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POMA - XV International Conference on Nonlinear Elasticity in Materials
Conference Location: Otranto, Italy Conference Date: 4 - 10 July 2010
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Evaluation of epoxy bonded joint quality using nonlinear acoustics

Christine La Rocca, Cedric Payan, and Joseph Moysan

POMA Volume 10, pp. 045001 (October 2010); (8 pages)

Online Publication Date: October 08, 2010

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The topic of ultrasonic evaluation of bonded joint quality is of interest in many fields such as aeronautics, civil engineering, nuclear industry... The main issue is to determine if the adhesive joint is "good" or not. Up to date, nobody is able to discern an adhesive from a cohesive joint before fracture. As an example, 10 samples prepared in the same time and same conditions (rougthness, cleaning agent, temperature, humidity...) won't have the same mechanical behaviour. 9 will fail at the presumed load, but one will break before. This study is aimed at exploring potentialities of Time Of Flight Modulation to discern an eventual change in the nonlinear signature of an aluminium/epoxy interface.
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43.25.Ba Parameters of nonlinearity of the medium
43.25.Dc Nonlinear acoustics of solids
43.25.Lj Parametric arrays, interaction of sound with sound, virtual sources
43.25.Zx Measurement methods and instrumentation for nonlinear acoustics
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Effect of carbonation on the nonlinear response of concrete

Fateh Bouchaala, Cedric Payan, and Vincent Garnier

POMA Volume 10, pp. 045002 (October 2010); (7 pages)

Online Publication Date: October 08, 2010

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The carbonation process results in an increase of the elastic properties of concrete, resulting in slightly increase of standard acoustic indicators such as wave speed. However, this evolution is too low to ensure an efficient carbonation assessment. The present communication focuses on the feasibility of carbonation assessment in concrete by applying Nonlinear Resonant Ultrasound Spectroscopy (NRUS). The results show that the nonlinear parameter is significantly affected by the presence of carbonation, which is interpreted with respect to the evolution of concrete microstructure in the presence of this pathology.
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43.25.Ba Parameters of nonlinearity of the medium
43.25.Dc Nonlinear acoustics of solids
43.25.Gf Standing waves; resonance
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Macro crack characterization by linear and nonlinear ultrasound in concrete

Audrey Quiviger, Jean-Philippe Zardan, Cedric Payan, Jean-Fraçois Chaix, Vincent Garnier, Joseph Moysan, and Jean Salin

POMA Volume 10, pp. 045003 (October 2010); (7 pages)

Online Publication Date: October 08, 2010

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Concrete Non Destructive Characterisation is one of the important stakes to evaluate the life duration in the present and future civil engineering structures. The damaging modes of the structures often imply the phases of the appearance and after growth of the cracks. We have to detect, identify and characterise them. The characterisation result must lead to a diagnosis of the criticality of a crack regarding the integrity of the structure and its ability to full fill its function. The aim of the present study is to determine the nature of a macro-crack (open or close) visible in surface and to give information on its depth. Two approaches are developed. The first one, based on diffuse ultrasound, provides information about the presence and the depth of an opened crack. The last, based on nonlinear ultrasound, gives information about the presence and the depth of a closed crack.
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43.20.Fn Scattering of acoustic waves
43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
43.25.Dc Nonlinear acoustics of solids
43.25.Lj Parametric arrays, interaction of sound with sound, virtual sources
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Break of reciprocity principle induced by cracks in concrete: experimental evidence and applications to nonlinear tomography

Caterina L. Bruno, Marco Scalerandi, Antonio S. Gliozzi, and Paola Antonaci

POMA Volume 10, pp. 045004 (October 2010); (11 pages)

Online Publication Date: October 08, 2010

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As largely demonstrated by many authors, localized cracks in heterogeneous media act as nonlinear scatterers; consequently, when an heterogeneous medium is perturbed by a mechanical excitation, its elastic response shows nonlinear features, dependent on the amplitude. Experiments presented here will show that the presence of localized nonlinear scatterers not only breaks the proportionality of the elastic response, but also affects the reciprocity principle, which thus, in some conditions, is no longer valid. Experiments performed on a concrete beam with a significant crack have demonstrated that the reciprocity principle holds true only when the amplitude of excitation is low or when the distance between the crack and the source/receiver is comparable (i.e. source/receiver are symmetric in space with respect to the crack). Besides highlighting the break of reciprocity, experiments have proved its dependence on the amplitude of excitation and on the position of the emitting and receiving transducers with respect to the crack. By taking advantage of these features, a nonlinear tomography of a cracked fibre-reinforced concrete beam was performed, allowing to reproduce an image of the scanned surface and to locate the position of the crack. The sensitivity of the approach to locate small localised nonlinear features is being investigated.
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43.25.Dc Nonlinear acoustics of solids
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Robustness of the SSM applied to damage assessment in concrete

Caterina L. Bruno, Pietro G. Bocca, Paola Antonaci, Antonio S. Gliozzi, and Marco Scalerandi

