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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。
In the Lamb wave damage imaging of complex aeronautical structures, Lamb wave dispersion easily spreads and distorts the signal wave packet, thus reducing the resolution of the signal and finally affecting the damage monitoring results, so the dispersion compensation of the Lamb wave has become an urgent need to be resolved An important issue. At present, the commonly used dispersion compensation method needs theoretical calculation of Lamb wave dispersion curve, which is difficult to apply to complex aeronautical structures. In this paper, the dispersion compensation of linearly-dispersive signal construction (LDSC) is carried out by using the relative wave number curve directly measured in the field to solve the problem that it is difficult to compensate the dispersion of the Lamb wave in the complex structure of aviation. LDSCs are then used in delayed superposition damage imaging to achieve high-resolution damage imaging. In order to reduce the influence of multi-reflection and complex aeronautical structures on imaging results, a quasi-broadband Lamb wave excitation waveform with sinusoidal modulation of 1.5 peaks was introduced. At last, the validity of the proposed method is proved by experiments on a real and complicated aircraft girder structure.