title: Impact imaging of aircraft composite structure based on a model-independent spatial-wavenumber filter.
abstract: The spatial-wavenumber filtering technique is an effective approach to distinguish the propagating direction and wave mode of Lamb wave in spatial-wavenumber domain. Therefore, it has been gradually studied for damage evaluation in recent years. But for on-line impact monitoring in practical application, the main problem is how to realize the spatial-wavenumber filtering of impact signal when the wavenumber of high spatial resolution cannot be measured or the accurate wavenumber curve cannot be modeled. In this paper, a new model-independent spatial-wavenumber filter based impact imaging method is proposed. In this method, a 2D cross-shaped array constructed by two linear piezoelectric (PZT) sensor arrays is used to acquire impact signal on-line. The continuous complex Shannon wavelet transform is adopted to extract the frequency narrowband signals from the frequency wideband impact response signals of the PZT sensors. A model-independent spatial-wavenumber filter is designed based on the spatial-wavenumber filtering technique. Based on the designed filter, a wavenumber searching and best match mechanism is proposed to implement the spatial-wavenumber filtering of the frequency narrowband signals without modeling, which can be used to obtain a wavenumber-time image of the impact relative to a linear PZT sensor array. By using the two wavenumber-time images of the 2D cross-shaped array, the impact direction can be estimated without blind angle. The impact distance relative to the 2D cross-shaped array can be calculated by using the difference of time-of-flight between the frequency narrowband signals of two different central frequencies and the corresponding group velocities. The validations performed on a carbon fiber composite laminate plate and an aircraft composite oil tank show a good impact localization accuracy of the model-independent spatial-wavenumber filter based impact imaging method.
authors.affiliation: State Key Lab of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
authors.forename: Lei
authors.initials: L
authors.lastname: Qiu
authors.affiliation: State Key Lab of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; Department of Air Force Military Transportation, Air Force Service College, Xuzhou 221000, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.affiliation: State Key Lab of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. Electronic address: ysf@nuaa.edu.cn.
authors.forename: Shenfang
authors.initials: S
authors.lastname: Yuan
authors.affiliation: Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
authors.forename: Zhongqing
authors.initials: Z
authors.lastname: Su
keywords: Composite structure; Impact imaging; Lamb wave; Linear piezoelectric sensor array; Spatial-wavenumber filter