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 27, Issue 6 - Dec 2007
Volume 27, Issue 5 - Oct 2007
Volume 27, Issue 4 - Aug 2007
Volume 27, Issue 3 - Jun 2007
Volume 27, Issue 2 - Apr 2007
Volume 27, Issue 1 - Feb 2007
Selecting the target year
Eddy Current Bobbin Probe Design for Steam Generator Tubes in NPPs
Nam, Min-Woo ; Lee, Hee-Jong ; Jee, Dong-Hyun ; Jung, Jee-Hong ; Kim, Cheol-Gi ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 89~96
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.
Characterization of Acoustic Emission Signal for Welding Flaw and Stress Corrosion of SPPH Steels
Kim, Sung-Dai ; Jung, Woo-Gwang ; Lee, Jong-O ; Jung, Yu-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 97~104
An investigation has been made on the relationship between characteristics of Acoustic Emission (AE) signal in welding flaw and the stress corrosion defect in-service for the high pressure pipe steel. In order to tackle the problem of welding flaw in high pressure pipe, specimens were made by the aid of the application of both corrosion liquid usage and a quenching method after local heating. The amplitude of signal was
in the territory which is suspected for defect, and the specimens which only have welding flaw showed gradients of 0.034, 0.034, 0.035. Moreover, there is a certain increase in gradient even though the differences are very slight. That is, corrosion specimens showed new gradients of 0.040, 0.039, 0.041 which put welding flaw and corrosion mechanism together. After pressurizing 3 minutes, AE signal has been detected from welding flaw easily in each part of the section. It is possible to predict the occurrence and also prevent the damage of stress corrosion crack which has characteristics of cleavage fracture.
Evaluation of 2D Shear Wave Velocity Imaging of Subground Using HWAW Method
Kim, Jong-Tae ; Park, Hyung-Choon ; Bang, Eun-Seok ; Park, Heon-Joon ; Kim, Dong-Soo ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 105~114
Two-dimensional imaging of
profile becomes more important in Korea because of the large horizontal variation of soil stiffness. To obtain a shear-wave velocity profile in geotechnical practice, various seismic nondestructive investigation methods are being frequently used. In this study, harmonic wavelet analysis of wave (HWAW) method is applied to the determination of
profile to overcome some of weaknesses in the existing surface wave methods. HWAW method which is based on time-frequency analysis using harmonic wavelet transform has been developed to determine phase and group velocities of waves. Field testing of this method is relatively simple and fast because one experimental setup which consists of one pair of receivers is needed to determine
profile of site. The proposed method uses the signal portion of the maximum local signal/noise ratio to evaluate the phase velocity to minimize the effects of noise, and uses single array inversion which considers receiver locations. Field tests were performed in 2 sites in order to evaluate accuracy of test method and estimate the applicability of 2-D imaging by HWAW method. Through field applications and comparison with other test results, the good accuracy and applicability of the proposed method were verified.
Self-Diagnosis for Fracture Prediction of Concrete Reinforced by New Type Rib CFGFRP Rod and CF Sheet
Park, Seok-Kyun ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 115~123
For investigating self-diagnosis applicability, a method based on monitoring the changes in the electrical resistance of carbon fiber reinforced concrete has been tested. Then after examining change in the value of electrical resistance at each flexural weight-stage of carbon fiber in CFGFRP (carbon fiber and glass fiber reinforcing plastic) with new type rib and carbon sheet for concrete reinforcing, the correlations of electrical resistance and load as a function of strain, deflection were analyzed. As the results, it is clarified that when carbon fiber rod, rib and sheet fracture, the electrical resistance of it increase largely, and specially in case of CFGFRP, afterwards glass fiber tows can be resist the load due to the presence of the hybrid (carbon and glass) reinforced fiber. Therefore, it can be recognized that reinforcing bar and new type rib of CFGFRP and sheet of CF could be applied for self-diagnosis of fracture in reinforced FRP concrete.
FBG Optical Fiber Sensors Embedded in Fiber Reinforced Polymer Composite Reinforcing Bars
Kim, Myong-Se ; Cho, Hyung-Sik ; Cho, Sung-Kyu ; Yoon, Jae-Jun ; Baek, Hyun-Deok ; Kim, Ki-Soo ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 124~133
In our research, we focused on the FBG sensor system which is one of the fiber optic sensor system. The FBG sensor system is used for structural measurements. The problem of FBG sensor is very thin and weak. The methods that can protect FBG optical fiber sensor front outside forces such as the impacts are investigated. The FBG sensor embedded in the fiber reinforced composites which can replace the reinforcing steel bars in concretes can be applied to the concrete structures by embedding to the composite materials. The progresses in tensile strength of FBG sensor embedded in the reinforcing FRP bars in the concrete structures compare to plain FBGs were observed and the good long term durability is expected.
Delamination Detection of FRP Sheet Reinforced Concrete Using Microstrip Patch Antenna
Rhim, Hong-Chul ; Lee, Hyo-Seok ; Woo, Sang-Kyun ; Song, Young-Chul ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 134~141
A series of experimental work has been conducted to evaluate the capability of microstrip patch antenna system in detecting delamination in fiber reinforced Plastic (FRP) sheet reinforced concrete. For that purpose, a prototype microstrip patch antenna was developed with 15 GHz center frequency and 1 GHz bandwidth. For the comparison, a horn antenna with 15 GHz center frequency and 10 GHz bandwidth was used for the measurements of the same specimens. The laboratory sire specimens have the dimensions of 600 mm (length)
600 mm (width)
50mm (thickness) with a series of delaminations of 300 mm (length)
5, 10, 15 mm (thickness). FRP of 1.5 mm thickness and epoxy of 3 mm thickness were placed on the top of artificially created delamination to represent actual FRP reinforced concrete condition. In all cases, the delamination has deen successfully identified. Also, it was shown that imaging results in microstrip patch antenna were improved by signal processing.
