ID 41
Title Electromagnetic nondestructive evaluation of rotating blades
Author Daigo Kosaka, Haoyu Huang, Noritaka Yusa, and Kenzo Miya
Published in E-Journal of Advanced Maintenance 1 (2009), 83-86.
Keywords rotary machine, pumps,electromagnetic field, vibration
Abstract This study proposes a method to nondestructively detect and evaluate tiny defects appearing at the tip of a rotating blade. The method utilizes a permanent magnet to generate a static magnetic field and detects the eddy currents induced by the blade moving inside the magnetic field. The eddy current is detected by the coil of the sensor. Experimental validations are carried out using a commercial pump. Artificial slits fabricated into the impeller were well detected in spite of the presence of a metallic case and a large lift-off.

ID 42
Title A project aiming at the enhancement of NDT&E of stress corrosion cracking
Author Noritaka Yusa, Kenzo Miya, Ichiro Komura, Zhenmao Chen
Published in International Journal of Applied Electromagnetics and Mechanics 33, pp. 1587-1590 (2010).
Keywords nondestructive testing, round-robin test, benchmark data, austenitic stainless steel
Abstract This paper introduces a research project the authors have proposed. The project aims to gather non-destructive testing data of stress corrosion cracking specimens and present them as benchmark data freely available to researchers in the field. Round-robin test using seven austenitic stainless steel plate specimens with artificial stress corrosion cracking is carried out, and they are measured using various non-destructive testing methods. The data measured are made available together with the results of destructive tests to confirm the true profile of the cracking.

ID 43
Title Numerical analysis of an electromagnetic nondestructive evaluation method for rotating machinery
Author Haoyu Huang, Ryo Kayata, Stephane Perrin, Noritaka Yusa, Kenzo Miya
Published in International Journal of Applied Electromagnetics and Mechanics 33 (2010), 1101-1107.
Keywords
Abstract

ID 44
Title An eddy current probe suitable to gain information about the depth of near-side flaws much deeper than the depth of penetration
Author Noritaka Yusa, Yasutomo Sakai, Hidetoshi Hashizume
Published in NDT&E International 44 (2010), 121-130.
Keywords electromagnetic non-destructive evaluation, defect characterization, inverse problem, quasi-static problem, skin depth
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 25 mm thick austenitic stainless steel plate with five artificial rectangular slits of 40 mm length, 0.5 mm width, and 1, 5, 10, 15, and 20 mm depth. The experiments confirm clear differences between signals generated by the five slits even although the exciter is driven at 50 kHz at which the depth of penetration is approximately 2.0 mm. 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.

ID 45
Title Fabrication of imitative stress corrosion cracking specimens suitable for electromagnetic nondestructive evaluations using solid state bonding
Author Noritaka Yusa, Tetsuya Uchimoto, Toshiyuki Takagi, Hidetoshi Hashizume
Published in Maintenology 10 (2011), 64-69
Keywords stress corrosion crack, SCC, performance demonstration, nondestructive evaluation, electrical resistance, diffusion bonding
Abstract This study proposes a method to fabricate an artificial defect that is almost identical to stress corrosion cracking from the viewpoint of electromagnetic nondestructive evaluations. The key idea is to realize a region having electrical resistance embedded inside a conductive materials using solid state bonding. A rough region is introduced into the surface of the materials to be bonded so that the region is partially bonded to realize electrical resistance. Experimental demonstrations are carried out using type 316L austenitic stainless steels. Eddy current tests and subsequent numerical evaluations are conducted to discuss the validity of the proposed method.

ID 46
Title Size, concentration and incubation time dependence of gold nanopaticle uptake into pancreas cancer cells and its future application to X-ray drug delivery system
Author Jade Duangao Trono, Kazue Mizuno, Noritaka Yusa, Tekahisa Matsukawa, Kazuhito Yokoyama, Mitsuru Uesaka
Published in Journal of Radiation Research 52 (2011), 103-109.
Keywords
Abstract

