Influence of a delamination on Lamb wave excitation by a nearby piezoelectric transducer

2020 ◽  
pp. 1045389X2091997 ◽  
Author(s):  
Alisa N Shpak ◽  
Mikhail V Golub ◽  
Inka Mueller ◽  
Artem Eremin ◽  
Jens Kathol ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Piezoelectric Transducer ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Boundary Integral ◽  
Experimental Investigations ◽  
Wave Excitation ◽  
Damage Scenarios ◽  
Active Sensor ◽  
Piezoelectric Wafer

This article presents the results of theoretical and experimental investigations of characteristic changes of Lamb wave excitation and scattering by a strip-like horizontal delamination in a layered elastic waveguide for Lamb waves induced by a piezoelectric wafer active sensor. The boundary integral equation method is used to describe wave propagation in an infinite layered waveguide with a delamination, while the frequency domain spectral element method is employed to model the dynamic behaviour of the piezoelectric wafer active sensor, which allows to simulate debonding between the piezoelectric wafer active sensor and the waveguide. Experimental investigations of the dynamic interaction of the piezoelectric wafer active sensor with a layered plate containing a horizontal delamination is conducted for several damage scenarios, showing a good agreement with the results obtained using the developed mathematical model. The obtained mathematical model is employed to analyse alteration of the piezo-induced Lamb waves including modes’ decomposition due to delamination. The conversion and/or conservation of the Lamb waves on account of a delamination is investigated. The electro-mechanical impedance of the piezoelectric transducer and the stress intensity factors of a delamination are analysed in dependence on the delamination location.

Effect of structural damping on the tuning between piezoelectric wafer active sensors and Lamb waves

2018 ◽  
Vol 29 (10) ◽  
pp. 2177-2191 ◽  
Author(s):  
Hanfei Mei ◽  
Victor Giurgiutiu
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Excitation Frequency ◽  
Structural Damping ◽  
Active Sensors ◽  
Piezoelectric Wafer Active Sensors ◽  
Active Sensor ◽  
Piezoelectric Wafer

Piezoelectric wafer active sensors have been widely used for Lamb-wave generation and acquisition. For selective preferential excitation of a certain Lamb-wave mode and rejection of other modes, the piezoelectric wafer active sensor size and the excitation frequency should be tuned. However, structural damping depends on the structure material and the excitation frequency and it will affect the amplitude response of piezoelectric wafer active sensor–excited Lamb waves in the structure, that is, tuning curves. Its influence on the piezoelectric wafer active sensor tuning reflects the effect of structural health monitoring configuration considered in the excitation. Therefore, it is important to have knowledge about the effect of structural damping on the tuning between piezoelectric wafer active sensor and Lamb waves. In this article, the analytical tuning solution of undamped media is extended to damped materials using the Kelvin–Voigt damping model, in which a complex Young’s modulus is utilized to include the effect of structural damping as an improvement over existing models. This extension is particularly relevant for the structural health monitoring applications on high-loss materials, such as metallic materials with viscoelastic coatings and fiber-reinforced polymer composites. The effects of structural damping on the piezoelectric wafer active sensor tuning are successfully captured by the improved model, with experimental validations on an aluminum plate with adhesive films on both sides and a quasi-isotropic woven composite plate using circular piezoelectric wafer active sensor transducers.

Effect of Lamb Wave Excitation Frequency on Detection of Delamination in Composite Plates

2011 ◽  
Author(s):  
Inho Kim ◽  
Ratneshwar Jha
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Excitation Frequency ◽  
Damage Index ◽  
Laser Doppler Vibrometer ◽  
Composite Plates ◽  
Experimental Investigations ◽  
Wave Excitation ◽  
Error Norm ◽  
Hilbert Huang Transform

This paper presents experimental investigations of the effect of Lamb wave excitation frequency on detection of a given delamination in composite plates. Typical aerospace type composite plates are used and integrated piezoelectric transducers function as both actuator and sensor. Also, a scanning Laser Doppler Vibrometer (LDV) is used for preliminary sensing of structural responses when excited by a single PZT actuator. Results in time domain are quantified by a damage index calculation based on modified L2 error norm. Phase difference calculations based on complex continuous wavelet transform (CWT) and Hilbert-Huang transform (HHT) are presented. Experimental results show a significant effect of incident Lamb waves on delamination signature.

scholarly journals Combination of Phase Matching and Phase-Reversal Approaches for Thermal Damage Assessment by Second Harmonic Lamb Waves

