Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/structcivil.69A.617

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejj.22-15004

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Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Guided elastic wave (GEW) transducers for structural health monitoring (SHM) can act as transmitters (senders) and receivers (sensors). Their performance in both cases depends on the structure to which they are coupled. Therefore, they must be characterized as system transducer- structure. The characterization of the transducer-structure as transmitter using a Scanning Laser Doppler Vibrometer (SLDV) is straightforward, whereas its characterization as receiver is non-trivial. We propose to exploit electromechanical reciprocity, which is an identity between the transfer functions of electrical-to-mechanical and mechanical-to-electrical conversions. For this purpose, the well-known electromechanical reciprocity theorem was adapted to the following situation: The two reciprocal states are “electrical excitation and detection of the surface velocity at point P” and “mechanical excitation at P and measurement of the electrical quantities”. According to the derived formulas, the quantities on the mechanical and electrical sides must be chosen appropriately to ensure reciprocity as well as that the corresponding transfer functions are equal. We demonstrate the reciprocity with experimental data for correctly chosen transfer functions and show the deviation in reciprocity for a different choice. Furthermore, we propose further applications of electromechanical reciprocity.

DOI： 10.3390/s23010150

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/jsceiii.3.J2_682

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The American Society for Nondestructive Testing, Inc.  

In this study, we applied the reverse time migration (RTM) method to ultrasonic defect imaging in anisotropic materials. RTM offered that the defect shape could be uniquely determined by calculating a cross correlation of the incident and the reverse propagated waves from the array transducer. 2D simulations demonstrated that defect imaging by the RTM method requires an accurate numerical setup. We validated our technique using measured scattered waves from a slit in unidirectional solidified 316L stainless steel. By using the elastic constants determined from the ultrasonic wavefield data, the slit shape was correctly reconstructed. This provides a proof of principle that the RTM method is effective in nondestructive imaging of composite structures containing anisotropic materials.

DOI： 10.32548/2022.me-04244

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11396/jjsndi.71.95

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME International  

<title>Abstract</title>
Several components of nuclear power plants are made of cast austenitic stainless steel (CASS) because of its high corrosion resistance and strength. The inservice inspection based on ultrasonic testing (UT) has to be conducted for CASS components in accordance with fitness-for-service codes such as the Japan Society of Mechanical Engineers Rules on Fitness-for-Service for Nuclear Power Plants. However, a high-accuracy evaluation of flaws in CASS components through UT is difficult because the ultrasonic waves are scattered and attenuated by coarse grains, and their beam is distorted by the anisotropy resulting from the grain orientations. Numerical simulations are useful and reasonable ways for better understanding the ultrasonic wave propagation behavior in CASS. To effectively achieve this, the simulation model should include a three-dimensional (3D) grain structure. If a casting simulation can predict the solidification structure in a CASS, the wave propagation could be simulated also for a more realistic situation. In this study, we predicted the solidification structure of statically CASS by using a cellular automaton (CA) coupled with the finite element method and fed this structure into an explicit finite element model (FEM) for simulating the propagation of waves emitted by angle beam probes. Afterward, these simulated wave propagations were compared with those measured by a 3D laser Doppler vibrometer (LDV), showing almost good agreement between predicted and experimental results.

DOI： 10.1115/1.4050076

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/jsceiii.2.J2_466

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10921-021-00765-x

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Other Link： http://link.springer.com/article/10.1007/s10921-021-00765-x/fulltext.html

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejam.77.2_I_137

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/nag.3117

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/nag.3117

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2472/jsms.69.586

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

J-GLOBAL

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Authorship：Lead author   Publishing type：Research paper (scientific journal)  

DOI： 10.11532/structcivil.66A.529

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejam.75.2_I_71

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier Ltd A numerical modeling of ultrasonic testing (UT) for a carbon fiber reinforced plastic (CFRP) material is presented. Due to the heterogeneity caused by the several unidirectional lamina stacked at different angle, the CFRP shows unique mechanical properties and leads to ultrasonic wave skewing and scattering. In this paper, we present a large-scale finite element (FE) simulation based on the image-based modeling approach. We model the mesoscopic heterogeneity of the CFRP in the numerical discretization by using the voxel of the same size. The determination of the anisotropic elastic stiffness of each lamina is essential to the FE simulation. Here, we estimated the parameters via an inversion method using wavefield visualization data. The parameters were fed into the 3D wave propagation simulations in the laminated CFRPs. The simulation and experimental results showed good agreement with respect to the wave velocity and the spread of the ultrasonic waves. It was found that the mesoscopic modeling and parameterization of the elastic stiffness of the lamina were important for the UT simulation.

DOI： 10.1016/j.compositesb.2019.107018

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Publishing type：Research paper (scientific journal)   Publisher：British Institute of Non-Destructive Testing (BINDT)  

A simulation-aided defect reconstruction method using an ultrasonic time-reversal approach that uses elastic constants determined by ultrasonic field data is proposed. Scattered waves from a defect are recorded using an array probe on a polystyrene wedge and the time-reversed waves are re-emitted in a finite element simulation. The target defect in these experiments is an electrical discharge machined slit in unidirectionally solidified SUS316L stainless steel. For the time-reversal analysis, two kinds of elastic constant of SUS316L derived from an electromagnetic acoustic resonance (EMAR) method and a laser scanning ultrasonic visualisation method are used. The through-wall extent of the electrical discharge machined slit can be visually estimated from the focal point of the ultrasonic wave in the numerical model using the elastic constants determined by the laser ultrasonic method. This provides a proof of principle that the method is working.

DOI： 10.1784/insi.2019.61.11.669

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier B.V. A pulsed laser illuminates a target zone that causes rapid thermoelastic expansion, generating broadband high-frequency ultrasonic wave (photoacoustic wave, PA wave). We developed a PA microscopy (PAM) with a confocal area of laser and ultrasonic wave for applications in nondestructive testing (NDT). The synthetic aperture focusing technique (SAFT) is applied in the PAM for the three-dimensional (3D) imaging of interior flaws. Here, we report proof-of-concept experiments for the NDT of a subsurface flaw in a thin laminar material. Graphical abstract (a) shows a specimen of carbon-fiber-reinforced plastic (CFRP) with an artificial delamination. Here, it should be noted that the group velocity varies directionally due to the strong anisotropy of the CFRP specimen (see Graphical abstract (b)). By considering the group velocity distribution in the SAFT, the shape and location of the subsurface delamination were accurately estimated as shown in Graphical abstract (c). Coating the surface of the CFRP specimen with a light-absorbent material improved the amplitude of the PA wave. This finding showed that the signal-to-noise ratio of the waves scattered from the flaws can be improved.

