• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.17-24
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• 2023

A post-processing technique for the measurement signal of a solenoid-type sensor is introduced. The solenoid-type sensor nondestructively evaluates an external tendon of prestressed concrete using the total flux leakage (TFL) method. The TFL solenoid sensor consists of primary and secondary coils. AC electricity, with the shape of a sinusoidal function, is input in the primary coil. The signal proportional to the differential of the input is induced in the secondary coil. Because the amplitude of the induced signal is proportional to the cross-sectional area of the tendon, sectional loss of the tendon caused by ruptures or corrosion can be identified by the induced signal. Therefore, it is important to extract amplitude information from the measurement signal of the TFL sensor. Previously, the amplitude was extracted using local maxima, which is the simplest way to obtain amplitude information. However, because the sampling rate is dramatically decreased by amplitude extraction using the local maxima, the previous method places many restrictions on the direction of TFL sensor development, such as applying additional signal processing and/or artificial intelligence. Meanwhile, the proposed method uses amplitude demodulation to obtain the signal amplitude from the TFL sensor, and the sampling rate of the amplitude information is same to the raw TFL sensor data. The proposed method using amplitude demodulation provides ample freedom for development by eliminating restrictions on the first coil input frequency of the TFL sensor and the speed of applying the sensor to external tension. It also maintains a high measurement sampling rate, providing advantages for utilizing additional signal processing or artificial intelligence. The proposed method was validated through experiments, and the advantages were verified through comparison with the previous method. For example, in this study the amplitudes extracted by amplitude demodulation provided a sampling rate 100 times greater than those of the previous method. There may be differences depending on the given situation and specific equipment settings; however, in most cases, extracting amplitude information using amplitude demodulation yields more satisfactory results than previous methods.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.447-452
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• 1995

경·중수로 연계 핵연료 주기 (Direct Use of Spent PWR Fuel in CANDU : DUPIC ) 기술개발의 핵물질 보장조치(Safeguards)는 경수로 사용후 핵연료를 중수로에 재 활용하기 위한 DUPIC 공정에 대한 최적 보장조치 시스템을 구축하여, 국제 원자력 기구(IAEA) 및 국제 원자력 사회에서 핵 투명성확보 및 신뢰도를 향상시키는 것을 기술개발의 목적으로 하고 있다. DUPIC 공정은 고립된 차폐시설내의 고준위 방사선장 하에서 가동되므로 타 시설에 비해 핵 물질 전용 가능성은 희박하지만, 전 공정이 원격제어 되야 하고, 조업조건이 정복해야 하므로 기존의 보장조치 기술보다 더욱 발전된 계량관리시스템, 측정시스템 및 감시시스템 등을 개발하여야 한다. 이를 위해 본 연구에서는 각 항목에 대한 요소 분석 및 각 항목별 향후 연구방향에 대해 분석하였다. DUPIC 공정 전반에 대한 핵물질 계량관리를 위해 물질수지구역 (Material Balance Area : MBA) 및 주요측정 지점 (Key Measurement Point : KMP )을 설정하여 각 측정지점별 측정방법 및 재고검증(Inventory Verification) 방법을 분석하였다. 최적 측정시스템을 개발하기 위해 적용 가능한 비파괴분석 방법들을 분석한 결과, 핵분열성 물질 함량을 정량적으로 측정할 수 있는 수동적 중성자 측정법이 가장 적합하다는 결론을 얻었다. 또한, 감시시스템을 개발하기 위해 전용전략의 주요 요소 및 전용경로 등을 분석하였으며, 핵물질 및 시설에 대한 물리적 방호체제를 DUPIC시설에 적용하기 위하여 물리적 방호에 필요한 방호체제 요소를 분석하여 DUPIC 시설을 위한 가상적인 방호체제를 구축하였다.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.08a
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• pp.70-83
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• 2004