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1961 ◽  
Author(s):  
Weibin Li ◽  
Shicheng Hu ◽  
Mingxi Deng
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Second Harmonic ◽  
Experimental Investigations ◽  
Phase Matching ◽  
Study Phase ◽  
Linear Wave ◽  
Material Degradation ◽  
Promising Alternative ◽  
Phase Reversal

It is known that measurement and extraction of the tiny amplitude of second harmonic Lamb waves are the main difficulties for practical applications of the nonlinear Lamb wave technique. In this study, phase-reversal approaches and phase matching technique are combined to build up the second-harmonic generation (SHG) of Lamb waves. A specific Lamb wave mode pair, which satisfied phase matching conditions, is selected to ensure the generation of cumulative second harmonic waves. Lamb wave signals with the same frequency but in reverse phase, propagating in the given specimen, are added together to counteract the fundamental waves, and simultaneously to enhance the signals of the second harmonic generated. The obtained results show that the phase-reversal approach can enhance the signals of second harmonic Lamb waves, and effectively counteract that of the fundamental waves. The approach is applied to assess the thermal-induced material degradation in the stainless steel plates. Distinctions of the acoustic nonlinearity parameters under different degraded levels are clearly shown in an improved repeatable and reliable manner, while those of linear wave velocity in the specimens are neglectable. The experimental investigations performed indicate that the proposed approach can be taken as a promising alternative for assessment of material degradation in its early stages.

scholarly journals Detection of coatings within liquid-filled tubes and containers by mode conversion of leaky Lamb waves

2013 ◽  
Vol 2 (1) ◽  
pp. 73-84 ◽  
Author(s):  
M. Schmitt ◽  
K. Schmidt ◽  
S. Olfert ◽  
J. Rautenberg ◽  
G. Lindner ◽  
...  
Keyword(s):  
Lamb Wave ◽  
Single Phase ◽  
Lamb Waves ◽  
Mode Conversion ◽  
Conversion Process ◽  
Outer Side ◽  
Acoustic Sensor ◽  
Wave Excitation ◽  
Excitation Mode ◽  
Leaky Lamb Waves

Abstract. In this paper, a new acoustic sensor principle for coating detection within liquid-filled tubes and containers based on mode conversion of leaky Lamb waves is introduced. Leaky Lamb waves are excited and detected by single-phase transducers, which are attached on the outer side of a tube or container. By transmission time and amplitude measurements, coating formation within the liquid-filled tube and container is detected non-invasively. This new sensor principle is subdivided into the separate considerations of Lamb wave excitation, mode conversion and inverse mode conversion. The Lamb wave excitation by a single-phase transducer is visualized by scanning laser Doppler vibrometer imaging. The mode conversion process of leaky Lamb waves is measured by membrane hydrophone measurements and Schlieren visualization; afterwards, the measured emission angles are compared with the theoretical one. The inverse mode conversion process of pressure waves back to leaky Lamb waves is visualized by Schlieren images. By merging the results of Lamb wave excitation, mode conversion and inverse mode conversion, the new sensor concept is explained. Theoretical considerations and measurement results of adhesive tape coating inside a liquid-filled plastic tube and a liquid-filled stainless steel container verify the new acoustic sensor principle. Finally the measuring sensitivity and the technical realization are discussed.

Non-axisymmetric Lamb wave excitation by piezoelectric wafer active sensors

2012 ◽  
Vol 174 ◽  
pp. 173-180 ◽  
Author(s):  
Jochen Moll ◽  
Mikhail V. Golub ◽  
Evgeny Glushkov ◽  
Natalia Glushkova ◽  
Claus-Peter Fritzen
Keyword(s):  
Lamb Wave ◽  
Wave Excitation ◽  
Active Sensors ◽  
Piezoelectric Wafer Active Sensors ◽  
Piezoelectric Wafer

Lamb Wave-Mode Tuning of Piezoelectric Wafer Active Sensors for Structural Health Monitoring

2007 ◽  
Vol 129 (6) ◽  
pp. 752-762 ◽  
Author(s):  
Giola B. Santoni ◽  
Lingyu Yu ◽  
Buli Xu ◽  
Victor Giurgiutiu
Keyword(s):  
Wave Packet ◽  
Lamb Wave ◽  
Load Transfer ◽  
Lamb Waves ◽  
Tone Burst ◽  
Wave Mode ◽  
Active Sensors ◽  
Tuning Curves ◽  
Piezoelectric Wafer Active Sensors ◽  
Piezoelectric Wafer

