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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 29, Issue 6 - Dec 2009
Volume 29, Issue 5 - Oct 2009
Volume 29, Issue 4 - Aug 2009
Volume 29, Issue 3 - Jun 2009
Volume 29, Issue 2 - Apr 2009
Volume 29, Issue 1 - Feb 2009
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Experimental Evidence and Analysis of a Mode Conversion of Guided Wave Using Magnetostrictive Strip Transducer
Cheong, Yong-Moo ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 93~97
An advantage of a magnetostrictive strip transducer for a long-range guided wave inspection is that the wave patterns are relatively clear and simple when compared to a conventional piezoelectric ultrasonic transducer. Therefore, if we can characterize the evolution of defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaws. However, when evaluating a signal during a realistic field examination, it should be careful because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. Mode converted signals from a realistic piping mockup were acquired and analysed. We found mode conversions between a torsional guided wave T(0,1) mode and a flexural F(1,3) or longitudinal L(0,2) mode generated by a magnetostrictive strip transducer. Based on the experimental observations, an interpretation of the source of the mode conversion is discussed in a viewpoint of electromagnetic properties and structure of the strip transducer.
Depth-Sizing Technique for Crack Indications in Steam Generator Tubing
Cho, Chan-Hee ; Lee, Hee-Jong ; Kim, Hong-Deok ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 98~103
The nuclear power plants have been safely operated by plugging the steam generator tubes which have the crack indications. Tube rupture events can occur if analysts fail to detect crack indications during in-service inspection. There are various types of crack indication in steam generator tubes and they have been detected by the eddy current test. The integrity assessment should be performed using the crack-sizing results from eddy current data when the crack indication is detected. However, it is not easy to evaluate the crack-depth precisely and consistently due to the complexity of the methods. The current crack-sizing methods were reviewed in this paper and the suitable ones were selected through the laboratory tests. The retired steam generators of Kori Unit 1 were used for this study. The round robin tests by the domestic qualified analysts were carried out and the statistical models were introduced to establish the appropriate depth-sizing techniques. It is expected that the proposed techniques in this study can be utilized in the Steam Generator Management Program.
The Influence of Distance between Current Supply Points on Potential Drop in DCPD
Lee, Jeong-Hee ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 104~107
It was verified that the effect of the distance between current input point and output point on direct current potential drop(DCPD) in the material with two-dimensional surface notch. If the distance between potential drop measuring points was fixed at a certain distance, the potential drop was decreased with increasing the distance between current input and output points. Hence it is the effect way to increase sensitivity in DCPD that the current input and output points should be located near the potential measuring points. DCPD was a useful method for surface crack sizing because the potential drop was proportional to the length of notch. When the current input and output points are located near the potential measuring points, even small length crack can be measured by DCPD technique.
Performance Comparison of Pipeline Defects' Length Estimation Using MFL Signals
Kim, Tae-Wook ; Rho, Yong-Woo ; Choi, Doo-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 108~113
MFL(magnetic flux leakage) inspection is a general method of non-destructive evaluation(NDE) of underground gas pipelines. Pipelines are magnetized by permanent magnets when MFL PIG(pipeline inspection gauge) gets through them. If defects or corrosions exist in pipelines, effective thickness is changed and thus variation of leakage flux occurs. The leakage flux signals detected by hall-sensors are analyzed to characterize defect's geometries such as length, width, depth, and so on. This paper presents several methods for estimating defect's length using MFL signals and their performances are compared for real defects carved in KOGAS pipeline simulation facility. It is found that 80% and 90% of minimum values for axial and peak values for radial signals respectively show the best performance in the point of length estimation error.
A Study on Techniques for Focusing Circumferential Array Guided Waves for Long Range Inspection of Pipes
Kang, To ; Kim, Hak-Joon ; Song, Sung-Jin ; Cho, Young-Do ; Lee, Dong-Hoon ; Cho, Hyun-Joon ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 114~121
Ultrasonic guided waves have been widely utilized for long range inspection of structures. Especially, development of array guided waves techniques and its application for long range gas pipe lines(length of from hundreds meters to few km) were getting increased. In this study, focusing algorithm for array guided waves was developed in order to improve long range inspectability and accuracy of the array guided waves techniques for long range inspection of gas pipes, and performance of the developed techniques was verified by experiments using the developed array guided wave system. As a result, S/N ratio of array guided wave signals obtained with the focusing algorithm was increased higher than that of signals without focusing algorithm.
Development of an SH Wave Magnetostrictive Transducer Module for Guided Wave Testing of Plate Structures
Cho, Seung-Hyun ; Park, Jae-Ha ; Kwon, Hyu-Sang ; Ahn, Bong-Young ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 122~129
Recently much attention has been paid to a guided wave due to its effective applicability to long range and fast inspection of structures. In guided wave based NDE, the appropriate selection of wave modes is one of important factors since the test performance is highly dependent on which mode of guided waves is employed. As far as plate-like structures are concerned, so far, SH guided wave has not been frequently applied compared to Lamb waves, which is mostly caused by the lack of proper and convenient transducers to generate and measure the SH waves. In this investigation, a new small-sized SH guided wave transducer based on magnetostriction is proposed. The present transducer was designed to be modular and be used with shear couplant to avoid the inconvenience of the existing magnetostrictive patch transducers, which comprises the ferromagnetic patch tightly bonded to a structure. The wave transduction mechanism and the detailed configuration of the present transducer are presented. Experimental verification is also conducted on test specimens and the results confirm the good performance of the present transducer module.