Corrosion Measurement Method Using Thermographical Information
Yun, Ju-Young ; Chung, Lan ; Roh, Young-Sook ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 142~147
In order to measure corrosion level of steel reinforcement rebar which is inside reinforced concrete structure, infrared thermographic technique was employed. Experimental test parameters were four different ambient temperatures and various levels of corrosion states (0, 1, 3, 5, 7 and 10% of weight loss). After analysis of temperature distributions of concrete surface, the amount of heat flux from the concrete surface is directly proportional to the corrosion level which is inside of concrete.
Quantitative Evaluation of Fiber Dispersion of the Fiber-Reinforced Cement Composites Using an Image Processing Technique
Kim, Yun-Yong ; Lee, Bang-Yeon ; Kim, Jeong-Su ; Kim, Jin-Keun ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 148~156
The fiber dispersion in fiber-reinferced cementitious composites is a crucial factor with respect to achieving desired mechanical performance. However, evaluation of the fiber dispersion in the composite PVA-ECC (polyvinyl alcohol-engineered cementitious composite) is extremely challenging because of the low contrast of PVA fibers with the cement-based matrix. In the present work, a new evaluation method is developed and demonstrated. Using a fluorescence technique on the PVA-ECC, PVA fibers are observed as green dots in the cross-section of the composite. After capturing the fluorescence image with a charged couple device (CCD) camera through a microscope, the fiber dispersion is evaluated using an image processing technique and statistical tools. In this image processing technique, the fibers are more accurately detected by employing an enhanced algorithm developed based on a discriminant method and watershed segmentation. The influence of fiber orientation on the fiber dispersion evaluation was also investigated via shape analyses of fiber images.
Crack Detection of Concrete Using Fiber Optic Cables
Cho, Nam-So ; Kim, Nam-Sik ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 157~163
Crack detection technique for concrete structures has been developed in this study. Experimental tests were carried out to detect a surface and internal crack, employing common fiber optic cables and OTDR(optical time domain reflectometry), an optical signal analyzer which is widely used to detect damages at fiber optic cables in the field of optical engineering. While initial concrete crack is ready to occur under cracking force, the occurrence and location of the crack are simultaneously detected to give the same damage to fiber optic cables which have been attached to and/or embedded into concrete in advance. It is obtained through successive tests that the principal factors for crack detection is the covering state of fiber optic cable, and total 4 tests including a preliminary test were conducted and the crack detection technique was verified. The practical usefulness would be expected at crack management and maintenance of concrete structures.
Spectral Energy Transmission Method for Crack Depth Estimation in Concrete Structures
Shin, Sung-Woo ; Min, Ji-Young ; Yun, Chung-Bang ; Popovics, John S. ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 164~172
Surface cracks in concrete are common defects that can cause significant deterioration and failure of concrete structures. Therefore, the early detection, assessment, and repair of the cracks in concrete are very important for the structural health. Among studies for crack depth assessment, self-calibrating surface wave transmission method seems to be a promising nondestructive technique, though it is still difficult in determination of the crack depth due to the variation of the experimentally obtained transmission functions. In this paper, the spectral energy transmission method is proposed for the crack depth estimation in concrete structures. To verify this method, an experimental study was carried out on a concrete slab with various surface-opening crack depths. Finally, effectiveness of the proposed method is validated by comparing the conventional time-of-flight and cutting frequency based methods. The results show an excellent potential as a practical and reliable in-situ nondestructive method for the crack depth estimation in concrete structures.
Surface Crack Evaluation Method in Concrete Structures
Lee, Bang-Yeon ; Yi, Seong-Tae ; Kim, Jin-Keun ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 173~182
Cracks in concrete structures should be measured to periodically assess potential problems in durability and serviceability. Conventional crack measurement systems depend on visual inspections and manual measurements of the crack features such as width, length, and direction using microscope and crack gage. However, conventional methods take long time as well as manpower, and lack quantitative objectivity resulted by inspectors. In this study, an evaluation technique for concrete surface cracks is developed using image processing and artificial neural network. Developed technique consists of three major parts: (1) crack detection (2) crack analysis and (3) pattern recognition. To examine validity of the technique developed in this study, crack analyzing tests were performed on the images obtained from various types of concrete surface cracks. The test results revealed that the system is highly effective in automatically analyzing concrete surface cracks in terms of features and patterns of cracks.
Evaluation of Mass Variation of Aspheric Glass tens Using Resonant Ultrasound Spectroscopy
Heo, Uk ; Im, Kwang-Hee ; Yang, In-Young ; Kim, Ji-Hoon ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 2, 2007, Pages 183~189
Ultra precise processed parts are required together with the development of optoelectronics industry. As important parts of optoelectronics industry, there are ferrule of optical connector and lens for optical devices. In particular, the lens requires high reliability with high precision without including flaws. These optical modules need ultra precise processing in order to reduce the loss of light sources and various nondestructive inspections are carried out in the finishing stage to separate good and bad quality products. Therefore, it was analyzed through the characteristics of response of amplitude and resonant frequency according to the mass variations of aspheric lens that is used currently in laser printers.