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Recent Progress on a Multi-Modal SHM System for Waveguides



We present a structural health monitoring (SHM) system based on the passive method of acoustic emission (AE) and the active methods of electromechanical impedance (EMI) and guided ultrasonic wave (GUW) methods. As all these methods can be deployed with the use of wafer-type piezoelectric transducers bonded or embedded to the structure of interest, this paper describes a unified SHM system where AE, EMI, and GUW are integrated in the same hardware/software unit. We assess the feasibility of this multi-modal monitoring in a large flat aluminum plate with six transducers. AE events are simulated by exciting a tone burst or using the conventional pencil-lead break test and the detected signals are processed with a source localization algorithm to identify the position of the source. For the active sensing, damage is simulated by adding a small mass to the plate: the raw waveforms are processed with a delay-and-sum algorithm to create an image of the plate whereas the electrical admittance of each transducer is analyzed using the statistical index of the root mean square deviation. The results presented in this paper show that the proposed system is robust, mitigates the weaknesses of each technique considered individually, and can be developed further to address the challenges associated with the SHM of complex structure


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