Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Abstract The results of rotating eddy current testing can be regarded as the results superposed by uniform eddy current testing in orthogonal directions. However, in the case of directional nondestructive testing problems, such as weld... more
Abstract The results of rotating eddy current testing can be regarded as the results superposed by uniform eddy current testing in orthogonal directions. However, in the case of directional nondestructive testing problems, such as weld detection, only the results from the induced current that is perpendicular to the crack have the greatest sensitivity. In contrast, the results from other induced current orientations may experience substantial noise generated by welds. In this work, a brief method is proposed to transform the results of rotating eddy current testing into the results of uniform eddy current testing at the desired eddy current orientation. The experiments indicated a good match between the signal distribution and amplitude of the transformed results and the results of the uniform eddy current testing. Moreover, the proposed method was applied for weld detection. The results revealed that the weld noise significantly decreased and that the locations of slits could be clearly identified. The results validated that the proposed method can improve the detection ability and expand the application of the rotating eddy current testing technique.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
This study reports a board game design that would be an effective tool for teaching and learning the best mix of national power sources in a class concerning energy and sustainability in higher education courses. A board game was... more
This study reports a board game design that would be an effective tool for teaching and learning the best mix of national power sources in a class concerning energy and sustainability in higher education courses. A board game was developed to understand the characteristics of power sources from a Japanese viewpoint based on an earlier study of the authors. The purpose of the game is to satisfy electricity demands by choosing power sources and procuring the resources necessary for power generation to help develop a country. A total of 50 undergraduate and graduate students were asked to assess the game. The results of the questionnaire-based survey conducted after the game confirmed the students’ evaluation that the game was highly enjoyable and could serve as an effective tool for energy and environmental education in high schools or universities. In addition, the average of “the ratio of the power sources proper to win the game” given by the students was similar to Japanese power m...
Research Interests:
Research Interests:
The authors gather eddy current signals due to artificial stress corrosion cracking so that the data may be available to other researchers. Three cracks are introduced into an austenitic stainless steel plate, eddy current measurements... more
The authors gather eddy current signals due to artificial stress corrosion cracking so that the data may be available to other researchers. Three cracks are introduced into an austenitic stainless steel plate, eddy current measurements are performed, and then the plate is destroyed to observe the cross-sectional profiles of the cracks. The authors will offer the data, as well as
Research Interests:
Research Interests:
Research Interests:
In this paper, a novel nondestructive strategy is proposed for distinguishing differences between a stress corrosion crack (SCC) and a fatigue crack (FC) based on signals from eddy current testing (ECT). The strategy consists of... more
In this paper, a novel nondestructive strategy is proposed for distinguishing differences between a stress corrosion crack (SCC) and a fatigue crack (FC) based on signals from eddy current testing (ECT). The strategy consists of measurement procedures with a special ECT probe and crack type judgment scheme based on an index parameter that is defined as the amplitude ratio of the measured signals. An ECT probe, which can induce eddy current flowing mainly in a selected direction, is proposed and applied to detect crack signals by scanning along the crack with different probe orientations. It is clear that the ratio of the amplitudes of signals detected for parallel and perpendicular probe orientations is sensitive to the microstructure of the crack, i.e., the parameter is much bigger for a fatigue crack than that of a SCC. Therefore, whether a crack is a SCC or a FC can be recognized nondestructively by comparing the index parameter with a threshold value that can be previously deter...
Research Interests:
Research Interests:
Research Interests:
This study applies five stochastic inversion methods to the reconstruction of three-dimensional volumetric defect regions from eddy current testing signals, and evaluates their efficiencies in relation to this problem. The five stochastic... more
This study applies five stochastic inversion methods to the reconstruction of three-dimensional volumetric defect regions from eddy current testing signals, and evaluates their efficiencies in relation to this problem. The five stochastic methods considered here are iterative local search, tabu search, simple genetic algorithm, parameter-free genetic algorithms, and simulated annealing. Since stochastic methods require evaluation of many solution candidates, simulations
Research Interests: Engineering, Parallel Computing, Tabu Search, Simulated Annealing, Genetic Algorithm, and 12 moreNon Destructive Testing, Nondestructive testing, Mathematical Sciences, Inverse Problem, Simple Genetic Algorithm, Inverse Method, Eddy Current, Inversion, Three Dimensional, Eddy Current Testing, Parallel Computer, and Iterated Local Search
ABSTRACT This study evaluates modeling of thermal fatigue cracks by the finite element method from the view point of eddy current testing. Five artificial thermal fatigue cracks introduced into type 304 stainless steel plates were... more
ABSTRACT This study evaluates modeling of thermal fatigue cracks by the finite element method from the view point of eddy current testing. Five artificial thermal fatigue cracks introduced into type 304 stainless steel plates were prepared for the research. Eddy current signals were gathered by a differential type plus point probe and subsequent destructive tests were performed to confirm the true profiles of the cracks. Numerical simulation based on the results of eddy current testing and destructive tests were carried out to show how the thermal fatigue cracks should be modeled in numerical simulations. The results of the numerical simulations revealed that thermal fatigue cracks tend to be much less conductive than stress corrosion cracks if they are assumed to have uniform conductivity inside. The results also imply that taking consideration of magnetization induced by the thermal fatigue process enables eddy current signals to be analyzed more quantitatively.
