Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
Editor in Chief :
Volume & Issues
Volume 24, Issue 6 - Dec 2004
Volume 24, Issue 5 - Oct 2004
Volume 24, Issue 4 - Aug 2004
Volume 24, Issue 3 - Jun 2004
Volume 24, Issue 2 - Apr 2004
Volume 24, Issue 1 - Feb 2004
Selecting the target year
Analysis of Dispersion Characteristics of Circumferential Guided Waves and Application to feeder Cracking in Pressurized Heavy Water Reactor
Cheong, Yong-Moo ; Kim, Sang-Soo ; Lee, Dong-Hoon ; Jung, Hyun-Kyu ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 307~314
A circumferential guided wave method was developed to detect the axial crack on the bent feeder pipe. Dispersion curves of circumferential guided waves were calculated as a function of curvature of the pipe. In the case of thin plate, i.e. infinite curvature, as the frequency increases, the
mode coincide and eventually become Rayleigh wave mode. In the case of pipe, however, as the curvature increases, the lowest modes do not coincide even in the high frequencies. Based on the analysis, a rocking technique using angle beam transducer was applied to detect an axial defect in the bent region of PHWR feeder pipe. Based on the analysis of experimenal data for artificial notches, the vibration modes of each signal were identified. It was found that the notches with the depth of )0% of wall thickness can be detected with the method.
Drawing of Impedance Plane Diagrams of Absolute Coil ECT Signals by finite Element Analysis
Shin, Young-Kil ; Lee, Yun-Tai ; Lee, Jeong-Ho ; Song, Myung-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 315~324
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.
A Study on the Measurement of Ultrasound Velocity to Evaluate Degradation of Low Voltage Cables for Nuclear Power Plants
Kim, Kyung-Cho ; Kang, Suk-Chull ; Goo, Charles ; Kim, Jin-Ho ; Park, Jae-Seok ; Joo, Geum-Jong ; Park, Chi-Seung ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 325~330
Several kinds of low voltage cables have been used in nuclear power plants for the supply of electric power, supervision, and the propagation of control signals. These low voltage tables must be inspected for safe and stable operation of nuclear power plants. In particular, the degradation diagnosis to estimate the integrity of low voltage rabies has recently been emphasized according to the long use of nuclear power plants. In order to evaluate their degradation, the surrounding temperature, hardness of insulation material, elongation at breaking point (EAB), etc. have been used. However, the measurement of temperature or hardness is not useful because of the absence of quantitative criteria; the inspection of a sample requires turning off of the power plant power; and, the electrical inspection method is not sufficiently sensitive from the initial through the middle stage of degradation. In this research, based on the theory that the ultrasonic velocity changes with relation to the degradation of the material, we measured the ultrasonic velocity as low voltage cables were degraded. To this end, an ultrasonic degradation diagnosis device was developed and used to measure the ultrasonic velocity with the clothing on the cable, and it was confirmed that the ultrasonic velocity changes according to the degradation of low voltage cables. The low voltage cables used in nuclear power plants were degraded at an accelerated rate, and EAB was measured in a tensile test conducted after the measurement of ultrasonic velocity. With the increasing degradation degree, the ultrasonic velocity decreased, whose potential as a useful parameter for the quantitative degradation evaluation was thus confirmed.
Experimental Studies on Ultrasonic Guided Waves for the On-Line Inspection of Structural Integrity of Nuclear Power Plants
Eom, Heung-Seop ; Kim, Jae-Hee ; Song, Sung-Jin ; Kim, Young-H. ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 331~340
Deployment of an advanced on-line monitoring of the component integrity offers a prospect of improved performance, enhanced safety, and reduced overall cost for nuclear power plants. Ultrasonic guided waves have been known as one of the promising techniques that could be utilized for on-line monitoring. The present work is aimed at developing a new method for on-line monitoring of the pipes during the operation period of nuclear power plants. For this purpose, the steam generator (S/G) tube was selected as an object of tile experiment. Dispersion corves and the incident angles corresponding to the specific modes were calculated for the S/G tube. The modes of guided waves were identified by the time-frequency diagrams obtained by the short time Fourier transform. It was experimentally confirmed that there was no mode conversion when the ultrasonic guided waves passed over the curved region of the S/G tube. An optimum mode of guided wave for the S/G tube was suggested and verified by the experiment.
