Cloaking, trapping and superlensing of lamb waves with negative refraction

AbstractWe report on experimental and numerical implementations of devices based on the negative refraction of elastic guided waves, the so-called Lamb waves. Consisting in plates of varying thickness, these devices rely on the concept of complementary media, where a particular layout of negative index media can cloak an object with its anti-object or trap waves around a negative corner. The diffraction cancellation operated by negative refraction is investigated by means of laser ultrasound experiments. However, unlike original theoretical predictions, these intriguing wave phenomena remain, nevertheless, limited to the propagating component of the wave-field. To go beyond the diffraction limit, negative refraction is combined with the concept of metalens, a device converting the evanescent components of an object into propagating waves. The transport of an evanescent wave-field is then possible from an object plane to a far-field imaging plane. Twenty years after Pendry’s initial proposal, this work thus paves the way towards an elastic superlens.

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Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.558.489 ◽

2013 ◽

Vol 558 ◽

pp. 489-500 ◽

Cited By ~ 6

Author(s):

Patrick Norman ◽

Claire Davis ◽

Cédric Rosalie ◽

Nik Rajic

Keyword(s):

Wave Field ◽

Lamb Waves ◽

Base Material ◽

Adhesive Layer ◽

Scattered Wave ◽

Phase Lag ◽

Wave Fields ◽

Surface Mount ◽

Frequency Regime ◽

Fibre Bragg Gratings

The application of Lamb waves to damage and/or defect detection in structures is typicallyconfined to lower frequencies in regimes where only the lower order modes propagate in order to simplifyinterpretation of the scattered wave-fields. Operation at higher frequencies offers the potentialto extend the sensitivity and diagnostic capability of this technique, however there are technical challengesassociated with the measurement and interpretation of this data. Recent work by the authorshas demonstrated the ability of fibre Bragg gratings (FBGs) to measure wave-fields at frequencies inexcess of 2 MHz [1]. However, when this work was extended to other thinner plate specimens it wasfound that at these higher frequencies, the cyanoacrylate adhesive (M-Bond 200) used to attach theFBG sensors to the plate was significantly affecting the propagation of the waves. Laser vibrometrywas used to characterise the wave-field in the region surrounding the adhesive and it was found that theself-adhesive retro-reflective tape applied to aid with this measurement was also affecting the wavefieldin the higher frequency regime. This paper reports on an experimental study into the influence ofboth of these materials on the propagating wave-field. Three different lengths of retro-reflective tapewere placed in the path of Lamb waves propagating in an aluminium plate and laser vibrometry wasused to measure the wave-field upstream and downstream of the tape for a range of different excitationfrequencies. The same experiment was conducted using small footprint cyanoacrylate film samplesof different thickness. The results show that both of these surface-mount materials attenuate, diffractand scatter the incoming waves as well as introducing a phase lag. The degree of influence of thesurface layer appears to be a function of its material properties, the frequency of the incoming waveand the thickness and footprint of the surface layer relative to the base material thickness. Althoughfurther work is required to characterise the relative influence of each of these variables, investigationsto date show that for the measurement of Lamb Waves on thin structures, careful considerationshould be given to the thickness and footprint of the adhesive layer and sensor, particularly in the highfrequency regime, so as to minimise their effect on the measurement.

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Water Level Sensing in a Steel Vessel Using A0 and Quasi-Scholte Waves

Journal of Sensors ◽

10.1155/2017/2596291 ◽

2017 ◽

Vol 2017 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Peng Guo ◽

Bo Deng ◽

Xiang Lan ◽

Kaili Zhang ◽

Hongyuan Li ◽

...

Keyword(s):

Water Level ◽

Guided Waves ◽

Mode Conversion ◽

Experimental Studies ◽

Low Frequency ◽

Steel Vessel ◽

Theoretical Predictions ◽

Travelling Time ◽

The Comparative Study ◽

Group Velocities

This paper presents a water level sensing method using guided waves of A0 and quasi-Scholte modes. Theoretical, numerical, and experimental studies are performed to investigate the properties of both the A0 and quasi-Scholte modes. The comparative study of dispersion curves reveals that the plate with one side in water supports a quasi-Scholte mode besides Lamb modes. In addition, group velocities of A0 and quasi-Scholte modes are different. It is also found that the low-frequency A0 mode propagating in a free plate can convert to the quasi-Scholte mode when the plate has one side in water. Based on the velocity difference and mode conversion, a water level sensing method is developed. For the proof of concept, a laboratory experiment using a pitch-catch configuration with two piezoelectric transducers is designed for sensing water level in a steel vessel. The experimental results show that the travelling time between the two transducers linearly increases with the increase of water level and agree well with the theoretical predictions.

