基于线性频散信号构建的复杂航空结构Lamb波高分辨率损伤成像

在对复杂航空结构的Lamb波损伤成像中,Lamb波频散容易使信号波包发生扩展和变形,从而降低信号的分辨率,并最终影响损伤监测结果,因此Lamb波频散补偿已成为急需解决的一个重要问题。目前常用的频散补偿方法需要理论计算Lamb波频散曲线,难以适用于复杂航空结构。本文利用现场直接测得的相对波数曲线进行线性频散信号构建(Linearly-dispersive signal construction,LDSC)的频散补偿处理,解决了航空复杂结构中Lamb波频散难以补偿的问题。然后,将LDSC用于延迟叠加损伤成像中,以实现高分辨率损伤成像。为了降低多反射的复杂航空结构形式对成像结果的影响,引入了1.5波峰正弦调制的准宽带Lamb波激励波形。最后通过在真实复杂的某型飞机大梁结构上的实验证明了所提方法的有效性。

Linearly-Dispersive Signal Construction Based Lamb Wave High Resolution Damage Imaging of Complicated Aircraft Structures

In Lamb wave d amage imaging of complicated aircraft structures, the signal wave packets can be easily elongated and deformed due to the dispersion of Lamb wave. The signal resolution is then degraded and the final damage imaging results could be affected . Lamb wave dispersion compensation has become an issue needing to be resolved immediately. However, the traditional dispersion compensation methods usually require the theoretically-calculated dispersion curves of Lamb waves and are hard to be applied in complicated aircraft structures. In this paper, with in-situ measured relative wavenumber curves, the compensation process of linearly-dispersive signal construction (LDSC) is performed to solve the difficult problem of dispersion removal of Lamb waves in complicated aircraft structures. Hereafter, LDSC is used in delay-and-sum imaging to realize high resolution damage imaging, during which the quasi-wideband excitation waveform of 1.5-cycle sine burst is introduced to reduce the influence of complicated aircraft structures. Finally, the proposed methods are verified by the experiment on the actual complicated aircraft beam.