A simulation study on the impact echo array technique for concrete structure NDT
01 Sep 2006-Nondestructive Testing and Evaluation (Taylor & Francis Group)-Vol. 21, Iss: 3, pp 123-140
TL;DR: In this article, a finite difference time domain (FDTD) model was employed for simulating the impact-echo method and absorbing boundary conditions were employed in the FDTD for efficient calculation.
Abstract: This paper simulates an impact-echo array technique for the two-dimensional imaging of defects in thick concrete structures. A finite difference time domain (FDTD) Model was employed for simulating the impact-echo method. The absorbing boundary conditions were employed in the FDTD for efficient calculation. The signals predicted using the FDTD models were then used for 2D image reconstruction of the cross-sectional region of the structure. The reconstruction algorithm uses time shifting (migration) of the signals based on point-source assumption for the impact sources. The images are represented in a typical “B-scan” format. Several types of defects were simulated, and parametric studies on the different parameters that influence the image quality during imaging of defects in concrete structures were examined.
Citations
More filters
TL;DR: In this article, the impact-echo method is applied to evaluate the grout quality in tendon ducts of post-tensioned structures nondestructively in the construction field on box girders under various grouting conditions.
Abstract: The impact-echo method is applied to evaluate the grout quality in tendon ducts of posttensioned structures nondestructively in the present study. As the main evaluation index, the dominant frequency (DFQ) is obtained from the frequency-domain spectrum, which is transformed from the original time-domain signal. The influences of several factors on the DFQ are investigated in detail both experimentally and numerically. These factors include size effect, slab thickness, tendon duct depth, affected range, DFQ shift, and grout strength. The experiments are conducted in the construction field on posttensioned box girders under various grouting conditions. The DFQs of each test point in a test area are integrated to draw a contour image based on their coordinates. Through the analysis of the contour image, grout quality in the tendon ducts can be evaluated accordingly. Grout defects are detected in some box girders and verified by chiseling these suspected ducts. The numerical studies, which can provide...
12 citations
Cites result from "A simulation study on the impact ec..."
...studies were also conducted in previous studies (Abraham et al. 2000; Alver and Ohtsu 2007, 2008; Cheng and Sansalone 1993; Cho et al. 2005; Lin et al. 1990; Schubert and Köhler 2008; Schubert and Marklein 2002; Sridharan et al. 2006; Zerwer et al. 2002; Zhang and Xie 2012)....
[...]
TL;DR: In this paper, the feasibility of detecting defects inside reinforced concrete (RC) structures by using multi-directional Synthetic Aperture Focusing Technique (SAFT) to create an image which contains the comprehensive information about the geometry of possible defects was discussed.
7 citations
TL;DR: In this paper, the spectrum of the impact-echo test is analyzed in a two-layer system with two frequency peaks expected in the spectrum, and it is shown that one frequency peak is expected in each layer.
Abstract: In the case of a two-layer system, the impact-echo test has classically assumed that two frequency peaks are expected in the spectrum. In this paper, the spectrum of the impact-echo test is...
5 citations
01 Jan 2012
5 citations
TL;DR: These studies confirm that MFA is an alternative to SAFT with little additional computational burden and can also be applied blindly, like SAFT, to effect synthetic focusing with distinct advantages in treating finite transducer effects, and in handling steered beam inspections.
Abstract: The suitability of the synthetic aperture imaging of defects using a matched filter approach on finite aperture transducers was investigated. The first part of the study involved the use a finite-difference time-domain (FDTD) algorithm to simulate the phased array ultrasonic wave propagation in an aluminum block and its interaction with side-drilled hole-like defects. B-scans were generated using the FDTD method for three active aperture transducer configurations of the phased array (a) single element and (b) 16-element linear scan mode, and (c) 16-element steering mode. A matched filter algorithm (MFA) was developed using the delay laws and the spatial impulse response of a finite size rectangular phased array transducer. The conventional synthetic aperture focusing technique (SAFT) algorithm and the MFA were independently applied on the FDTD signals simulated with the probe operating at a center frequency of 5 MHz and the processed B-scans were compared. The second part of the study investigated the capability of the MFA approach to improve the SNR. Gaussian white noise was added to the FDTD generated defect signals. The noisy B-scans were then processed using the SAFT and the MFA and the improvements in the SNR were estimated. The third part of the study investigated the application of the MFA to image and size surface-crack-like defects in pipe specimens obtained using a 45° steered beam from a phased array probe. These studies confirm that MFA is an alternative to SAFT with little additional computational burden. It can also be applied blindly, like SAFT, to effect synthetic focusing with distinct advantages in treating finite transducer effects, and in handling steered beam inspections. Finally, limitations of the MFA in dealing with larger-sized transducers are discussed.
