【作者】 张建华；

【导师】 王继新；

【作者基本信息】 吉林大学 ， 机械设计及理论， 2013， 硕士

【摘要】 风力机恶劣的运行环境，叶片主要承受随机交变载荷，导致其失效的主要原因是疲劳破坏，因此对其疲劳寿命的预测显得尤其重要。疲劳应力谱是进行结构疲劳寿命预测的重要依据，风力机叶片的实测疲劳应力谱数据难以获得，在这种情况下，寻求一种合理的风力机叶片疲劳寿命工程估算方法显得十分必要。本文结合“吉林大学科学前沿与交叉学科创新项目的资助（编号201103116）”，在借鉴参考国内外相关研究成果的基础上，对风力机叶片疲劳寿命的工程估算方法进行了研究，主要的研究内容和结论分述如下：⑴分析了长期风速模拟对于风力机叶片疲劳寿命估算的意义，详细介绍了马尔可夫链理论和MCMC理论，并应用MCMC法建立了风速的预测模型，基于1年的历史风速数据模拟产生了用于叶片疲劳寿命估算的10年风速数据。对模拟结果进行了分析，结果表明MCMC方法在长期风速模拟方面效果良好。⑵建立了1.5MW级风力机风轮的几何模型，运用ANSYS Workbench中流固耦合分析功能对风力机风轮进行了数值仿真分析，获得了各个风速工况下叶片的危险节点位置及其应力值，并通过曲线拟合获得风速和危险节点应力的响应函数。结合MCMC模拟产生的长期风速数据，获得了疲劳分析所需的等效疲劳应力谱，为最终叶片疲劳寿命估算奠定了基础。⑶分析了极值载荷在叶片疲劳寿命估算过程中的意义，介绍了目前常用的极值载荷外推方法，重点介绍了POT极值外推理论及基本步骤，并应用POT理论对叶片危险节点的等效疲劳应力谱进行了有效的极值外推。针对POT方法中阈值的确定难题，从优化设计的角度出发，提出了一种通过优化确定最优阈值的方法，结果表明这种方法简单易行，可以有效地确定最优阈值。⑷介绍了用于疲劳寿命预测的线性疲劳损伤理论和非线性疲劳损伤理论，运用雨流计数法得到了疲劳应力谱的幅值频次分布，选取幂函数方程构造了叶片玻璃钢材料S-N曲线。基于Miner线性疲劳累积损伤理论，通过应力-寿命法估算了1.5MW级风力机叶片的疲劳寿命。估算寿命约23年，满足风力机叶片设计寿命20年以上的要求。通过寿命估算结果分析表明，本文提出的风力机叶片疲劳寿命工程估算方法是一种可行的计算方法。更多还原

【Abstract】 The wind turbine is exposed to various harsh environment, the blade subjectedto alternating load may usually tend to fatigue failure, so the fatigue life prediction isespecially important. Load spectrum is the foundation of fatigue life prediction, atpresent, since it lacks of measured load spectrum of the wind turbine blade, to seek areasonable fatigue life estimation method for wind turbine blade is extremelynecessary.Combined with Jilin university scientific frontier and interdisciplinaryinnovation project funding (No:201103116) and on the basis of referencing thedomestic and foreign relevant research, fatigue life estimation method for windturbine blade have been researched in present paper, the main works and researchcontents are listed as follows:⑴The significance of long-term wind speed simulation for fatigue lifeestimation of wind turbine blade is analyzed, the theory of Markov chain andMCMC is detailed, and MCMC method is applied to establish the forecast model ofthe wind speed data. Based on1year wind speed data,10years wind speed data usedfor fatigue life estimation is simulated. The simulation results are analyzed, showingthat the MCMC method in terms of long-term wind speed simulation goes well.⑵The geometry model of1.5MW wind turbine rotor is established, numericalsimulation analysis of the rotor is conducted using ANSYS Workbench to obtaindangerous node and its stress value of each wind speed conditions. Then, theresponse function of wind speed and dangerous node stress is obtained. Combinedwith long-term wind speed simulation, the equivalent fatigue load spectrum isobtained, laying a foundation for the final blade fatigue life estimation.⑶The significance of the extreme load in the process of blade fatigue lifeestimation is analyzed, commonly used extreme extrapolation methods areintroduced, mainly the POT method and its basic steps, which is applied toextrapolate extreme load of the equivalent fatigue load spectrum. For the thresholddetermination problem, from the viewpoint of optimizing design, an optimizationmethod is put forward to determine the optimal threshold. The result indicates thatthis method is simple and effective. ⑷The linear fatigue damage theory and nonlinear fatigue damage theory areintroduced, the amplitude frequency distribution is obtained using rainflow countingmethod, the blade fiberglass material S-N curve is obtained selecting the powerfunction equation. Based on Miner linear fatigue cumulative damage theory, thefatigue life of1.5MW wind turbine blade is estimated through the stress-life method.The result is23years, meeting the requirements for wind turbine blade design life.The life estimation result shows that the fatigue life estimation method for windturbine blade presented in this paper is a feasible method.更多还原