The safety diagnosis of cultural assets is Primarily focused on its non-destructiveness. Research on the nondestructive diagnosis and conservation of masonry cultural heritage is the key which is considered by technologic kernel. Geophyscial Prospecting as nondestructive diagnostic technology plays an important role in the characterization of the foundation of stone pagodas. It is natural that understanding of shallow subsurface condition beneath them is essential for their structural safety diagnosis. As an example, the nondestructive geophysical methods were applied to two three-story stone pagodas, Seokgatap (height 10.8 m, width 4.4 m, weight 82.3 ton) and Dabotap (height 10.4 m, width 7.4 m, weight 123.2 ton) which were built in 791 at Bulkuksa temple. An earlier archaeological investigation shows that stone pagodas have experienced severe weathering process and are slightly leaning, which will threaten their stability At the base part of Dabotap, an offset of the stone alignment is also observed. Direct measurements of ultrasonic velocities was introduced for the mechanical properties of the stone The velocity ranges of ultrasonic waves for Dabotap and Seokgatap are 1217${\~}$4403 m/s and 584${\~}$5845 m/s, respectively, and the estimated averages of the uniaxial compressive strength are 463 kg/$cm^2$ and 409 kg/$cm^2$, respectively. Site characteristics, around the pagodas are determined by the measurement of multiple properties such as seismic velocity, resistivity, image of ground-penetrating radar, On the basis of the higher velocity structure, the site of Seokgatap appears to have solider stability than the Seokgatap site. Near the pagodas, higher(up to 2200 $\Omega$m) resistivity is present whereas their outskirts have as low as 200 $\Omega$m. By the combined results of each geophyscial methods, the subsurface boundaries of two stone pagodas are revealed. The Dabotap site is in the form of an octagon having 6-m-long side with the depth of ${\~}$4 m, whereas the Seokgatap site is the 8 ${\times}$ 10 m rectangle with the depth of 3 m. These subsurface structures appear to reflect the original foundations constructed against the stone load of ${\~}8 ton/m^2$. At the subsurface beneath the northeast of each pagoda, low seismic velocity as well as low resistivity is prominent. It is interpreted to represent the weak underground condition which Is the possible cause of the slightly leaning pagodas toward the NNW.

• Journal of Radiation Industry
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• v.9 no.3
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• pp.153-159
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• 2015

Reliability of printed circuit board (PCB), which is based on high integrated circuit technology, is having been important because of development of electric and self-driving car. In order to answer these demand, automated X-ray inspection (AXI) is best solution for PCB non-destructive test. PCB is consist of plastic, copper, and, lead, which have low to high Z-number materials. By using dual energy X-ray imaging, these materials can be inspected accurately and efficiently. Dual energy X-ray imaging, that have the advantage of separating materials, however, need some solution such as energy separation method and enhancing efficiency because PCB has materials that has wide range of Z-number. In this work, we found out several things by analysis of X-ray energy spectrum. Separating between lead and combination of plastic and copper is only possible with energy range not dose. On the other hand, separating between plastic and copper is only with dose not energy range. Moreover the copper filter of high energy part of dual X-ray imaging and 50 kVp of low energy part of dual X-ray imaging is best for efficiency.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.162-169
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• 2012

This study detected SCC defects of dissimilar metal welded(STS304 and SA106 Gr. b) pipes using the ultrasonic infrared thermography method and the lock-in image treatment method among infrared thermography method. The infrared excitement equipment has 250 Watt of output and 20 kHz of frequency. By using the ultrasound infrared thermography method, the internal defects of dissimilar metal weld joints of pipes used at nuclear power plants could get detected. By an actual PT test, it was observed that the cracks inside the pipe existed not as a single crack but rather as a multiple cracks within a certain area and generated a hot spot image of a broad area on the thermography image. In addition, UT technology could not easily defects detected by the width of $10\;{\mu}m$ fine hair cracks. but, ultrasound infrared thermography technique was defect detected.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.4
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• pp.268-274
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• 2015

Weld overlay was first used in power plants in the US in the early 1980s as an interim method of repairing the welds of flawed piping joints. Weld overlaid piping joints in nuclear power plants must be examined periodically using ultrasonic examination technology. Portable phased array ultrasonic technology has recently become available. Currently, the application of preemptive weld overlays as a mitigation technique and/as a method to improve the examination surface condition for more complex configurations is becoming more common. These complex geometries may require several focused conventional transducers for adequate inspection of the overlay, the original weld, and the base material. Alternatively, Phased array ultrasonic probes can be used to generate several inspection angles simultaneously at various focal depths to provide better and faster coverage than that possible by conventional methods. Thus, this technology can increase the speed of examinations, save costs, and reduce radiation exposure. In this paper, we explain the general sequence of the inspection of weld overlay and the results of signal analysis for some PAUT (phased array ultrasonic testing) signals detected in on-site inspections.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.367-372
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• 2018

