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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 33, Issue 6 - Dec 2013
Volume 33, Issue 5 - Oct 2013
Volume 33, Issue 4 - Aug 2013
Volume 33, Issue 3 - Jun 2013
Volume 33, Issue 2 - Apr 2013
Volume 33, Issue 1 - Feb 2013
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Detection of Acoustic Signal Emitted during Corrosion of 304 Stainless Steel
Wu, Kaige ; Choe, Chan-Yang ; Byeon, Jai-Won ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 409~414
DOI : 10.7779/JKSNT.2013.33.5.409
In this work, corrosion of 304 stainless steel was evaluated by using acoustic emission(AE) technique. AE measurement system was set for detecting acoustic signal during accelerated corrosion test of the specimen. AE signal started to be detected after the time of pitting corrosion initiation was evaluated by anodic polarization curve. Pitting corrosion damage was confirmed by optical microscopic observation of the surface morphology. AE cumulative counts and amplitude according to corrosion time could be divided into three stages. These trends were discussed in relation with changing pitting corrosion mechanism. Feasibilities of AE technique for evaluation of corrosion damage and mechanism were suggested.
Acoustic Emission of Heat Treated Compacted Graphite Iron under 873~1173 K
Nam, Ki-Woo ; Ahn, Byung-Kun ; Lee, Soo-Chul ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 415~421
DOI : 10.7779/JKSNT.2013.33.5.415
CGI is gaining popularity in applications that require either greater strength, or lower weight than cast iron. Recently, compacted graphite iron has been used for diesel engine blocks, turbo housings and exhaust manifolds. This paper were assessed acoustic emission characteristics according to the mechanical properties change of degraded CGI340 during 1-24 hours at 873~1173 K. In results of pencil lead fracture test, the dominant frequency and the velocity of base metal were 97 kHz and 5490 m/sec, respectively. The base metal in a tensile test was obtained relatively high dominant frequency. However, the heat treated materials, the longer the heat treatment time, the higher the heat treatment temperature, were obtained in the area of lower frequencies. This phenomenon appears by long-term use.
Leakage Localization with an Acoustic Array that Covers a Wide Area for Pipeline Leakage Monitoring in a Closed Space
Park, Choon-Su ; Jeon, Jong-Hoon ; Park, Jin-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 422~429
DOI : 10.7779/JKSNT.2013.33.5.422
It is of great importance to localize leakages in complex pipelines for assuring their safety. A sensor array that can detect where leakages occur enables us to monitor a wide area with a relatively low cost. Beamforming is a fast and efficient algorithm to estimate where sources are, but it is generally made use of in free field condition. In practice, however, many pipelines are placed in a closed space for the purpose of safety and maintenance. This leads us to take reflected waves into account to the beamforming for interior leakage localization. Beam power distribution of reflected waves in a closed space is formulated, and spatial average is introduced to suppress the effect of reflected waves. Computer simulations and experiments ensure how the proposed method is effective to localize leakage in a closed space for structural health monitoring.
The Characteristics of Acoustic Emission Signal under Composite Destruction on GFRP Gas Cylinder
Jee, Hyun-Sup ; Lee, Jong-O ; Ju, No-Hoe ; So, Cheal Ho ; Lee, Jong-Kyu ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 430~435
DOI : 10.7779/JKSNT.2013.33.5.430
This study is investigation of the characteristics for acoustic emission signal generated by destruction on glass fiber bundles and specimen that was machined composite materials surrounding the outside of GFRP cylinder. The Amplitude of acoustic emission signal gets bigger as the cutting angle of knife increases. Accordingly, the number of hits in destruction of composite materials specimen have more in longitudinal direction (longitudinal direction to the glass fiber) than in hoop direction (horizontal direction to the glass fiber) while the amplitude of signals were bigger in hoop direction than longitudinal direction. It was found out that the amplitude of the glass fiber breakage is more than 40 dB and that the amplitude of signal for matrix crack was less than 40 dB because matrix crack signal was not observed when threshold value is 40 dB and matrix crack signal suddenly appered when threshold value is 32 dB. The slope of the amplitude is related to the acoustic emission source and the slope of the amplitude of the horizontal and vertical directions are 0.16 and 0.08. In particular, The slope of the amplitude of longitudinal direction breakage appear similar to the glass fiber breakage and therefore Acoustic emission source of longitudinal direction breakage is estimated the glass fiber breakage.
