The 17th International Symposium on
Applied Electromagnetics and Mechanics(ISEM 2015)

Program Booklet

Awaji Yumebutai International Conference Center
Awaji City, Hyogo, Japan
15-18 September, 2015
http://www.org.kobe-u.ac.jp/isem2015/home.html

Hosted by
ISEM 2015 Organizing Committee
Supported by
The Japan Society of Applied Electromagnetics and Mechanics, andJapan Society of Maintenology
Sponsored by
Tateisi Science and Technology Foundation,
Tsutomu Nakauchi Convention Foundation,
Hyogo International Association, andOrganization of Advanced Science and Technology, Kobe University㼀㼔㼑㻌㻝㻣㼠㼔㻌㻵㼚㼠㼑㼞㼚㼍㼠㼕㼛㼚㼍㼘㻌㻿㼥㼙㼜㼛㼟㼕㼡㼙㻌㼛㼚㻌㻭㼜㼜㼘㼕㼑㼐㻌㻱㼘㼑㼏㼠㼞㼛㼙㼍㼓㼚㼑㼠㼕㼏㼟㻌㼍㼚㼐㻌㻹㼑㼏㼔㼍㼚㼕㼏㼟

Flat/Film Infinity Coils and Backside Defect Searching
Shunichi HAMANAKA, Yoshifuru SAITO
Graduate School of Electrical and Electronics Engineering, Hosei University, 3-7-2 Kajinotyo
Koganei, 184-8584, Tokyo, Japan

Iliana MARINOVATechnical University of Sofia 1756, Sofia, Bulgaria

Manabu OHUCH, Takaharu KOJIMAEMIC (Denshijilki Industry) Co, Ltd, 115-0051, Tokyo, Japan

Abstract. Previously, we have proposed an infinity coil as a high sensibility ECT sensor. This
paper has evaluated a possibility of the backside defect searching by the low frequency
excitation of a modified infinity coil whose exciting coils are the flat/film shape to adapt to thecurverved test targets.
In the present paper, we have elucidated the liftoff characteristics of the backside defectsearching when employing the low frequency excitation to our flat/film shape infinity coil.

1 Introduction
The modern mass transportation vehicles, e.g. air plane, high-speed train, carrying a large
number of people are required the ultimate highest safety as well as reliability.
To keep the highest safety and reliability, nondestructive testing is one of the mostimportant key maintenance technologies, because most of the frame materials are composedof metallic materials.
Operating principle of ECT is fundamentally based on the detection of magnetic field
distribution change due to the defect in the targets. To realize this principle, we have two
methodologies. One detects the defect in the target as a change of input impedance of theexciting coil. This is because the magnetic field distribution is changed by the detour eddy
currents flowing around the defect in the target which corresponds to the secondary circuit ofa single phase transformer [1-3]. The other ECT sensor equips a sensing coil in addition to theexciting coils for detecting the magnetic field change caused by the detour eddy currents
flowing around the defect. The former and latter are called the impedance sensing and sensing
coil types, respectively.
The sensing coil type is further classified into two variations. Most popular sensing coiltype employs a spatial differential coil, and also the other type whose surface of the sensing
coil is perpendicularly installed to those of the exciting coil. As is well known the spatialdifferential coil detects the uniformity of the magnetic field distribution. Similarly the othertype whose surface of sensing coil is perpendicularly installed to those of exciting coil detects
only the magnetic fields caused by the detour eddy currents due to the defect in the target.Our
developed flat/film shape infinity coil is one of the these types. A key idea of our flat/film
shape infinity coil is that the sensing coil wound around a ferrite bar is installed at the lowest
magnetic field intensity region between the north and south poles of exciting coils [1].
This paper tries to clarify the liftoff characteristics of the backside defect searching whenemploying a low frequency excitation to the flat/film shape infinity coil. As a result, it isrevealed that the low frequency excited flat/film shape infinity coil is capable of detecting thebackside defects over 1mm liftoff