DOI： 10.1016/j.ultras.2019.05.006

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PubMed

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/ecj.12164

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ecj.12164

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

© 2019 The Institute of Electrical Engineers of Japan. Ultrasonic wave generated by interaction of the material with pulsed lasers is known to photoacoustic (PA) wave. In this study, the PA imaging is applied to the nondestructive testing for carbon fiber reinforced plastic (CFRP). When subsurface flaws are in CFRP, the detection of the flaws is sometimes challenging because the trailing signal from the surface interferes with the scattered signal from the flaws. Here we developed a PA microscopy (PAM) to reconstruct the location and the shape of the subsurface flaws. The PAM employs a confocal arrangement of optical and acoustic lens to maximize the intensity of generated PA waves. To enhance the lateral resolution of the image, we introduced the synthetic aperture focusing technique (SAFT). In the SAFT, it is necessary to consider direction-dependent group velocities due to the strong anisotropy in CFRP. The performance of the PA imaging combined with the SAFT was checked with artificial delaminations in a cross-ply CFRP specimen. It was shown that the PA wave had a wide frequency band and our method offered a high spatial resolution image.

DOI： 10.1541/ieejeiss.139.142

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1063/1.503163

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/transjsme.18-00192

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejam.74.I_75

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejam.73.I_115

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRITISH INST NON-DESTRUCTIVE TESTING  

An ultrasonic measurement method has been developed to determine the crystal growth angle of a unidirectional solidification material by using an ultrasonic array probe. Candidate crystal growth directions of the unidirectional solidification material are derived to within an error of +/- 5 degrees by evaluating the wave height levels of echoes measured with the focal laws of each assumed crystal growth angle. Moreover, high-precision ultrasonic testing is realised based on the focal laws considered with the candidate crystal growth angle.

DOI： 10.1784/insi.2017.59.7.351

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This study proposes an elastodynamic time-reversal imaging method for the shape reconstruction of flaws with the traction-free boundary. The proposed method is a generalization of the synthetic aperture focusing technique (SAFT) implemented with the aid of time-reversal back-propagation computation. The reconstruction formula is derived from the boundary condition applied on the flaw boundary without using a diffraction theory yielding an inherently normalized objective function. No restriction is imposed on the wave source or the material properties as long as the wave medium is linearly elastic and lossless. There are two major advantages with the proposed method. First, it is free from ray tracing. The method can thus work with an arbitrary source and the wave modes including inhomogeneous waves. Second, signal conditioning is not required to focus a scattered field to the correct location in the reconstructed image. Numerical examples are presented to demonstrate the performance and benefits of the proposed method. In the numerical examples, the shape of cavities and cracks in an elastic layer is reconstructed from synthetic data. The results show that the method works well with the reverberating incident fields in which inhomogeneous and body waves coexist. Also demonstrated is that the curvature of the cavities is resolved well at the scale of the incident wave length. Through the numerical examples, the method is shown to be a versatile imaging method potentially useful for ultrasonic nondestructive characterization of small flaws. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.wavemoti.2016.12.007

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

© 2017 Author(s). The use of fiber reinforced plastics (FRPs) as structural components has significantly increased in recent years. FRPs are made of stacks of plies, each of which is reinforced by fibers. When modeling ultrasonic wave propagation in FRPs, it is important to introduce three-dimensional mesoscopic and microscopic structures to account for the anisotropy and heterogeneity caused by fiber orientation and the lay-up of laminates. In this study, a finite element method using an image-based modeling is applied to simulation of ultrasonic wave propagation in a carbon FRP (CFRP). Here, the elastic stiffness of a single ply is determined using a homogenization method, where a CFRP microstructure is incorporated on the basis of a two-scale asymptotic expansion. The wave propagation in a CFRP specimen composed of unidirectionally aligned fibers is calculated, and the simulation results are compared to visualization results obtained for ultrasonic wave propagation using a laser scanning device.

DOI： 10.1063/1.4974729

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRITISH INST NON-DESTRUCTIVE TESTING  

When a guided wave is applied to a structural component in civil infrastructure, it is important to note the dimensions of the cross-section and the heterogeneity of the components. In this study, we propose a wireless measurement system to measure the guided wave in the kHz frequency range. The guided wave was excited with an impact hammer. It was then received with wireless accelerometers at multiple points. In order to enhance the accuracy of the guided wave testing, a propagation mode representing wave packets with different wave velocities is required. A semi-analytical finite element method was utilised to obtain the dispersion curve of the propagation mode. The numerically calculated and the measured dispersion curves showed good agreement for the I-beam metal specimen. Wave components with zero group velocity were observed in the measured dispersion curve. Investigations revealed that the components were caused by a natural vibration mode.

DOI： 10.1784/insi.2017.59.2.77

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASCE-AMER SOC CIVIL ENGINEERS  

Nondestructive testing in concrete is complex due to its nonhomogeneous ingredients. The presence of varying sizes of aggregates in concrete results in nonlinear characteristics. This paper aims to compare mortar and normal concrete with varying aggregate sizes. The specimens are damaged gradually with loading and unloading paths. Fast Fourier transform (FFT) of the recorded time domain waveforms is conducted to show the frequency spectra. The amplitude of the second harmonic frequency is used as a reference to the internal damage. The analysis of the nonlinear ultrasonic parameter second harmonic amplitude is used according to each loading branch with two damage levels: total and incremental. Results showed that the magnitude of the total damage produced by mortar at the last loading branch was relatively lower than all of the concrete mixes with different sizes of aggregates. The magnitude of the incremental damage produced by mortar in every step load consistently increased as the load increased. For the normal concrete with different sizes of aggregates, the highest total damage was obtained when mixed with large aggregates. According to a previous study using a finite-element model, increasing the aggregates' size in concrete increased the crack width. This could have led to the increase in the magnitude of the normalized second harmonic ratio. On the other hand, the incremental damage of concrete with different sizes of aggregates varied per loading branch. These results indicated the complexity of concrete as a heterogeneous material where it grew differently through formation of microcracks that varied from one loading branch to another.

