Minimum variance guided wave imaging in a quasi-isotropic composite plate

Abstract

Ultrasonic guided waves are capable of rapidly interrogating large, plate-like structures for both nondestructive evaluation and structural health monitoring (SHM) applications. Distributed sparse arrays of inexpensive piezoelectric transducers offer a cost-effective way to automate the interrogation process. However, the sparse nature of the array limits the amount of information available for performing damage detection and localization. Minimum variance techniques have been incorporated into guided wave imaging to reduce the magnitude of imaging artifacts and improve the imaging performance for sparse array SHM applications. The ability of these techniques to improve imaging performance is related to the accuracy of a priori model assumptions, such as scattering characteristics and dispersion. This paper reports the application of minimum variance imaging under slightly inaccurate model assumptions, such as are expected in realistic environments. Specifically, the imaging algorithm assumes an isotropic, non-dispersive, single mode propagating environment with a scattering field independent of incident angle and frequency. In actuality, the composite material considered here is not only slightly anisotropic and dispersive but also supports multiple propagating modes, and additionally, the scattering field is dependent on the incident angle, scattered angle, and frequency. An isotropic propagation velocity is estimated via calibration prior to imaging to implement the non-dispersive model assumption. Imaging performance is presented under these inaccurate assumptions to demonstrate the robustness of minimum variance imaging to common sources of imaging artifacts.

Understanding and Exploiting the Effects of Loading on Ultrasonic Sensing Systems for Structural Health Monitoring

“…However, it is not the only possible analysis method. Signal difference and correlation based methods in common use could also be applied, as could adaptive imaging methods that have been used for similar problems [46,47]. Modeling to better understand the expected load-dependent response from both cracks and other sources of scattering could also enable better analysis methods.…”

Damage localization in geometrically complex aeronautic structures using canonical polyadic decomposition of Lamb wave difference signal tensors

“…Some attempts to use the amplitude of the scattered signals are also reported in the literature [25,26] leading to the "amplitude" class of methods. Another class of methods, called "delay and sum", sums over all possible paths the scattered signal delayed as if it originates from a given position in order to infer the probability that the damage is present at that position [27,28,29,30,31,32]. Extending that idea, methods termed "correlation" rely on physical models of waves propagation.…”

Investigation of the scattering of Lamb waves from a generalized circular cavity by using Poisson/Mindlin plate theories and numerical simulation

“…Therefore, it would be very useful if we could gain deeper insight into the scattering pattern of Lamb waves from defects for the purpose of defect characterization and/or localization in nondestructive testing (NDT) and structural health monitoring (SHM) applications. 1,2…”