scholarly journals Lamb Waves Topological Imaging of Multiple Blind Defects in an Isotropic Plate

2019 ◽  
Vol 24 (2) ◽  
pp. 320-326 ◽  
Author(s):  
Wen-Fa Zhu ◽  
Hai-Yan Zhang Zhang ◽  
Meng-Yun Xu ◽  
Guo-Peng Fan
Keyword(s):  
Lamb Wave ◽  
Isotropic Plate ◽  
Lamb Waves ◽  
Mode Conversion ◽  
Image Resolution ◽  
Imaging Method ◽  
Wave Fields ◽  
Face To Face ◽  
Element Simulation ◽  
Reference Medium

The study investigates the feasibility of the Lamb wave topological imaging method for detecting multiple blindholes in an isotropic plate. The topological imaging method is performed based on the computations of two wave fields, a forward and an adjoint, in the defect-free reference medium using different emitting sources. The image is computed by multiplying the forward and adjoint wave fields together and integrating them over time or frequency. The interferences of multimode aliasing and the scattering effect can thus be eliminated at the defectfree positions with an improved image resolution. To investigate the physical mechanism, the refocusing process of the multimode Lamb waves at the defect positions is presented by a face-to-face comparison between the snapshots of the forward and adjoint wave fields using the finite element simulation. The Lamb wave topological imaging method is numerically and experimentally verified to identify multiple blind-holes in an isotropic aluminium plate. The results demonstrate that the topological imaging method enables the suppression of the sartefacts resulting from the mode conversion and achieve high-resolution imaging of the blind defects

scholarly journals Weighted Structured Sparse Reconstruction-Based Lamb Wave Imaging Exploiting Multipath Edge Reflections in an Isotropic Plate

Sensors ◽  
2020 ◽  
Vol 20 (12) ◽  
pp. 3502
Author(s):  
Caibin Xu ◽  
Zhibo Yang ◽  
Mingxi Deng
Keyword(s):  
Lamb Wave ◽  
Isotropic Plate ◽  
Lamb Waves ◽  
Correlation Coefficients ◽  
Sparse Reconstruction ◽  
Imaging Method ◽  
Structured Sparsity ◽  
Large Area ◽  
Prediction Technique ◽  
Wave Imaging

Lamb wave-based structural health monitoring techniques have the ability to scan a large area with relatively few sensors. Lamb wave imaging is a signal processing strategy that generates an image for locating scatterers according to the received Lamb waves. This paper presents a Lamb wave imaging method, which is formulated as a weighted structured sparse reconstruction problem. A dictionary is constructed by an analytical Lamb wave scattering model and an edge reflection prediction technique, which is used to decompose the experimental scattering signals under the constraint of weighted structured sparsity. The weights are generated from the correlation coefficients between the scattering signals and the predicted ones. Simulation and experimental results from an aluminum plate verify the effectiveness of the present method, which can generate images with sparse pixel values even with very limited number of sensors.

Numerical and experimental investigation of damage severity estimation using Lamb wave–based imaging methods

2018 ◽  
Vol 30 (4) ◽  
pp. 618-635 ◽  
Author(s):  
Asaad Migot ◽  
Yeasin Bhuiyan ◽  
Victor Giurgiutiu
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Interaction ◽  
Crack Size ◽  
Imaging Method ◽  
Size Estimation ◽  
Local Approach ◽  
Imaging Methods ◽  
Imaging Results ◽  
Scattering Wave

In this article, estimation of crack size, shape, and orientation was investigated numerically and experimentally using Lamb waves. A hybrid global–local approach was used in conjunction with the imaging methods for the numerical simulation. The hybrid global–local approach allowed fast and efficient prediction of scattering wave signals for Lamb wave interaction with crack from various incident directions. The simulation results showed the directionality effect of the scattering wave signals and suggested an optimum transmitter–sensor configuration. Two imaging methods were used: one involves the synthetic time reversal concept and the other involves Gaussian distribution function. Both imaging methods show very good agreement during simulations. Experiments were designed and conducted based on the simulated results. A network of eight piezoelectric wafer active sensors was used to capture the scattering waves from the crack. Both the pitch-catch and pulse-echo experimental modes were used. The directionality effect of incident Lamb waves on the imaging results was studied. The effect of summation, multiplication, and combined algorithms for each imaging method was studied. It was found that both methods can successfully predict the crack size and orientation. An attempt was made to use these imaging methods for detecting and sizing smaller sized damage (1- to 3-mm-diameter hole). It was found that these methods can successfully localize the hole, but size estimation was a bit challenging because of the smaller dimensions. The scattering waves for various hole sizes were studied.

