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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 23, Issue 6 - Dec 2003
Volume 23, Issue 5 - Oct 2003
Volume 23, Issue 4 - Aug 2003
Volume 23, Issue 3 - Jun 2003
Volume 23, Issue 2 - Apr 2003
Volume 23, Issue 1 - Feb 2003
Selecting the target year
Evaluation of Drilled Shaft's End Condition by Impact-Echo Method
Kim, Dong-Soo ; Kim, Hyung-Woo ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 89~97
Experimental model studies were carried out to evaluate the end condition for drilled shafts by applying elastic impact on the top of the shaft, which is one of the various methods using stress waves. Typical impact responses corresponding to the various end conditions including free, fixed, rock-socketed, and soft-bottom with good and poor side contact conditions, were investigated. In order to simulate these renditions, mock-up shaft models made of cement mortar were used. Small-scale laboratory experiments were also performed, and field tests were carried out for the shafts that were socketed into weathered rock. It is found that the rock-socketed condition and depth of penetration into rock ran be identified from the reflection at the interface between the soil and rock in the waveform. The soft bottom rendition can be identified, only when the side contact between shaft and surrounding rock is poor, whereas it cannot be identified when the side contact is good because the waveform is similar to that of fixed end rendition.
Comparison of Longitudinal Wave Velocity in Concrete by Ultrasonic Pulse Velocity Method and Impact-Echo Method
Lee, Hoi-Keun ; Lee, Kwang-Myong ; Kim, Young-H. ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 98~106
Nondestructive test (NDT) provides much information on concrete without damage of structural functions. Of NDT methods, elastic wave propagation methods, such as ultrasonic pulse velocity (UPV) method and impact-echo (IE) method, have been successfully used to estimate the strength, elastic modulus, and Poisson's ratio of concrete as well as to detect the internal microstructural change and defects. In this study, the concretes with water-binder ratio ranging from 0.27 to 0.50 and fly ash content of 20% were made and then their longitudinal wave velocities were measured by UPV and IE method, respectively. Test results showed that the UPV is greater than the longitudinal wave velocity measured by the If method, i.e., rod-wave velocity obtained from the same concrete cylinder. It was found that the difference between the two types of velocities decreased with increasing the ages of concrete and strength level. Moreover, for the empirical formula, the dynamic Poisson's ratio, static and dynamic moduli of elasticity, and velocity-strength relationship were determined. It was observed that the Poisson's ratio and the modulus of elasticity determined by the dynamic method are greater than those determined by the static test. Consequently, for the more accurate estimation of concrete properties using the elastic wave velocities, the characteristics of these velocities should be understood.
Inspection of Underground Slurry Wall for LNG Storage Tank
Kim, Young-H. ; Jo, Churl-Hyun ; Lim, Seong-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 107~115
Nondestructive testing was carried out in order to evaluate the structural integrity and construction quality of the slurry wall of the underground LNG storage tank. 9 test points were selected, and the wall thickness, rebar spacing, and compressive strength of the slurry wall were evaluated by stress wave impact-resonance method, GPR, sonic velocity, and rebound testing, respectively. As results, the wall thickness, rebar sparing and estimated compressive strength satisfy the design criteria.
Acoustic Emission Behavior during Damage Development of Reinforced Concrete Beam
Park, Phi-Lip ; Jeong, Jung-Chae ; Kim, Dong-Jin ; Huh, Yong-Hak ; Huh, Yong-Hak ; Yoon, Dong-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 116~124
As a preliminary study for applying the acoustic emission(AE) technique to assess the integrity of concrete structures, AE behavior of a reinforced concrete beam under cyclic loads of various loading stage was examined by laboratory experiments. By analyzing failure behavior of a reinforced concrete beam in the AE point of view, it was presumed that major sources of AE signals in concrete were micro-crack initiation, development of flexural and diagonal tension crack, and the friction between track surfaces. In addition, cyclic loading tests and failure test were carried out to obtain the AE responses under various loading conditions. The analysis of the signal patterns was aimed at discussing the differences between the normal signal and the abnormal signal, which represent the safe condition and the condition of developing damage, respectively. In this study, especially, the behavior of friction signals from crack surfaces, which were usually treated as noises, was considered as a typical pattern of the normal signal. As a result, significant differences between the normal and abnormal signal patterns were observed in the such parameters as the AE hit rate, magnitude of the primary or secondary AE peak, and AE response according to the sensor location. Based on the preliminary results, this new approach for practical AE application may provide a promising method for estimating the level of damage and distress in concrete structures
Detection Subsurface Voids in Concrete Using Simulation Analysis of Radar Responses for frequency Variations
Park, Seok-Kyun ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 125~132
This study introduces a simulation model of radar responses from subsurface voids in concrete for their frequency variations. In this model, resolution and attenuation characteristics due to frequency variations are analyzed at each material interface which has different electromagnetic property. This model aims at the selection of best frequency of radar which can analyze the thickness of voids in concrete from radar responses. It can also be applied to estimate the limitation of propagation depth of radar on subsurface voids in concrete. The computed results show the radar images obtained by using a radar signal processing technique using convolution.