Research Interests:
ABSTRACT This study measures electrical resistance of a stress corrosion crack directly by the four-terminal method to discuss appropriate modeling from the viewpoint of electromagnetic nondestructive evaluation. Two type-316 stainless... more
ABSTRACT This study measures electrical resistance of a stress corrosion crack directly by the four-terminal method to discuss appropriate modeling from the viewpoint of electromagnetic nondestructive evaluation. Two type-316 stainless steel plate specimens containing artificial stress corrosion cracks were prepared, and columnar samples containing penetrating cracks were cut from the plates for the measurements. The results obtained agree with recent reports discussing appropriate numerical modeling of stress corrosion cracking on the basis of finite element simulations. In contrast, this study also reveals that it is not always valid to assume that a stress corrosion crack has uniform conductivity internally.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
This study discusses numerical modeling of fatigue and stress corrosion cracking in eddy current simulations. Ten fatigue crack specimens and another 10 stress corrosion crack specimens are prepared for this purpose. The specimens are... more
This study discusses numerical modeling of fatigue and stress corrosion cracking in eddy current simulations. Ten fatigue crack specimens and another 10 stress corrosion crack specimens are prepared for this purpose. The specimens are made of type 316 stainless steel and measure 10mm in thickness for a general evaluation of the model. Eddy current inspections of the specimens are performed using a differential type plus point probe; the specimens then undergo destructive tests to confirm the true profiles of the cracks. Subsequent numerical simulations are conducted to evaluate the equivalent conductivity and width of the cracks. The simulations demonstrate that a fatigue crack can be modeled as a non-conductive region, and it is not necessary to know exactly how wide the opening of a fatigue crack is. They also revealed, in contrast, that stress corrosion cracking needs to be modeled as a conductive region with a certain width.
Research Interests: Engineering, Electromagnetism, Modeling, Finite element method, Stress corrosion cracking, and 13 moreMetrology, Numerical Simulation, Stainless Steel, Conductivity, Finite element simulation, Eddy Current, Numerical Model, Stress Corrosion Cracking, Eddy Current Testing, Austenitic stainless steel, Non Destructive Evaluation, Non Destructive Test, and Destructive test
ABSTRACT This study proposes an approach to gain information about the depth of near-side flaws using eddy currents. The approach utilizes only two coils, one of which works as an exciter and the other as a detector, like conventional... more
ABSTRACT This study proposes an approach to gain information about the depth of near-side flaws using eddy currents. The approach utilizes only two coils, one of which works as an exciter and the other as a detector, like conventional eddy current testing using a transmitter–receiver probe. The uniqueness of this approach is that signals obtained by this approach change significantly with the depth of a flaw even though the flaw is much deeper than the depth of penetration. After the physical background of the approach is explained, its validity is confirmed in experiments. The experiments utilize a 25mm thick austenitic stainless steel plate with five artificial rectangular slits of 40mm length, 0.5mm width, and 1, 5, 10, 15, and 20mm depth. The experiments confirm clear differences between signals generated by the five slits even although the exciter is driven at 50kHz at which the depth of penetration is approximately 2.0mm. Subsequent finite element simulations are carried out to confirm the validity of the experimental results and to support discussion about the physical background of the approach.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Engineering, Calculus, Finite Element Methods, Computational Modeling, Magnetic Materials, and 14 moreFinite Element, Finite Element Analysis, Magnetism, Physical sciences, Vectors, Ferromagnetic Materials, Three Dimensional, Inspection, Eddy Current Testing, Electromotive Force, Electromagnetic Forces, Remote Field Eddy Current Testing, Magnetic Flux, and Supercomputer
Research Interests:
Research Interests:
ABSTRACT This study experimentally investigates the efficacy of TE11 mode microwaves in detecting bend-region cracks. Three types of bends with different dimensions were deployed in a 3 m piping system and then tested, with an axial or... more
ABSTRACT This study experimentally investigates the efficacy of TE11 mode microwaves in detecting bend-region cracks. Three types of bends with different dimensions were deployed in a 3 m piping system and then tested, with an axial or circumferential slit machined at different angular positions to simulate a crack. The TE11 mode microwaves were excited using self-designed TE11 mode microwave probes and utilised for crack detection. The experimental results show clear reflection peaks at the bend position, demonstrating the feasibility of applying TE11 mode microwaves in the detection of bend-region cracks. Furthermore, the peak location of reflection is in accordance with the angular position of the slit. The findings also indicate that the peak amplitude of reflection is affected by the factors of mode conversion of microwaves at a bend. In addition, the experimental results also manifest an excellent signal-to-noise ratio to both two types of slits, suggesting that the microwave NDT is a powerful tool for bend-region inspection.
