Structural Health Monitoring Using PZT Transducer Network and Lamb Waves

2010 ◽  
Author(s):  
J. Q. Mou ◽  
L. Martua ◽  
Y. Q. Yu ◽  
Z. M. He ◽  
C. L. Du ◽  
...  
Keyword(s):  
Health Monitoring ◽  
Lamb Waves ◽  
Numerical Models ◽  
Excitation Frequency ◽  
Ultrasonic Waves ◽  
Short Time Fourier Transform ◽  
Test Plate ◽  
Optimal Excitation ◽  
Short Time ◽  
To Receive

Structure health monitoring (SHM) using ultrasonic waves is an emerging technology that can be applied to real-time detect, locate and quantify the structural damages in aircraft structures. In this paper, the monitoring of crack growth at rivet holes in an aluminum test plate using a PZT transducer network and Lamb waves is investigated. The thin disc PZT transducers surface mounted at the test plate are used as actuators to transmit the windowed sinewave bursts and sensors to receive the ultrasonic Lamb waves. The symmetrical S0 mode and antisymmetrical A0 mode of the Lamb waves in the structures are studied with correlated theoretical, experimental and numerical analysis. The optimal excitation frequency is determined for the test plate. Finite element method (FEM) numerical models for simulations of the wave propagations and interactions with the holes and cracks in the plate are developed and verified with the experimental results. The wave responses modes and characteristics for detection of the cracks at the rivet holes are analyzed. The Lamb wave signals in the PZT transducer network are processed with the short time Fourier transform (STFT). It is demonstrated that the time of flight and the energy transmission ratio of the S0 wave are sensitive to the cracks in the structure.

Structural Health Monitoring of Composite Scarf Repairs with Guided Waves

2012 ◽  
Vol 518 ◽  
pp. 328-337 ◽  
Author(s):  
Sofia Pavlopoulou ◽  
Costas Soutis ◽  
Wieslaw Jerzy Staszewski
Keyword(s):  
Health Monitoring ◽  
Guided Waves ◽  
Lamb Waves ◽  
Early Stage ◽  
Ultrasonic Waves ◽  
Image Correlation ◽  
Patch Repair ◽  
Original Structure ◽  
Damage Indices ◽  
Defect Recognition

The interest in composite repair technologies has been recently increased following the wide applications of composite materials in aerospace industry. Bonded patch repair technologies provide an alternative to mechanically fastened repairs with significantly higher performance. Scarf repairs offer great advantages compared to external patch repairs since they provide higher stiffness by matching ply to ply the original structure and by reducing stress discontinuities in the repaired region. Ultrasonic guided waves have been extensively used for the health monitoring of complex structures due to their remarkable ability of defect recognition. The authors have previously investigated the extraction of the instantaneous characteristics of Lamb waves for the monitoring of an aluminium repaired structure, highlighting the potential use of such waves in the inspection of repaired structures [1]. In the current study, the behaviour of a scarf repair was monitored with guided ultrasonic waves excited by low profile, surface bonded piezoceramic transducers under longitudinal tensile loading. Appropriate damage indices were extracted and the results were correlated with images taken through a 3-Dimensional Digital Image Correlation (3-D DIC) technique. The correlation of the extracted features with the early stage damage is performed and conclusions about the recovered strength through the scarf repair are deduced. Finally the study compares results obtained from the on-line analysis and from off-line techniques such as ultrasonic C-scanning and X-ray radiography.

scholarly journals Wave Frequency Effects on Damage Imaging in Adhesive Joints Using Lamb Waves and RMS

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1842 ◽  
Author(s):  
Erwin Wojtczak ◽  
Magdalena Rucka
Keyword(s):  
Damage Identification ◽  
Lamb Waves ◽  
Excitation Frequency ◽  
Visual Assessment ◽  
Adhesive Joints ◽  
Ultrasonic Waves ◽  
Steel Plates ◽  
Wave Frequency ◽  
Destructive Testing ◽  
Wide Range

Structural adhesive joints have numerous applications in many fields of industry. The gradual deterioration of adhesive material over time causes a possibility of unexpected failure and the need for non-destructive testing of existing joints. The Lamb wave propagation method is one of the most promising techniques for the damage identification of such connections. The aim of this study was experimental and numerical research on the effects of the wave frequency on damage identification in a single-lap adhesive joint of steel plates. The ultrasonic waves were excited at one point of an analyzed specimen and then measured in a certain area of the joint. The recorded wave velocity signals were processed by the way of a root mean square (RMS) calculation, giving the actual position and geometry of defects. In addition to the visual assessment of damage maps, a statistical analysis was conducted. The influence of an excitation frequency value on the obtained visualizations was considered experimentally and numerically in the wide range for a single defect. Supplementary finite element method (FEM) calculations were performed for three additional damage variants. The results revealed some limitations of the proposed method. The main conclusion was that the effectiveness of measurements strongly depends on the chosen wave frequency value.

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.

