| 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 |
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 |
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 |
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 Beamfs 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 Beamfs-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.
|
