为更精确地预测风电支撑结构焊缝与螺栓在含大量低应力循环（低于疲劳极限）的变幅荷载作用下的疲劳寿命,提出一种考虑低应力损伤饱和效应和强化效应的风电结构疲劳损伤评估模型。该模型在前人提出的非线性连续介质损伤力学（NLCD）模型基础上,引入新的特征变量对原有模型进行改进,对所搜集的相关高、低应力变幅疲劳试验数据进行分析拟合,将所提模型与工程中广泛使用的Miner准则和原NLCD模型进行对比。结果表明,在低应力循环占比较高的情况下,Miner准则无法考虑低应力循环的损伤贡献而导致预测结果偏高,NLCD模型考虑到每次低应力循环的损伤无限累加而导致预测结果趋于保守。相比之下,修正模型具有更优的精度,同时能较好地预测疲劳寿命随高应力幅值、低应力幅值、高-低应力循环周次比等参数的变化趋势,初步验证了所提出模型的有效性和正确性。
Abstract
To more accurately predict fatigue life in wind turbine support structures subjected to amplitude loads featuring numerous low-stress cycles （below the fatigue limit）, a new fatigue damage model considering low stress damage saturation and strengthening effects is proposed in this paper. The model is based on the nonlinear continuum damage mechanics （NLCD） model proposed by Chaboche, and incorporates the mechanism assumptions of fatigue crack propagation under high and low stress alternating cycles proposed by Tokaji. The model introduces the saturation cycle number and the strengthening coefficient into the mathematical model to respectively limit the infinite accumulation of fatigue damage under low-stress cycles and further consider the strengthening effect caused by a large number of low-stress cycles. Furthermore, this paper derives the calculation formulas for the saturation cycle number and the strengthening coefficient through mathematical deduction, and clarifies their physical meanings and experimental testing methods. Based on this, this paper analyzes and fits the collected high and low stress amplitude fatigue test data, and compares the proposed model with the widely used Miner criterion in engineering and the original NLCD model. The results show that when the proportion of low-stress cycles is high, the Miner criterion cannot consider the damage contribution of low-stress cycles and leads to a high prediction result, and the NLCD model considers the infinite accumulation of damage caused by each low-stress cycle, resulting in a conservative prediction result. In contrast, the proposed model has better accuracy and can more accuately predict the trend of fatigue life with parameters such as high stress amplitude, low stress amplitude, and high-low stress cycle ratio, preliminarily verifying the effectiveness and correctness of the proposed model.
关键词
风电机组 /
疲劳损伤 /
强化效应 /
损伤饱和 /
非线性连续介质损伤力学模型
Key words
wind turbines /
fatigue damage /
strengthening effect （metal） /
damage saturation /
continuum damage mechanics
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基金
国家自然科学基金（52308186）; 中国博士后科学基金（2023M742501）; 四川省科技计划（2023NSFSC0890; 2023YFG0090）
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