A single transmitter multi-receiver (STMR) PZT array for guided ultrasonic wave based structural health monitoring of large isotropic plate structures
TL;DR: In this article, a new compact sensor configuration comprising a single transmitter and multi-receivers (STMR) is presented for the in situ structural health monitoring (SHM) of large plate-like isotropic structures.
Abstract: A new compact sensor configuration comprising a single transmitter and multi-receivers (STMR) is presented for the in situ structural health monitoring (SHM) of large plate-like isotropic structures. The STMR exploits the long-range propagation characteristics of ultrasonic guided Lamb waves and a phase reconstruction algorithm to provide defect detection and location capability under non-dispersive as well as dispersive regimes of guided waves. Simulations are performed on defect-free and defective finite plates of aluminum to demonstrate the various features of the STMR system. Experiments were carried out on 1 mm thick aluminum plates initially using a pair of individual sensors and subsequently using a prototype STMR array. The simulated results of the STMR performance were validated well through these experiments. Features of the STMR system such as its small footprint, the relatively simple data acquisition and processing discussed here have applications in the SHM of plate-like structures, and particularly of aerospace structures.
Citations
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TL;DR: In this article, an in situ method for damage detection in thin-wall structures using embedded two-dimensional ultrasonic phased arrays is presented. Butts et al. used piezoelectric wafer active sensors to generate and receive guided Lamb waves propagating in the plate-like structure.
287 citations
TL;DR: In this paper, the authors used Lamb wave detection for detection of thin-walled structures due to their long propagation capability and sensitivity to a variety of different types of damage types.
Abstract: Lamb waves have shown great potentials in damage detection of thin-walled structures due to their long propagation capability and sensitivity to a variety of damage types. However, their practical ...
102 citations
Cites background from "A single transmitter multi-receiver..."
...Many researchers have contributed to the studies of SHM/NDE using Lamb wave methods (Alleyne and Cawley, 1992a, 1992b; Anton et al., 2007; Dalton et al., 2001; Ong and Chiu, 2012; Rajagopalan et al., 2006; Staszewski et al., 2007; Tua et al., 2004; Worlton, 1957)....
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TL;DR: In this article, a hybrid lead zirconate titanate (PZT)-laser vibrometer system and frequency-wave number analysis is used to acquire high-resolution time-space Lamb wavefield excited by a PZT actuator.
Abstract: Lamb waves are dispersive and multi-modal, which makes the interpretation of Lamb wave signals very difficult in either the time or frequency domain. In the this article, we present our studies on Lamb wave propagation characterization and crack detection using a hybrid lead zirconate titanate (PZT)-laser vibrometer system and frequency–wave number analysis. A scanning laser Doppler vibrometer is used to acquiring high-resolution time–space Lamb wavefield excited by a PZT actuator. The recorded wavefield is then transformed to frequency–wave number domain by two-dimensional Fourier transform. Wave spectrum in the frequency–wave number domain shows clear distinction among Lamb wave modes being present. These concepts are illustrated through several experimental tests. However, the space information is lost during this transformation. A short-space two-dimensional Fourier transform is then adopted to obtain the frequency–wave number spectra at various spatial locations, resulting in the space–frequency–wave...
86 citations
TL;DR: A novel method of guided wave-based structural health monitoring is developed in which no direct baseline data are required to identify structural damage and this new method accomplishes reference-free damage detection by acquiring what is referred to as an instantaneous baseline measurement for analysis.
