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

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.

Download Full-text

Numerical simulation of internal defect imaging with the longitudinal wave generated by laser induced ultrasonic array

Modern Physics Letters B ◽

10.1142/s0217984921501037 ◽

2020 ◽

pp. 2150103

Author(s):

Hao Sui ◽

Kesi Li ◽

Zhenyu Zhu ◽

Le Cheng ◽

Xiaorong Gao ◽

...

Keyword(s):

Longitudinal Wave ◽

Phased Arrays ◽

Synthetic Aperture ◽

Wave Component ◽

The Finite Element Method ◽

Internal Defect ◽

Longitudinal Waves ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique ◽

Defect Imaging

To verify the performance of longitudinal waves induced by laser phased arrays (LPA) for detection and quantitative evaluation in internal defects, the finite element method (FEM) is utilized to establish the models of LPA scanning processing. The interaction of longitudinal wave and internal defect is analyzed. Besides, the two components of the reflected longitudinal waves (the longitudinal wave component [Formula: see text] and the shear wave component [Formula: see text] are focused on the imaging of defects with the synthetic aperture focusing technique (SAFT) and total focusing method (TFM) algorithms. It shows that the imaging of internal sub-millimeter defect is obtained using the LPA. The defect size and location are simultaneously calculated, with the relative error being 6.7% and 2.9%, respectively. The proposed longitudinal wave-based LPA is a promising method for the imaging and evaluation of internal micro defects.

Download Full-text

Three-dimensional ultrasonic imaging employing a time-domain synthetic aperture focusing technique

IEEE Transactions on Instrumentation and Measurement ◽

10.1109/19.52534 ◽

1990 ◽

Vol 39 (2) ◽

pp. 441-444 ◽

Cited By ~ 4

Author(s):

J. Waszak ◽

R. Ludwig

Keyword(s):

Time Domain ◽

Ultrasonic Imaging ◽

Three Dimensional ◽

Synthetic Aperture ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique

Download Full-text

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

10.20855/ijav.2019.24.21479 ◽

2019 ◽

Vol 24 (2) ◽

pp. 320-326 ◽

Cited By ~ 2

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

Download Full-text

Assessment of lamb wave dispersion in cornea using shear wave imaging optical coherence tomography (SWI-OCT)

10.1117/12.2040368 ◽

2014 ◽

Author(s):

Shang Wang ◽

Kirill V. Larin

Keyword(s):

Optical Coherence Tomography ◽

Shear Wave ◽

Lamb Wave ◽

Wave Dispersion ◽

Optical Coherence ◽

Shear Wave Imaging ◽

Wave Imaging ◽

Imaging Optical Coherence Tomography

Download Full-text

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

Insight - Non-Destructive Testing and Condition Monitoring ◽

10.1784/insi.2021.63.11.659 ◽

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.

Download Full-text

Research on SAFT Imaging Method of Array Probes in Concrete Structures

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.189.265 ◽

2012 ◽

Vol 189 ◽

pp. 265-269 ◽

Cited By ~ 2

Author(s):

Qiu Feng Li ◽

Pang Huang ◽

Yin Liao

Keyword(s):

Linear Array ◽

Imaging Technique ◽

Structural Characteristics ◽

Concrete Structures ◽

Imaging Method ◽

Geometrical Relation ◽

Scan Data ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique ◽

Detecting Method

Because of the need of rapid detection of internal defects and embedded object in concrete structures, a detecting method with linear array probes is presented here, which is the high-resolution and efficient imaging technique for concrete structures by combining with synthetic aperture focusing technique (SAFT). Firstly, array simulation data are processed to be amalgamated B-scan data of concrete structures according to the structural characteristics of linear array; And then the B-scan data are reconstructed in the light of geometrical relation of ultrasonic path and SAFT; At last, the structural imaging figure are calculated. It can be shown from simulation results that the method is effective, and the embedded object in model can be identified effectively.

Download Full-text

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

Sensors ◽

10.3390/s20123502 ◽

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.

Download Full-text