铝合金疲劳裂纹分布式光纤监测与扩展预测方法

Distributed Optical Fiber Monitoring and Propagation Prediction Method for Fatigue Crack of Aluminum Alloy

针对典型航空航天器金属结构易产生疲劳裂纹损伤等问题,该文提出了一种基于光纤Bragg光栅(FBG)传感器的典型单边缺口铝合金试件疲劳裂纹监测与扩展预测方法。借助有限元仿真法,数值模拟得到单边缺口试件不同长度疲劳裂纹裂尖附近应变场分布特征,给出了FBG传感器优化布局形式。通过疲劳加载试验,获得FBG传感器中心波长偏移量随疲劳裂纹扩展响应特性,建立了中心波长偏移量与裂纹长度关系的预测模型。根据不同位置FBG传感器中心波长-应变响应特征,辨识疲劳裂纹所在区域。在此基础上,依据中心波长偏移量与裂纹长度关系模型,实现针对5种不同裂纹扩展长度的有效预测,平均误差为1.6 mm。研究表明,该文所提方法具有非视觉测量和实时性好等优点,能为实现航空航天结构健康监测与剩余寿命评估提供有力依据。

Aiming at the fatigue crack damage of typical aircraft and spacecraft metal structures,a fatigue crack monitoring and propagation prediction method for typical unilateral notched aluminum alloy specimens based on fiber Bragg grating(FBG)sensor is proposed in this paper.With the help of finite element simulation method,the strain distribution characteristics near the crack tip of fatigue crack with different length of unilateral notch specimens are obtained by numerical simulation,and the optimal layout of FBG sensors is given.Through fatigue loading test,the response characteristics of the center wavelength offset of FBG sensor with fatigue crack growth are obtained,and the prediction model of the relationship between the center wavelength offset and the crack length is established.According to the central wavelength-strain response characteristics of FBG sensors at different locations,the fatigue crack region is identified.On this basis,according to the model of the relationship between the central wavelength offset and the crack length,the effective prediction of five different crack growth lengths is achieved with an average error of 1.6 mm.The results show that the proposed method has the advantages of non-visual measurement and good real-time performance,and can provide a strong basis for health monitoring and residual life assessment of aerospace structures.