scholarly journals Lamb wave imaging method based on difference signal in reverse path

2019 ◽  
Vol 68 (12) ◽  
pp. 124301
Author(s):  
Jing-Pin Jiao ◽  
Hai-Ping Li ◽  
Cun-Fu He ◽  
Bin Wu ◽  
Yan Xue
Keyword(s):  
Lamb Wave ◽  
Imaging Method ◽  
Wave Imaging ◽  
Reverse Path

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.

Multi-defect detection based on ultrasonic Lamb wave sign phase coherence factor imaging method

2021 ◽  
Vol 63 (11) ◽  
pp. 659-666
Author(s):  
Meng-Ke Zhang ◽  
Guo-Peng Fan ◽  
Wen-Fa Zhu ◽  
Shu-Bin Zheng ◽  
Xiao-Dong Chai ◽  
...  
Keyword(s):  
Lamb Wave ◽  
Performance Indicator ◽  
Signal To Noise Ratio ◽  
Scattered Signal ◽  
Imaging Method ◽  
Signal To Noise ◽  
Full Matrix ◽  
Wave Imaging ◽  
Array Performance ◽  
Scattering Signal

The ultrasonic Lamb wave total focusing method (TFM) only uses the amplitude of the defective scattered signal for virtual focused imaging, while ignoring the phase information of the scattered signal and the dispersion characteristics of the Lamb wave, resulting in low imaging resolution and easily produced artefacts in imaging. To solve this problem, an ultrasonic Lamb wave imaging method based on phase coherence is proposed in this paper and the sign coherence factor (SCF) in the full matrix scattering signal is extracted. Moreover, the method uses the SCF to weight the amplitude of the full matrix scattering signal, suppresses the side lobes of the defect echo signal and the Lamb wave dispersion effect, improves the ultrasonic Lamb wave imaging resolution and weakens the artefacts. Finally, single- and multiplehole defects in aluminium plates are detected for experimental validation using an ultrasonic phased array. The array performance indicator and signal-to-noise ratio are used as indicators for quantitative assessment of imaging performance. The results show that compared with the TFM imaging, the SCF imaging can effectively suppress the noise and scattered signal side lobes, improve the array performance indicator (API) by 69.1% and improve the signal-to-noise ratio (SNR) by 73.9%. In addition, the SCF imaging can effectively weaken the interference of scattered signals between multiple through-hole defects, resulting in fewer artefacts in imaging.

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.

scholarly journals Plate-like structure damage location identification based on Lamb wave baseline-free probability imaging method

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401668570 ◽  
Author(s):  
Dongsheng Li ◽  
Zihao Jing ◽  
Mengdao Jin
Keyword(s):  
Lamb Wave ◽  
Time Window ◽  
Free Probability ◽  
Structural Response ◽  
Guided Wave ◽  
Time Of Arrival ◽  
Imaging Method ◽  
Detection Techniques ◽  
Damage Location ◽  
Ultrasonic Guided Wave

Damage-scattering signal extraction using conventional ultrasonic guided wave–based damage detection techniques requires the measurement of baseline data under pristine condition. This study proposes a baseline-free ultrasonic guided wave damage localization and imaging method based on Lamb wave baseline-free probability imaging method. Although traditional Lamb wave probability imaging can monitor damage location in plate-like structures, the absolute time of arrival and magnitude of the signal are affected by several factors and are therefore difficult to obtain. This study also proposes a probability-based hyperbola diagnostic imaging method that is based on different times of arrival and has no magnitude information. A distributed active sensor network conforming to a pulse-echo configuration and time window functions is developed to separate damage-scattering signals from structural response signals. Continuous wavelet transform is used to calculate the time of flight of damage signal waves. The numerical simulation and experiments validate the effectiveness of the proposed method in identifying damage.

