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.

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.

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.

Corrosion Detection/Quantification on Thin-Wall Structures Using Multi-Mode Sensing Combined With Statistical and Time-Frequency Analysis

2009 ◽  
Author(s):  
Lingyu Yu ◽  
Victor Giurgiutiu ◽  
Jingjiang Wang ◽  
Yong-June Shin
Keyword(s):  
Frequency Analysis ◽  
Lamb Wave ◽  
Thin Wall ◽  
Active Sensors ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Electromechanical Impedance ◽  
Piezoelectric Wafer Active Sensors ◽  
Damage Indicator ◽  
Piezoelectric Wafer

In this paper, we present a multiple mode sensing methodology to detect active corrosion in aluminum structure utilizing the broadband piezoelectric wafer active sensors. This method uses ultrasonic Lamb wave complemented with the electromechanical impedance measurement to detect, quantify, and localize the corrosion progression in plate-like structures. The ultimate objective of this research is to develop in-situ multimode sensing system for the monitoring and prediction of critical aerospace structures that can be used during in-service period, recording and monitoring the changes over time. The test experiments were conducted on an aluminum plate installed with a five sensor network using 7-mm piezoelectric wafer active sensors. The corrosion was emulated as material loss of an area of 50mm 38mm on the other surface of the plate. Detection of corrosion and its growth was first conducted using the Lamb wave method in pitch-catch mode. The corroded area resulted in a thickness loss on the Lamb wave propagation and caused the amplitude and phase changes in the structural responses. The experimental data was first evaluated by the statistics-based damage indicator using root mean square deviation. Though the damage indicator is able to detect the presence of the corrosion and identify the corrosion location quantitatively, it failed in giving the right indication of corrosion development. A more corrosion signal processing based method, the cross time-frequency analysis, was proposed and used to analyze the phase characteristics of the data set. This cross time-frequency analysis was found more reliable and precise for detecting the corrosion progression compared with the damage indicator method.

Temperature Effects on Piezoelectric Wafer Active Sensors

2015 ◽  
Author(s):  
Linlin Ma ◽  
Xiaoyi Sun ◽  
Bin Lin ◽  
Lingyu Yu
Keyword(s):  
Analytical Model ◽  
Temperature Effects ◽  
Spent Nuclear Fuel ◽  
Pressure Vessels ◽  
Ultrasonic Waves ◽  
Final Report ◽  
Active Sensors ◽  
Sensing System ◽  
Piezoelectric Wafer Active Sensors ◽  
Piezoelectric Wafer

This paper discusses the temperature effects of using piezoelectric wafer active sensors (PWAS) technologies for structural health monitoring (SHM) in pressure vessels and piping (PVP) applications, e.g. dry cast storage system (DCSS). The research into monitoring of DCSS health has experienced a dramatic increase following the issuance of the Blue Ribbon Commission (BRC) on America’s Nuclear Future Final Report in 2012. The interim storage of spent nuclear fuel from reactor sites has gained additional importance and urgency for resolving waste-management-related technical issues. PWAS have emerged as one of the major SHM technologies developed particularly for generating and receiving acousto-ultrasonic waves for the purpose of continuous monitoring and diagnosis. Durability and survivability of PWAS under temperature effects was first tested in experiments. The analytical model of PWAS based sensor and sensing system under temperature effects was then developed. This paper compared the analytical model and experimental results of PWAS under temperature changes. Since the environmental variability of a sensing system includes changes in both the sensors and the sensing methodology including acoustic emission (AE), guided ultrasonic waves (GUW), and electro-mechanical impedance spectroscopy (EMIS), we also performed several temperature exposure with different PWAS sensing configurations under a controlled oven. The potential of PWAS for DCSS applications has been explored. The paper ends with conclusions and suggestions for further work.

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