Identification of Guided-Wave Modes in Pipings of Power Plants by using Air-coupled Transducer
Park, Ik-Keun ; Kim, Hyun-Mook ; Kim, Yong-Kwon ; Song, Won-Joon ; Cho, Yong-Sang ; Jhang, Kyung-Young ; Cho, Youn-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 341~347
In order to inspect the piping effectively, one of the important components in the facility of power plants, the ultrasonic guided wave was generated by a tomb transducer and was received in a non-contact fashion by using an air-coupled transducer. The guided wave modes that ran be generated by the comb transducer in piping are predicted from the theoretical dispersion curves and the element spacing of a comb transducer. Moreover, to receive the specific modes, the receiving angle of the air-coupled transducer is calculated from Snell's law between the phase velocities of guided waves and the sound velocity of air. The guided wave modes obtained in experiments are identified from the result of time-frequency analysis such as wavelet transform and two-dimensional fast Fourier transform.
Implementation of Ultrasonic Immersion Technique for Babbitt Metal Debonding in Turbine Bearing
Jung, Gye-Jo ; Park, Sang-Ki ; Cho, Yong-Sang ; Park, Byung-Cheol ; Kil, Doo-Song ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 348~353
This study is aimed for the implementation of ultrasonic method to assess the reliability of turbine bearings. A modified ultrasonic immersion technique was carried out in both laboratory experiment and field application. From the laboratory results, we confirmed that the condition of interface layer between the babbitt and base metal be monitored by the C-Scan. The C-scan image by the ultrasonic immersion test can be used successfully to observe the condition of interface layer. The testing with a focused transducer provides a promising approach for estimating the extent of the damaged region and observing the interface layer effectively. The difference of the ultrasonic reflection ratio between the bonding and debonding area at the interface layer is one of the key parameters for assessing the extent of the damaged area; additionally, the reflection amplitude exhibits a favorable correlation with the overall damage level. The technique developed in this study was applied to the inspection of the turbine bearings at several power plants in Korea whereby the applicability in the field can be ascertained.
SH Wave Scattering from Cracks: Comparisons of Approximate and Exact Solutions
Jeong, Hyun-Jo ; Park, Moon-Cheol ; Song, Sung-Jin ; Schmerr, L.W. ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 354~361
This Paper describes a crack scattering model for SH wave based on the boundary integral equation(BIE) method, where the fundamental unknown is crack opening displacement(COD). When a time harmonic plane wave was incident on a 2-D isolated crack (slit) of width 2a, the COD distributions were numerically calculated as a function of ka. The calculated COD agreed well with results obtained with other methods. The far-field scattering amplitude, which completely characterizes the flaw response, was calculated in two ways. The Kirchhoff approximation and the BIE-COD exact formulation were compared in terms of incidence angle and frequency ka in a pulse-echo mode. Maximum response was obtained for both methods at the specular reflection direction. Away from the specular direction, the Kirchhoff approximation becomes less accurate. The time domain crack response was also calculated using a band-limited spectrum of center frequency 10 MHz. At oblique incidence to the crack both methods show the existence of an antisymmetric flash points occurring from the crack edge. The Kirchhoff approximation provides an exact time interval between flash points, although it unrealistically gives the same amplitude.
Estimation of Collapse Moment for Wall Thinned Elbows Using Fuzzy Neural Networks
Na, Man-Gyun ; Kim, Jin-Weon ; Shin, Sun-Ho ; Kim, Koung-Suk ; Kang, Ki-Soo ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 362~370
In this work, the collapse moment due to wall-thinning defects is estimated by using fuzzy neural networks. The developed fuzzy neural networks have been applied to the numerical data obtained from the finite element analysis. Principal component analysis is used to preprocess the input signals into the fuzzy neural network to reduce the sensitivity to the input change and the fuzzy neural networks are trained by using the data set prepared for training (training data) and verified by using another data set different (independent) from the training data. Also, two fuzzy neural networks are trained for two data sets divided into the two classes of extrados and intrados defects, which is because they have different characteristics. The relative 2-sigma errors of the estimated collapse moment are 3.07% for the training data and 4.12% for the test data. It is known from this result that the fuzzy neural networks are sufficiently accurate to be used in the wall-thinning monitoring of elbows.