DOI： 10.1061/(ASCE)MT.1943-5533.0001726

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

<p>The contact and non-contact behaviors of material interfaces generate harmonics arising from interactions with large amplitude incident waves. In this phenomenon, which is called contact acoustic nonlinearity (CAN), intermittent impacts by an incident wave cause the interface contact phase to alternate between contact and separation. This paper proposes a method for numerical simulation of CAN using an elastodynamic finite integration technique (EFIT). The accuracy of the EFIT simulation was verified through comparison with an analytical solution. In one-dimensional CAN theory, a wave penetrating at an interface demonstrates a sawtooth waveform indicating that the interface is closing with a constant velocity. Simulation results revealed that the closing velocity is determined by the compressive stress of the material, and experimental measurements on a polymethylmethacrylate specimen revealed the harmonics caused by the sawtooth wave.</p>

DOI： 10.1299/mel.16-00605

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

A three-dimensional visualization system was developed to investigate the dynamic state of bridge components using portable sensors located at multiple points. The system utilizes wireless data transfer and real-time signal processing for on-site output of the dynamic oscillation of bridge components. Vibrational modes (bending, twisting, and translation) are determined upon excitation by an external load. In this study, a sensor fusion technique was introduced to enhance the accuracy of motion visualization. An angular velocity sensor and an accelerometer were mounted within each sensor box. The same sensor boxes were prepared, and boxes were placed at 12 positions in all. The performance of the system was checked using a mock-up reinforced concrete beam. In cyclic loading tests of the mock-up, variations in the natural vibration frequency and its mode shape were observed. It was shown that disturbance of the initial motion may be used to detect crack initiation, and that changes in the mode shape may be used to detect the location of the damaged area. (C) 2016 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.proeng.2017.04.462

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The use of ultrasonic ways to conduct nondestructive evaluation has significantly increased in recent years. A post-processing beam-forming technique that utilizes a complete set of signals of all combinations of transmission and reception el-ements was proposed as an array imaging technique. In this study, a delay-and-sum beam reconstruction method utilizing post-processing was applied to the imaging of internal voids and reinforced steel bars in concrete material. Due to the high attenuation of the ultrasonic wave in concrete, it is necessary to use an ultrasonic wave as the incident wave at low frequencies and high in-tensities. In this study, an array transducer with a total of 16 elements was designed on the basis of a multigaussian beam model. The center frequency of the transducer was 50 kHz, and low frequency imaging was achieved by performing computations using a graphics processing unit accelerators in the post processing beam formation. The results indicated that the shapes of through holes and steel bars in a concrete specimen with 700 mm height were reconstructed with high resolution.

DOI： 10.1063/1.4974634

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Association for Computer Methods and Advances in Geomechanics (IACMAG)  

The aim of this study is to identify several cavities in the ground by Particle Filter and Elastic Wave Simulation. The degraded area or cavity in the ground can bring great disaster. To prevent and repair them, accurate identification of position and size of these cavities is essential. However, it is very difficult to identify them with only geophysical exploration. This paper focuses on the identification of two and three cavities in the ground. To analyze the propagation of elastic wave, Elastic Finite Integration Technique (EFIT) was applied, which is a type of Finite Difference Method (FDM). Receivers were placed both on and under the ground. In the first step, analysis was carried out on a model with two and three cavities in any position of the ground. Elastic waves were generated from one transmitter placed on the ground. The elastic wave was scattered by the material interfaces and the velocity in the horizontal direction was recorded by twenty receivers, 8 placed above and 12 placed under the ground. These velocities in the horizontal direction were used as observation data. In the second step, the position and size of the cavities were identified by Particle Filter. 10000 models with varying position and size of cavity (assumed to be a circle) were generated. In each case, only one cavity was assumed in the ground. The velocities in the horizontal direction from these models were used as simulation data. Particle Filter was applied to observation data and simulation data, and the likelihood of each particle was calculated. Although only one cavity was assumed in each model, two or three peaks were found in the distribution of likelihood. From this result, the number of cavities has been also identified as well as their position and the size.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

&nbsp;We have analyzed the periodically measured data using the high-accuracy pavement-condition measuring vehicle in expressways of Shikoku, to fully understand the progress of porous asphalt pavement damages. As a result, it is found that when the local subsidence phenomena occur, they would develop from cracks to potholes in a short time. It is very difficult to find these damages earlier even through the conventional evaluation indexes (cracks, rutting, flatness) or survey frequency. This study makes it possible to quantify the risk of pothole occurrences, by identifying the damaging index of accelerating the local subsidence phenomena on the porous pavement by applying Survival Time Analysis, and by estimating the Survival Curve classified by the damaging factors which influence the increasing pothole occurrence risks. This report will be the basic documents for the repair planning which will prolong the porous asphalt pavement life, and contribute to reducing the pothole occurrence risks by proposing the quantifying evaluation flow based on the analysis results.

DOI： 10.2208/jscejpe.72.I_115

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

In this study, we used a flexible array transducer to obtain images of flaws in materials with irregular surfaces. The transducer was manufactured from a 1-3 composite made of piezoelectric zirconate titanate and epoxy resin, and covered with neoprene rubber layers. An approach that involved combining a flexible array transducer and full matrix capture (FMC) is effective, because the surface geometry and flaw signal data can be separately measured and merged during post-processing. The disadvantage of the flexible array transducer is its narrow frequency band due to the thin damping material. To enhance the spatial resolution, we used the scattering amplitude extracted from raw signal data. We also introduced a numerical apodization technique to suppress the influence of side lobe. We validated the performance of the proposed method by measuring the signals from artificial flaws in aluminum specimens, performing high-speed FMC imaging using graphic processing unit computation. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ndteint.2016.04.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

When modeling ultrasonic wave propagation in metals, it is important to introduce mesoscopic crystalline structures because the anisotropy of the crystal structure and the heterogeneity of grains disturb ultrasonic waves. In this paper, a three-dimensional (3D) polycrystalline structure generated by multiphase-field modeling was introduced to ultrasonic simulation for nondestructive testing. 3D finite-element simulations of ultrasonic waves were validated and compared with visualization results obtained from laser Doppler vibrometer measurements. The simulation results and measurements showed good agreement with respect to the velocity and front shape of the pressure wave, as well as multiple scattering due to grains. This paper discussed the applicability of a transversely isotropic approach to ultrasonic wave propagation in a polycrystalline metal with columnar structures. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ultras.2015.12.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

