基于Lamb波的平尾大轴裂纹扩展监测

平尾大轴作为在役飞机的主承力构件,其轴内变厚度截面处存在应力集中现象,是疲劳断裂高发的关键部位。针对平尾大轴变截面处裂纹损伤,研究其基于主动Lamb波的裂纹深度在线监测方法。首先,通过线切割制造真实损伤,对压电传感器采集的监测信号进行Shannon连续复数小波变换,去噪提取Lamb波信号;其次,重点研究了不同模式Lamb波的4种损伤因子对大轴裂纹深度的表征能力,结果表明,基于A_0模式的互相关损伤因子对裂纹深度的表征效果最佳;最后,利用A_0模式的互相关损伤因子实现了平尾大轴裂纹萌生及裂纹尺寸的定量化监测,为平尾大轴的在线监测提供了方法基础。

Crack Growth Monitoring of Horizontal Stabilizer Shaft Based on Lamb Wave

As a main bearing part of in-service aircraft, horizontal stabilizer shaft has a slender cavity with variable thickness section. Stress concentration often occurs at the variable thickness section, which results in fatigue crack and thus lead to fatigue fracture. In this paper, an on-line monitoring method of crack depth at variable thickness section based on active Lamb wave is studied.First, the real damage produced by wire cutting is monitored by active Lamb wave, and the response signals are extracted by Shannon continuous complex wavelet transform to eliminate noise. Second, the response signals are analyzed by 4 damage indices emphatically to characterize the rule of crack depth growth. The result shows that the cross-correlation damage index of A0 mode can effectively characterize the rule of crack depth growth best. Finally, the cross-correlation damage factor of A0 mode is used to monitor crack initiation and crack size quantification, which lays the foundation for the on-line monitoring of the horizontal stabilizer shaft. This research has an important application value in realizing the on-line monitoring of the crack in horizontal stabilizer shaft and guiding the service time prolong as well as maintenance of in-service aircraft.