强衰减各向异性结构损伤的导波双重聚焦扫描MUSIC成像

先进飞行器重要部位的结构材料和形式非常复杂，如石英陶瓷热防护结构、大尺寸变厚度复合材料壁板等，加之恶劣的服役环境，迫切需要面向上述结构的高准确性直接损伤监测方法。导波是非常可能解决其损伤监测的重要方法，但导波监测方法在先进飞行器结构上应用时存在强衰减各向异性特征，导致损伤信号信噪比低、幅相各向异性严重，造成监测准确性低的瓶颈问题。本项目将阵列激励聚焦扫描与多重信号分类（MUSIC）成像方法相结合，首先建立强衰减各向异性结构上的阵列导波信号模型，研究导波幅相补偿机制，校正各向异性造成的导波幅相误差；然后研究虚拟阵列变换聚焦扫描的MUSIC成像方法实现激励传感信号双重聚焦，解决损伤信号低信噪比问题，提高MUSIC成像方法的准确性和可靠性。最后面向典型强衰减各向异性结构上典型损伤形式，建立演示验证平台并开展方法的工程适用性验证优化。本项目研究对促进飞行器结构健康监测技术的工程应用具有重要意义。

The material components and types of important spots on advanced aircrafts are very complex, including the thermal protective structures of silica ceramics, large size composite panels with variable thickness and so on. With the serious service environment, it is very necessary to realize accurate direct damage monitoring for above structures. The guided waves based method is a potential technique to solve this problem. However, when the guided waves based damage monitoring method is applied on these aircraft structures, the attenuation and anisotropy are very serious during the propagation of guided waves. Thus, the signal to noise ratio (SNR) of the damage scattered signal is low and the propagation velocities along different directions are variable, resulting in the low accuracy of damage monitoring. This project combines the transmitter confocal scanning technique with multiple signal classification (MUSIC) based imaging method. Firstly, the propagation model of guided waves on attenuated and anisotropic structures is researched. On this base, the amplitude and phase compensated array signal model is constructed, which could calibrate the array signal errors resulted from the structural anisotropy. Then, the virtual array transformation based transmitting confocal scanning is combined with MUSIC based imaging method to realize transmitting-sensing focusing, which could code with the low SNR of the damage scattered signal and improve the accuracy and reliability of MUSIC based damage imaging. At last, facing the typical damage on typical high-attenuated and anisotropic structures, the demonstration platform will be built to verify and optimize the engineering suitability of the proposed method. This research is of great significance to promote the practical engineering application of SHM technology for aircraft structures.