To understand the characteristics of ultrasonic wave propagation in concrete more completely, we propose a time domain simulation tool based on the finite integration technique (FIT) and an image-based modeling approach. When modeling ultrasonic wave propagation in concrete, it is important to introduce three-dimensional mesoscopic and microscopic structures because ultrasonic waves in solids are transmitted by mechanical interaction between adjacent media. In this paper, wave velocity, center frequency, and attenuation of ultrasonic waves in concrete are evaluated quantitatively by comparing the waveforms obtained by FIT simulation with those obtained by experimental measurement. It was observed that these factors were in good agreement between the simulation and measurements. It was also observed that amplitude of the transmitted signal was sensitive to the allocation pattern of the aggregates. Thus, attenuation due to multiple scattering by aggregates is more dominant than the attenuation by intrinsic absorption and geometrical spreading in concrete. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.conbuildmat.2014.12.049

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/transjsme.15-00471

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/s40712-015-0050-y

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Language：Japanese   Publisher：日本工業出版  

CiNii Books

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

Guided wave has already been introduced to a wide variety of nondestructive testing especially for plate and pipe components. The shape of the cross section of the infrastructure is different in every portion, and the components consist of heterogeneous materials such as concrete and reinforced steel bar. Therefore it is useful to know the property of the guided wave in the target material prior to the testing. In this research, we adopted two numerical tools to assist the guided wave testing. One is the semi-analytical finite element method (SAFE), and the other is the elastodynamic finite integration technique (EFIT). The SAFE and EFIT were used to obtain the dispersion curve and the transient wave propagation, respectively. These methods were validated with the experimental measurement using an I-beam metal specimen. In the measurement, we used a wireless experimental system to receive signals of the guided wave. The guided wave was excited with an impact hammer, and then received with wireless accelerometers at multiple points. The simulation results and measurements showed good agreement with respect to the velocity dispersion curve, and the polarization shape in the propagation.

DOI： 10.2208/jscejam.71.I_813

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Acoustical Society of Japan  

To better understand wave propagation and scattering phenomena in noncontact ultrasonic testing (UT), we have developed a time domain simulation tool to model wave propagation in air and solids. The tool is based on the finite integration technique (FIT) and an image-based modeling approach. The image-based FIT can treat the calculation of acoustic, elastic, and coupled waves in a unified grid form. In this paper, we first investigate the accuracy of the interface condition in FIT modeling by comparing numerical results with analytical solutions of transmission and reflection coefficients. Then we validate the FIT using measured signals in guided wave testing with air-coupled transducers. To simulate noncontact UT, a fine mesh is required in the FIT because the wavelength in air is much smaller than that in a solid. To solve the numerical problem with the finer mesh at high speed, we introduce a parallel computation technique with general-purpose computing on graphics processing units (GPUs). It is shown that the noncontact UT simulation can be executed within a reasonable time and with reasonable accuracy using multiple GPUs.

DOI： 10.1250/ast.35.260

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejam.70.10

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

To better understand the characteristics of ultrasonic wave propagation in concrete, we propose a time domain simulation tool. The tool is based on the elastodynamic finite integration technique (EFIT). When modeling ultrasonic wave propagation in concrete, it is important to introduce a three-dimensional (3D) concrete structure including aggregate distribution. Because ultrasonic waves in solids are propagating as a consequence of the mechanical interaction between adjacent media. In this paper, the wave velocity, center frequency, and attenuation of ultrasonic wave in concrete were quantitatively evaluated by comparing the waveforms obtained by the EFIT simulation with those found in experimental measurements. These values were in good agreement between the simulation and the measurement. Since the amplitude of the ultrasonic wave is sensitive to the allocation pattern of aggregates, it can be understood that the scattering attenuation is more dominant than attenuations due to the intrinsic absorption and geometrical spreading in concrete.

DOI： 10.2208/jscejam.70.I_203

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Language：Japanese  

DOI： 10.2208/jscejam.69.I_19

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Using a MEMS sensor network, we develop a three dimensional visualization system of dynamic behavior for a bridge deck. In our system, time series of acceleration data measured simultaneously at multisite are transferred to a laptop computer at a base-station with the wireless data connection, and then converted to displacement data by a numerical integral method. From the visualization results, the characteristic vibration modes including bending and torsional higher modes can be identified by applying digital filters of narrow bands. Here, the data measurement for the deck of a pedestrian bridge is conducted, and some characteristic vibration modes are extracted from the visualization results. The vibration modes obtained from the experiment show good agreements with numerical results obtained by a finite element method based on the Lanczos method.

DOI： 10.11532/structcivil.59A.1170

J-GLOBAL

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The present study explores mode conversion of shear horizontal (SH) guided wave when it impinges on smooth defects in plates. The fundamental (SH0) and the first higher (SH1) modes were selectively generated by an electromagnetic acoustic transducer in aluminum plates and the propagating modes at various points were detected by a pinducer. The defects had a flat bottom region and tapered edges. Remaining thickness at the bottom defected region was smaller than the so-called cut-off thickness of SH1 mode. Both modes exhibited unique mode conversion behaviors in tapered edge, which were interpreted with the dispersion relation. Total reflection of SH1 mode was also observed at a specific condition. Numerical simulation revealed that the continuous wavenumber change in the tapered region and the consequent zero value at cut-off thickness cause this total reflection. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ndteint.2011.10.004

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Most commercial ultrasonic phased array systems implement B- and C-scan methods which use flight time and amplitude of flaw echoes. However, these methods are based on the fundamental ray-tracing theory in homogeneous media, and they are not directly applicable to heterogeneous media because of the complicated phenomenon of wave propagation. Time reversal techniques are adaptive methods that can be used in nondestructive evaluation to improve flaw detection in heterogeneous media. In this study, we propose a simulation-aided flaw imaging method based on the time reversal approach. Scattered waves from a flaw are recorded using an array transducer, and the time-reversed waves are re-emitted in the image-based FIT simulation. The re-emitted waves propagate through the heterogeneous media and focus on the flaw. The shape of the flaw can be visually estimated from the focal point of the ultrasonic wave in the simulation.

