8 April 2009 Nonlinear piezoelectric impedance modulation and its application to crack detection
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In this paper, a structural health monitoring (SHM) methodology that can detect and characterize local structural damages in early stage is developed, by merging the concepts of two existing SHM principles, a piezoelectric impedance-based methodology and a nonlinear wave modulation spectroscopy. The presented SHM system mainly consists of a piezoelectric element bonded on the structural surface, a high-frequency harmonic voltage source, and a current detector. When the structure is subjected to a dynamic load at low-frequencies, it vibrates, and the scattering conditions for the high-frequency elastic waves in the vicinity of the inherent damages will change in synchronization with the structural vibration. This nonlinear effects of vibro-acoustic interaction between the low-frequency vibration and the high-frequency wave field causes the change in the driving-point impedance at the high frequency range, which can significantly modulate the coupled electro-mechanical impedance (or admittance) of the piezoelectric element. Therefore, if the piezoelectric element is driven by a fixed amplitude high-frequency harmonic voltage source, the nonlinear modulation of the coupled admittance can be observed as the amplitude and phase modulation of the current flowing through the piezoelectric element. A simplified modeling study of the above-mentioned nonlinear piezoelectric impedance modulation successfully leads to a damage evaluation index that assesses the intensity of the modulation of the modal stiffness. Experiments using a cracked beam are conducted to see how the impedance modulation can be observed and to examine the performance of the proposed method.
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Arata Masuda, Tomohiro Shinagawa, Daisuke Iba, Akira Sone, "Nonlinear piezoelectric impedance modulation and its application to crack detection", Proc. SPIE 7295, Health Monitoring of Structural and Biological Systems 2009, 72951X (8 April 2009); doi: 10.1117/12.815900; https://doi.org/10.1117/12.815900

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