㼀㼔㼑㻌㻝㻣㼠㼔㻌㻵㼚㼠㼑㼞㼚㼍㼠㼕㼛㼚㼍㼘㻌㻿㼥㼙㼜㼛㼟㼕㼡㼙㻌㼛㼚㻌㻭㼜㼜㼘㼕㼑㼐㻌㻱㼘㼑㼏㼠㼞㼛㼙㼍㼓㼚㼑㼠㼕㼏㼟㻌㼍㼚㼐㻌㻹㼑㼏㼔㼍㼚㼕㼏㼟

2 Experiments

Fig. 1 Reference ECT signal processor“ET-5002” produced by EMIC Co. LTD.

Fig. 2 Detected signal vs. Liftoff characteristic

In our experiments, we have employed the two laminated copper plates as a test target, theupper is the normal copper plate having 2mm thickness, 10cm length, 2cm width, and thebackside is composed of 2 independent plates contructing a line crack having a 1mm depth
and 2mm width.
Consideration of the skin depth, the absolute sensibility and higher frequency noise signals
accompanying the practical measurements have led to employ the 2kHz as the best excitation
frequency.
We measured the signals due to the backside defect by means of the commercial based
signal processing device "ET-5002" shown in Fig1 while the flat/film shape infinity coil wasscanned along a test target surface. Operating principle of the ET-5002 is that the equilibriumbalanced condition of the bridge circuit picks up only the discontinuity of signals when thesensor scans over the defect. Liftoff distance was changed from 0.2mm to 3mm. The gain
60dB and 10Hz-256kHz band pass filter were set up to the ET-5002 for the backside defectsearching.

Fig.2 shows detected signals by the flat/film infinity coil when scanning a surface of thetarget piece having a backside defect. Observe the detected signals makes it possible to findthe 5 distinct peaks in each of the liftoff positions. Each of the detected signals at the fivedifferent liftoff positions suggests the existence of backside defect in the target piece. Also, it
is found that the amplitude of the detected signals is inversely proportional to the lift-off
distances.
3 Conclusion
In the present paper, we have employed the low frequency excitation of flat/film shape
infinity coil to search for the backside defect of the metallic target when changing the liftoff
distances from 0.2mm to 3mm. As a result, it has been clarified that the low frequency
excitation of flat/film shape infinity coil makes it possible to search for the backside defects
along with the signal processing device ET-5002 enhancing the S/N ratio.
References[1] Hiroki Kikuchihara, Iliana Marinova, Yoshifuru Saito, Manabu Ohuchi, Hideo Mogi and Yoshiro Oikawa,
Optimization of the Eddy Current Testing, Digest of The 15th Biennial IEEE Conference on
Electromagnetic Field Computation, Oita Japan November 11-14,WC4-4, PP.495. 2012.
[2] Hiroki Kikuchihara, Yoshifuru Saito, Enhance the Sensibility of the ECT Sensor, Journal of the Japan
Society of Applied Electromagnetics and Mechanics, Vol.21, No.3, 2013.
[3] Kouki Maruyama, Iliana Marinova, and Yoshifuru Saito, Enhance the Sensibility of the Resonance type
ECT Sensor, JAPMED'8, pp. 130-131, 2013.

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Ingeniously Coil Connection and its Application to theTesla Coils
Kazuya Okuda1, a, Iliana Marinova2,b and Yoshifuru Saito1,c1

c/o Y.Saito Lab., Graduate School of Electronics and Electrical Engineering,
Kajino Koganei, Tokyo 184-8584, Japan

2

Dept. of Electrical Apparatus, Technical University of Sofia, 1756 Sofia, Bulgariaakazuya.okuda.2n@stu.hosei.ac.jp, biliana@tu-sofia.bg, cysaito@hosei.ac.jp

Abstract. This paper proposes a simple method to get the stabilized discharging
characteristics by the Tesla coil without additional electronic circuits. Also, it is revealed
that an ingenious coil connection changes the Tesla coil into a dramatically stable highvoltage dischargeable source.