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Inspection of Concrete-Metal Rod Interface Using Guided Waves

10.1115/imece2000-1647 ◽

2000 ◽

Author(s):

Won-Bae Na ◽

Tribikram Kundu ◽

Mohammad R. Ehsani

Keyword(s):

Lamb Wave ◽

Guided Waves ◽

Lamb Waves ◽

Guided Wave ◽

Ultrasonic Transducers ◽

Interface Debonding ◽

Long Distance ◽

Steel Rebar ◽

Steel Bars ◽

Steel Rebars

Abstract The feasibility of detecting interface degradation and separation of steel rebars in concrete beams using Lamb waves is investigated in this paper. It is shown that Lamb waves can easily detect these defects. A special coupler between the steel rebar and ultrasonic transducers has been used to launch non-axisymmetric guided waves in the steel rebar. This investigation shows that the Lamb wave inspection technique is an efficient and effective tool for health monitoring of reinforced concrete structures because the Lamb wave can propagate a long distance along the reinforcing steel bars embedded in concrete as the guided wave and is sensitive to the interface debonding between the steel rebar and concrete.

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Determination of Vibration Source Locations in Laminated Composite Plates Using Lamb Wave Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.123-125.899 ◽

2010 ◽

Vol 123-125 ◽

pp. 899-902

Author(s):

Chao Du ◽

Qing Qing Ni ◽

Toshiaki Natsuki

Keyword(s):

Lamb Wave ◽

Guided Waves ◽

Lamb Waves ◽

Laminated Composite ◽

Composite Plates ◽

Wave Dispersion ◽

Laminated Plates ◽

Vibration Source ◽

Arrival Times ◽

Wave Velocities

Signals propagate on plate-like structures as ultrasonic guided waves, and analysis of Lamb waves has been widely used for on-line monitoring. In this study, the wave velocities of symmetric and anti-symmetric modes in various directions of propagation were investigated. Since the wave velocities of these two modes are different, it is possible to compute the difference in their arrival times when these waves propagated the distance from the vibration source to sensor. This paper presents an evaluation formulation of wave velocity and describes a generalized algorithm for locating a vibration source on a thin, laminated plate. With the different velocities of two modes based on Lamb wave dispersion, the method uses two sensors to locate the source on a semi-infinite interval of a plate. The experimental procedure supporting this method employs pencil lead breaks to simulate vibration sources on quasi-isotropic and unidirectional laminated plates. The transient signals generated in this way are transformed using a wavelet transform. The vibration source locations are then detected by utilizing the distinct wave velocities and arrival times of the symmetric and anti-symmetric wave modes. The method is an effective technique for identifying impact locations on plate-like structures.

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Early Fatigue Damage Evaluation of Nonlinear Guided Wave Imaging in Hyperelastic Materials

10.1115/qnde2021-75051 ◽

2021 ◽

Author(s):

Chengwei Zhao ◽

Sunia Tanweer ◽

Jian Li ◽

Min Lin ◽

Xiang Zhang ◽

...

Keyword(s):

Fatigue Damage ◽

Guided Waves ◽

Lamb Waves ◽

Tone Burst ◽

Guided Wave ◽

Third Order ◽

Hyperelastic Materials ◽

Third Order Elastic Constants ◽

Wave Imaging ◽

Processing Platform

Abstract Nonlinear ultrasonic guided waves have superior sensitivity of the early fatigue damage. This paper investigates the analysis of the second harmonics of Lamb waves in a free boundary aluminum plate, and the internal resonance conditions between the Lamb wave primary modes and the second harmonics. The Murnaghan’s model is implemented in a finite element (FE) analysis to describe the hyperelastic constitutive relation for nonlinear acoustic modeling. The second harmonics of s0 mode are actuated by a 60kHz Hanning-windowed tone burst. A guided wave signal processing platform is developed for tomographic imaging. The different stages of fatigue are reflected by the changes of third-order elastic constants (TOECs) in Murnaghan’s model. The reconstructed damage locations match well with the actual ones cross different degrees and depths of fatigue.

