基于模态频率的缺口梁疲劳裂纹扩展寿命预测

Fatigue crack growth life prediction for a notched beam based on modal frequency

从试验出发,研究了含V型缺口悬臂梁在循环载荷作用下的疲劳裂纹扩展特性及其模态频率变化规律,分析了模态频率与裂纹扩展增量间的关联性。将裂纹扩展增量作为损伤参量,建立了基于模态频率下降率与损伤参量的关系。基于损伤力学,建立了裂纹损伤与循环加载次数的演化模型。结合模态频率下降率与裂纹损伤参量的关系,提出了一种基于模态频率下降率的缺口梁疲劳裂纹扩展寿命预测方法,实现了基于当前裂纹损伤和对应循环次数的疲劳裂纹扩展剩余寿命预测。结果表明,模态频率下降率对缺口梁的疲劳裂纹扩展寿命敏感,该方法预测的疲劳裂纹扩展寿命与实测的疲劳裂纹扩展寿命基本吻合。

Starting from tests of notched beams,fatigue crack growth characteristics and change law of modal frequencies for a V shape-notched cantilever beam under cyclic loads were studied to analyze the relation between modal frequencies and crack growth increment.Crack growth increment was taken as damage parameter to establish the relation between the decline rate of the first order modal frequency and damage parameter.Then,an evolution model for crack damage versus cyclic loading number was set up based on the damage mechanics.A prediction method of fatigue crack growth life was proposed for a cantilever notched beam based on the decline rate of modal frequency using the relation between modal frequency decline rate and crack damage parameter to realize predicting residual fatigue crack growth life of a cantilever beam based on the current crack damage and the corresponding loading cycle number.Results showed that the modal frequency decline rate is sensitive to the fatigue crack growth life of a notched beam;the fatigue crack growth life predicted using the proposed method is basically consistent to the measured one.