1. Introduction
Stable discharging is essential to the discharge machining, lighting, metal welding
connection, and so on. The Tesla coil may be the oldest method generating high voltage
source for discharging [1]. Further the Tesla coil may be regarded as one of the corelesstransformer whose secondary induced voltage is extremely high. Apply a primal input
source having one of the resonant frequencies of secondary coil makes it possible togenerate a high secondary voltage. This secondary high voltage discharges from anexternally attached electrode working as a resonant capacitor. However, its discharging
characteristic is intermittently and not so stable. Thereby, this requires equipping the otherelectronics to obtain the stable and continuous discharge.
This paper proposes a simple method to get the stable discharging characteristics by the
Tesla coil without additional electronic circuits, i.e., a simple ingenious connection of
secondary circuits changes the Tesla coil into a dramatically stable discharge generator [2].
2. Resonant Tesla Coils
A typical conventional Tesla coil which is composed of the two coaxial finite length
solenoid coils. The number of the outer primal and inner secondary coils are small andextremely large, respectively. Thereby, the Tesla coil is one of the coreless transformer
whose transform ratio a=N1/N2 are extremely small, where N1 and N2 denote the number ofturns of primal and secondary coils, respectively.
When a coupling between the primal and secondary coils through a common magnetic
flux is high, it is possible to obtain a high secondary induced voltage. However, theircoupling is very small so that the Tesla coil could not use as a normal voltage boost up
transformer.

Fig.1 A typical Tesla coil㼀㼔㼑㻌㻝㻣㼠㼔㻌㻵㼚㼠㼑㼞㼚㼍㼠㼕㼛㼚㼍㼘㻌㻿㼥㼙㼜㼛㼟㼕㼡㼙㻌㼛㼚㻌㻭㼜㼜㼘㼕㼑㼐㻌㻱㼘㼑㼏㼠㼞㼛㼙㼍㼓㼚㼑㼠㼕㼏㼟㻌㼍㼚㼐㻌㻹㼑㼏㼔㼍㼚㼕㼏㼟

Fig. 2 shows a frequency characteristic of the secondary coil. Obviously, the secondary
coil has the multiple resonant frequencies between the stray capacitance and leakage
inductance. Thereby, it is essential to attach an external capacitor to fix a particularresonant frequency. After attaching the capacitor, it is possible to remove the effect of
secondary leakage flux by the capacitor, i.e., a resonant phenomena, when supplying theresonant frequency to the primal coil. This leads to the desired high voltage determined bytransformer ratio a.
On the other side, a resonant connection utilizing a capacitance between the inner andouter layer coils of the secondary winding exhibits a single resonant frequency
characteristic as shown in Fig.2 [2]. A major resonant frequency in Fig. 2 is nearly 20MHz.
On the contrary the single resonant frequency in Fig. 3 is nearly 30KHz. Difference
between them is quite large frequency so that an ingeniously connection of the coils neverrequires an external resonant capacitor and creates the reasonable single resonant frequency
characteristic.

Fig.2 Frequency characteristic of the secondary coil.

Fig.2 Frequency characteristic of the secondary coil when employing resonant connotation.

3. Conclusion
As shown above, we have succeeded in obtaining the single resonant frequency
characteristic whose resonant frequency is relatively low. Thereby, it is possible to workout the devices, e.g., discharge machining, lighting, metal welding connection which
require the stable discharging.
One of the innovative facts is that a simple ingeniously connection of the coils change
the multi resonant into single resonant characteristics and removes the external electronicparts such as the external capacitor and high frequency processing elements.
References[1] http://www.teslasociety.com/teslacoil.htm[2] Y.Midorikawa, S.Hayano and Y.Saito, " A multi-resonant type inductor having notch filtering
capability," IEEE Transaction on Magnetics,Vol.MAG-32, No.5,Sep.,1996,pp.4998-5000.

