• Proceedings of the KIEE Conference
• /
• 2008.10b
• /
• pp.375-376
• /
• 2008

송전선로에 절연물로 사용되는 애자는 설치 이후 장시간 사용에 따라 고전압 스트레스, 기계적 스트레스, 열 및 환경 스트레스 등으로 열화가 진행되기 때문에 안정적인 전력설비 운영을 위하여 활건 애자 비파괴 열화 상태 점검이 필요하다. 본 연구에서는 비파괴 상태 진단 감시 기술인 주파수 응답 함수 측정을 통한 고유 진동수 분석을 통하여 현재 활선 애자로 사용되고 있는 NGK210, KRI210, NGK300 및 KRI300 4가지 종류 애자의 동특성 실험을 수행하였으며, 이를 통하여 애자의 결함이 발생하였을 때 고유진동수 변화를 분석하였다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.1
• /
• pp.54-59
• /
• 2010

After the advent of B787(Boeing Co.), a civil aircraft using composite materials more than 50% of it total structural weight for weight savings，best performances and efficiencies, various endeavors to develop and apply the state of art of structural health monitoring(SHM) technologies for composite aircraft have been made for many years. Despite their plentiful advantages composite aircraft structures are susceptible to the hidden or barely visible impact damages(BVID) and excessive loads that if unchecked may lead to lower structural integrity, loss of operational performance and finally a sudden catastrophic failure of the aircraft structure. In this paper background of SHM technology and relevant technologies for application of SHM technology to the composite aircraft in the near future and requirements for certification of SHM system are shortly presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.92-95
• /
• 2003

본 논문에서는 철도차량 견인전동기에 대한 상태진단 및 상시감시 기술에 관하여 소개하였다. 권선의 절연상태 진단을 위한 비파괴 시험법에서는 부분방전량 Q에 대한 평균열화도 $\Delta$로 표현되는 D-Map에 의해 잔여 절연내력(residual dielectric strength)을 예측하고, 기기의 운전이력측면에서 기동-정지 횟수와 열적, 전기적 및 열싸이클 스트레스 등에 의해 각 열화 인자를 고려한 운전시간에 기반한 N-Y 수명예측을 수행한다. 그리고 견인전동기의 전류에 대한 온라인 상태감시를 통해 베어링 고장, 고정자 및 전기자 고장, 고장 또는 전동기축 손상에 기인하는 비정상 운전상태 의 감지를 수행한다.

• Electrical & Electronic Materials
• /
• v.7 no.1
• /
• pp.42-48
• /
• 1994

The preventive diagnosis technique for power system is being highlighted as a research area for deterioration of insulation in machinery because of high-voltage power system. We make efforts to develop not only diagnosis of aging state but also detection of defects in the initial stage from preventive diagnosis technique. Especially, partial discharge is actively studied as a non-destructive diagnosis technique and very useful because partial discharge measurement reduces damage than conventional diagnosis technique. The loaded stress during this test is smaller than that of other diagnosis techniques. But the continuous research for various complicated analysis method is required because partial discharge has very small signals and its signals have complex forms. In this paper, the measurement of partial discharge was investigated and studied on many specimens with void. We made samples having artificial voids and measured partial discharge. In order to use as a practical diagnosis technique, we studied ways of measurement, measured illustrations and types of partial discharge which could be used in order to diagnose defects of power machinery.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.6
• /
• pp.120-127
• /
• 2016

Several problems including respiratory and skin disorders due to the problems for sick house syndrome have occurred, there appears echo friendly materials to solve the problems. The research is lacking in quality management techniques ocher concrete using nondestructive tests. In this research, the experimental works were conducted to study the initial quality control for the compressive strength of Ocher concrete(21 MPa). The purpose of this study is the implementation platform for quality management of ocher concrete using nondestructive tests. It uses the relationship between the compressive strength and ultrasonic pulse velocity of the ocher concrete to estimate the compressive strength of the ocher concrete. And using the impact echo method to estimate the thickness of the ocher concrete. The platform is based on a Java script, so that the user can obtain the data through the platform.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.14 no.2
• /
• pp.112-121
• /
• 1994