3 citations
Cites methods from "A simulation study on the impact ec..."
...other methods of synthetic focusing of the received data using a post-processing approach have been reported in the literature [4], [5]....
[...]
References
More filters
TL;DR: Numerical experiments and numerical comparisons show that the PML technique works better than the others in all cases; using it allows to obtain a higher accuracy in some problems and a release of computational requirements in some others.
9,875 citations
"A simulation study on the impact ec..." refers background in this paper
...The most popular material absorber based ABCs are the PML (Perfectly Matched Layer) proposed by Berenger (1994), where the domain under consideration, is assumed to be surrounded by another sub-domain, having the same impedance as the main domain....
[...]
TL;DR: In this paper, highly absorbing boundary conditions for two-dimensional time-domain electromagnetic field equations are presented for both two-and three-dimensional configurations and numerical results are given that clearly exhibit the accuracy and limits of applicability of these boundary conditions.
Abstract: When time-domain electromagnetic-field equations are solved using finite-difference techniques in unbounded space, there must be a method limiting the domain in which the field is computed. This is achieved by truncating the mesh and using absorbing boundary conditions at its artificial boundaries to simulate the unbounded surroundings. This paper presents highly absorbing boundary conditions for electromagnetic-field equations that can be used for both two-and three-dimensional configurations. Numerical results are given that clearly exhibit the accuracy and limits of applicability of highly absorbing boundary conditions. A simplified, but equally accurate, absorbing condition is derived for two- dimensional time-domain electromagnetic-field problems.
2,553 citations
"A simulation study on the impact ec..." refers background or methods in this paper
...Some of the existing differential equation based ABCs include (a) the Reynolds Boundary condition (Reynolds 1978), (b) the Lindman’s boundary condition (Lindman 1975) which is based on potential approach, and (c) the Mur’s second order boundary condition (Mur 1981)....
[...]
...Some of the existing differential equation based ABCs include (a) the Reynolds Boundary condition (Reynolds 1978 ), (b) the Lindman's boundary condition (Lindman 1975 ) which is based on potential approach, and (c) the Mur's second order boundary condition (Mur 1981 )....
[...]
...The obtained reflection and transmission energy is much smaller than the absorbing boundary conditions reported by Mur (1981), Reynolds (1978) and Clayton and Engquist (1977)....
[...]
TL;DR: In this article, boundary conditions are derived for numerical wave simulation that minimize artificial reflections from the edges of the domain of computation, based on paraxial approximations of the scalar and elastic wave equations.
Abstract: Boundary conditions are derived for numerical wave simulation that minimize artificial reflections from the edges of the domain of computation. In this way acoustic and elastic wave propagation in a limited area can be efficiently used to describe physical behavior in an unbounded domain. The boundary conditions are based on paraxial approximations of the scalar and elastic wave equations. They are computationally inexpensive and simple to apply, and they reduce reflections over a wide range of incident angles.
1,019 citations
TL;DR: In this article, three different methods for deriving radiating boundary conditions for the elastic wave equations are presented, including exact absorbing boundary conditions, for both P (longitudinal) and S (transverse) waves generated from a surface source.
762 citations
"A simulation study on the impact ec..." refers background in this paper
...The obtained reflection and transmission energy is much smaller than the absorbing boundary conditions reported by Mur ( 1981 ), Reynolds ( 1978 ) and Clayton and Engquist ( 1977 )....
[...]
TL;DR: In this article, the boundary conditions for the discrete wave equation are constructed using projection operators, and the separation of waves into ingoing and outgoing waves inherent in these boundary conditions greatly facilitates diagnostics.
354 citations
"A simulation study on the impact ec..." refers methods in this paper
...Some of the existing differential equation based ABCs include (a) the Reynolds Boundary condition (Reynolds 1978), (b) the Lindman’s boundary condition (Lindman 1975) which is based on potential approach, and (c) the Mur’s second order boundary condition (Mur 1981)....
[...]