ID 47
Title Electromagnetic modeling of stress corrosion cracks in Inconel welds
Author Haoyu Huang, Noritaka Yusa, Kenzo Miya, Hidetoshi Hashizume, Takehiko Sera, Shinro Hirano
Published in E-Journal of Advanced Maintenance 2 (2010/2011), 168-180.
Keywords electromagnetic nondestructive evaluation, eddy current testing, nuclear power plant, nickel-based alloy, finite element method, numerical modeling, natural crack, inverse problem, Alloy 600
Abstract This study evaluates suitable numerical modeling of stress corrosion cracks appearing in Inconel welds from the viewpoint of electromagnetic nondestructive evaluations. The stress corrosion cracks analyzed in this study are five artificial ones introduced into welded flat plate, and three natural ones found in a pressurized nuclear power plant. Numerical simulations model a crack as a planar region having a uniform conductivity inside and a constant width, and evaluate the width and conductivity that reproduce the maximum eddy current signals obtained by experiments. The results obtained validate the existence of the minimum value of the equivalent resistance, which is defined by the width divided by conductivity. In contrast, the values of the width and conductivity themselves vary across a wide range. The results also lead to a discussion about (1) the effect of probe utilized on the numerical model, (2) the difference between artificial and natural stress corrosion cracks, and (3) the difference between stress corrosion cracks in base metals and those in Inconel welds in their models. Electromagnetic characteristics of four different Inconel weld alloys are additionally evaluated using a resistance tester and a vibrating sample magnetometer to support the validity of the numerical modeling and the generality of results obtained.

ID 48
Title Four-terminal measurement of the distribution of electrical resistance across stress corrosion cracking
Author Noritaka Yusa, Hidetoshi Hashizume
Published in NDT&E International 44 (2011), 544-546.
Keywords Electrical properties, Contacts, Metals and alloys, Simulation and modeling, Electromagnetic nondestructive evaluation, Austenitic stainless steel
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 cracking 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.

ID 49
Title Feasibility study of Flibe blanket with Cs
Author Hidetoshi Hashizume, Noritaka Yusa, Kentaro Matsui
Published in Fusion Science and Technology 60 (2011), 523-527.
Keywords
Abstract The present study clarifies feasibility of a new concept for the Flibe blanket system with Cesium from the thermonuclear viewpoint. Through this study it was revealed at first that the melting temperature of Flibe can be lowered with adding the CsF. And then the tritium breeding ratio when 137Cs was mixed in the Flibe was evaluated by using the neutron transport calculation code of MVP. The numerical results indicate that the TBR decreases gradually by adding Cs substituted for Beryllium.

ID 50
Title Nondestructive evaluation of wall thinning inside a pipe using the reflection of microwaves with the aid of signal processing
Author Yasutomo Sakai, Noritaka Yusa, Hidetoshi Hashizume
Published in Nondestructive Testing and Evaluation 27 (2012), 171-184
Keywords electromagnetic nondestructive evaluation, time-of-flight, wall thinning, degradation, finite element method
Abstract This study demonstrates that the reflection of microwave propagating inside a pipe enables one to non-destructively detect and locate wall thinnings appearing inside the pipe. A signal processing method is proposed to compensate for the dispersion of microwave and to make the reflection due to a wall thinning clearer. After fundamental characteristics of the microwave signals were evaluated using three-dimensional finite element simulations, verifications were carried out both by experiments and numerical simulations using straight brass pipes whose outer diameter and wall thickness were 25 mm and 3 mm respectively. The verifications revealed that imposing the signal processing method provided a clear indication of the location of wall thinning, and no significant deterioration was observed even when the pipe was as long as 2,000 mm. The verifications also showed that the amplitude of reflection signal was almost proportional to the volume of wall thinning, which agreed with another report, and the reflections were sufficiently clear even when the edge of a flaw was not stepwise but curved like actual wall thinnings.

ID 51
Title Numerical analysis of microwave NDT applied to piping inspection
Author Yasutomo Sakai, Noritaka Yusa, Hidetoshi Hashizume
Published in Materials Transactions 53 (2012), 627-630.
Keywords Microwave, Piping, Finite Element Method, Electro-magnetic NDT, Wall Thinning
Abstract Numerical simulations using finite element software were carried out to discuss the physical background of nondestructive inspections of pipes using microwaves. The simulations were conducted using an axisymmetric configuration modeling pipe with wall thinning to evaluate the effect of the profile of the wall thinning on the microwave propagation. Both rectangular and quasi-racetrack wall thinnings were considered. The numerical simulations showed the presence of wall thinning attenuates microwaves at particular frequencies. An empirical formula was proposed to evaluate the profile of wall thinning for the particular frequencies. Although the formula was based on the results of numerical simulations considering only rectangular wall thinning, it is also applicable to the evaluation of quasi-racetrack wall thinning.

