Research On Spatial—Wavenumber Filter Based Structural Health Monitoring And Imaging Method

With the rapid development of aviation science and technology, the security and economy of aircraft are becoming more and more prominent. Aircraft structural health monitoring(SHM) technologies, which play a vital role in ensuring the application of new materials, increasing the security of aircraft and reducing the maintenance cost of aircraft, have attracted extensive attentions. Based on the piezoelectric sensors array and Lamb wave, this paper focuses on a spatial-wavenumber filter imaging method, which is able to monitor the damage and impact of the aircraft structure. This method provides a novel technological mean for aircraft SHM. The main researches and innovations of this paper are as follows:(1) To deal with the near-field and blind angle of the spatial-wavenumber filter imaging method in SHM applications. An imaging method based on near-field optimization and cross-shaped array implemented for omni-directional damage imaging is proposed. Besides, according to the blind angle optimization of cross-shaped array, another fusion damage angle stack based omni-directional imaging method without Lamb wave velocity is proposed. This method is independent on the Lamb wave velocity while handle with the near-field and blind angle problem. The experimental verifications of the two methods are performed on the glass fiber epoxy composite laminates plate.(2) Aiming at the problem of depending on Lamb wavenumber of the spatial-wavenumber filter imaging method in SHM applications, a novel spatial-wavenumber filter construction method based on wavenumber searching and best match mechanism is studied. Based on the cross-shaped array, wavenumber searching and best match spatial-wavenumber filter, a damage imaging method is proposed, realizing the damage localization of no blind angle and without using the Lamb wavenumber. The novel spatial-wavenumber filter and the novel damage imaging method are experimented on an aluminum plate and a carbon fiber composite laminates plate respectively. The results show that the proposed imaging method without using the Lamb wavenumber can localize the damage with no blind angle, and the influence brought by the array element position error is small.(3) To deal with the problem that impact imaging is difficult to be realized by the spatial-wavenumber filter imaging method, an impact frequency narrowband signals extraction method and an impact distance estimation method are studied. And based on the cross-shaped array, wavenumber searching and best match spatial-wavenumber filter, an impact imaging method is proposed. This method extends the application of spatial-wavenumber filter imaging method to the impact monitoring. The proposed impact imaging method is experimentally studied on a carbon fiber composite laminates plate. The results show that the proposed impact imaging method without using the Lamb wavenumber can localize the impact with no blind angle.(4) The studied spatial-wavenumber filter imaging method of this paper is verified on the composite panel with variable thickness of a real aircraft fuel tank structure. The validation results show a good accuracy of damage and impact localization. Among them, the direction estimation error is no more than 2 degrees, the damage localization errors are less than 2 cm, and the maximum impact localization error is no more than 3.2 cm.