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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 21, Issue 6 - Dec 2001
Volume 21, Issue 5 - Oct 2001
Volume 21, Issue 4 - Aug 2001
Volume 21, Issue 3 - Jun 2001
Volume 21, Issue 2 - Apr 2001
Volume 21, Issue 1 - Feb 2001
Selecting the target year
Numerical Analysis of Magnetic Flux Leakage Inspection
Lee, Hyang-Beom ; Kim, Sean ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 485~492
In this paper, electro-magnetic numerical analysis of MFL(magnetic flux leakage) method is presented. For the electromagnetic numerical analysis, 2-D FEM(finite element method) is used. The magnetic vector potential is used as a variable. The analysis of the magnetic field considering the magnetic nonlinearity is performed for the effect of the magnetic salutation. For the verification of the validity of the numerical simulation results, by using the lab-made experimental setup, non-destructive inspection is performed. The SM 45C carbon steel is used as a specimen and the artificial defects are made on the specimen. The non-destructive testing for the detection of the defect is performed. The results according to the variation oi the defect depth and the defect shape are obtained. The experimental results are compared to the numerical ones, and we conclude that the numerical results are similar to the experimental ones. So the possibility of simulation of the MFL by using the numerical analysis is shown in this paper.
Finite Element Modeling of Perturbation Fields due to Colonies of Stress Corrosion Cracks(SCCs) in a Gas Transmission Pipeline
Yang, Sun-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 493~500
The detection of axial cracks using conventional MFL pig is a significant challenge in the gas pipeline inspection. In this study, a technique using interaction of circumferentially induced torrents with axial stress corrosion crack is presented. The feasibility of this technique is investigated using finite element modeling. Finite element analysis of such interaction is a difficult problem in terms of both computation time and memory requirements. The challenges arise due to the nonlinearity of material properties, the small sire of tight cracks relative to that of the magnetizer, and also time stepping involved in modeling velocity effects. This paper presents an approach based on perturbation methods. The overall analysis procedure is divided into 4 simple steps that can be performed sequentially. Modeling results show that this technique can effectively detect colonies of SCC as well as single SCC.
Evaluation of Eddy Current Signals from the Inner Wall Axial Cracks of Steam Generator Tubes
Choi, Myung-Sik ; Hur, Do-Haeng ; Lee, Doek-Hyun ; Park, Jung-Am ; Han, Jung-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 501~509
For the enhancement of ECT reliability on the primary water stress corrosion cracks of nuclear steam generator tubes, of which the occurrence is on the increase, it is important to comprehend the signal characteristics on crack morphology and to select an appropriate probe type. In this paper, the sizing accuracy and the detectability for the inner wall axial cracks of tubes were quantitatively evaluated using the following specimens: the electric discharge machined notches and the corrosion cracks which were developed on the operating steam generator tubes. The difference of eddy current signal characteristics between pancake and axial coil were also Investigated. The results obtained from this study provide a useful information for more precise evaluation on the inner wall axial tracks oi stram generator tubes.
Classification of Axis-symmetric Flaws with Non-Symmetric Cross-Sections using Simulated Eddy Current Testing Signals
Song, S.J. ; Kim, C.H. ; Shin, Y.K. ; Lee, H.B. ; Park, Y.W. ; Yim, C.J. ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 510~517
This paper describes an initial study for the application of eddy current pattern recognition approaches to more realistic flaw characterization in steam generator tubes. For this purpose, finite-element model-based theoretical eddy current testing (ECT) signals are simulated from 5 types of OD flaws with the variation in flaw size parameters and testing frequency. In addition, three kinds of software are developed for the convenience in the application of steps in pattern recognition approaches such as feature extraction feature selection and classification by probabilistic neural networks (PNNs). The cross point of the ECT signals simulated from flaws with non-symmetric cross-sections shows the deviation from the origin of the impedance plane. New features taking advantages of this phenomenon are added to complete the feature set with a total of 18 features. Then, classification with PNNs are performed based on this feature set. The PNN classifiers show high performance for the identification of symmetry in the cross-section of a flaw. However, they show very limited success in the interrogation of the sharpness of flaw tips.
Feasibility Study of Remote Field Eddy Current Testing for Nonmagnetic Steam Generator Tubes
Shin, Young-Kil ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 518~525
As steam generator (SG) tubes have aged, new and subtle flaws have appeared. Most of them start growing from outside the tubes. Since signals from outer diameter (OD) defects are very weak compared to those from inner diameter (ID) defects in the conventional eddy current testing due to skin effect, this paper studies the feasibility of using remote field eddy current (RFEC) technique, which has shown equal sensitivity to ID and OD defects in the ferromagnetic pipe inspection. Finite element modeling studies show that the operating frequency needs to be increased up to a few hundred kHz in order for RFEC effects to occur in the nonmagnetic SG tube. The proper distance between exciter and sensor coils is also found to be about 1.5 OD, which is half the distance used in the ferromagnetic pipe inspection. Defect signals obtained by the designed RFEC probe show equal sensitivity to ID and OD defects and the existence of linear relationship between defect depth and phase signal strength. These results tell us that RFEC inspection is feasible even in nonmagnetic steam generator tubes.
