Locating and characterizing a crack in concrete with diffuse ultrasound: A four-point bending test

Abstract

This paper describes an original imaging technique, named Locadiff, that benefits from the diffuse effect of ultrasound waves in concrete to detect and locate mechanical changes associated with the opening of pre-existing cracks, and/or to the development of diffuse damage at the tip of the crack. After giving a brief overview of the theoretical model to describe the decorrelation of diffuse waveforms induced by a local change, the article introduces the inversion procedure that produces the three dimensional maps of density of changes. These maps are interpreted in terms of mechanical changes, fracture opening, and damage development. In addition, each fracture is characterized by its effective scattering cross section.

Coda-wave monitoring of continuously evolving material properties and the precursory detection of yielding

“…In the structural concrete bending tests by Zhang et al (2016) which applied fixed reference CWI and CWD and the work by Larose et al (2015) where only CWD was applied the authors noted the increase in error of both relative velocity and the decorrelation coefficient as inelastic deformation progressed. While this can be easily overcome by the manual selection of a new reference point during monitoring, we suggest that where the long term, continuously monitoring of both gradual, and sudden inelastic changes is required a rolling reference is the preferred choice.…”

Monitoring Local Changes in Granite Rock Under Biaxial Test: A Spatiotemporal Imaging Application With Diffuse Waves

“…Recently, a time‐lapse differential tomography technique named Locadiff (Larose et al, ) was developed to explore spatiotemporal changes based on analytical diffuse sensitive kernels together with a linearized inversion technique. Although Locadiff is still an ongoing project, the performance of this method was assessed through numerical studies (Pacheco & Snieder, ; Planès et al, ) and applied to imaging velocity changes and structural changes both in seismology (Obermann et al, , ) and in nondestructive testing and evaluation (Larose, Obermann, et al, ; Zhang et al, ). Using another inversion procedure, it even showed a potential to image high‐resolution subwavelength (∼1/15 λ , λ = 0.75 mm) changes (Xie et al, ).…”

Non-destructive evaluation of containment walls in nuclear power plants

“…A new technique Locadiff allows locating the modification generated by the early stage of cracking by measuring the spatiotemporal de-correlation of scattered waves and by solving the corresponding inverse problem. This technique was applied on a real-size concrete specimen and on a four point bending test specimen [2] to map the mechanical changes, fracture opening, and damage development. The crack detection and repair are also studied by coda wave interferometry [14].…”

“…The Locadiff technique [2] uses the evolution of the diffused waves obtained from a transducers network (Fig. 8a: 10 emitters, 10 receivers).…”

“…1b). The NDT techniques implemented are: surface waves [17], diffuse waves [15], localization and diffusion [2], time reversal [18], acoustic emission [1], digital image correlation [19], resistivity. WP3 laboratory tests and results will be developed in this paper.…”