This paper discusses the feasibility of ultrasonic C-scan technique for nondestructive evaluation of spot weld quality. Ultrasonic evaluation for spot weld quality was performed by immersion method with the mechanical and the electronic scanning of point-focussed ultrasonic beam(25 MHz). For the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of the corona bond from nugget, preliminary infinitesimal gap experiment by newton ring is tried in order to set up the optimum ultrasonic test condition. Ultrasonic image data obtained were confirmed and compared by optical microscope and SAM(Scanning Acoustic Microscope) observation of the spot-weld cross section. The results show that the nugget diameter can be measured with the accuracy of 1.0mm, and voids included in nugget can be detected to $10{\mu}m$ extent with simplicity and accuracy. Finally, it was found that it is necessary to make a profound study of definite discrimination of corona bond from nugget and the approach of quantitative evaluation of nugget diameter by utilizing the various image processing techniques.

• Korean Journal of Heritage: History & Science
• /
• v.56 no.1
• /
• pp.100-116
• /
• 2023

The Sinamsa Temple was built in the late Goryeo Dynasty and a gilt-bronze seated Buddha is enshrined in Geungnakjeon hall in the precinct. Various damages occurred in the gilt layer of the Buddha, such as peeling of the gilt layer and deteriorating gloss. In the study, the conservation conditions of the inside and outside on the statue were accurately investigated, and the making technique was interpreted through the material characteristics and non-destructive diagnosis of the statue. As a result, it is estimated that gold-gilding layer is pure gold, coloration pigment of black is carbon, green is malachite, atacamite and verdigris, red is red lead and cinnabar, respectively. In the deterioration evaluation, peeling, cracking, break out and exfoliation of the gilt layer are confirmed as damages, but the conservation condition is relatively wholesome. However, the gloss of the gilt layer is calculated to be wider in the poorer part than the maintenance part. The ultrasonic velocity of the statue was calculated to be 1,230 to 3,987 (mean 2,608) m/s and showed a relatively wide range. In infrared thermography, peeling was not confirmed, and no special bonding marks were found. In endoscope, some biological damage and corrosion were observed on the surface of the internal metal, and sealed artifacts were identified. Manufacturing technique based on the study, it is considered that the gilt-bronze seated Buddha was cast at once, and the mold was inverted to inject molten metal.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.1
• /
• pp.45-52
• /
• 2016

Blast furnaces are crucial equipment for steel production. A typical furnace risks unexpected accidents caused by contraction and expansion of the walls under an environment of high temperature and pressure. In this study, an acoustic emission (AE) monitoring system was tested for evaluating the large-scale structural health of a blast furnace. Based on the growth of shell cracks with the emission of high energy levels, severe damage can be detected by monitoring increases in the AE energy parameter. Using this monitoring system, steel mill operators can establish a maintenance period, in which actual shell cracks can be verified by cross-checking the UT. From this study, we expect that AE systems permit early fault detection for structural health monitoring by establishing evaluation criteria based on the severity of shell cracking.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.4
• /
• pp.315-322
• /
• 2008

Valves in power plants are leaking internally by various damages including insertion of foreign objects on seat, seat crack, defects and fatigue crack of stem packing or welds etc. due to severe operating conditions such as high temperature and high pressure for extended period time. Acoustic emission(AE) technology should be applied in order to diagnose precisely and evaluate these valve internal leak. In this paper, results of studies which have accomplished in actual power plant are presented. We have analyzed background noise, AE signal level and frequency spectrum through laboratory tests on the basis of various actual conditions in power plant, and also have considered evaluation methods on the background noise, AE properties and the detectable minimum leak rate according to valve leak conditions through comparing with results of field tests in power plant. As a result of these studies, we conformed that evaluation of internal leak conditions including discrimination of leak or not, and the detectable minimum leak rate is possible, and also it is expected to contribute to safe operation and prevention of energy loss in power plants.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.5
• /
• pp.551-563
• /
• 2012

Medical ultrasound systems have been used since 1950s, and are now widely used in most hospitals as indispensable diagnostic imaging systems. Since array probe was introduced in 1970s, beamforming technology using electronic signal processing has been adopted to the medical ultrasound system, and has been improved. Beamforming is a important technology which defines the resolution of the ultrasound system. In this paper, the technologies are introduced from basic beamforming principles to current trend. They include principles of beamforming using array probe, basic theory, and practical implementation, and recent topics of synthetic aperture imaging, adaptive beamforming, 2-dimensional beamforming using 2-dimensional array are also introduced. These various technologies will improve system performances continuously by merging innovatively with various technologies in other fields.