DOI： 10.1299/jmmp.6.771

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejam.68.I_227

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejam.67.I_885

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Language：English   Publishing type：Research paper (international conference proceedings)  

A signal prediction simulation tool for ultrasonic testing (UT) has been developed by combining the finite integration technique (FIT) with an image-based modeling approach. A realistic numerical model of a target can be made directly from digital images such as X-ray CT and three dimensional point cloud data. The image-based FIT for UT is accelerated using graphics processing units (GPUs) with Compute Unified Device Architecture (CUDA) Fortran. The methodology is described, and checked by numerical experiments using multiple GPU boards. The calculation speed can be dramatically improved compared to that obtained by running the same simulation on a conventional CPU. As an application of the image-based FIT, we propose a simulation-aided flaw reconstruction method for UT by means of the time reversal approach. Scattered waves from a flaw are recorded using an array transducer, and the time-reversed waves are re-emitted to numerical model in the FIT simulation. The re-emitted waves propagate through the heterogeneous media and focus on the flaw. The shape of the flaw can be visually estimated from the focal point of the ultrasonic wave in the simulation.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Presently, ultrasonic and electromagnetic waves are often used for the quantitative nondestructive testing of concrete. The evaluation of material deterioration and detection of defects in concrete are carried out using ultrasonic waves. On the other hand, the positions of reinforced bars can be reconstructed by using electromagnetic waves. In order to gain a better understanding of ultrasonic and electromagnetic waves in concrete, it is useful to model the wave propagation and scattering process explicitly in the time domain. This study presents a technique for numerical time domain modelings of ultrasonic and electromagnetic waves. Our simulation tool is based on a combination of the finite integration technique (FIT) and an image-based modeling approach. The FIT is a grid-based spatial discretization method that works in conjunction with a leap-frog-type explicit scheme. In the image-based modeling approach, geometries of concrete are determined using a digital image, e.g., a cross-sectional image or CT data. Then the processed pixel or voxel data are directly fed into the FIT. We demonstrate simulations of the contact ultrasonic method and electromagnetic radar method for concrete. The utility of the image-based FIT is validated with experimentally measured data.

DOI： 10.1299/jcst.6.28

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Three dimensional (3D) image-based FIT has been proposed to predict ultrasonic wave in a target material with complex outer surfaces or various inclusions. In this study, we accelerate the 3D image-based FIT by means of some explicit parallelization techniques. By adopting flat MPI and MPI I/O techniques, our programming code can execute with a high speed and show good scalabilities in large size problems. Here we introduce a new image-based modeling that the target model can be made with a 3D curve measurement apparatus based on the light pattern projection method. The surface irregularities of the corroded part in a steel plate can be precisely modeled and the ultrasonic wave simulation for the corroded steel plate is demonstrated.

DOI： 10.1063/1.4716303

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Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, a new method for reconstructing a shape of plate thinning from reflection coefficients of ultrasonic guided SH or Lamb waves is presented. The inverse formulation is based on the integral form of scattered waves by plate thinning flaws. By introducing the far field expression of Green's functions and Born approximation into the integral equation, a Fourier transform pair is obtained between the shape function of thinning flaw and reflection coefficients in frequency domain. The shape functions of thinning flaws are reconstructed by means of the inverse Fourier transform of reflection coefficients of guided waves. Numerical examples are illustrated to show the validity and effectiveness of our inverse approach. It is shown that flaws' locations and depths are well estimated if the frequency ranges for the inverse Fourier transform are chosen properly, corresponding to the flaw configurations.

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DOI： 10.2208/jscejam.67.I_161

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

There is a phased array technique which makes use of flaw echoes, measured by every two-element combination as a pulser and a receiver, to synthesize high amplitude beams for any arbitrary angle and/or focal depth. Using this full waveform sampling and processing (FSAP) technique, we show a flaw reconstruction method for the angle beam phased array ultrasonic testing. In the case of the angle beam testing, it is necessary to estimate a beam path from a wedge to a specimen appropriately and to consider the mode conversion at the wedge-specimen interface. The main feature of our method is the use of processed wave data, called "scattering amplitude", which is extracted from each flaw echo. First, the basic principle of the reconstruction method is described and then some flaw reconstructions are demonstrated. The resolution of the flaw images and the accuracy of flaw sizing can be improved by means of the scattering amplitude. © 2011 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaia.77.1112

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaia.77.111

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

This paper presents a numerical time domain modeling of acoustic, elastodynamic, and coupled waves. Our simulation tool is based on the finite integration technique (FIT) and combined with an image-based modeling approach. The FIT is a grid-based spatial discretization method that works in conjunction with a leap-frog type explicit scheme. In our simulation, geometries of targets are determined by a digital image, then the processed pixel or voxel data is directly fed into the wave simulation by the FIT. Here the modeling and simulation of the wave propagation in a concrete material including fluid-solid interactions and a non-contact ultrasonic testing are demonstrated.

DOI： 10.1063/1.3591920

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Time domain simulation tools for ultrasonic wave propagation in a target material with a complex outer surface or various inclusions are developed by combining the finite integration technique (FIT) and the finite element method (FEM) with an image-based modeling. In our simulation, the geometry of the target is determined by a digital image such as X-ray picture, CAD data, etc. and the processed voxel data is directly fed into the numerical calculation with the FIT or FEM. The accuracy of the two methods is discussed by comparison with the boundary element method. A simulation of the ultrasonic testing for a concrete material is shown with the 3-D image-based FIT.

DOI： 10.1063/1.3591839

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11396/jjsndi.59.231

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Non-Destructive Inspection  

There is a phased array technique which makes use of scattered longitudinal waves, measured by every two-element combination as a pulser and a receiver, to synthesize high amplitude beams for any arbitrary angle and/or focal depth. Using this full waveform sampling technique, we show a new flaw reconstruction method with strong focused beams at all pixels of the imaging area. The main feature of our method is the use of processed wave data, called "scattering amplitude", which is extracted from each flaw echo in the signal matrix. First, the basic principle of the imaging method is described and then some ultrasonic imagings are demonstrated. An apodization technique can also be incorporated in our imaging method. Here, the availability of the apodization is shown in comparison with multi-point imaging.

