复杂频散航空结构中损伤的频谱弯折早期成像

In Lamb wave damage early monitoring for aviation structures, the resolution and signal-to-noise ratio (SNR) of diagnostic signals can be easily reduced by Lamb wave dispersion. This makes the extraction of damage information hard and finally, the monitoring results would be seriously affected. On the other hand, because of the higher Lamb wave frequencies and complicated structures in damage early monitoring, the multiple Lamb wave modes would simultaneously exist with their dispersion characteristics hard to be theoretically calculated, resulting in much difficulty to dispersion compensation. Dispersion compensation has become an important issue required to be urgently solved in Lamb wave damage early monitoring of aviation structures. In this project, to solve the issue, the spectral warping dispersion compensation method is put forward and applied to realize damage early imaging of complicated aviation structures. The main research contents include: the theory and method of broadband spectral warping selective dispersion compensation for high frequency multi-mode Lamb waves, optimum estimation of dispersion curves in complicated structures based on spectral warping matching dispersion compensation, spectral warping-based delay-and-sum damage early synthesis imaging, and simulation and experimental validation. Then, the spectral warping dispersion compensation method for high frequency multi-mode Lamb waves in complicated structures is developed, to solve the difficult issue of dispersion compensation in damage early monitoring and realize the high accuracy and high resolution damage early imaging in the complicated aviation structures. The search would provide the new damage early monitoring technology for the large civil aircraft structures.

在对航空结构的Lamb波损伤早期监测中，Lamb波频散容易降低信号分辨率和信噪比，使早期损伤的信息提取变得困难，并最终严重影响监测结果。另一方面，早期监测中较高的Lamb波频率和复杂的结构形式引起结构中多个Lamb波模式并存和频散特性难以理论计算的问题，又给频散补偿带来难度。频散补偿已成为航空结构Lamb波损伤早期监测中急需解决的重要难题。为此，本项目提出研究频谱弯折的频散补偿方法，并用于实现复杂航空结构的损伤早期成像。通过研究高频多模式Lamb波的宽带频谱弯折选择性频散补偿原理及方法、复杂结构中频散曲线的频谱弯折匹配性频散补偿最优估计、基于频谱弯折的延迟叠加损伤早期综合成像以及仿真和实验验证，提出复杂结构中高频多模式Lamb波的频谱弯折频散补偿方法，解决早期监测中的频散补偿难题，实现对复杂航空结构的高精度和高分辨率损伤早期成像。本研究将为大型民机结构中损伤的早期监测提供新的技术实现手段。

在航空结构Lamb波早期损伤监测中，Lamb波频散容易降低信号分辨率和信噪比，使早期损伤的信息提取变得困难，并最终严重影响监测结果。另一方面，早期监测中较高的Lamb波频率和复杂的结构形式引起结构中多个Lamb波模式并存和频散特性难以理论计算的问题，又给频散补偿带来难度。频散补偿已成为航空结构Lamb波早期损伤监测中急需解决的重要难题。为此，本项目分别研究了高频多模式Lamb波的宽带频谱弯折选择性频散补偿原理及方法、复杂结构中频散曲线的频谱弯折匹配性频散补偿最优估计、基于频谱弯折的延迟叠加损伤早期综合成像方法，以及上述方法的仿真和实验验证，提出了复杂结构中高频多模式Lamb波的频谱弯折选择性自适应频散补偿方法、基于频谱弯折的复杂结构高分辨率和高精度早期损伤成像方法，建立了典型航空结构实验验证系统。本项目研究解决了实际复杂航空结构早期损伤监测中高频Lamb波多个模式并存和频散特性难以理论计算的Lamb波频散补偿问题，并为实际复杂航空结构Lamb波高分辨率和高精度早期损伤成像提供了有效的新技术手段。