Research Interests:
Research Interests:
This study reports on a dual-port, side-incident microwave probe dedicated to the non-destructive inspection of metal pipes. Two types of side-incident probes (LJ and JL) are proposed to emit TM01- and TM02-mode microwaves into the pipe... more
This study reports on a dual-port, side-incident microwave probe dedicated to the non-destructive inspection of metal pipes. Two types of side-incident probes (LJ and JL) are proposed to emit TM01- and TM02-mode microwaves into the pipe under test, and each type of probe has two ports used to inspect in two opposite directions. Numerical simulations are conducted to study the dimensional parameters affecting the transmission characteristics of the probe and optimize the probe to obtain better mode purity and transmission directivity. The simulation results also suggest that the optimal probe dimensions for one inner pipe diameter can be applied to another diameter by multiplying the dimensions by a factor that is determined by the ratio of two diameters. Two LJ-type, side-incident probes, one with an inner diameter of 19 mm and one of 39 mm, are fabricated according to the simulation results. Experimental verification is subsequently carried out to test the detection directivity of ...
Research Interests:
Abstract Local wall thinning is a common form of degradation in carbon steel pipes, and a low frequevdvdncy electromagnetic method is proposed in this study to inspect such wall thinning defects. In addition, an appropriate method needs... more
Abstract Local wall thinning is a common form of degradation in carbon steel pipes, and a low frequevdvdncy electromagnetic method is proposed in this study to inspect such wall thinning defects. In addition, an appropriate method needs to be developed to solve the inverse problem, which is to estimate defect size based on the inspection signal. Resolving the inverse problem of nondestructive inspection usually involves a machine learning algorithm and training data should be large and realistic to enable the algorithm to produce an accurate and reliable estimate of defect size. However, the acquisition of such training data is sometimes time-consuming and costly. Therefore, this study aims to estimate the size of local wall thinning based on the inspection signal by developing a new method to generate training data for a machine learning algorithm. With the aid of signals obtained from numerical simulation, a multivariate probabilistic model is proposed to infer a joint distribution over features extracted from measured multi-frequency signals from the low frequency electromagnetic inspection method. The joint distribution is subsequently leveraged to quickly generate sufficient training data for a Gaussian process regression algorithm that uses the signal features as the input to estimate defect size. The multivariate probabilistic model is proved able to reasonably characterize the joint distribution over the features. Moreover, the trained algorithm has been validated by experimental data and it is confirmed it can be used to estimate the residual thickness of a pipe wall with errors within tolerance and high reliability even when the lift-off is changed.
Research Interests:
Abstract In this study an approach is proposed to probabilistically evaluate wall thickness and the probability of pipe failure when subjected to wall thinning based on the results of periodic non-destructive evaluations. Electromagnetic... more
Abstract In this study an approach is proposed to probabilistically evaluate wall thickness and the probability of pipe failure when subjected to wall thinning based on the results of periodic non-destructive evaluations. Electromagnetic acoustic resonance (EMAR) has been adopted as a specific non-destructive method to evaluate pipe wall thickness. A probabilistic model correlating the true and evaluated thicknesses was proposed on the basis of the results of laboratory experiments to measure 38 artificially corroded carbon steel plates. A Bayesian approach was proposed to estimate the probability of true thickness and the probability of failure from results of multiple non-destructive evaluations at certain time intervals. The approach was applied to the analyses of several virtual periodic EMAR evaluations of pipe wall thickness that gradually became thinner, whose results demonstrate that the proposed approach is effective regardless of the variability of corrosion rates.
Research Interests:
Abstract For the efficient use of frequency components, a frequency mixed feature for pulsed eddy current testing (PECT) or multi-frequency eddy current testing (MultiECT) was proposed for nonferromagnetic plate thickness measurement. An... more
Abstract For the efficient use of frequency components, a frequency mixed feature for pulsed eddy current testing (PECT) or multi-frequency eddy current testing (MultiECT) was proposed for nonferromagnetic plate thickness measurement. An evolutionary algorithm multigene genetic programming was employed to mix the frequency components using the best linearity as a target. Time domain and frequency domain finite element simulations of PECT and MultiECT were conducted. The simulation results revealed that, in terms of thickness measurement, a mixed feature comprising two or three frequencies was more linear and accurate than the traditional peak time and decay coefficient of PECT. Experiments were conducted to validate the results of the simulations and to test the mixed feature in aluminum plate thickness evaluations. The experimental results also revealed that the use of more frequencies did not always increase the accuracy of thickness evaluations. Proper frequency component selection was more efficient than blindly increasing frequency numbers.