Development of Automatic Ultrasonic Testing Techniques of Low Pressure Turbine Blade of Nuclear Power Plants
Yang, Seung-Han ; Lee, Jeong-Bin ; Kim, Young-Ho ; Yoon, Byung-Sik ; Kim, Yong-Sik ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 371~377
As the turbine running duration in nuclear power plants increases, cracks have been found in the pin finger type blade root area. The nondestructive examination for the blade root area has been carried out by manual ultrasonic examination during the overhaul period, but because of necessity to improve the reliability, we developed an automatic ultrasonic examination system and technique. To demonstrate the performance of the developed automatic ultrasonic examination system, low pressure turbine blades in the 2nd and 3rd stages of nuclear power plants were examined using the developed system. Its applicability nuclear power plant turbine roots of various types was also confirmed.
Round Robin Test for Performance Demonstration System of Ultrasonic Examination Personnel
Yoon, Byung-Sik ; Yang, Seung-Han ; Kim, Yong-Ho ; Kim, Yong-Sik ; Yang, Dong-Soon ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 378~383
The Korean Performance Demonstration(KPD) System for the ultrasonic testing personnel, equipments and procedures applicable to the Class 1 and 2 piping examination for nuclear power plant in Korea has been established. A round robin test was conducted in order to compare the examination results by the method of Performance Demonstration(PD) with the traditional dB-drop method. The round robin test shows that the reliability of the PD method is better than that of the dB-drop method. As a result, adoption of the PD method to the in-service inspection of the nuclear power plants will improve the reliability of the ultrasonic test results.
The Experience of Inservice Inspection for Yonggwang Nuclear Power Plant Unit 6
Kim, Young-Ho ; Nam, Min-Woo ; Yang, Seung-Han ; Yoon, Byung-Sik ; Kim, Yong-Sik ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 384~389
As the increase of the operation year of nuclear power plants, the probabilities of the degradation of the major facilities and materials in the nuclear power plants are increased. The integrity of those facilities shall be monitored and verified by the non-destructive examination methods with the regulation codes, so called inservice inspection(ISI). The ISI of Yonggwang unit 6 was performed in four different parts, 1) non-destructive examinations for the components, piping weldments and structures, 2) automated ultrasonic examinations for pressure vessels, 3) visual examinations for the interior structures of the reactor, 4) eddy current examinations for the steam generator tubes. As the results, there was no severe indication and all detected indications were evaluated as non-relavent. Especially for the examinations of the piping weldments, PD(Performance Demonstration) was applied as a W examination method defined in the 1995 edition of ASME Code Sec. XI. The implementation of the PD for the piping weld results in an improvement of the reliability of the UT examinations.
Development of Pre-Service and In-Service Information Management System (iSIMS)
Yoo, H.J. ; Choi, S.N. ; Kim, H.N. ; Kim, Y.H. ; Yang, S.H. ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 390~395
The iSTMS is a web-based integrated information system supporting Pre-Service and In-Service Inspection(PSI/ISI) processes for the nuclear power plants of KHNP(Korea Hydro & Nuclear Power Co. Ltd.). The system provides a full spectrum coverage of the inspection processes from the planning stage to the final report of examination in accordance with applicable codes, standards, and regulatory requirements. The major functions of the system includes the inspection planning, examination, reporting, project control and status reporting, resource management as well as objects search and navigation. The system also provides two dimensional or three dimensional visualization interface to identify the location and geometry of components and weld areas subject to examination in collaboration with database applications. The iSIMS is implemented with commercial software packages such as database management system, 2-D and 3-D visualization tool, etc., which provide open, updated and verified foundations. This paper describes the key functions and the technologies for the implementation of the iSIMS.
Nondestructive Testing and Applications for Electric Power Plant Equipments by Acoustic Emissin Technology
Lee, Sang-Guk ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 396~409
Diagnosis f structural integrity is the basis for correct treatment of and countermeasures against progressive structural abnormalities. An exact diagnosis is at present the most reliable means for determining the soundness of structures during power plant operations. Acoustic emission(AE) technology has recently strengthened its application base, and practitioners' understanding of the technique's fundamentals. This paper presents the results of a survey and assessment on AE monitoring applications in nuclear, fossil and hydraulic power plant. The main objective of this paper was to obtain information on various applications of AE technology in electric power plant.
Maintenace of Power Plant facilities and Nondestructive Inspection (II) -Nuclear Power Plants-
Park, Ik-Keun ; Kang, Suk-Chull ;
Journal of the Korean Society for Nondestructive Testing, volume 24, issue 4, 2004, Pages 410~430