Application of Acoustic Emission Technique and Friction Welding for Excavator Hose Nipple
Kong, Yu-Sik ; Lee, Jin-Kyung ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 436~442
DOI : 10.7779/JKSNT.2013.33.5.436
Friction welding is a very useful joining process to weld metals which have axially symmetric cross section. In this paper, the feasibility of industry application was determined by analyzing the mechanical properties of weld region for a specimen of tube-to-tube shape for excavator hose nipple with friction welding, and optimized welding variables were suggested. In order to accomplish this object, friction heating pressure and friction heating time were selected as the major process variables and the experiment was performed in three levels of each parameter. An acoustic emission(AE) technique was applied to evaluate the optimal friction welding conditions nondestructively. AE parameters of accumulative count and event were analyzed in terms of generating trend of AE signals across the full range of friction weld. The typical waveform and frequency spectrum of AE signals which is generated by friction weld were discussed. From this study the optimal welding variables could be suggested as rotating speed of 1300 rpm, friction heating pressure of 15 MPa, and friction heating time of 10 sec. AE event was a useful parameter to estimate the tensile strength of tube-to tube specimen with friction weld.
Source Location on Full-Scale Wind Turbine Blade Using Acoustic Emission Energy Based Signal Mapping Method
Han, Byeong-Hee ; Yoon, Dong-Jin ; Huh, Yong-Hak ; Lee, Young-Shin ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 443~451
DOI : 10.7779/JKSNT.2013.33.5.443
Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect any further growth or expansion of preexisting defects or to characterize failure mechanisms. Recently, this kind of technique, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures like a huge wind turbine blade. In this study, the activities of AE signals generated from external artificial sources was evaluated and located by new developed signal mapping source location method and this test is conducted by 750 kW full-scale blade. And a new source location method was applied to assess the damage in the wind turbine blade during step-by-step static load test. In this static loading test, we have used a full scale blade of 100 kW in capacity. The results show that the acoustic emission activities give a good agreement with the stress distribution and damage location in the blade. Finally, the applicability of the new source location method was confirmed by comparison of the result of source location and experimental damage location.
Damage Monitoring for Wind Turbine Blade using Impedance Technique
Huh, Yong-Hak ; Kim, Jongil ; Hong, Seonggu ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 452~458
DOI : 10.7779/JKSNT.2013.33.5.452
Impedance based monitoring technique was investigated to evaluate the damage occurring in wind turbine blade. In this study, PVDF film piezo sensors were patched on the 10 kW wind turbine blade, and impedance was measured over the frequency range of 1~200 MHz under fatigue loading. With applying fatigue loads on the blade, change in maximum deflection of the blade and local strain values could be obtained from the strain gages attached on the blade, and difference of the impedance signatures was also observed. From these data, it could be found that local damage or geometrical change in the blade structure happened. To quantitatively compare the impedance signature patterns, a statistical algorithm, scalar damage metric M was used. It was calculated from the impedance signatures considering fatigue loads and location of the sensors. The metric values were compared to correlate the metrics with damage in the blade.
FBG Sensor Probes with Silver Epoxy for Tracing the Maximum Strain of Structures
Im, Jooeun ; Kim, Mihyun ; Choi, Ki-Sun ; Hwang, Tae-Kyung ; Kwon, Il-Bum ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 459~464
DOI : 10.7779/JKSNT.2013.33.5.459
Structures can be evaluated their health status by allowable loading criteria. These criteria can be determined by the maximum strain. Therefore, in order to detect this maximum strain of structures, fiber optic Bragg grating(FBG) sensor probes are newly designed and fabricated to perform the memorizing detection even if the sensor system is on-and-off. The probe is constructed with an FBG optical fiber embedded in silver epoxy. When the load is applied and removed on the structure, the residual strain remains in the silver epoxy to memorize the maximum strain effect. In this study, a commercial Al-foil bonded FBG sensor probe was tested to investigate the detection feasibility at first. FBG sensor probes with silver epoxy were fabricated as three different sizes. The detection feasibility of maximum strain was studied by doing the tensile tests of CFRP specimens bonded with these FBG sensor probes. It was investigated the sensitivity coefficient defined as the maximum strain divided by the residual strain. The highest sensitivity was 0.078 of the thin probe having the thickness of 2 mm.
Electrical Characteristics Measurement of Eddy Current Testing Instrument for Steam Generator in NPP
Lee, Hee-Jong ; Cho, Chan-Hee ; Yoo, Hyun-Joo ; Moon, Gyoon-Young ; Lee, Tae-Hun ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 465~471
DOI : 10.7779/JKSNT.2013.33.5.465
A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.
Principle of Digital Holographiy
Kim, Kyeong-Suk ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 472~478
Measurement of Elastic Constants Using Resonant Ultrasound Spectroscopy
Cheong, Yong-Moo ;
Journal of the Korean Society for Nondestructive Testing, volume 33, issue 5, 2013, Pages 479~486