• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1963-1965
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• 2000

This paper deals with a problem of detecting the inner corrosion of the ACSR(Aluminum Conductor Steel Reinforced) power lines using a detector which consists of an ECT(Eddy Current Test) sensor, a constant current service, a signal processing unit, and a RF transmitter/receiver unit. The detector runs on the ACSR transmission line and inspects the corrosion of the conductor using the technic of the nondestructive eddy current test. The experimental result shows this detector can efficiently find the zinc loss in ACSR power lines.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.2
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• pp.198-202
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• 2002

Beacuse intergranular attack (IGA), one of the locallized corrosion forms occurring on steam generator tubes, can not be fabricated by an electric discharge machining method, there are few data for the eddy current test (ECT) characteristics of IGA. In this paper, the characteristics of eddy current signals are evaluated using nonexpanded tubes with IGA defects formed in 0.1 M sodium tetrathionate solution at $40^{\circ}C$. The detectability and sizing accuracy of IGA were discussed in terms of the coil type and frequency of the ECT probes.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.450-457
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• 2009

Periodical thermal shock can introduce defects in thermal barrier coating made by layers of CoNiCrAlY bond coating(BC) and $ZrO_2-8wt%Y_2O_3$ ceramic top coating(TC) on Inconel-738 substrate using plasma spraying. Thermal shock test is performed by severe condition that is to heat until $1000^{\circ}C$ and cool until $20^{\circ}C$. As the number of cycle is increased, the fatigue by thermal shock is also increased. After test, the micro-structures and mechanical characteristics of thermal barrier coating were investigated by SEM, XRD. The TGO layer of $Al_2O_3$ is formed between BC and TC by periodical thermal shock test, and its change in thickness is inspected by eddy current test(ECT). By ECT test, it is shown that TGO and micro-crack can be detected and it is possible to predict the life of thermal barrier coating.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.6
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• pp.426-432
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• 1999

A plus-point eddy current test(ECT) probe was developed to examine the defects on the welds of pumps, valves, and pipings which are the major components of the electric power plants, non-destructive evaluation (NDE) techniques for detecting and sizing the flaws were studied adapting this probe. Differential plus-point ECT probe is consists of two "I"-type coils crossed each other and has an advantage having a small influence on the sensitivity by lift-off variation to the conventional types of probe. The specimens with crack-like electro discharge machining(EDM) notches on the weld of type 304 stainless-steel were fabricated in order to evaluate the plus-point ECT probe response to the flaws. NDE techniques to detect and size the flaws and estimate the flaw type were established with this specimens.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.159-165
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• 2008

In this paper the signal analysis of eddy current test using transmit-receive(T/R) pancake coil of ECT array probe using electromagnetic finite element method(FEM) is performed. For characteristics analysis, the notch defect is used. The depth of defect is 40[%] of steam generator tube thickness, and inside defect and outside defect are used as simulation examples. The signal analysis is performed according to the variation of receive coil position. The receive coil is positioned $0[^{\circ}]$, $30[^{\circ}]$, $60[^{\circ}]$, $90[^{\circ}]$ of circumferential position of transmit coil. To obtain e electromagnetic characteristics of robes, the governing equation is derived from Maxwell's equations, and the problem is solved using the 3-dimensional finite element method. The signal magnitude of inside defect is bigger than that of outside defect, and the signal difference can be seen according to the variation of position of receive coil. The experimental signal and numerical signal of ASME standard tube show similar results. The results in this paper can be helpful when the ECT signals from ECT array probe are evaluated and analyzed.

• Journal of Magnetics
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• v.20 no.3
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• pp.312-316
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• 2015

Unlike conventional Eddy Current Test (ECT), Pulsed Eddy Current (PEC) uses a multiple-frequency current pulse through the excitation coil. In the present study, the detection of subsurface cracks using a specially designed probe that allows the detection of a deeper crack with a relatively small current density has been attempted using the PEC technique. The tested sample is a piece of 304 stainless steel (SS304) with a thickness of 30mm. Small electrical discharge machining (EDM) notches were put in the test sample at different depths from the surface to simulate the subsurface cracks in a pipe. The designed PEC probe consists of an excitation coil and a Hall sensor and can detect a subsurface crack as narrow and shallow as 0.2 mm wide and 2 mm deep. The maximum distance between the probe and the defect is 28 mm. The peak amplitude of the detected pulse is used to evaluate the cracks under the sample surface. In time domain analysis, the greater the crack depth the greater the peak amplitude of the detected pulse. The experimental results indicated that the proposed system has the potential to detect the subsurface cracks in stainless steel plates.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.89-96
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• 2007