Abstract: A novel method of guided wave-based structural health monitoring is developed in which no direct baseline data are required to identify structural damage. Conventional wave propagation structural health monitoring techniques involve the comparison of structural response data to a prerecorded baseline or reference measurement taken while the structure is in pristine condition. The need to compare new data to a prerecorded baseline can present several complications, including data management issues and difficulty in accommodating the effects of varying environmental and operational conditions on the data. To address the complications associated with baseline comparison, this new method accomplishes reference-free damage detection by acquiring what is referred to as an instantaneous baseline measurement for analysis. The instantaneous baseline technique is validated through both analytical and experimental testing. Analytical tests show that the instantaneous baseline method is able to correctly identify simulated damage. It is found experimentally that nonpermanent damage in the form of removable putty as well as permanent damage in the form of corrosion and cuts are all identifiable in thin aluminum plate test structures without direct comparison to baseline data when implementing the instantaneous baseline method.
86 citations
TL;DR: A wavelet based cumulative damage index has been studied which shows monotonic sensitivity against the severity of the damage, which is most desired in a Structural Health Monitoring system.
86 citations
Additional excerpts
...Several imaging techniques available in the literature are Local Interaction Simulation Approach (LISA) [21,22], images using phase reconstruction [23], Synthetic Aperture Focusing Technique (SAFT) [24], damage influence map [25], difference image based on optimal baseline subtraction [26], and fusion method based image [27]....
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References
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Book•
01 Sep 2004
TL;DR: In this article, the theory of elasticity was introduced and basic formulas and concepts in complex variables in the theory and application of wave propagation were discussed. But the authors did not consider the effects of wave scattering on the wave propagation experiments.
Abstract: Preface 1. Introduction 2. Dispersion principles 3. Unbounded isotropic and anisotropic media 4. Reflection and refraction 5. Oblique incidence 6. Wave scattering 7. Surface and subsurface waves 8. Waves in plates 9. Interface waves 10. Layer on a half space 11. Waves in rods 12. Waves in hollow cylinders 13. Guided waves in multiple layers 14. Source influence 15. Horizontal shear 16. Waves in an anisotropic layer 17. Elastic constant determination 18. Waves in viscoelastic media 19. Stress influence 20. Boundary element methods Bibliography Appendices A. Ultrasonic nondestructive testing principles, analysis and display technology B. Basic formulas and concepts in the theory of elasticity C. Basic formulas in complex variables D. Schlieren imaging and dynamic photoelasticity E. Key wave propagation experiments Index.
2,570 citations
"A single transmitter multi-receiver..." refers background in this paper
...Although Lamb waves are dispersive and multi-moded [4], several attempts have been made exploiting synthetic array techniques to increase the signal to noise ratio, to achieve beam steering, and to compensate for dispersion effects [5–9]....
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TL;DR: The results indicate that Lamb waves may be used to find notches when the wavelength to notch depth ratio is on the order of 40, and the 2-D Fourier transform method is used to quantify Lamb wave interactions with defects.
Abstract: The interaction of individual Lamb waves with a variety of defects simulated by notches is investigated using finite-element analysis, and the results are checked experimentally. Excellent agreement is obtained. It is shown that a 2-D Fourier transform method may be used to quantify Lamb wave interactions with defects. The sensitivity of individual Lamb waves to particular notches is dependent on the frequency-thickness product, the mode type and order, and the geometry of the notch. The sensitivity of the Lamb modes a/sub 1/, alpha /sub 0/, and s/sub 0/ to simulated defects in different frequency-thickness regions is predicted as a function of the defect depth to plate thickness ratio and the results indicate that Lamb waves may be used to find notches when the wavelength to notch depth ratio is on the order of 40. Transmission ratios of Lamb waves across defects are highly frequency dependent. >
912 citations
"A single transmitter multi-receiver..." refers background in this paper
...Guided waves, particularly Lamb waves, use the bounding surfaces of a plate to propagate long distances and are therefore attractive for inspection of large area structures especially in terms of the time consumed for inspection [2, 3]....
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TL;DR: In this article, the applicability of the time-reversal concept to guided waves in plate-like structures, where the stress waves are dispersive and of multi-modes, was investigated.
