,可相对准确、快速地计算结构的疲劳寿命。分析结果表明,采用Dirlik概率模型的频域分析法能较准确地反映海上风机支撑结构在随机载荷作用下的疲劳损伤情况,计算结果误差在可接受范围内。

Dynamic response analysis of supporting structure of an offshore wind turbine was carried out,and the load spectrum and power spectral density function of structural risk node was calculated.Combining fatigue damage accumulation model and Dirlik probability model,the fatigue life of support structure was figured up in time and frequency domain respectively.The frequency domain method use probability density function instead of stress cycle counting which consumes too much time.After that the fatigue life of supporting structure risk node of an offshore wind turbine was calculated by the time domain method and the frequency domain method respectively.The results show that the frequency domain method of Dirlik＇ probability model can reflect the structure fatigue damage relatively accurately under the random loading for the supporting structure.The relative error of the frequency domain method compared to time domain method is within the acceptable range,which can be used to estimate fatigue life under long-term random alternating loads for supporting structure of an offshore wind turbine.