DOI： 10.11396/jjsndi.59.277

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.11345/nctam.58.9

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The ultrasonic testing (UT) for an austenitic steel with welds is difficult due to the acoustic anisotropy and local heterogeneity. The ultrasonic wave in the austenitic steel is skewed along crystallographic directions and scattered by weld boundaries. For reliable UT, a straightforward simulation tool to predict the wave propagation is desired. Here a combined method of elasto-dynamic finite integration technique (EFIT) and digital image processing is developed as a wave simulation tool for UT. In our simulation, a picture of the surface of the steel bar with a V-groove weld is scanned and fed into the image based EFIT modeling. An example of a two dimensional simulation of a phased array UT in an austenitic steel bar is demonstrated.

DOI： 10.1299/jsmemecjo.2009.6.0_423

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

A multi-Gaussian beam (MGB) model without the paraxial approximation has been proposed in order to calculate off-axis wave fields from an ultrasonic transducer as well as on-axis wave fields. Using this MGB model, we can model three dimensional (3-D) elastic wave fields radiated from an array transducer to a solid with an efficient computational time. In this paper, brief formulations of the MGB model are described first and then the accuracy of the MGB model is checked in comparison with results of the Rayleigh-Sommerfeld numerical integral model. As applications of the MGB model, we investigate performances of both linear and matrix phased array transducers using the MGB model. Also the 3-D wave fields from the matrix phased array transducer in solid are visualized.

DOI： 10.1299/kikaia.75.1468

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jsceja.65.505

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The ultrasonic testing (UT) of an austenitic steel with welds is difficult due to the acoustic anisotropy and local heterogeneity. The ultrasonic wave in the austenitic steel is skewed along crystallographic directions and scattered by weld boundaries. For reliable UT, a straightforward simulation tool to predict the wave propagation is desired. Here a combined method of elastodynamic finite integration technique (EFIT) and digital image processing is developed as a wave simulation tool for UT. The EFIT is a grid-based explicit numerical method and easily treats different boundary conditions which are essential to model wave propagation in heterogeneous materials. In this study, the EFIT formulation in anisotropic and heterogeneous materials is briefly described and an example of a two dimensional simulation of a phased array UT in an austenitic steel bar is demonstrated. In our simulation, a picture of the surface of the steel bar with a V-groove weld is scanned and fed into the image based EFIT modeling.

DOI： 10.1299/jmmp.3.1256

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

A time domain simulation tool for the ultrasonic propagation in concrete is developed using the elastodynamic finite integration technique (EFIT) and the image-based modeling. The EFIT is a grid-based time domain differential technique and easily treats the different boundary conditions in the inhomogeneous material such as concrete. Here, the geometry of concrete is determined by a scanned image of concrete and the processed color bitmap image is fed into the EFIT. Although the ultrasonic wave simulation in such a complex material requires much time to calculate, we here execute the EFIT by a parallel computing technique using a shared memory computer system. In this study, formulations of the EFIT and treatment of the different boundary conditions are briefly described and examples of shear horizontal wave propagations in reinforced concrete are demonstrated. The methodology and performance of parallelization for the EFIT are also discussed.

DOI： 10.1299/jmmp.2.1462

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

A finite difference time domain method (FDTD) is based on a grid-based time domain differential technique, in which wave equations are solved in a leapfrog manner. It is required to discretize a whole target domain into computational grids with an adequate size. Therefore computational burden increases if the computational domain is much larger than the wave length. To solve such a large-scale problem in high speed, we apply a parallel computing technique to the FDTD. OpeuMP is an interface to execute program codes in parallel using a shared memory system of computers. As an example of large-scale analysis, SH wave propagations in concrete material are demonstrated in this study.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Publishing type：Research paper (international conference proceedings)   Publisher：AIP  

DOI： 10.1063/1.2902731

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

To enhance the detectability in the phased array UT, it is essential to have well knowledge on the characteristics of ultrasonic waves from array transducers. This paper proposes a mathematical model of the array transducer and a simulation tool to predict the flaw echoes. The modeling of an array transducer is based on the Rayleigh-Sommerfeld integral and the scattered waves from flaws are calculated with the fast multipole BEM (FMBEM). By using the FMBEM, we can solve large scale scattering problems with relatively low computational cost. Here we focus on the transient wave analysis, in which a pulse-shaped wave is used for exciting elements of the array transducer.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

NDT techniques based on the ultrasonic phased array technology are applied in various industrial contexts. For the reliable application of phased array techniques, it is essential to have well knowledge on the characteristics of radiated beam profile from array transducer and ultrasonic wave propagation in test materials. This paper proposes a mathematical model of the phased array transducer and a simulation tool to estimate transmitted waves from the transducer and scattered waves from flaws. The simulation tool is based on the BEM, and a pulse shaped wave is used in this analysis for the transient wave propagation. Here wave fields are visualized to understand the feature of scattered waveforms measured at the array transducer.

DOI： 10.1299/kikaia.73.88

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Other Link： https://jlc.jst.go.jp/DN/JALC/00289895120?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Ultrasonic matrix array transducers have the advantage of receiving flaw echoes simultaneously at various points on a flat surface of the test material. Here we propose 3-D imaging techniques to reconstruct flaw shapes with the array transducer. These techniques are based on linearized inverse scattering methods in the frequency domain. The principal operation of these methods is the integration of the wave data in the K-space. In this study, the 3-D fast Fourier transform is introduced into the inversion algorithm to evaluate the integral in the K-space. Performance of the 3-D imaging technique is demonstrated by using the numerically calculated waveforms by the fast multipole BEM.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/journalam.10.61

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

A numerical modeling of an interface including a local imperfection and simulation of the ultrasonic wave propagation through the interface are described in this paper. We propose an imperfection model with the interface condition depending on displacement-stress states. This phenomenon generates superharmonics in the transmitted wave through the interface. The interface model is incorporated into a time domain boundary element method and transmitted waveforms are calculated. Simulation results show that the amplitude ratio of superharmonic waves changes according to the initial opening gap and the length of the imperfection area.

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Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes a mathematical model based on a linear time-shift invariant (LTI) system for nondestructive ultrasonic testing (UT). We consider here an entire model of the immersion UT including ultrasonic wave generation in water, transmission from water to solid and vice versa, and scattering by flaws in the solid. A multi-Gaussian beam model is introduced to express wave propagation in both transmission and reception processes. The scattering process is calculated by means of boundary element method. These processes are expressed by frequency dependent modules in the LTI system, and the total output signal is obtained as a product of the modules. The performance of this model is shown by numerical simulations of flaw-echoes from internal and surface-breaking cracks.