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Immunity of the second harmonic shear horizontal waves to adhesive nonlinearity for breathing crack detection

Structural Health Monitoring ◽

10.1177/14759217211057138 ◽

2021 ◽

pp. 147592172110571

Author(s):

Fuzhen Wen ◽

Shengbo Shan ◽

Li Cheng

Keyword(s):

Crack Detection ◽

Guided Waves ◽

Lamb Waves ◽

Second Harmonic ◽

Sh Waves ◽

High Order Harmonic ◽

Thin Walled Structures ◽

Harmonic Shear ◽

Contact Acoustic Nonlinearity ◽

Shear Horizontal

High-order harmonic guided waves are sensitive to micro-scale damage in thin-walled structures, thus, conducive to its early detection. In typical autonomous structural health monitoring (SHM) systems activated by surface-bonded piezoelectric wafer transducers, adhesive nonlinearity (AN) is a non-negligible adverse nonlinear source that can overwhelm the damage-induced nonlinear signals and jeopardize the diagnosis if not adequately mitigated. This paper first establishes that the second harmonic shear horizontal (second SH) waves are immune to AN while exhibiting strong sensitivity to cracks in a plate. Capitalizing on this feature, the feasibility of using second SH waves for crack detection is investigated. Finite element (FE) simulations are conducted to shed light on the physical mechanism governing the second SH wave generation and their interaction with the contact acoustic nonlinearity (CAN). Theoretical and numerical results are validated by experiments in which the level of the AN is tactically adjusted. Results show that the commonly used second harmonic S0 (second S0) mode Lamb waves are prone to AN variation. By contrast, the second SH0 waves show high robustness to the same degree of AN changes while preserving a reasonable sensitivity to breathing cracks, demonstrating their superiority for SHM applications.

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Gravity wave generation by large scale bubbles

Symposium - International Astronomical Union ◽

10.1017/s0074180900158401 ◽

1988 ◽

Vol 123 ◽

pp. 383-386

Author(s):

Axel Brandenburg

Keyword(s):

Gravity Wave ◽

Fourier Transformation ◽

Large Scale ◽

Lamb Waves ◽

Vertical Direction ◽

Hydrodynamic Equations ◽

Propagating Waves ◽

Pressure Scale ◽

Isothermal Atmosphere ◽

Small Disturbances

The response of an isothermal atmosphere to small disturbances in entropy is studied taking compressible effects fully into account. The method of Green's functions is applied to solve the linearized hydrodynamic equations by Fourier transformation. A bubble may be created by perturbing the entropy within a finite volume. At first Lamb waves will be then emitted radially and the bubble undergoes a series of Brunt-Väisälä oscillations. We find that horizontally propagating waves are generated only by large bubbles “exceeding a radius of about ten pressure scale heights, whereas smaller bubbles lead to motions propagating principally in the vertical direction.

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Warped Wigner-Hough Transform for Defect Reflection Enhancement in Ultrasonic Guided Wave Monitoring

Mathematical Problems in Engineering ◽

10.1155/2012/358128 ◽

2012 ◽

Vol 2012 ◽

pp. 1-15 ◽

Cited By ~ 3

Author(s):

Luca De Marchi ◽

Emanuele Baravelli ◽

Giampaolo Cera ◽

Nicolò Speciale ◽

Alessandro Marzani

Keyword(s):

Hough Transform ◽

Guided Waves ◽

Lamb Waves ◽

Guided Wave ◽

Nonlinear Signal Processing ◽

Localization Accuracy ◽

Time Frequency ◽

Ultrasonic Guided Wave ◽

Inspection Systems ◽

Nonlinear Signal

To improve the defect detectability of Lamb wave inspection systems, the application of nonlinear signal processing was investigated. The approach is based on a Warped Frequency Transform (WFT) to compensate the dispersive behavior of ultrasonic guided waves, followed by a Wigner-Ville time-frequency analysis and the Hough Transform to further improve localization accuracy. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested by analyzing numerically simulated Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented for real-world structural health monitoring applications.

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