Remote Field Energy Flow Path at Nonmagnetic Coaxial Tubes
Yi, Jae-Kyung ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 526~531
The flow of remote field eddy current energy is studied at nonmagnetic coaxial tubes by using both experiments and finite element calculations based on commercial software package. The results showed that remote field eddy current energy at coaxial tubes flow along over the outer surface of external tube, not through the gap between internal and external tubes. This means that the through wall transmission characteristic of remote field eddy current testing (RFECT) is still valid at tube in tube configurations and the RFECT could be potential nondestructive technique for crack detection, spacer location and gap sizing at the coaxial CANDU fuel channel tubes.
Evaluation Technology of Degradation of Metallic Alloy using Electrical Resistivity
Nahm, Seung-Hoon ; Yu, Kwang-Min ; Ryu, Jae-Cheon ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 532~541
Developments of nondestructive evaluation techniques for reduction of strength or toughness by aging of material have been carried out, and the method using electrical resistivity is one of them. In this study, to examine the application of electrical resistivity to the evaluation of degradation of metallic alloy, ten different non-magnetic materials were selected as test materials. Electrical resistivities measured by DC two-point probe method and those measured by non-contact type eddy current method were compared with each other. In addition, to examine the application possibility of four-point probe technology in field, the electrical resistivities for 1Cr-lMo-0.25V steel measured by DC two-point probe method and four-point probe method were compared with each other Differences between two measured values for the 1Cr-1Mo-0.25V steel were 0.6%. Therefore, the four-point probe method can be applied to the estimation of the degradation of metallic alloy. ect.
Fiber-Optic Current Transformer for the Over Current Protection Relay
Song, Min-Ho ; Yang, Chang-Soon ; Ahn, Seong-Joon ; Park, Byoung-Seok ; Lee, Byoung-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 542~548
A robust, accurate, broad-band, alternating current sensor using fiber-optics is being developed as a part of optical over current protection relay system. The sensor uses the Faraday effect in optical fiber and polarimetric measurements tc sense electrical current. The current sensing coil consists of a length of twisted optical fiber and Faraday rotator mirror to suppress the linear birefringence effect. Due to its single-ended closed path structure, it can not only be easily installed to the target with great isolation from other fields in the vicinity, but the sensitivity can be increased by using multiple turns. This paper reports on the theoretical backgrounds of the sensor design and the preliminary experimental results.
A Study on the Evaluation of Material Degradation for 1Cr-1Mo-0.25V Steel using Linear and Nonlinear Ultrasonics
Kim, Jeong-Pyo ; Seok, Chang-Sung ; Song, Sung-Jin ; Kim, Young-Hwan ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 549~555
Ultrasonic is a powerful nondestructive technique for getting the information of flaws and material properties of in-services facilities. We prepared 4 different 1Cr-1Mo-0.25V specimens by Isothermal aging at
. We evaluated material degradation using ultrasonic parameters, velocity, attenuation and harmonic generation. Attenuation and nonlinear parameter derived from harmonic generation efficiency increased as degradation. Especially the second harmonic of the fundamental wave in the 1,820h aging material was observed to exceed 20dB more than that in the un-aged material. But velocity remained virtually the same for all specimens. We concluded that nonlinear parameter and attenuation are sensitive to material degradation, but velocity was not. It'll be a good parameter for evaluating the material degradation.
Development of Remote Field Eddy Current Pipeline Inspection System
Jeong, Jin-Oh ; Yi, Jae-Kyung ; Kim, Hyoung-Jean ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 556~560
Remote field eddy current testing (RFECT) with through-wall transmission characteristic is being applied to pipes ranging from small tubes of heat exchanger to natural gas supply pipelines. Cast iron pipes with nominal diameter of 100mm are used primarily as the waterline pipes. The leakage of water occurs due to defects in the pipes caused by vibration of automobiles and corrosion. But, the use of direct inspection methods such as insertion of inspection equipment inside the pipelines has been limited due to its lack of economical efficiency. Economical development of inspection equipments is possible since RFECT method can be easily employed for system integration and quantitative evaluation of both inside and outside defects. In this study, the development of underground pipeline inspection system was tarried out by using RFECT method in consideration of the characteristics of waterline network. This paper specifically describes the design and production of RFECT pipeline inspection pig using centralizer mechanism, development of remote field eddy current signal acquisition and processing software, and review of RFECT system operation procedures.
Eddy Current Testing using Encircling Differential Probe for Research Reactor Fuel Rods
Lee, Yoon-Sang ; Kim, Chang-Kyu ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 5, 2001, Pages 561~564
The cladding area of HANARO Research Reactor fuel rods should be checked not to have any defects larger than the size required at QA documents by using eddy torrent testing method doting fabrication process. To apply eddy current testing inspection to the fuel rods, encircling differential probes and standard specimen were designed and fabricated. The impedance of the fabricated probes was measured with impedance analyzer in order to cheek that the probe has a suitable impedance for the inspection frequency, and with this probe and MIZ-40A eddy current equipment, the detectability of this probes was investigated. The developed probes could detect artificial notch with 2mm length 10% depth of cladding thickness in cladding area. In addition, the probe was successfully applied to detect the defects in cladding area doting fabrication of the research reactor rods.