Search

Your search keyword '"Le Bas, Pierre-Yves"' showing total 94 results
Start Over Author "Le Bas, Pierre-Yves"
94 results on '"Le Bas, Pierre-Yves"'

53. Three component time reversal: Focusing vector components using a scalar source

Author

UCL, Ulrich, T. J., Van Den Abeele, Koen, Le Bas, Pierre-Yves, Griffa, Michele, Anderson, Brian E., Guyer, Robert A., UCL, Ulrich, T. J., Van Den Abeele, Koen, Le Bas, Pierre-Yves, Griffa, Michele, Anderson, Brian E., and Guyer, Robert A.

Abstract

In acoustics, it is known that, for a given response signal at an arbitrary location, reciprocity and time reversal (TR) can be used to focus high levels of acoustic energy at that position. In solid media, elastic waves generally induce different disturbances in three directions. In this paper, both experimental and numerical wave propagation results for solid materials demonstrate the ability to use a scalar source, a three component detector and the reciprocal TR process to selectively focus each of the different vector components, either individually or collectively. The principle is explained from an analytical point of view. The numerical and experimental study demonstrates excellent temporal and spatial focalization. Applications of the selective vector component focusing can be found in damage imaging techniques using both linear or nonlinear ultrasonic waves.

Published
2009

62. Three-dimensional treatment of nonequilibrium dynamics and higher order elasticity.

Author

Martin Lott, Payan, Cédric, Garnier, Vincent, Vu, Quang A., Eiras, Jesús N., Remillieux, Marcel C., Le Bas, Pierre-Yves, and Ulrich, T. J.

Subjects
NON-equilibrium reactions, ELASTICITY, ELASTIC waves, STRAIN tensors, MATHEMATICAL constants
Abstract

This letter presents a three-dimensional model to describe the complex behavior of nonlinear mesoscopic elastic materials such as rocks and concrete. Assuming isotropy and geometric contraction of principal stress axes under dynamic loading, the expression of elastic wave velocity is derived, based on the second-order elastic constants (λ, µ), third-order elastic constants (l, m, n), and a parameter α of nonclassical nonlinear elasticity resulting from conditioning. We demonstrate that both softening and recovering of the elastic properties under dynamic loading is an isotropic effect related to the strain tensor. The measurement of the conditioning is achieved using three polarized waves. The model allows the evaluation of the third-order elastic constants uncoupled from conditioning and viscoelastic effects. The values obtained are similar to those reported in the literature using quasi-static loading. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

82. Nonlinear Acoustic Testing for Concrete Materials Evaluation.

Author

Shokouhi, Parisa, Rivière, Jacques, Le Bas, Pierre-Yves, and Ulrich, T. J.

Subjects
CONCRETE testing, NONLINEAR acoustics, PRESTRESSED concrete
Abstract

This paper summarizes the results of three nonlinear acoustic tests performed on a series of stress-damaged concrete samples. The three tests were: nonlinear resonant "ultrasound" spectroscopy (NRUS), scaling subtraction method (SSM), and dynamic acousto-elastic testing (DAET). The test samples were cut out of a large concrete block emulating common field investigation scenarios, where the quality of an existing structure was examined at different locations. One sample was left intact while the others were pressed to 10, 20, 30, 40, 60, and 70% of the (nominal) ultimate compressive strength of their common concrete mixture. NRUS was performed on all samples, whereas SSM and DAET were conducted on a subset of samples. In addition, the conventional (linear) resonant "ultrasound" spectroscopy and ultrasonic pulse velocity measurements for all samples are reported. The authors present the theoretical background of nonlinear acoustic testing, discuss the principles and outcome of each test, and compare the corresponding results of linear and nonlinear acoustic techniques. The obtained results attest to the high sensitivity of nonlinear acoustic measurements (that is, estimated nonlinear elastic material parameters) to the presence of microcracks. While NRUS, SSM, and DAET clearly differentiate between intact and moderately damaged samples, neither linear wave velocities nor (linear) dynamic elastic moduli can reliably delineate undamaged and damaged concrete. [ABSTRACT FROM AUTHOR]

Published
2017

84. Experimental implementation of reverse time migration for nondestructive evaluation applications.

Author

Anderson, Brian E., Griffa, Michele, Le Bas, Pierre-Yves, Ulrich, Timothy J., and Johnson, Paul A.

Abstract

Reverse time migration (RTM) is a commonly employed imaging technique in seismic applications (e.g., to image reservoirs of oil). Its standard implementation cannot account for multiple scattering/ reverberation. For this reason it has not yet found application in nondestructive evaluation (NDE). This paper applies RTM imaging to NDE applications in bounded samples, where reverberation is always present. This paper presents a fully experimental implementation of RTM, whereas in seismic applications, only part of the procedure is done experimentally. A modified RTM imaging condition is able to localize scatterers and locations of disbonding. Experiments are conducted on aluminum samples with controlled scatterers. [ABSTRACT FROM AUTHOR]

Published
2011
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results