Nonlinear piezoelectric impedance modulation and its application to crack detection

Abstract

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.

Detection and localization of contact-type damages via nonlinear impedance modulation of piezoelectric materials bonded on a beam structure

“…(46), the damage evaluation index is defined as follows. Note that the damage index derived in this section is fundamentally the same as that described in the previous paper, 12 but the mathematical formulation is slightly modified.…”

“…Masuda et al 12 have proposed a self-sensing, novel integrity monitoring methodology, which can be sensitive to the incipient contact-type defects by combining the concepts of the NWM-based methodologies with the piezoelectric impedance-based methodologies. 13 It has been shown that, when the structure involving defects is subjected to a low-frequency vibrational load (pump), the coupled electro-mechanical admittance of the PE in high-frequency range is perturbed in synchronization with the low-frequency pump load, so that the current response flowing through the PE induced by the high-frequency harmonic probe voltage source is modulated both in amplitude and phase.…”

Nonlinear piezoelectric impedance modulation induced by a contact-type failure and its application in crack monitoring

“…Preliminary tests (for detail see [45]) showed that, for a steel beam specimen with a fatal transverse crack initiated from a pre-produced notch made by electrical discharge machining (EDM), modulation was observed in the current response to the probe voltage of approximately 60 kHz, under a cyclic transversal pumping load of approximately 1 Hz applied by hand. In contrast, no visible modulation was found for intact specimens with or without the EDM notch.…”

“…For this reason, a simpler self-sensing technique, which requires merely a single piezoelectric active sensor, is desired. Masuda et al [43] have proposed a self-sensing, baseline-free SHM methodology, which can be sensitive to the incipient contact-type failures even in the hidden form, by combining the concepts of the PI-based and NWM-based methodologies. In this approach, a single piezoelectric active sensor is utilized just as the PI-based SHM setup, and driven by a high-frequency harmonic probe voltage.…”