㼀㼔㼑㻌㻝㻣㼠㼔㻌㻵㼚㼠㼑㼞㼚㼍㼠㼕㼛㼚㼍㼘㻌㻿㼥㼙㼜㼛㼟㼕㼡㼙㻌㼛㼚㻌㻭㼜㼜㼘㼕㼑㼐㻌㻱㼘㼑㼏㼠㼞㼛㼙㼍㼓㼚㼑㼠㼕㼏㼟㻌㼍㼚㼐㻌㻹㼑㼏㼔㼍㼚㼕㼏㼟

Design Strategy of The Practical Flat ҄ Coil
Takahiro Hyuga, N. Ishikawa, Yoshifuru SAITO
Graduate School of Electrical and Electronics Engineering, Hosei University, 3-7-2 Kajino Koganei,
184-8584, Tokyo, Japan

Iliana MARINOVATechnical University of Sofia 1756, Sofia, Bulgaria

Manabu OHUCH, Takaharu KOJIMAEMIC (Denshijilki Industry) Co, Ltd, 115-0051, Tokyo, Japan(infinity) coil for the high sensitive eddy current
Abstract. Previously, we had proposed ancoils. Because of the requirements of thesensor and worked out several prototype of thepractical environments, e.g.. defects searching in the tight slits and curved surfaces, we havefurther developed the flexible flat/film coils.
In the present paper, consideration to the practical use to the design of prototype the flat/film
coil lead an employment of the two semi-circle exciting coils. Experimental and 3D FEM
simulations verify the validity of our practical design direction of the flat/film coil..

1 Introduction
Since most of the human products as well as infrastructures aremechanically supported by the iron or its composites, then nondestructive
testing of metallic materials is of paramount important work to keep ourdaily life.

Previously we have succeeded in exploiting a new highsensibility eddy current testing (ECT) sensor called the ҄ coil [1].
Figure 1 shows one of the prototypes of our ҄ coil. Eventhogh the Fig. 1 The First Prototype
developmens of the first trototype design was carrying out, strorongof The ҄ coil.
requirements to use the defect searching between the tight slit spaces
because of the searching for the defects after assembles, and for the curved surfaces such as
pipes.
To respond this requirement, we had exploited a flat ҄ coil [2]. Remarkarbly this new flat҄ coil displayed a versatile capabilities for the defect searching cauved serface and highsensibility compared with the old one as shown in Fig.1.
This paper is concerning to decide the degin direction of the flat ҄ coil, e.g., cicular or
square closs-section shape and the flat excaiting coils shoud be wound remaing or not emaing
the cetrers of flat excaiting coils.
Finally, the first prototype degin direction of the flat Ğ coil is focused on the two key
points, i,e, one is the shape of exciting coils, which enlarges the zero magnetic field region
between the two adjacent coils constructing the north and south poles alternatively, and thesecond the shape of flat exciting coils whether each of the coils should be fully wound until nospace or not fully wound remaining some space, namely each of the exciting coil surfaces
does not has any area otherwise has a space enclosed by an exciting coil.

