In this paper, a technique called 'excitelet' is presented for the imaging of damage in structures using the correlation of the signals measured at elements of piezoceramic arrays with dispersed versions of the excitation signal. This approach is presented as an extension of classical imaging techniques and takes advantage of the chirplet-based matching pursuit algorithm. The applicability for sparse and compact arrays is investigated experimentally on an aluminum plate and comparison with the existing embedded ultrasonic structural radar (EUSR) algorithm is performed for A0 and S0 modes for three frequency ranges of interest. Significant improvement of imaging quality is demonstrated with respect to imaging techniques using time-of-flight (ToF) and group velocity considerations for both sparse and compact piezoceramic array arrangements.

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This paper aims at providing a framework for assessing the detection and localization performance of guided wave-based structural health monitoring (SHM) imaging systems. The assessment exploits a damage identification metric (DIM) providing a diagnostic of the structure from an image of the scatterers generated by the system, allowing detection, localization, and size estimation of the damage. Statistical probability of detection (POD) and probability of localization (POL) curves are produced based on values of the DIM for several damage sizes and positions. Instead of relying on arduous measurements on a significant number of structures instrumented in the same way, a model-based approach is considered in this paper for estimating POD and POL curves numerically. This approach is first illustrated on a simplistic model, which allows characterizing the robustness of the SHM system for various levels of noise in test signals. An experimental test case using a more realistic case with an artificial damage is then considered for validating the approach. A good agreement between experimental and numerical values of the DIM and derived POD and POL curves is observed.

This article investigates metrics to assess and compensate for the degradation of the adhesive layer of surface-bonded piezoceramic transducers for structural health-monitoring applications. Capacitance, resonance frequency, and modal damping parameters are derived from admittance curves using a lumped parameter model to monitor the degradation of the transducer adhesive layer. A pitch-catch configuration is then used to discriminate the effect of bonding degradation on actuation and sensing. It is shown that below the first mechanical resonance frequency of the piezoceramic transducers, the degradation causes a decrease in the amplitude of the transmitted and received signals, while above resonance, in addition to a decrease in the amplitude of the transmitted and received signals, a linear phase shift is observed. A signal-correction factor is proposed to adjust signals based on adhesive degradation evaluated using the measured modal damping. The benefits of the signal-correction factor are demonstrated in the frequency domain for both the A 0 and S 0 modes.