DOI： 10.2208/jsceseee.23.287s

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/journalam.9.107

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/journalam.8.95

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11396/jjsndi.54.562

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Ultrasonic linear array transducer has the advantage of receiving flaw echoes simultaneously at various points on a flat surface of the specimen. We here develop new inverse scattering methods for the imaging of flaw shapes using the array transducer. In this study, an algorithm of synthetic aperture focusing technique is combined with the linearized inverse scattering methods to reconstruct flaw shape functions. Since these methods are performed by means of 2-D FFT, high-speed imaging of flaw shapes is possible with a portable computer. In numerical simulations, the imaging results show the appropriate shape and location of internal flaws.

DOI： 10.1299/jsmemecjo.2005.1.0_679

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Language：English   Publishing type：Research paper (scientific journal)  

A modified three-dimensional inverse scattering method is applied to reconstruct the shape of a three-dimensional flaw in a cylindrical specimen. In this modified method, a measurement plane is restricted to the plane perpendicular to the axis of the cylindrical specimen. Thus the cross-sectional image of the flaw can be obtained. By moving the measurement plane along the axis of the cylindrical specimen, the cross-sectional image is obtained for each measurement plane. The three-dimensional flaw image is reconstructed by piling up the obtained cross-sectional images. Cylindrical specimens with a cylindrical cavity model and with a hemi- spheroidal cavity model are prepared. The performance of the modified method to reconstruct the three-dimensional flaw is verified by using the experimentally measured waveforms.

DOI： 10.2208/jsceseee.22.193s

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The linearized inverse scattering methods based on the Born and Kirchhoff approximations are investigated with an emphasis on applicability of the transverse (T)-transverse (T) pulse-echo mode. The linearized methods for the longitudinal (L) -longitudinal (L) pulse-echo mode are first summarized for the latter use of comparison. Then the linearization process for the T-T mode is presented. In order to recognize a difference in the scattering amplitudes for the L-L and T-T modes, the backscattered waveforms are calculated for a defect model of two cavities and the effect of strong interactions is visualized for the T-T mode. The linearized inverse scattering analysis is carried out for both of the L-L and T-T modes by utilizing the whole backscattered waveforms. The performance of the geometrical reconstruction for the T-T mode inversion is discussed in comparison with the L-L mode inversion. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/S0955-7997(03)00054-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TRANS TECH PUBLICATIONS LTD  

The Born inverse scattering method is applied to the shape reconstruction of flaws in the concrete materials. To accelerate the inversion process, the algorithm of the fast Fourier transform is introduced in the integration process of the scattering amplitude. The concrete specimens with flaw models are prepared and the scattered waveforms from flaws are acquired in the pulse-echo mode. The shape of flaws is reconstructed by using the measured waveforms and the performance of the inversion method is demonstrated experimentally.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/journalam.7.271

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The elastodynamic boundary element method (BEM) is applied to the visualization of the scattered wave field through a fluid-solid interface. In the formulation of BEM, the multigaussian beam model is introduced in order to express the incident wave field radiated from the immersion transducer. The unknown quantities on the crack boundary are determined by the BEM, their the wave field around the crack in solid is visualized with the integral representation of the scattered wave. To obtain the scattered waveforms in fluid, a far-field expression of the Green's function for a fluid-solid coupling medium is adopted in this study.

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Language：English   Publishing type：Research paper (scientific journal)  

This chapter provides an overview of 3D Born and Kirchhoff inverse scattering methods, which are modified for a cylindrical specimen that includes 3D flaws. The measurement area in the modified methods is restricted in the plane perpendicular to the axis of the cylindrical specimen. The incident wave with the Gaussian amplitude profile is introduced in the numerical analysis, to examine the effect of the incident beam radius. The modified methods are applied to the aluminum specimen with a cylindrical flaw and the performance of the modified methods is confirmed by the experimental measurement. The reconstructed images showed that the inversion with the wide incident beam gave the representative size of the flaw and the narrow beam gave the cross-sectional image of the flaw. It is preferable to select the radius of the ultrasonic beam adequately according to the purpose and accuracy of the inspection. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/B978-008044268-6/50021-1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：土木学会  

DOI： 10.2208/journalam.6.69

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

The elastodynamic inversions for the ultrasonic pitch-catch mode are investigated in order to take advantage of the waveforms measured at multi-points. The inversion is based on Born or Kirchhoff approximation to linearize the integral expression for the scattered wave. The multi-point measurements are applied to the shape reconstructions for two flaws of a cavity and a crack. It is confirmed that the adjacent part of two flaws is clearly reconstructed by the multi- point measurements, even though the dynamic interaction effects of flaws are included in the measured waveforms.

DOI： 10.2208/jscej.2003.745_143

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/journalam.6.1073

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WIT PRESS  

The elastodynamic boundary element method is applied to the ultrasonic nondestructive evaluation with an emphasis on visualization of the scattered wave field around flaws. First, the unknown quantities on the flaw boundaries are determined by the boundary element method. Then near field calculations are performed by using the integral representation of the scattered wave field. The calculated near fields are visualized in the vicinity of flaws. The results of the near field visualization are useful to interpret the far field backscattered waveforms. The backscattered waveforms at the transducer position are obtained from the far field expression of the scattered wave. It is shown from the numerical examples that the combination of the far field backscattered waveform and the near field visualization makes it possible to characterize the geometrical property of flaws.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The linearized inverse scattering methods based on Born and Kirchhoff approximations are utilized for the flaw reconstruction in an elastic material with flat surfaces. The flaw shape can be reconstructed through the 2-D FFT of scattering amplitudes in the K-space. The scattering amplitudes are extracted from the measured waveforms by data processing with the reference waveforms from a small circular hole.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Three dimensional Born and Kirchhoff inverse scattering methods are modified to convenient forms for a cylindrical specimen that includes three dimensional defects. The measurement area in the modified methods is restricted in the plane perpendicular to the axis of cylindrical specimen. The modified methods are applied to the cement paste specimen with an egg-shaped defect and the performance of the modified methods is confirmed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Two linearized inverse scattering methods are investigated to reconstruct the shape of flaws in the elastic solid. One is based on the Born approximation and the other is based on the Kirchhoff approximation. The Born inversion is sensitive to the volumetric flaw but not to a crack-like flaw. On the other hand, the Kirchhoff inversion reacts to both boundaries of volumetric and crack-like flaws. The combined use of Born and Kirchhoff inversions leads to the classification method of flaw type. The performance of the proposed classification procedure is demonstrated by the numerical simulations and then by the experimental measurements for the two-dimensional models of flaws. An example for the three-dimensional shape reconstruction is also shown by using the numerically calculated backscattering amplitudes. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0165-2125(02)00035-5