The bobbin probe examination is basic and the important method among other ECT techniques for the steam generator tube integrity assesment that is practiced during each plant outage. The bobbin probe is one of the essential components which consist of the whole ECT examination system, and provides us a decisive data for the evaluation of tube integrity in compliance with acceptance criteria described in specific procedures. The selection of examination probe is especially important because the quality of acquired ECT data is determined by the probe design characteristics, such as geometry and operation frequency, and has enormous effects on examination results. In this study, An optimal differential bobbin probe is designed for the steam generator tube inspection in nuclear power plants(NPPs). Based on the test results for electrical and ECT signal characteristics, the prototype bobbin probe satisfies all the criteria.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.6
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• pp.511-518
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• 2013

Steam Generator (SG) tube, as a barrier isolating the primary coolant system from the secondary side of nuclear power plants (NPP), must maintain the structural integrity for the public safety and their efficient power generation. So, SG tubes are subject to the periodic examination and the repairs if needed so that any defective tubes are not in service. Recently, corrosion related degradations were detected in the tubes of the domestic OPR-1000 NPP, as a form of axially oriented outer diameter stress corrosion cracking (ODSCC). According to the studies on the factors causing the heat fouling as well as developing corrosion cracking, densely scaled deposits on the secondary side of the SG tubes are mainly known to be problematic causing the adverse impacts against the soundness of the SG tubes [1]. Therefore, the processes of various cleaning methods efficiently to dissolve and remove the deposits have been applied as well as it is imperative to maintain the structural integrity of the tubes after exposing to the cleaning agent. So qualification test (QT) should be carried out to assess the perfection of the chemical cleaning and QT is to apply the processes and to do ECT. In this paper, the chemical cleaning processes to dissolve and remove the scaled deposits are introduced and results of ECT on the artificial crack specimens to determine the effectiveness of those processes are represented.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.315-324
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• 2004

In eddy current testing(ECT), differential probes have been frequently used since they .an reduce the number of parameters that influence ECT signals. However, differential signal is actually the difference of the two coils' impedance so that signal prediction and interpretation are not easy, On the other hand, absolute coil signal is rather straightforward to predict and analyze. Therefore, combined use of the two types of signals would increase the test reliability. In this paper, absolute coil signals from Inconel plate and tubes are predicted by the finite element analysis and efforts of lift-off, fill-factor, conductivity, operating frequency, test specimen thickness, inner diameter defects, and outer diameter defects are investigated. As a result, various impedance plane diagrams are drawn and analyzed. Significant practical knowldege about absolute signals is accumulated and similar characteristics of the two types of signal could be understood. Finally, slope angle versus defect depth calibration corves are prepared for three different frequencies.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.118-124
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• 2003

응축기, 증발기, 전열관에 사용되는 Fin Tube는 열전달효율 향상을 위하여 Fin의 높이 를 증가시키고, Tube의 최소두께를 얇게 가공하는 경향으로 발전하고 있다. 따라서, Fin Tube의 와전류탐상(ECT; Eddy Current Testing)에 의한 결함검출에 더욱 어려움이 예상된다. 본 연구에서는 Fin Tube의 Fin 높이를 3단계로 변화시켜 Tube를 제작하고, Tube에 축 방향결함, 원주방향결함, 원형결함을 각각 Fin Tube의 안쪽에 최소두께의 20%, 40%, 60% 의 동일결함율을 갖는 인공결함 시험편을 제작하였다. 제작한 원형결함시험편에 와전류탐상을 수행하여 Fin 높이에 따른 최적주파수의 변화를 연구하였다. Fin높이가 다른 원형결함 시험편에 1~20KHz 주파수를 적용한 결과 최적주파수는 12KHz로 Fin높이에 크게 영향을 받지 않음을 밝혔다 또한 Fin높이에 따른 최적주파수변화는 크지 않으나 Fin 높이가 높을수록 100%관통결함의 위상각(40')에 근접하여 나타났다. 축방향결함, 원주방향결함, 원형결함을 갖는 시험편에 와전류탐상을 수행한 결과 원형결함을 갖는 시험편의 신호 감도가 축방향결함, 원주방향결함보다 좋게 나타났다.