scholarly journals Time-Domain Topological Energy Imaging Method of Concrete Cavity Defect by Lamb Wave

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Wen-Fa Zhu ◽  
Wei Shao ◽  
Le-Le Peng ◽  
Guo-Peng Fan ◽  
Xing-Jie Chen ◽  
...  
Keyword(s):  
Time Domain ◽  
Lamb Wave ◽  
Wave Dispersion ◽  
Imaging Method ◽  
Sound Fields ◽  
Wave Imaging ◽  
Reference Medium ◽  
Synthetic Aperture Focusing ◽  
Synthetic Aperture Focusing Technique ◽  
Defect Imaging

This paper presents an ultrasonic Lamb wave imaging method based on time-domain topological energy to address artifacts in the results of traditional ultrasound imaging methods. This method is based on topological theory and the calculation of the direct and adjoint sound fields in a defect-free reference medium. It focuses the direct and adjoint sound fields at the cavity defect using time reversal and their time-domain topological energy as the pixel values of the image to reduce the artifacts. The physical mechanism of time-domain topological energy (TDTE) imaging is revealed by finite element simulation and experiment. The feasibility of this method for multilayer concrete cavity defect imaging is verified. Compared with the traditional synthetic aperture focusing technique (SAFT) imaging method, the numerical simulation and experimental results show that the method can overcome the influence of ultrasonic Lamb wave dispersion and locate cavity defects with high accuracy and few artifacts. These features indicate the potential of the method in imaging damage concrete structures.

Finite Element Simulation of Lamb Wave with Piezoelectric Transducers for Composite Plate Damage Detection

2009 ◽  
Vol 79-82 ◽  
pp. 1095-1098 ◽  
Author(s):  
Wen Zhong Qu ◽  
Li Xiao
Keyword(s):  
Finite Element ◽  
Damage Detection ◽  
Finite Element Simulation ◽  
Lamb Wave ◽  
Composite Plate ◽  
Lamb Waves ◽  
Piezoelectric Transducers ◽  
Thin Plates ◽  
Diagnostic Tools ◽  
Element Simulation

Structural health monitoring (SHM) is an emerging research area with multiple applications. Lamb waves are ultrasonic elastic waves that travel inside and along thin plates and is frequently used as diagnostic tools to detect damage in plate-like structures. In this paper, a transient dynamic finite element simulation of Lamb wave with piezoelectric transducers for damage detection in a composite plate is carried out. The embedded cross-shaped piezoelectric active sensor arrays were used to generate and receive guided Lamb waves propagating in the plate structure. A full-scale FEM model for the laminate was created using three-dimensional eight-node layered structural solid element and piezoelectric active sensors were created using coupled field elements on the commercial finite element code ANSYS platform. The beam forming technique of Lamb waves is used to locate damage in the plate .The results of the numerical simulation demonstrate the effectiveness of the approach.

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.

Scattering analysis of nonlinear Lamb waves at delaminations in composite laminates

2021 ◽  
pp. 107754632199014
Author(s):  
Reza Soleimanpour ◽  
Ching-Tai Ng
Keyword(s):  
Harmonic Generation ◽  
Lamb Wave ◽  
Composite Laminates ◽  
Lamb Waves ◽  
Mode Conversion ◽  
Experimental Studies ◽  
Acoustic Nonlinearity ◽  
Higher Harmonic Generation ◽  
Higher Harmonic ◽  
Contact Acoustic Nonlinearity

This study investigates the higher harmonic generation of the Lamb wave at a delamination due to contact acoustic nonlinearity, which is a clapping phenomenon between sublaminate surfaces due to the Lamb wave interaction with the delamination. In this study, higher harmonics of the Lamb wave induced at the delamination in composite laminates are studied in detail. This study performs both numerical and experimental studies. A three-dimensional finite element model is proposed for predicting the propagation of nonlinear Lamb waves in composite laminates and is verified using experimentally measured data. The results show the proposed numerical model can reasonably predict higher harmonic generated by contact acoustic nonlinearity. It is found that the delamination is the major source of contact acoustic nonlinearity in the composite laminates. A mode conversion study is also carried out to gain further physical insight into the higher harmonic generation of the Lamb wave at the delamination.