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

A shape reconstruction method in an inhomogeneous material is investigated by using the ultrasonic waveforms in this study. The frequency characteristics of phase velocity due to inhomogeneity of the material are introduced to the Born and Kirchhoff inversion algorithms. Here, the mortar specimens containing volume fractions of 5% and 10% inclusions are prepared. The results show that the Born and Kirchhoff inversions reconstruct the shape and size of the artificial defect in mortar specimens.

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/journalam.5.67

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Two linearized inverse scattering methods are investigated to classify the defect type in an elastic body. The methods are based on the Born and Kirchhoff approximations for the unknown displacement in the integral representation of scattered field. From the result of experimental measurement, the Born inversion reconstructs the volume of defects and the Kirchhoff inversion reconstructs the surface of defects. The combination of two inversion methods leads to the classification between volumetric defect and crack.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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DOI： 10.2208/journalam.4.15

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：土木学会  

DOI： 10.2208/journalam.3.91

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

A method of evaluating the macroscopic shape of defects in microscopically inhomogeneous material such as inclusion-reinforced composites is proposed by considering the order of scales that describes the mechanical behaviors (or physical phenomena). By using the method of multi-scale asymptotic expansions for field variables, the averaging technique with representative volume elements for inhomogeneous media becomes a reasonable tool to deal with the medium as a homogeneous one in macroscale. Therefore the linearized inverse scattering method along with Kirchhoff approximations can be applied to identify the shape of defects in macroscopically homogeneous media since the homogenization procedure replaces the media by homogeneous ones. Numerical examples show the capability of the proposed method to determine the shape of cracks whose sizes are much larger than the microscopic heterogeneities, which are invisible for ultrasonic waves.

DOI： 10.1299/kikaia.65.552

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Other Link： https://jlc.jst.go.jp/DN/JALC/00059805083?from=CiNii

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：土木学会  

DOI： 10.2208/journalam.1.167

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Lead author   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Language：Japanese   Publisher：日本工業出版  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this research, a flexible array transducer is used in conjunction with the full-waveform sampling and processing (FSAP) technique. The FSAP technique makes use of scattered longitudinal waves, measured by every two-element combination of the array transducer as a pulser and a receiver, to synthesize high amplitude beams for any points in an inspection area. Using a GPU calculation method, the FSAP can be executed at high speed while taking the irregular surface profile into account. Here, we develop a prototype for the FSAP imaging system using a high speed multiplexer which can switch ultrasonic transmission and reception in the two-element combination. The flaw reconstruction time in a metal with irregular surfaces is approximately 3 s in the case of 24 × 24 elements combinations.

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

It is essential for the nondestructive ultrasonic testing to predict the wave propagation mode in a long object such as pipe, plate, among others. To obtain the propagation mode in long objects with complicated cross section and local inhomogeneity, the semi-analytical finite element method (SAFE) has been proposed previously. In this study, the validity of the SAFE is checked with ultrasonic signals. Instead of using measured signals, we here use numerical signals which are calculated with the elastodynamic finite integration technique (FIT). The propagation mode and dispersion curves obtained from the SAFE and the FIT show a good agreement.

CiNii Books

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This study presents a flaw reconstruction method in concrete material with the full-waveform sampling and processing (FSAP) technique The FSAP is an ultrasonic phased array technique which makes use of scattered waves, measured by every two-element combination as a pulser and a receiver, to synthesize high amplitude beams for any focal point Here, we investigate the property of wave field in concrete using the elastodynamic finite in-tegration technique (EFIT) Since it is shown that wave dispersion is not significant in a frequency range of this measurement, a constant velocity is used in flaw reconstructions by the FSAP An internal flaw located on the depth of approximately 200mm can be reconstructed using an array transducer with 200 kHz center frequency

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

CiNii Books

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：English   Publisher：Steering committee of symposium on ultrasonic electronics  

CiNii Books

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Language：English   Publisher：Steering committee of symposium on ultrasonic electronics  

CiNii Books

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

Nowadays ultrasonic and electromagnetic waves are often used for the quantitative nondestructive testing of concrete. The evaluation of material deterioration and detection of defects in concrete are carried out using the ultrasonic wave. On the other hand, the position of reinforced bars can be reconstructed by using the electromagnetic wave. In order to obtain a better understanding of propagation of both ultrasonic and electromagnetic waves in concrete, it is effective to model the wave propagation and scattering process explicitly in the time domain. This study presents a numerical time domain modeling of ultrasonic and electromagnetic waves. Our simulation tool is based on the finite integration technique (FIT) and combined with an image based modeling approach. The FIT is a grid-based spatial discretization method that works in conjunction with a leap-frog type explicit scheme. In the image based modeling, geometries of concrete are determined by a digital image, e.g. a cross-sectional picture, CT data, etc. Then the processed pixel or voxel data are directly fed into the FIT. Here simulations of the contact ultrasonic method and electromagnetic radar method for concrete are demonstrated.

CiNii Books

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Language：Japanese  

J-GLOBAL

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：English   Publisher：Steering committee of symposium on ultrasonic electronics  

CiNii Books

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Language：Japanese  

CiNii Books

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DOI： 10.11345/japannctam.59.0.178.0

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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DOI： 10.1063/1.1916659

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：日本工業出版  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A linearized inverse scattering method is applied to the reconstruction of a damaged part in the interface of materials. In this study, cement-based material with a reinforcing steel bar is prepared, where a damaged part exists on the interface of the steel bar and cement-based materials. The experimental measurement is performed and it is shown that the linealized method reconstructs the part of imperfections on the interface.

DOI： 10.1299/jsmezairiki.2002.0_515

CiNii Books

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Event date： 2018.3

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Event date： 2017.10

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Event date： 2017.8

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Event date： 2017.8

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