Ultrasonic Nondestructive Testing Of Inhomogeneous Isotropic And Anisotropic Media Modeling And Imaging
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Ultrasonic Nondestructive Testing of Inhomogeneous Isotropic and Anisotropic Media: Modeling and Imaging
Author: Chinta, Prashanth Kumar
language: en
Publisher: kassel university press GmbH
Release Date: 2013-01-01
This thesis discusses ultrasonic testing by means of numerical modeling and image reconstruction techniques using elastic and acoustic wave fields. Numerical modeling of elastic waves (part one of the thesis) is used to understand the elastic wave scattering due to material defects and the propagation of surface waves in inhomogeneous isotropic and anisotropic media, with special emphasis on transversely isotropic and orthotropic media. Different imaging techniques (part two of the thesis) are investigated to develop a software, implemented in Matlab, which can give imaging results immediately after the measurement almost in real time as it can read and process the data obtained directly from the measurement. Acoustic wave scattering using analytical techniques and imaging techniques based on Radon transform are investigated. The data obtained from the Radon transform are subjected for imaging utilizing the filtered back projection algorithm and the Fourier slice theorem. The fundamentals of elastic wave propagation in solids are extensively elaborated. The point source synthesis to compute the Green’s functions for anisotropic media and the plane wave synthesis to compute slowness, phase and group velocity surfaces are studied. The elastic integral equations for the so called stretched coordinate system are derived. Based on these equations the numerical tool ’Three-dimensional Elastodynamic Finite Integration Technique’ (3D-EFIT) has been enhanced to treat not only isotropic media but also anisotropic media. For fast computation, the 3D-EFIT code using the Message Passing Interface (MPI) is used by which processing on massive parallel computers is made possible. In 3D-EFIT the Convolutional Perfectly Matched Layers (CPML) can also be applied to absorb the elastic body waves as well as the surface and evanescent waves. 3D-EFIT for homogeneous anisotropic media is validated by comparing computed Green’s functions with an analytical solution. After the validation, the applications of EFIT such as elastic wave modeling in inhomogeneous austenitic steel welds and inhomogeneous orthotropic wooden structures are presented. The results of the 2D-EFIT and 3D-EFIT modeling are compared against measurements performed at Federal Institute for Materials Research and Testing (BAM). After the modeling part of the thesis, inverse scattering techniques for fast imaging of inhomogeneities are studied. For three-dimensional imaging of defects in concrete, the Synthetic Aperture and Focusing Technique (SAFT) and Fourier Transformed Synthetic aperture Focusing Technique (FT-SAFT) are applied to data measured using a transducer array. The seismic Dip-Moveout (DMO) method has been utilized to convert measured bistatic data into monostatic data. A special treatment of SAFT as a technique for back propagation of the wave fields using time reversal, utilizing the knowledge of the geometry, is presented. Finally, time domain anisotropic SAFT (AnSAFT) is studied for image reconstruction of defects in inhomogeneous geometry with orthotropic crystal structure of the embedding medium.
Acoustical Imaging
Author: L. Masotti
language: en
Publisher: Springer Science & Business Media
Release Date: 2012-12-06
This volume contains 131 of the papers presented at the 22nd International Symposium on Acoustical Imaging. This meeting, which was held for the first time in Florence, Italy, on September 3-6, 1995, allowed an intense and friendly exchange of ideas between over 150 researchers from 26 different countries of Europe (70%), America (20%), Asia and Australia (10%). The Symposium started on Sunday, September 3, with the opening Session held in the magnificent 'Salone dei 500' in Palazzo Vecchio; this included invited talks by Peter WeHs and Hua Lee, who reviewed the State of the Art in Acoustical Imaging research. One hundred and forty papers, selected from the nearly 200 submitted Abstracts, were presented in 11 non-parallel oral Sessions and one Poster Session. This year a 'Best Poster' award was introduced, which was won by V. Miette, M. Fink and F. Wu. Also, a special session on Acoustical Microscopy was organized by Walter Arnold, in which invited speakers Ioie Iones, Oleg Kolosov, Andrew Briggs and Ute Rabe reviewed the capabilities of this em erging topic.
Acoustical Imaging
Author: Leonardo Marotti
language: en
Publisher: Springer Science & Business Media
Release Date: 1996
Contains 131 papers presented at the September 1995 symposium. Arrangement is in sections on the mathematics and physics of acoustical imaging, novel approaches in biomedical imaging, tissue characterization, flow imaging, transducers and arrays, imaging systems and techniques, underwater and indust