POMA Volume 10, pp. 045005 (October 2010); (7 pages)

Online Publication Date: October 19, 2010

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The Scaling Subtraction Method (SSM) has been proposed in recent years as an effective nonlinear nondestructive technique to evaluate the damage level in concrete and other media and monitor its progression as a function of external actions. Here we show experimental data to prove the robustness of the method with respect to the variation of a number of factors related to either the environmental and testing conditions or the size and geometrical characteristics of the elements tested, as well as to the type of damage and the excitation frequency. An experimentally-derived evolution law is also presented as a first attempt to describe compressive damage progression in concrete in a unified approach.
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43.25.Dc Nonlinear acoustics of solids
43.35.Yb Ultrasonic instrumentation and measurement techniques
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
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Using time-reversal to locate non-volcanic tremor and to fulfill the monitoring objectives of the nuclear-test ban treaty

Carene S. Larmat, Paul A. Johnson, and Robert A. Guyer

POMA Volume 10, pp. 045006 (December 2010); (14 pages)

Online Publication Date: December 10, 2010

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In this paper are presented the latest results of our group effort to apply Time Reversal (TR) to different seismology problems. The first problem considered is source location of non-volcanic tremor (NVT). NVT episodes involve quasi-continuous emissions of seismic energy making the identification of distinct events and phase arrival times very difficult. We locate 2 NVT episodes that were recorded near Hemet: one triggered by the 2002 Denali earthquake and one by the 2009 Mexicali earthquake. Locations indicate sources slightly off the known scarp of tectonic faults. In both cases, determination of the source mechanism is impossible. The second problem is determination of the depth of seismic events. There is currently no robust method to estimate the depth of small events (below Mw5.0), when depth determination is crucial in discriminating small earthquakes from man-made blast, since the blast will have to be within about 2 km of the surface where few earthquakes occur. We propose to use stacked autocorrelation (AC) signal to extract depth phases (i.e. phases reflected off the surface). AC is a variant form of TR. We show promising results from sparse IRIS stations in China for three nuclear blasts and a deep earthquake.
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43.20.Fn Scattering of acoustic waves
43.60.Jn Source localization and parameter estimation
43.60.Tj Wave front reconstruction, acoustic time-reversal, and phase conjugation
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Ultrasonic imaging of stress corrosion crack formed in high temperature pressurized water using subharmonic phased array

Yoshikazu Ohara, Yohei Shintaku, Satoshi Horinouchi, Makoto Hashimoto, Yuichi Yamaguchi, Minoru Tagami, and Kazushi Yamanaka

POMA Volume 10, pp. 045007 (December 2010); (8 pages)

Online Publication Date: December 15, 2010

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Closed stress corrosion cracks (SCCs) have been generated in high temperature pressurized water in weld parts of important structure of atomic power plants. The depth of closed SCCs is often underestimated or overlooked, since the ultrasound is transparent through the closed cracks. This leads to catastrophic accidents. To solve this problem, we have developed a novel imaging method, namely, the subharmonic phased array for crack evaluation (SPACE), on the basis of subharmonic waves and a phased array algorithm. In this study, we formed an SCC in heat affected zone of weld part of austenitic stainless steel in high temperature pressurized water (280 deg C) to simulate those formed in actual atomic power plants. Then we imaged the SCC using SPACE with LN array transmitter. As a result, the subharmonic images visualized the crack tip which was deeper than in the fundamental images corresponding to linear phased-array image. Thus, we demonstrated that SPACE with LN array transmitter is useful in reducing the underestimation of closed-crack depths.
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43.25.Dc Nonlinear acoustics of solids
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Hysteretic Elastic Systems

H. Alicia Kim, James A. Tencate, and Robert A. Guyer

POMA Volume 10, pp. 045008 (December 2010); (10 pages)

Online Publication Date: December 15, 2010

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The macroscopic behavior of a system of elastic elements that can be in one of two states, depending on the relationship between the stress they carry to a critical stress (different for each elastic element), is studied. There are two extreme cases: (1) in which the critical stress is hysteretic (there is microscopic hysteresis) and (2) in which the critical stress is not hysteretic (there is no microscopic hysteresis). The first case is that well studied in the context of geophysics, commonly referred to as the Preisach model [1] (macroscopic hysteresis is conferred by microscopic hysteresis). The second case, less familiar, has hysteresis that arises from the interaction of elastic elements. The second case corresponds to the T=0 random field Ising model, RFIM [2]. This system is studied in a two-dimensional finite element environment. The phase space for behavior of the system is mapped and the finite element is formulated to reflect Preisach and RFIM behavior. The numerical examples demonstrate that macroscopic hysteresis is observed in both models.
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43.25.Dc Nonlinear acoustics of solids
43.25.Ts Nonlinear acoustical and dynamical systems
43.40.At Experimental and theoretical studies of vibrating systems
43.40.Qi Effect of sound on structures, fatigue; spatial statistics of structural vibration
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