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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
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Volume & Issues
Volume 20, Issue 6 - Dec 2000
Volume 20, Issue 5 - Oct 2000
Volume 20, Issue 4 - Aug 2000
Volume 20, Issue 3 - Jun 2000
Volume 20, Issue 2 - Apr 2000
Volume 20, Issue 1 - Feb 2000
Selecting the target year
Application of One-Sided Stress Wave Velocity Measurement Technique to Evaluate Freeze-Thaw Damage in Concrete
Lee, Joon-Hyun ; Park, Won-Su ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 269~275
It is well recognized that damage resulting from freeze-thaw cycles is a serious problem causing deterioration and degradation of concrete. In general, freeze-thaw cycles change the microstructure of the concrete ultimately leading to internal stresses and cracking. In this study, a new method for one-sided stress wave velocity measurement has been applied to evaluate freeze-thaw damage in concrete by monitoring the velocity change of longitudinal and surface waves. The freeze-thaw damage was induced in a
concrete specimen in accordance with ASTM C666 using s commercial testing apparatus. A cycle consisted of a variation of the temperature from -14 to 4 degrees Celsius. A cycle takes 4-5 hours with approximately equal times devoted to freezing-thawing. Measurement of longitudinal and surface wave velocities based on one-sided stress wave velocity measurement technique was made every 5 freeze-thaw cycle. The variation of longitudinal and surface wave velocities due to increasing freeze-thaw damage is demonstrated and compared to determine which one is more effective to monitor freeze-thaw cyclic damage progress. The variation in longitudinal wave velocity measured by one-sided technique is also compared with that measured by the conventional through transmission technique.
Application of Acoustic Emission for Assessing Deterioration in Reinforced Concrete Beams
Yoon, Dong-Jin ; Park, Phi-Lip ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 276~284
The acoustic emission (AE) behavior of reinforced concrete beams tested under flexural loading was investigated to characterize and identify the source of damage. This research was aimed at identifying the characteristic AE response associated with micro-crack development, localized crack propagation, corrosion, and debonding of the reinforcing steel. Concrete beams were prepared to isolate the damage mechanisms by using plain, notched-plain, reinforced, and corroded-reinforced specimens. The beams were tested using four-point cyclic step-loading. The AE response was analyzed to obtain key parameters such as the time history of AE events, the total number and rate of AE events, and the characteristic features of the waveform. Initial analysis of the AE signal has shown that a clear difference in the AE response is observed depending on the source of the damage. The Felicity ratio exhibited a correlation with the overall damage level, while the number of AE events during unloading can be an effective criterion to estimate the level of corrosion distress in reinforced concrete structures. Consequently, AE measurement characterization appears to provide a promising approach for estimating the level of deterioration in reinforced concrete structure.
Signal Characteristics of Multi-coil Probe for the Test of Reinforcement Embedded in Concrete
Kim, Young-Joo ; Lee, Seung-Seok ; Yoon, Dong-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 285~289
This study suggests a rebar detection technique for simultaneous detection of size and cover of embedded reinforcement in concrete. The structure of the probe made in this study is somewhat different from commercial ones. This probe has three sensing coils. Rebar size and cover depth can be evaluated by detecting and analyzing the signal from them. Amplitude and phase variation of each coil in the probe was investigated using an impedance analyzer and the loci of transfer functions of the coils were analyzed. The locus of transfer function from the sensing coil positioned inside excitation coil was simple as well known, but the others from the coils outside excitation coil were not so. Actual experiment on rebar detection was performed with our probe and an eddy current test system for various rebar sizes and depths. The signal shape according to variation of cover depths showed the same tendency with the transfer function loci acquired by impedance analyzer. The different variation pattern of signal enabled to evaluate rebar size and cover depth simultaneously.