ID 52
Title An accurately controllable imitative stress corrosion cracking for electromagnetic nondestructive testing and evaluation
Author Noritaka Yusa, Tetsuya Uchimoto, Toshiyuki Takagi, Hidetoshi Hashizume
Published in Nuclear Engineering and Design 245 (2012), 1-7.
Keywords electromagnetic nondestructive evaluation, eddy current testing, SCC, artificial defect, performance demonstration, solid state welding
Abstract This study proposes a simple and cost-effective approach to fabricate an artificial flaw that is identical to stress corrosion cracking especially from the viewpoint of electromagnetic nondestructive evaluations. The key idea of the approach is to embed a partially-bonded region inside a material by bonding together surfaces that have grooves. The region is regarded as an area of uniform non-zero conductivity from an electromagnetic nondestructive point of view, and thus simulates the characteristics of stress corrosion cracking. Since the grooves are introduced using electro-discharge machining, one can control the profile of the imitative stress corrosion cracking accurately. After numerical simulation to evaluate the spatial resolution of conventional eddy current testing, six specimens made of type 316L austenitic stainless steel were fabricated on the basis of the results of the simulations. Visual and eddy current examinations were carried out to demonstrate that the artificial flaws well simulated the characteristics of actual stress corrosion cracking. Subsequent destructive test confirmed that the bonding did not change the depth profiles of the artificial flaw.

ID 53
Title Fabrication of imitative stress corrosion cracking specimen using lithography and solid state bonding
Author Noritaka Yusa, Hidetoshi Hashizume@
Published in International Journal of Applied Electromagnetics and Mechanics 39 (2012), 291-296.
Keywords non-destructive testing and evaluation, electromagnetic non-destructive testing, finite element simulations, electric resistance, modelling
Abstract This study proposes a method to fabricate artificial flaws whose response to non-destructive testing, especially electromagnetic non-destructive testing, is the same as that of stress corrosion cracking. Sacked metallic films containing through-grooves are sandwiched between metallic blocks and then bonded using solid state bonding. The profiles of the through-grooves are accurately controlled with the aid of the lithography technique, which allows a three-dimensional discontinuity to be embedded inside a material. Since the spatial distribution of the discontinuity is small compared to the spatial resolution of non-destructive testing methods, the method allows the response of stress corrosion cracking to be simulated. Specimens are fabricated using type 316L austenitic stainless steel, and validated using eddy current testing.

ID 54
Title Design and development of a new micro-beam treatment planning system: effectiveness of algorithms of optimization and dose calculations and potential of micro-beam treatment
Author Hidenobu Tachibana, Hiroyuki Kojima, Noritaka Yusa, Satoshi Miyajima, Akihisa Tsuda, Takashi Yamashita@
Published in Radiological Physics and Technology 5 (2012), 186-198.
Keywords Micro-beam, Treatment planning system, Pseudo Beamfs Eye View, Steepest descent, Superposition/convolution, Monte Carlo@
Abstract A new treatment planning system (TPS) was designed and developed for a new treatment system, which consisted of a micro-beam-enabled linac with robotics and a real-time tracking system. We also evaluated the effec-tiveness of the implemented algorithms of optimization and dose calculations in the TPS for the new treatment system. In the TPS, the optimization procedure consisted of the pseudo Beamfs-Eye-View method for finding the opti-mized beam directions and the steepest-descent method for determination of beam intensities. We used the super-position-/convolution-based (SC-based) algorithm and Monte Carlo-based (MC-based) algorithm to calculate dose distributions using CT image data sets. In the SC-based algorithm, dose density scaling was applied for the calcu-lation of inhomogeneous corrections. The MC-based algorithm was implemented with Geant4 toolkit and a phase-based approach using a network-parallel computing. From the evaluation of the TPS, the system can optimize the direction and intensity of individual beams. The accu-racy of the dose calculated by the SC-based algorithm was less than 1 % on average with the calculation time of 15 s for one beam. However, the MC-based algorithm needed 72 min for one beam using the phase-based approach, even though the MC-based algorithm with the parallel comput-ing could decrease multiple beam calculations and had 18.4 times faster calculation speed using the parallel computing. The SC-based algorithm could be practically acceptable for the dose calculation in terms of the accuracy and compu-tation time. Additionally, we have found a dosimetric advantage of proton Bragg peak-like dose distribution in micro-beam treatment

ID 55
Title Numerical modeling of thermal fatigue cracks from the viewpoint of eddy current testing
Author Noritaka Yusa, Hidetoshi Hashizume, Iikka Virkkunen, Mika Kemppainen
Published in Maintenology 11(3), 73-78.
Keywords electromagnetic nondestructive evaluation, finite element method, numerical simulation, conductivity
Abstract This study discusses a suitable numerical modeling of a thermal fatigue crack from the viewpoint of eddy current testing. Five artificial thermal fatigue cracks, introduced into type 304L austenitic stainless steel plates with a thickness of 25 mm, are prepared; and eddy current inspections are carried out to gather signals using an absolute type pancake probe and a differential type plus point probe. Finite element simulations are then carried out to evaluate a proper numerical model of the thermal fatigue cracks. In the finite element simulations, the thermal fatigue cracks are modeled as a semi-elliptic planar region on the basis of the results of the destructive tests. The width and internal conductivity are evaluated by the simulations. The results of the simulations reveal that the thermal fatigue cracks are regarded as almost nonconductive when the internal conductivity is assumed to be uniform inside.