Damage localization with fiber Bragg grating Lamb wave sensing through adaptive phased array imaging

2018 ◽  
Vol 18 (1) ◽  
pp. 334-344 ◽  
Author(s):  
Zhenhua Tian ◽  
Lingyu Yu ◽  
Xiaoyi Sun ◽  
Bin Lin
Keyword(s):  
Fiber Bragg Grating ◽  
Electromagnetic Interference ◽  
Lamb Wave ◽  
Phased Array ◽  
Minimum Variance ◽  
Bragg Grating ◽  
Damage Localization ◽  
Weighting Factors ◽  
Wave Imaging ◽  
Grating Array

Fiber Bragg gratings are known being immune to electromagnetic interference and emerging as Lamb wave sensors for structural health monitoring of plate-like structures. However, their application for damage localization in large areas has been limited by their direction-dependent sensor factor. This article addresses such a challenge and presents a robust damage localization method for fiber Bragg grating Lamb wave sensing through the implementation of adaptive phased array algorithms. A compact linear fiber Bragg grating phased array is configured by uniformly distributing the fiber Bragg grating sensors along a straight line and axially in parallel to each other. The Lamb wave imaging is then performed by phased array algorithms without weighting factors (conventional delay-and-sum) and with adaptive weighting factors (minimum variance). The properties of both imaging algorithms, as well as the effects of fiber Bragg grating’s direction-dependent sensor factor, are characterized, analyzed, and compared in details. The results show that this compact fiber Bragg grating array can precisely locate damage in plates, while the comparisons show that the minimum variance method has a better imaging resolution than that of the delay-and-sum method and is barely affected by fiber Bragg grating’s direction-dependent sensor factor. Laboratory tests are also performed with a four–fiber Bragg grating array to detect simulated defects at different directions. Both delay-and-sum and minimum variance methods can successfully locate defects at different positions, and their results are consistent with analytical predictions.

scholarly journals An Aircraft Pallet Damage Monitoring Method Based on Damage Subarea Identification and Probability-Based Diagnostic Imaging

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Bin Liu ◽  
Tingzhang Liu ◽  
Yue Lin ◽  
Jianfei Zhao
Keyword(s):  
Diagnostic Imaging ◽  
Lamb Wave ◽  
Damage Index ◽  
Imaging Method ◽  
Monitoring Method ◽  
Study Results ◽  
Damage Monitoring ◽  
Weighted Algorithm ◽  
Damage Simulation ◽  
Monitoring Area

To improve the safety and economy of aircraft pallet use, an aircraft pallet damage monitoring method based on damage subarea identification and probability-based diagnostic imaging is proposed. In the proposed method, first, the large aircraft pallet monitoring area is divided into rectangular subareas, and a piezoelectric transducer sensor is pasted on each vertex of the rectangular subarea that is used to excitation and sensing the Lamb wave. Second, the damage subarea is identified according to the diagonal damage indexes. Third, the damage position in the damage subarea is calculated using the probability-based diagnostic imaging method and coordinate probability weighted algorithm. Finally, the aircraft pallet damage can be localized based on the damage subarea position. Frequency selection and damage simulation study results show that the Lamb wave is sensitive to aircraft pallet damage whose centre frequency ranges from 50 kHz to 150 kHz, and the damage index of a steel ball is less than that of all real aircraft pallet damage from 95 kHz to 125 kHz. The verification results show that the proposed method can locate aircraft pallet damage with an error of less than 2 cm.

Thin-Plate Imaging Inspection Using Scattered Waves Cross-Correlation Algorithm and Non-Contact Air-Coupled Transducer

2020 ◽  
Vol 4 (2) ◽  
Author(s):  
Wenfeng Xiao ◽  
Lingyu Yu
Keyword(s):  
Lamb Wave ◽  
Cross Correlation ◽  
Lamb Waves ◽  
Imaging Technique ◽  
Laser Doppler Vibrometer ◽  
Correlation Method ◽  
Single Mode ◽  
Wave System ◽  
Wave Imaging ◽  
Incident Waves

Abstract This paper presents a non-contact air-coupled Lamb wave imaging technique using a two-dimensional (2D) cross-correlation method that not only detects the damage but also precisely quantifies for orientations and sizes. The air-coupled transducers (ACT) is used together with a scanning laser Doppler vibrometer (SLDV) for sensing, making a fully non-contact Lamb wave system used for this study. We first show that single-mode Lamb wave actuation can be achieved by the ACT-based on Snell's law. Detailed study and characterization of the directional ACT Lamb waves are conducted. For damage detection, a 2D cross-correlation imaging technique that uses the damage introduced scattered waves of all directions is proposed for correlating with the incident waves. The frequency-wavenumber filtering technique is used to implement the acquisition of the scatted waves and incident waves, respectively. In the end application to notches with various orientations and various sizes in terms of depth and length is given. The results show the proposed technique can precisely imaging the damages and can quantitatively evaluate the damage size in terms of length and depth.

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.

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