Self Diagnosis Technique of Concrete Structure Repaired and Strengthened by Carbon fiber Sheets Using Optical fiber Sensors
Kim, Ki-Soo ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 133~139
In order to extend the life time of building and civil infra-structure, nowadays, patch type fibrous composite materials are widely used. Repaired concrete columns and beams gain the stiffness and strength, but they lose toughness and show brittle failure. Usually, the cracks of concrete structures are visible with naked eyes and the status of the structure in the life cycle is estimated with visible inspection. After repairing of the structure, crack visibility is blocked by repaired carbon sheets. Therefore, structural monitoring after repairing is indispensible and self diagnosis method with optical fiber sensor is very useful. In this paper, peel-out effects is detected with optical fiber sensors and the strain difference between main structure and repaired carbon sheets when they separate each other.
Research on the Security of Infrastructures Using fiber Optic ROTDR Sensor
Park, Hyung-Jun ; Koh, Kwang-Nak ; Kwon, Il-Bum ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 140~147
A detection technique is studied to determine the location and the weight of an intruder into infrastructure using fiber optic ROTDR (Rayleigh optical time domain reflectometry) sensor. Fiber optic sensing plates buried in sand are prepared to measure the intruder effects. The signal of ROTDR was analyzed to confirm the detection performance. The constructed ROTDR system could be used up to 12km at the pulse width of 30ns. The location error was less than 3m and the weight could be detected into three levels of grade, such as 20kgf, 40kgf and 60kgf.
A Study on the Optimal Conditions of friction Welding for JLF & STS304 Using AE Technique
Yoon, Han-Ki ; Lee, Sang-Pill ; Kong, Yu-Sik ; Lee, Jin-Kyung ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 148~155
Japanese low activation terrific steel(JLF) is a good material for the parts of heat exchanger such as blanket and diverter. At first, JLF was developed as a candidate for structural materials in nuclear fusion applications. However, the development of the jointing technique of JLF steel to other materials is important for wide applications of this material to the industry fields. Recently the jointing technologies including diffusion bonding, brazing, roll bonding, explosive bonding and hot iso-static pressing have been studied for the heterogeneous materials of JLF-1 steel(Fe-9Cr-2W-V-Ta) and stainless steel(STS304). Friction welding is one of the most popular welding methods for two different kinds of materials. In this paper, the JLF-1 steel was jointed to SIS304 by friction welding method and the optimal conditions of the friction welding discussed. Acoustic emission was used as a nondestructive technique to evaluate the weld quality in processing.
Fatigue Behavior of STS316L Weldments and Degradation Characteristic Evaluation by Ultrasonic Test
Nam, Ki-Woo ; Park, So-Soon ; Ahn, Seok-Hwan ; Do, Jae-Yoon ; Park, In-Duck ;
Journal of the Korean Society for Nondestructive Testing, volume 23, issue 2, 2003, Pages 156~164
STS316L had been used as the structural material for energy environmental facilities, because austenite stainless steels like 316L have superior mechanical properties of which toughness, ductility, corrosion resistant and etc. However, those welded structures are receiving severe damage due to increasing of the aged degradation. Most studies until now have been carried out against fatigue behaviors of weldments, and were not well studied on nondestructive evaluation methods. In this study, the fatigue crack propagation behavior of STS316L weldment usually used for vessels of the nuclear power plant was investigated. Also, the degradation characteristics of 316L stainless steel weldments were evaluated by the ultrasonic parameter such as ultrasonic velocity, attenuation factor and time-frequency analysis. The results of this study can be used as a basic data for the prediction of the fatigue crack life of weldments structures without disjointing or stopping service of structures in service.