Comparative Study Between CWT and STFT for On-Line Health Monitoring Applications in Systems Under Random Excitation

2001 ◽  
Author(s):  
Raul J. Alonso ◽  
Mohammad Noori ◽  
Arata Masuda ◽  
Zhikun Hou
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Health Monitoring ◽  
Random Excitation ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Random Loads ◽  
On Line ◽  
Short Time ◽  
Monitoring Application

Abstract Two time-frequency signal analysis methods, based on results of Continuous Wavelet Transform, and the Short Time Fourier Transform are compare for the purpose of on-line health monitoring application in systems subjected to random loads. A classic example with a simple signal is used to differentiate the characteristics of the two transforms suggesting the possible preference of a Wavelet Transform based approach over the Short Time Fourier Transform. Another example including a single degree of freedom system subjected to random loads proves how the inherent variable window capabilities on the Wavelet Transform perform better than the constant window length nature of the Short Time Fourier Transform for on-line health monitoring application.

scholarly journals Piezo-Optical Active Sensing With PWAS and FBG Sensors for Structural Health Monitoring

2014 ◽  
Author(s):  
Bin Lin ◽  
Victor Giurgiutiu
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Composite Structures ◽  
Excitation Frequency ◽  
Ultrasonic Waves ◽  
Detection Methods ◽  
Active Sensing ◽  
Electromechanical Impedance ◽  
Structural Health ◽  
Fbg Sensors

This paper presents the investigation of piezo-optical active sensing methodology for structural health monitoring (SHM). Piezoelectric wafer active sensors (PWAS) have emerged as one of the major structural health monitoring (SHM) technology; with the same installation of PWAS transducers, one can apply a variety of damage detection methods; propagating acousto-ultrasonic waves, standing waves (electromechanical impedance) and phased arrays. In recent years, fiber Bragg gratings (FBG) sensors have been investigated as an alternative to piezoelectric sensors for the detection of ultrasonic waves. FBG have the advantage of being durable, lightweight, and easily embeddable into composite structures as well as being immune to electromagnetic interference and optically multiplexed. In this paper, the investigation focused on the interaction of PWAS and FBG sensors with structure, and combining multiple monitoring and interrogation methods (AE, pitch-catch, pulse-echo, phased-array, thickness mode, electromechanical impedance). The innovative piezo-optical active sensing system consists of both active and passive sensing. PWAS and FBG sensors are bonded to the surface of the structure, or are integrated into structure by manufacturing process. The optimum PWAS size and excitation frequency for energy transfer was determined. The FBG sensors parameters (size, spectrum, reflectivity, etc.) for ultrasonic guided waves sensing were also evaluated. We focused on the optimum FBG length and design to improve the sensitivity, coverage, and signal to noise ratio. In this research, we built the fundamental understanding of different sensors with optimum placement. Calibration and performance improvements for the optical interrogation system are also discussed. The paper ends with conclusions and suggestions for further work.

scholarly journals Strain Sensitivity Enhancement of Broadband Ultrasonic Signals in Plates Using Spectral Phase Filtering

2021 ◽  
Vol 11 (6) ◽  
pp. 2582
Author(s):  
Lucas M. Martinho ◽  
Alan C. Kubrusly ◽  
Nicolás Pérez ◽  
Jean Pierre von der Weid
Keyword(s):  
Fourier Transform ◽  
Guided Waves ◽  
Strain Level ◽  
Energy Concentration ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Frequency Representation ◽  
The Fourier Transform ◽  
Short Time ◽  
Sensitivity Gain

The focused signal obtained by the time-reversal or the cross-correlation techniques of ultrasonic guided waves in plates changes when the medium is subject to strain, which can be used to monitor the medium strain level. In this paper, the sensitivity to strain of cross-correlated signals is enhanced by a post-processing filtering procedure aiming to preserve only strain-sensitive spectrum components. Two different strategies were adopted, based on the phase of either the Fourier transform or the short-time Fourier transform. Both use prior knowledge of the system impulse response at some strain level. The technique was evaluated in an aluminum plate, effectively providing up to twice higher sensitivity to strain. The sensitivity increase depends on a phase threshold parameter used in the filtering process. Its performance was assessed based on the sensitivity gain, the loss of energy concentration capability, and the value of the foreknown strain. Signals synthesized with the time–frequency representation, through the short-time Fourier transform, provided a better tradeoff between sensitivity gain and loss of energy concentration.

An efficient short-time Fourier transform algorithm for grinding wheel condition monitoring through acoustic emission

2021 ◽  
Vol 113 (1-2) ◽  
pp. 585-603
Author(s):  
Wenderson N. Lopes ◽  
Pedro O. C. Junior ◽  
Paulo R. Aguiar ◽  
Felipe A. Alexandre ◽  
Fábio R. L. Dotto ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fourier Transform ◽  
Condition Monitoring ◽  
Grinding Wheel ◽  
Short Time Fourier Transform ◽  
Short Time
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