Defects in aging infrastructures such as pre-stressed concrete bridges and cable bridges can cause a collapse of the entire structure. Defects, however, are often located inside of the structures that they are not visible from the outside. For example, in PSC bridges, because reinforcement steels are encased by exterior covers, corrosion and void on the reinforcement steel cannot be detected with a visual inspection. Therefore, in this paper, a new non-destructive evaluation(NDE) method that can detect defects inside of structures is presented. The new method utilizes sending of electrical signals, a method often utilized in electrical engineering to detect any discontinuities on power cables. In order to confirm the applicability and accuracy of the method, some experiments were conducted in the laboratory. And to overcome the hardship of conducting experiments on real structures due to their enormous size, simualtions were conudcted using a commercial program, COMSOL. The results of the experiments were analyzed and compared to confirm the accuracy of the simualtions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.30-38
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• 2023

As the number of old buildings subject to safety inspection increases, the burden on designated institutions and management entities that are responsible for safety management is increasing. Accordingly, when selecting buildings subject to safety inspection, appropriate safety inspection standards and appropriate technology are essential. The current safety inspection standards for old buildings give low scores when it is difficult to confirm damage such as cracks in structural members due to finishing materials. This causes the evaluation results to be underestimated regardless of the actual safety status of the structure, resulting in an increase in the number of aging buildings subject to safety inspection. Accordingly, this study proposed a thermal imaging technique, a non-destructive and non-contact inspection, to detect cracks inside finishing materials. A concrete specimen was produced to observe cracks inside the finishing material using a thermal imaging camera, and thermal image data was measured by exciting a heat source on the concrete surface and cracked area. As a result of the measurement, it was confirmed that it was possible to observe cracks inside the finishing material with a width of 0.3mm, 0.5mm, and 0.7mm, but it was difficult to determine the cracks due to uneven temperature distribution due to surface peeling and peeling of the wallpaper. Accordingly, as a result of performing data analysis by deriving the amplitude and phase difference of the thermal image data, clear crack measurement was possible for 0.5mm and 0.7mm cracks. Based on this study, we hope to increase the efficiency of field application and analysis through the development of technology using big data-based deep learning in the diagnosis of internal crack damage in finishing materials.

• Journal of the KSME
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• v.16 no.4
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• pp.19-25
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• 1976

가동검사의 검사결과는 이미 전에 실시한 가동중검사 결과와 비교 검토하게 된다. 비교 검토한 결과, 변화가 일어나지 않았으면 그것으로 좋으나, 만일 변화가 일어났다면 그 검사 결과를 평가 하여 어떠한 조치를 취할 것인가를 결정하게 된다. 이 경우 조치라 함은 어떤 변화가 일어난 부 분을 수리, 대체하거나, 또는 다음 검사 기간까지는 구조적 건전성에 관계 없다는 것이 확실히 규 명될 경우, 방치하는 것 등을 말한다. 그러나, 가동중검사에는 이미 언급하였듯이 그전의 검사 결 과와 비교 검토하게 되는데, 그때에 기초가 될 자료가 필요하다. 그래서 발전소의 일차냉각계통에 대한 수압시험이 완료되면 가동전검사(Pre-Service-Inspection)-사용점검사라고도 한다-를 수행 하여 가동중검사에 대한 기초자료로 삼는다. 가동점검사는 가동중검사 때에 상호 비교검토할 기 초 자료를 취하는 것이 목적이므로, 가동전 검사시의 검사방법 및 기술 등을 포함한 검사조건은, 앞으로 시행될 가동검사때의 예측되는 검사조건과 될 수 있는대로 동일한 상태가 되도록하여 그 검사결과 치를 비교함에 있어, 일어난 변화는 진정으로 원자료를 가동함에 의해 일어났다는 것을 보증할 수 있도록 하여야 한다. 이에 따라 특히 가동에 따라 접근하여 검사할 수 없는, 방사능의 오염될 부분의 가동전 검사에서도 가동중 검사시에 사용될것으로 예상되는 종류의 원격조정장치 룰 사용하여 비파괴검사를 사용하고 그 기록을 유지보관하여야 한다.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2070-2072
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• 2004

극 초단의 임펄스를 사용하여 지중 매설물을 탐색하기 위한 지반탐사 영상 레이더를 개발하였다. 개발된 지반 탐사 레이더는 Gaussian 임펄스, 임펄스 송수신을 위한 초 광대역 소형 모노폴 안테나, 수신 신호 저장을 위한 고속 A/D로 구성된다. 탐지 깊이와 시스템의 크기를 고려하여 임펄스 발생기 및 초광대역 안테나가 설계되었다. 지중 매설물의 영상화를 위해 여러 가지 이미지 기법이 사용되었다. 발표에서는 구현된 시스템의 시제품을 소개하고, 개발된 시제품을 사용하여 가상의 모래 시험장에서 측정된 결과를 보일 것이다.