㼀㼔㼑㻌㻝㻣㼠㼔㻌㻵㼚㼠㼑㼞㼚㼍㼠㼕㼛㼚㼍㼘㻌㻿㼥㼙㼜㼛㼟㼕㼡㼙㻌㼛㼚㻌㻭㼜㼜㼘㼕㼑㼐㻌㻱㼘㼑㼏㼠㼞㼛㼙㼍㼓㼚㼑㼠㼕㼏㼟㻌㼍㼚㼐㻌㻹㼑㼏㼔㼍㼚㼕㼏㼟

2 Practical Prototype Design of ĞCoil
Operating principle of original flat Ğ coil is that two adjacent coils constructing the northand south poles alternatively set a zero magnetic field region and keep this zero magnetic
fields situation when eddy currents are flowing along the paths in parallel to the exciting coils.
If the eddy currents could not flow the paths in parallel to the exciting coil on the test
specimen, then a zero magnetic field region between the two exciting coil moves toward theother position. This means that a sensing coil located at a mid position of two exciting coil ispossible to detect the disturbed magnetic fields, i.e., the defect in the test specimen could be
detected from the sensing coil signal.
By means of the intensive 3D FEM simulation and experimental works, this paper reveals
that the sensibility of the flat Ğ coil could be enhanced by enlarging the zero magnetic fieldregion between the two adjacent exciting coils. This has been simply carried out by enlarging
a two adjacent point to a two adjacent line. Effect of this exciting coil layout modificationreflects on the output larger amplitude of sensing signals than those of conventional one. Also,
we have carried out the 3D FEM simulations as well as experiments to the 10 turns coilhaving a space and the 20 turns having no space. Figure 2 shows the tested coils and their
response signals to a straight line defects tilted 45 degree to the sensor coil of the Ğ coils.

(a-1) 10 Turns(a-2) 10 Tures (Simulated)(b-1) 20 Turns(a-3) 10 Tures (Experimented)(b-2) 20 Tures (Simulated)(b-3) 20 Tures (Experimented)

Fig. 2. The first tested flat ҄ coils.
The Green and Red lines are denoting the sensor output signals and noises, respectively.
As described above we have succeeded in decided to work out the first prototype design.
References[1] H. Kikuchihara et al, Development of a New High Sensitive Eddy Current Sensor, Materials Science Forum
Vol. 792 (2014), 98-103.
[2] K. Maruyama et al, Developments of Flat Coil for Defect Searching in the Curved Surfaces, E-Journal ofAdvanced Maintenance, in printing.

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Frequency Fluctuation Signal Processingand
Its Application to the Barkhausen Signals
Mirai IIDA, Yoshifuru SAITO
Graduate School of Electrical and Electronics Engineering, Hosei University, 3-7-2 Kajinotyo
Koganei, 184-8584, Tokyo, Japan

Iliana MARINOVATechnical University of Sofia 1756, Sofia, Bulgaria

Abstract. Among a lot of signal processing methods, frequency fluctuation approach is rarely used.
Only the 1/f frequency fluctuation is well known as a figure of healing activations. In the present
paper, a generalized frequency fluctuation signal processing method is introduced to analyse the
Barkhausen signals accompanying with the magnetization of the ferromagnetic materials. As a result,
it is revealed that the situations of ferromagnetic materials under stressed or not are visualized in athree dimensional space.

1 Introduction
Barkhausen signal is observed in the ferromagnetic materials when they are magnetizing. It is
well known that the Barkhausen signals are very sensitive to the physical external stress andradioactive damage to the ferromagnetic materials.
The iron and its composite ferromagnetic materials are widely used for main frame materials
to support the mechanical structures in many artificial products and constructions. Because of
their essential role, they are always got mechanical stress and they keep their past mechanicalstress histories. Nondestructive detection of their mechanical stress as well as residual stress is ofparamount importance for keeping the safety of the mechanical structures, since it is possible tosee ahead of time what extent the mechanical structure will maintain their strength for further use.
The past researches concerning to a relationship between the Barkhausen signal and appliedmechanical stress have revealed that Barkhausen signals are very sensitive to the mechanicalstress and radioactive damage but any deterministic regularity has not been found [1,2]. Only amacroscopic regularity has been reported by means of a frequency fluctuation analysis approach[3]
This paper makes it possible to generalize 1st order frequency fluctuation of the conventional
analysis to the nth order frequency fluctuation analysis. As a result, it is succeed in visualizing thespecimen's situations under stressed or not stressed from their Barkhausen signals.
2 Generalized frequency fluctuation analysis
Conventional 1/f frequency analysis is that application of the 1st order least squares to the both
Fourier power spectrum and frequency extracts the 1st order frequency fluctuation, i.e., Log of
Fourier power spectrum is approximated by Log of a0 + a1f, yields a 1st order frequency
fluctuation characteristic, where a0 and a1 are the 0th and a 1st order frequency fluctuation terms,
respectively. If the frequency fluctuation term a1 takes a1=1, then we have the 1/f frequency
fluctuation. One of the most famous frequency fluctuations is the 1/f frequency fluctuation, which
can be observed in most of the natural phenomena such as natural wind, sea water waves, river
flow sound and so on gives a healing effect to the mentalities via human sensibilities [4].

