沙堆疲劳损伤累积模型的研究

Research on sand pile model of cumulative fatigue damage

由于材料具有循环硬化与软化、循环蠕变与松弛等特性,导致其在变幅循环应力作用下的疲劳损伤与加载顺序密切相关。国内外研究者提出了许多损伤累积模型,但有些模型未明确地阐述加载顺序的影响。通过分析影响疲劳损伤的重要因素,提出伴随损伤、视在损伤和耦合损伤新概念,结合模糊理论定量计算由耦合效应引起的耦合损伤,建立了一个能考虑加载顺序对疲劳损伤累积影响的沙堆疲劳损伤累积模型。选取16Mn和316L不锈钢材料的试验数据进行疲劳寿命预测,分析结果表明,所建立的模型能适用于不同加载顺序下的疲劳损伤累积计算,L-H和H-L两种加载顺序下疲劳寿命的预测结果与试验结果吻合良好,其寿命预测误差分散带基本在2倍因子内,预测精度高,便于工程应用。

The fatigue damage under variable amplitude cyclic stress is closely related with the loading sequence because of the cyclic hardening and softening cyclic creep and relaxation,and other characteristics of materials.Many domestic and foreign researchers have proposed models of damage accumulation,but some models are not explicitly described effect of the loading sequence.Therefore,new concepts of the adjoining damage,apparent damage and coupled damage were proposed by analyzing key factors affecting fatigue damage.Coupled damage produced by coupled effect was calculated quantitatively with the fuzzy theory.The sand pile model of cumulative fatigue damage is built by taking into account the effects of fatigue damage accumulation of loading sequence.Fatigue lives of 16Mn and 316L stainless steel were predicted and compared with test data.The results showed that the model can be applied to different loading sequence for calculating accumulative fatigue damage.Predicted results of fatigue life under two sequences of L-H and H-L were in good agreement with experimental ones.Scatter band of predicted life error was within a factor of 2.This model is convenient for engineering application with high precision.