Damage quantification of aluminum plates using SC-DTW method based on Lamb waves

2021 ◽  
Author(s):  
Daiping Wei ◽  
Xiaofeng Liu ◽  
Bangxin Wang ◽  
Zhi Tang ◽  
Lin Bo
Keyword(s):  
Time Series ◽  
Lamb Waves ◽  
Mode Conversion ◽  
Bending Test ◽  
Shape Context ◽  
Damage Degree ◽  
Element Simulation ◽  
Alignment Problem ◽  
Aluminum Plates ◽  
Dynamic Time

Abstract Lamb waves were utilized to quantify micro-crack damage in aluminum plates, and the scattering and mode conversion of Lamb waves passing through cracks were analyzed. The dynamic time warping (DWT) method was used to match and compare each Lamb wave time series that represented different damage degrees. The matching difference between the damaged plate and undamaged plate was taken as a marker to measure the damage degree of the workpiece. At the same time, due to the pathological alignment of traditional DTW methods, the shape context (SC) profile recognition method was introduced to optimize the algorithm for calculating the distance between sampling points in the DTW method and solve the pathological alignment problem. Finally, the SC-DTW method based on Lamb waves was verified by the finite element simulation model and bending test of aluminum plates. The results showed that the method was feasible for quantifying the damage degree of aluminum plates and had a great advantage in the analysis and processing of time series in low-sampling frequency and high-noise scenarios.

scholarly journals Lamb wave–based detection of a controlled disbond in a lap joint

2017 ◽  
Vol 17 (3) ◽  
pp. 668-683 ◽  
Author(s):  
Wern Hann Ong ◽  
Nik Rajic ◽  
Wing Kong Chiu ◽  
Cedric Rosalie
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Mode Conversion ◽  
Numerical Study ◽  
Lap Joints ◽  
Single Frequency ◽  
Lap Joint ◽  
Frequency Selection ◽  
Almost All ◽  
Shed Light

Lap joints are widely used across many critical structures such as aircraft and bridges. Lamb waves have long been proposed to monitor lap joints against defects such as disbonds. However, there are many challenges which must be answered to make use of Lamb wave technology. Frequency selection is often overlooked, and many authors will select a single frequency without knowing if other frequencies will result in better sensitivity. Another challenge is the features (mode conversion, attenuation, reflection) associated with damage are also inherent in a lap joint. This sharing of features can lead to confusion (false positive/negative) depending on the chosen damage detection strategy. Furthermore, almost all proposed methods require a baseline reading of the structure in its flawless state. Relying on a baseline reading can result in false positives due to shifts in sensor outputs caused by ageing and inconsistent environmental conditions. Instead of a baseline, this article proposes a technique which uses strategically positioned sensors to detect Lamb wave modes generated only in the presence of a disbond. The technique is first developed using a numerical study and then verified with an experimental study. Several frequencies are trialled and detailed in this article which shed light on the ideal frequency selection when using this method.

Finite Element Simulation of Damage Detection of Stiffened Plate under Temperature Variation

2011 ◽  
Vol 230-232 ◽  
pp. 75-79
Author(s):  
Wen Zhong Qu ◽  
Li Xiao
Keyword(s):  
Finite Element ◽  
Damage Detection ◽  
Finite Element Simulation ◽  
Lamb Wave ◽  
Elevated Temperatures ◽  
Lamb Waves ◽  
Thin Plates ◽  
Diagnostic Tools ◽  
Stiffened Plate ◽  
Element Simulation

Lamb waves are ultrasonic elastic waves that travel inside and along thin plates and is frequently used as diagnostic tools to detect damage in plate-like structures. In this paper, a transient dynamic finite element simulation of Lamb wave with piezoelectric transducers for damage detection in a stiffened plate under different temperature condition is carried out on the commercial finite element code ANSYS platform. Simulations are conducted over a temperature range. The changes in temperature-dependent material properties are used to measure the differences in the response signal’s waveform. The baseline selection method and baseline signal stretch method are used to compensate the temperature influence on Lamb wave propagation. The results of the numerical simulation demonstrate the effectiveness of the temperature compensation approach and the simulated damage on the stiffened plate can be defected effectively under elevated temperatures environment.

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