An analytical and experimental investigation of the Lamb wave-mode tuning with piezoelectric wafer active sensors (PWASs) is presented. The analytical investigation assumes a PWAS transducer bonded to the upper surface of an isotropic flat plate. Shear lag transfer of tractions and strains is assumed, and an analytical solution using the spacewise Fourier transform is reviewed, closed-form solutions are presented for the case of ideal bonding (i.e., load transfer mechanism localized at the PWAS boundary). The analytical solutions are used to derive Lamb wave-mode tuning curves, which indicate that frequencies exist at which the A0 mode or the S0 mode can be either suppressed or enhanced. Extensive experimental tests that verify these tuning curves are reported. The concept of “effective PWAS dimension” is introduced to account for the discrepancies between the ideal bonding hypothesis and the actual shear-lag load transfer mechanism. The paper further shows that the capability to excite only one desired Lamb wave mode is critical for practical structural health monitoring (SHM) applications such as PWAS phased array technique (e.g., the embedded ultrasonics structural radar (EUSR)) and the time reversal process (TRP). In PWAS phased array EUSR applications, the basic assumption of the presence of a single low-dispersion Lamb wave mode (S0) is invoked since several Lamb wave modes traveling at different speeds would disturb the damage imaging results. Examples are given of correctly tuned EUSR images versus detuned cases, which illustrate the paramount importance of Lamb wave-mode tuning for the success of the EUSR method. In the TRP study, an input wave packet is reconstructed at a transmission PWAS when the signal recorded at the receiving PWAS is reversed in the time domain and transmitted back to the original PWAS. Ideally, TRP could be used for damage detection without a prior baseline. However, the application of TRP to Lamb waves SHM is impended by the dispersive and multimodal nature of the Lamb waves. The presence of more then one mode usually produces additional wave packets on both sides of the original wave packet due to the coupling of the Lamb wave modes. The PWAS Lamb wave tuning technique described in this paper is used to resolve the side packets problem. Several tuning cases are illustrated. It is found that the 30kHz tuning of the A0 Lamb wave mode with a 16-count smoothed tone burst leads to the complete elimination of the side wave packets. However, the elimination was less perfect for the 290kHz tuning of the S0 mode due to the frequency sidebands present in the tone-burst wave packet.

Lamb Wave Tuning Between Piezoelectric Wafer Active Sensors and Host Structure: Experiments and Modeling

2006 ◽  
Author(s):  
Giola B. Santoni ◽  
Victor Giurgiutiu
Keyword(s):  
Lamb Wave ◽  
Integral Transform ◽  
Lamb Waves ◽  
Composite Plates ◽  
Ultrasonic Waves ◽  
Active Sensors ◽  
Piezoelectric Wafer Active Sensors ◽  
Isotropic Plates ◽  
Piezoelectric Wafer ◽  
Alternating Voltage

In structural health monitoring (SHM), a network of embedded sensors permanently bonded to the structure is used to monitor the presence and extent of damage. The sensors can actively interrogate the structure through ultrasonic waves. Among the ultrasonic waves, Lamb waves are quite convenient because they can propagate at large distances in plates and then interrogate a large area. Lamb waves in a plate can be produced with piezoelectric wafer active sensors (PWAS) that are small, inexpensive, unobtrusive transducers. PWAS can be surface-mounted on an existing structured or placed inside composite materials. PWAS sensors use the piezoelectric principle. An alternating voltage applied to the PWAS terminals produces an oscillatory expansion and contraction of the PWAS. An oscillatory expansion and contraction of the PWAS produces an alternating voltage at the PWAS terminals. PWAS are bonded to the structure through an adhesive layer; the coupling with the investigated structure is higher then conventional transducers. If the PWAS bonded to the structure is excited, it couples its in-plane motion with the Lamb wave particle motion on the material surfaces. In previous studies, the Lamb wave mode tuning between PWAS and isotropic plates has been observed experimentally and theoretically. Recently experiments have been performed to verify the presence of tuning between bonded PWAS and composite plates. In the present paper, it will be discussed a method, normal mode expansion (NME), for predicting the tuning frequencies of the PWAS-plate structure. This method can be used for both isotropic and non-isotropic material. Experimental values for the tuning frequencies in isotropic plates are compared with the theoretically data obtain with integral transform solution and NME.

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