Abstract: This paper presents an experimental and theoretical investigation of the applicability of the time-reversal concept to guided waves in plate-like structures, where the stress waves are dispersive and of multi-modes. It is shown that temporal and spatial focusing can be achieved through time reversal, although the dispersive behaviour of the flexural waves renders it impossible to exactly reconstruct the waveform of the original excitation. Based on the principle of the time-reversal concept, a digital imaging method suitable for distributed sensor/actuator networks has been developed. This new method, which overcomes the limitation of the conventional phased array method that operates under pulse-echo mode, provides an efficient imaging method for locating and approximate sizing of structural damages. In addition, it has been shown that signal strengths can be considerably enhanced by applying the present synthetic time-reversal method, thus reducing the number of sensors and actuators required to achieve a given signal-to-noise ratio.
504 citations
TL;DR: A signal processing technique makes use of a priori knowledge of the dispersion characteristics of a guided wave mode to map signals from the time to distance domains to improve spatial resolution in guided wave inspection applications.
Abstract: Guided acoustic and ultrasonic waves have been utilized in various manners for non-destructive evaluation and testing. If a guided wave mode is dispersive, a pulse of energy will spread out in space and time as it propagates. For a long-range guided wave inspection application, this constrains the choice of operating point to regions on the dispersion curves where dispersion effects are small. A signal processing technique is presented that enables this constraint on operating point to be relaxed. The technique makes use of a priori knowledge of the dispersion characteristics of a guided wave mode to map signals from the time to distance domains. In the mapping process, dispersed signals are compressed to their original shape. The theoretical basis of the technique is described and an efficient numerical implementation is presented. The robustness of the technique to inaccuracies in the dispersion data is also addressed. The application of the technique to experimental data is shown and the resulting improvement in spatial resolution is demonstrated. The implications of using dispersion compensation in practical systems are briefly discussed.
349 citations
"A single transmitter multi-receiver..." refers methods in this paper
...To compensate for the guided wave dispersion [ 16 ], each column in the T matrix is fast Fourier transformed to yield a matrix F containing the complex spectra at equi-spaced points in the frequency, ω, domain....
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TL;DR: Experimental data obtained from a guided wave array containing electromagnetic acoustic transducers (EMAT) elements for exciting and detecting the S/sub 0/ Lamb wave mode in a 5-mm thick aluminium plate are processed with both algorithms and the results are discussed.
Abstract: Omni-directional guided wave array transducers contain a circular pattern of elements that individually behave as omni-directional point transmitters or receivers. The data set acquired from such an array contains time-domain signals from each permutation of transmitter and receiver. A phased addition algorithm is developed that allows an omni-directional, B-scan image of the surrounding plate to be synthesized from any geometry of array. Numerically simulated data from a single reflector is used to test the performance of the algorithm. The results from an array containing a fully populated circular area of elements (Type I array) are found to be good, but those from an array containing a single ring of elements (Type II array) contain many large side-lobes. An enhancement to the basic phased addition algorithm is presented that uses deconvolution to suppress these side-lobes. The deconvolution algorithm enables a Type II array to equal the performance of a Type I array of the same overall diameter. The effect of diameter on angular resolution is investigated. Experimental data obtained from a guided wave array containing electromagnetic acoustic transducers (EMAT) elements for exciting and detecting the S/sub 0/ Lamb wave mode in a 5-mm thick aluminium plate are processed with both algorithms and the results are discussed.
269 citations
"A single transmitter multi-receiver..." refers background or methods in this paper
...Then, the frequency domain data in F are transformed to wavenumber domain data using a linear interpolation scheme [10] resulting in a matrix, W, of equi-spaced data in the wavenumber domain....
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...The array configuration, described in greater detail elsewhere [5], consists of a single transmitter to ensure uniform coverage and avoid non-uniform insonification associated with beam formation reported for the multi-transmitter multi-receiver (MTMR) system [10]....
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...It has been shown that the use of multiple transducers in a phased manner provides improved transduction and increases the area of coverage [10]....
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