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

Abstract

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.

An Internal Defect Detection Algorithm for Concrete Blocks Based on Local Mean Decomposition-Singular Value Decomposition and Weighted Spatial-Spectral Entropy

“…At present, prevailing non-destructive testing (NDT) methodologies for concrete, such as the impact echo method [1][2][3], ground-penetrating radar method [4][5][6], X-ray computed tomography method [7,8], infrared thermography [9,10], and ultrasonic detection method [11][12][13][14], have demonstrated significant efficacy. However, each of these NDT methods bears inherent limitations.…”

Edge and Notch Detection in a Plate Using Time Reversal Process of Leaky Lamb Waves

“…This operation is made possible because of the completeness of the fundamental Lamb modes as proven by Kirrmann [3]. Meanwhile, the topological energy method [22,[24][25][26][27][28] requires the numerical solution of only two problems: the direct problem where the experimental source is generated in the healthy corresponding structure and the adjoint problem where the source is the time-reversed difference between the ultrasonic field measured on the transducers of the inspected medium and the reference medium. This time-reversed source can be interpreted as the time-reversed signature of the defects and could provide data of very good quality.…”