㼀㼔㼑㻌㻝㻣㼠㼔㻌㻵㼚㼠㼑㼞㼚㼍㼠㼕㼛㼚㼍㼘㻌㻿㼥㼙㼜㼛㼟㼕㼡㼙㻌㼛㼚㻌㻭㼜㼜㼘㼕㼑㼐㻌㻱㼘㼑㼏㼠㼞㼛㼙㼍㼓㼚㼑㼠㼕㼏㼟㻌㼍㼚㼐㻌㻹㼑㼏㼔㼍㼚㼕㼏㼟On the other side, we generalize this conventional 1st order frequency fluctuation to the nthorder frequency fluctuation characteristics, i.e., Log of Fourier power spectrum is approximatedby a Log of a0 + a1f+a2f2+ ...+ anfn, where a0, a1, a2, ,..., an are the 0th, 1st 2nd, ... ,nth orderfrequency fluctuation terms, respectively. Careful examination of the coefficients a0, a1, a2, ,..., anleads to the precise frequency fluctuation characteristic of the Barkhausen signals.
According to our experimental results, all of the frequency fluctuation characteristics are
sufficiently represented up to the 4th order terms. Fig.1 shows a typical relationship between thefrequency characteristic and 4th order least squares curve.
Let the normalized 1st, 2nd, 3rd, 4th order frequency fluctuation coefficients be respectively thecoordinate values on the x-, y-, z-axes, and point shade color, then up to the 4th order frequency
fluctuation characteristics locate the three dimensional space coordinate position and point shadecolor.

Fig. 1 A typical relationship between the frequency
characteristic and 4th order least squares curve.

Fig. 2 The visualized stress situations by the 4th orderfrequency fluctuation analysis to the 30 specimens.

To check the validity of our approach, we have carried out the frequency fluctuation analysis
to the 30 silicon steel sheet specimens when they are stressed and not stressed. Fig.2 shows thestress situations to the 30 silicon steel specimens. In Fig.2, the normalized 1st, 2nd, 3rd, 4th orderfrequency fluctuation coefficients are respectively the coordinate values on the x-, y-, z-axes, andpoint shade color. Comparison among the different specimens of this diagram visualizes an eachof the distinct characteristics depending on their mechanical stress conditions.
3 Conclusion
As shown above, we have succeed in visualizing the stress situations of the silicon steel sheetsin the 3 dimensional space whose coordinates are composed of the terms representing the higher
order frequency fluctuation of their Barkhausen signals.
References[1] R M. Bozorth: Ferromagnetism, p. 462 (IEEE PRESS)[2] M. Katsumata, S. Hayano and Y. Saito: A Study of Barkhausen Phenomenon Visualization, The Visualization
Society of Japan, B203, July, 2003.
[3] S. Nojima and Y. Saito: Application of Frequency Fluctuation to Barkhausen Signals and its Application, J.
Magn. Soc. Jpn., 35, 380-385, 2011.
[4] M. Teranishi, K. Maruyama, S. Hayano, and Y. Saito: Visualization of 1/f Frequency Component in Dynamic
Image of Natural Phenomena, The Visualization Society of Japan, B108, July, 2005..