Electromechanical impedance-based measurements for damage detection and characterization in medium-thick plates

Implementing the electromechanical impedance-based (EMI) method as a structural health monitoring (SHM) technique for medium-thick plates presents challenges, as the measured signals often lack essential features crucial for signal processing. Additionally, the maximum sensing range and minimum detectable damage size of piezoelectric transducers (PT)s are critical factors affecting the effectiveness of EMI measurements. Damage characterization that determines whether existing damage is growing or stable is also demanding. To address these issues, a steel plate of 2000 x 1350 x 20 mm3 was examined using four PTs of varying thicknesses to identify the best signal-to-noise ratio (SNR). Anew metric called the summation of exceeding metrics (SEM) was introduced for damage characterization. Results showed that a PT with a thickness of 200 mu m, providing a satisfactory SNR, could detect a 3 mm hole at a distance of 1600 mm. Additionally, the proposed metric; SEM; with a novel re-scaling step for the measured signals, effectively monitored damage progression.