Non-destructive Inspection of Top-Down Construction Joints of Column in SRC Structure using Ultrasonic Method
Park, Seok-Kyun ; Baek, Un-Chan ; Lee, Han-Bum ; Kim, Myoung-Mo ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 290~295
The joint treatment of concrete is one of the technical problems in top down construction method. Joints created with the top down construction result in serious weakness from the aspects of both structural and water-barrier function. Ultrasonic method was used for the inspection of top down construction joints of a various column in SRC structure in this study. The advantages and limitations of this method for non-destructive inspection in top down construction joints are investigated. As a result, it has been verified that the semi-direct measurement method is more effective than the other methods for detecting the voids of construction joints using ultrasonic method.
A Study on the Determination of Concrete Thickness and Effective Measurement Area using Radar
Rhim, Hong-Chul ; Lee, Ji-Hoon ; Son, Byung-Oh ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 296~304
Radar is becoming a popular tool for condition assessment of concrete structures. The advancement of radar method to concrete structures requires a systematic approach, which incorporates the fundamentals of radar theory and the characteristics of concrete as a material with electromagnetic properties. The research work presented in this paper deals with the establishment of effective measurement area for radar measurements, the determination of concrete thickness using radar, and the calculation of the dielectric constant of concrete from radar measurements. As results, formulas have been suggested to determine optimum measurement area for concrete, using radar and concrete thickness has been successfully identified for specimens used in this work. In the experiments, five concrete specimens which have the dimensions of 900mm (length)
600mm (width) with thickness variation from 50mm to 250mm are used.
Measurements and Data Interpretation for the Detection of Steel Bars and Delamination inside Concrete
Rhim, Hong-Chul ; Park, Ki-Joon ; Lee, Soong-Jae ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 305~313
To determine detection capabilities of locating steel bars and delamination inside concrete, commercially available nondestructive testing (NDT) equipments have been tested. The equipments include two radar systems and two electromagnetic method systems. The inclusions are a 19 mm diameter steel bar and 50 mm thick delamination embedded at different cover depths from the surface of concrete specimens. For the steel bar, attempts were made to determine the size of the bars by changing the diameter of the bars. A sample result of measuring horizontal spacing between doubly reinforced bars is presented in this paper. Experimental results on various measurement cases are discussed. Application of numerical modeling technique for the simulation of radar measurements and improved output display of radar measurements are also presented.
Multi-layered Gap Measurement on In-Vessel Cerium Retention Using Ultrasonic Wave Reflective Pattern Analysis and Frequency Diversity Signal Processing
Koo, Kil-Mo ; Sim, Cheul-Mu ; Kim, Jong-Hwan ; Kim, Sang-Baik ; Kim, Hee-Dong ; Park, Chi-Seung ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 314~321
A gap between a
thermite and lower head vessel is formed in the lower-plenum arrested vessel attack(LAVA) experiment which is the 1st phase study of simulation of naturally arrested vessel attack in vessel(SONATA-IV). The gap measurement using a conventional ultrasonic method would be lack of a reliability due to the structure complexity and the metallurgical grain size change of the lower head HAZ occurred by a thermite
melt or a
. The grain echoes having false signals and lower S/N ratio signals are detected due to a multiple scattering, a mode conversion and an attenuation of a ultrasonic resulted from at the interface of increased grain size zone. In this test, the signals pattern was classified to understand the behavior of the ultrasonic in a multi-layer specimen of solid-liquid-solid of assuming that the thermite and the lower head vessel is immersed. The polarity threshold algorithm of frequency diversity gives us the enhancement about 6dB of the ratio S/N.
Detectability Measurement of GPR for Buried Target in Self-Designed Test Field
Son, Soo-Jung ; Shin, Byoung-Chul ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 322~328
In this paper, we were investigated the detectability on various specimen in self-designed test field using the GPR system with three antenna elements. The GPR system was constantly radiated 730MHz frequency. To examine the detectability on various condition, the test were experimented using different materials, size and buried depth. As an adjusted wave-propagation velocity, the location of hyperbolic curve pattern were displayed B-scan CRT. And the pattern was exactly positioned when it was compared to the real buried-depth. Therefore, we can confirm similarity between the wave-propagation velocity and previous results.
Nondestructive Testing of Concrete Structure
Kim, Young-Hwan ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 4, 2000, Pages 329~341