ID 56
Title Evaluation of sensitivity of remote field eddy current testing and low-frequency eddy current testing for inspecting grooves of metal plate
Author Jing Wang, Noritaka Yusa, Hongliang Pan, Toshiyuki Takagi, Hidetoshi Hashizume
Published in Materials Transactions 54(1) (2013), 90-95.
Keywords electromagnetic nondestructive evaluation, finite element simulation, sensitivity, depth of penetration, eddy currents, metal plate
Abstract We compare remote field eddy current testing and low-frequency eddy current testing from the viewpoint of sensitivity to back-side grooves in a metal plate. We carry out experiments using three metal plates with different depths of artificial grooves. A U-shape magnetic shield gives rise to a remote field eddy current as occurs in pipe inspection. The experiments show that the two methods have almost the same sensitivity to back-side grooves if a relatively low frequency and relatively far coil interval are used, which is also validated by three-dimensional finite-element simulations. We conduct numerical investigations to find the reason for this condition.
ID 57
Title Discussion on modeling of thermal fatigue cracks in numerical simulation based on eddy current signals
Author Jing Wang, Noritaka Yusa, Hongliang Pan, Mika Kemppainen, Iikka Virkkunen, Hidetoshi Hashizume
Published in NDT&E International 55 (2013), 96-101.
Keywords thermal fatigue crack, numerical modeling, finite element method, eddy current testing
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.

ID 58
Title Enhancement of microwave nondestructive testing method for the inspection of pipes by optimizing the microwave probe profile
Author Kota Sasaki, Noritaka Yusa, Takashi Wakai, Hidetoshi Hashizume
Published in Maintenology 12 (2013), 81-86.
Keywords microwave, nondestructive testing, pipe wall thinning, finite-element simulation, pipe diameter
Abstract This study reports the development of a new microwave probe for the nondestructive testing of a pipe. Three-dimensional finite element simulations are carried out to optimize the profile of a microwave probe, whose results show that a probe with elliptic profile enables smaller reflection at the probes as well as much better single-mode propagation inside the pipe than conventional ones. Experimental validations are carried out using a straight brass pipe with an inner diameter of 39 mm and a total length of 2 m. The results of the experiments clearly demonstrate that the new microwave probe provides clearer signals due to simulated rectangular wall thinning.

ID 59
Title Study of a methodology of identifying important research problems by the PIRT process
Author Takayuki Aoki, Toshiyuki Takagi, Ichiro Komura, Takashi Furukawa, Noritaka Yusa, Ryoichi Urayama
Published in Transactions of the Atomic Energy Society of Japan 12 (2013), 231-241.
Keywords PIRT, ultrasonic testing, eddy current testing, fatigue, SCC, crack detection, crack sizing, accuracy, influential factor
Abstract This paper proposes a new methodology of identifying important research problems to be solved to improve performance of some specific scientific technologies by the PIRT (Phenomena Identification and Ranking Table) process that has been used as a methodology for demonstrating the validation of best estimate simulation codes in USNRC licensing of nuclear power plants. It keeps fundamental concepts of the original PIRT process, but has a feature of making it possible to identify important influential factors affecting performance of the technologies from the viewpoint of the figure of merit and problems associated with them, which need to be solved to improve the performance. And also this paper demonstrates an effectiveness of the developed method by showing a specific example of the application to physical events or phenomena in object having fatigue or SCC crack(s) under ultrasonic testing and eddy current testing.

ID 60
Title Diversity and integration of rotating machine health monitoring methods
Author Shigeru Kanemoto, Norihiro Yokotsuka, Noritaka Yusa, Masahiko Kawabata
Published in Chemical Engineering Transactions 33 (2013), 169-174.
Keywords
Abstract Health monitoring for rotating machines is investigated through two kinds of mock-up experimental data analysis. One is an anomaly mock-up test of roll bearing type rotating machine. Here, inner ring defect anomaly is simulated and its operating data are measured by both attached type accelerometer sensor and non-attached type microphone. Three kinds of signal pre-processing methods, frequency spectrum, principal component analysis and cepstrum, are applied to discriminate normal and abnormal states using several different classification algorithms, such as adaboost or random forest. Through analysis of their performance with the help of receiver operating characteristic (ROC) curve, the importance of diversified health monitoring methods is discussed. Another mock-up experiment is an accelerated test of roll bearing wear. Here, acoustic emission counts, accelerometer signal and wear particle number in lubricating oil are measured. Using these observation data, we make clear the relationships between deterioration mechanisms of bearing and behaviour of different observations.