Development of Ultrasonic Testing System for In-Service Inspection of the Shrunk-on Type LP Turbine Roter
Park, Joon-Soo ; Seong, Un-Hak ; Ryu, Sung-Woo ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 130~136
Turbine, which is one of major components in nuclear power plants, requires reliable nondestructive inspections. But, accessibility of transducers is limited and interpretation of acquired signals is not easy at all due to the complication. So, in this study, we have fabricated mock-up specimens of real size and shape. we applied pulse-echo method and time-of-flight diffraction(TOFD) method for precise inspection of turbine key and wheel bore. And phased array ultrasonic testing method was adopted for wheel dovetail of turbines by using mock-up. Furthermore, an automatic scanner system was developed for in-service inspection of the developed methods.
Signal Analysis of Eddy Current Array Probe According to Size Variation of FBH Defects
Kim, Ji-Ho ; Lim, Geon-Gyu ; Lee, Hyang-Beom ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 137~144
In this paper, the signal analysis of eddy current array probe was performed to analyze the electromagnetic characteristics with the variation of FBH(flat bottomed hole) defects size on steam generator tube in NPP(nuclear power plants) using the electromagnetic finite element method. To obtain the electromagnetic characteristic of probes, the governing equation was derived from Maxwell's equations, and the individual problem was analyzed by using the 3-dimensional finite element method. For the simulation FBH defects were used. The depth of FBH defects were 20%, 40%, 60%, 80% and 100% of steam generator(SG) tube thickness, and it was assumed that the defects were located on the tube outside. And the operation frequencies of 100 kHz, 300 kHz and 400 kHz were used. Material of specimen was Inconel 600 which is usually used for SG tubes in NPP. The signal difference could be observed according to the size variation of depth of FBH defects and operation frequencies. The results in this paper can be helpful when the ECT(eddy current testing) signals from EC array probe are evaluated and analyzed.
Development of a Multi-Channel Ultrasonic Testing System for Automated Ultrasonic Pipe Inspection of Nuclear Power Plant
Lee, Hee-Jong ; Cho, Chan-Hee ; Cho, Hyun-Joon ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 145~152
Currently almost all in-service-inspection techniques, applied in domestic nuclear power plants, are partial to field inspection technique. These kinds of techniques are related to managing nuclear power plants by the operation of foreign-produced inspection devices. There have been so many needsfor development of native in-service-inspection device because there is no native diagnosis device for nuclear power plant inspection yet in Korea. In this research, we developed several core techniques to make an automated ultrasonic pipe inspection system for nuclear power plants. A high performance multi-channel ultrasonic pulser/receiver module, an A/D converter module and a digital main CPU module were developed and the performance of the developed modules was verified. The S/N ratio, noise level and signal acquisition performance of the developed modules showed proper level as we designed in the beginning.
Current Status and Investigation of International Co-operative Research Program-PINC(Program for the Inspection of Nickel Alloy Components)
Kim, Kyung-Cho ; Kang, Sung-Sik ; Song, Kyung-Ho ; Chung, Koo-Kap ; Chung, Hae-Dong ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 153~161
After several PWSCCs were found in Bugey(France), Ringhals(Sweden), Tihange(Belgium), Oconee, Arkansas, Crystal Fever, Davis-Basse, VC Summer(U.S.A.), Thuruga(Japan), USNRC and PNNL started the research on PWSCC, that is, PINC project. The aim of this project is to fabricate and obtain representative NDE mock-ups with flaws to simulate tight PWSCC cracks, to identify and quantitatively assess NDE methods for accurately detecting, sizing and characterizing tight cracks such as PWSCC, to document the range of locations and crack morphologies associated with PWSCC and observed responses and to incorporate findings from other ongoing PWSCC research programs, as appropriate. By participating in PINC project, Korean morphology technique about PWSCC and NDE technique have improved and become similar lever with other advanced country. Therefore, the evaluation technique of integrity for nickel alloy component has been improved by cooperation with university, research institute and industries.
Risk Assessment Technology of LNG Plant System
Choi, Song-Chun ; Ha, Je-Chang ; Lee, Mee-Hae ; Jo, Young-Do ; Chang, Yoon-Suk ; Choi, Shin-Beom ; Choi, Jae-Boong ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 162~170
As one of promising solutions to overcome high oil price and energy crisis, the construction market of high value-added LNG plants is spotlighted world widely. The purpose of this manuscript is to introduce domestic activities to develop risk assessment technology against overseas monopolization. After analyzing relevant specific features and their technical levels, risk assessment program, non-destructive reliability evaluation strategy and safety criteria unification class are derived as core technologies. These IT-based convergence technologies can be used for enhancement of LNG plant efficiency, in which the modular parts are related to a system with artificial optimized algorithms as well as diverse databases of facility inspection and diagnosis fields.
The Technical State of Diagnosis in the Petrochemical Plants
Kim, Sung-Moon ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 2, 2009, Pages 171~180