• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.359-364
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• 1996

'93.4월에 고리원자력 4호기 운전중(원자로 출력 100%, 발전기 출력 975MWe) 주증기 차단밸브 (MSIV)의 닫힘으로 인해 발전소가 정지되었다. 밸브분해 점검결과 밸브스템이 Back Seat Ring 조립부위 Notch 부위에서 Steam Flow와 평행한 방향으로 절단되어, 밸브스템의 손상원인을 규명하기 위한 본 연구에서는 피로해석절차도에 따라 S-N 곡선에 근거하여 피로해석을 수행하였다. 피로해석결과 밸브스템의 초기균열 생성원인은 Stem Notch 부위의 제작결함과 발전소 정지시 밸브를 급속히 닫을 때 작용하는 충격하중등에 의해 발생된 것으로 추정되며 인장평균응력과 관내 유체의 진동하중의 변동응력이 조합하여 피로균열을 가속시켜 파손을 일으킨 것으로 사교된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.21-23
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• 2019

This paper aims to develop a VR device prototype for reducing eye fatigue. As VR devices become popular, it is hoped that many cases of eye fatigue will be reported, and that the problems of VR devices will be corrected and repaired for a better future so that the fast speed and dynamic environment of 4th industrial revolution can be enjoyed with ease. In this paper, VR devices with a description of VR devices, eye fatigue related cases, time-out sensor for reducing eye fatigue, and eyeball massage functions were designed, and a VR device prototype was developed. These features can help reduce fatigue even if used for long periods of time by blocking electromagnetic waves harmful to the human body, and the future of VR could develop in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1227-1233
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• 2010

In the hot section of a gas turbine, the turbine blades were protected from high temperature by providing a thermal barrier coating (TBC) as well as by cooling air flowing through internal passages within the blades. The cooling air then passed through discrete holes on the blade surface, creating a film of cooling air that further protects the surface from the hot mainstream flow. The holes are subjected to stresses resulting from the lateral growth of thermally grown oxide, the thermal expansion misfit between the constituent layers, and the centrifugal force due to high-speed revolution; these stresses often result in cracking. In this study, the deformation and cracks occurring near a hole on a heat-resistant alloy subjected to thermo-mechanical cycling were investigated. The experiment showed that cracks formed around the hole depending on the applied stress level and the number of cycles. These results could be explained by our analytic solution.

• The Science & Technology
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• v.29 no.4 s.323
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• pp.16-17
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• 1996

인공섬유가 마술사처럼 요술을 부린다. 카멜레온처럼 색깔이 변하고 향기를 내뿜으며 세균감염도 막아주는 기능섬유가 우리나라에서도 본격 개발되고 있다. 내부온도를 높여주는 축열보온섬유와 내부온도를 떨어뜨리는 자외선ㆍ적외선 차단섬유는 물론 피로회복기능의 바이오 세라믹 복지가 나왔고 강철보다 강한 탄소섬유도 개발되어 섬유업계에 혁명의 바람이 거세게 일고 있다.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.158-164
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• 2003

The air circuit breaker (ACB) with the spring-actuated mechanism was studied to improve the fatigue-proof characteristics of its link. The low-cycle fatigue fracture phenomenon occurred on the critical link, called h-link, of ACB from the repeated rapid closing and opening operations. To analyze the cause of failure, dynamic FE-analysis on the b-link part of ACB was performed considering tile velocity and acceleration of the links per time as boundary conditions, which were obtained by using ADAMS. Also, the S-N curve obtained by experiments was used to investigate requirement on the fatigue-proof characteristics. Then, to reduce the maximum tensile stress on the h-link, three types of h-link were examined and one of them was selected.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.363-368
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• 2024

Steel structures used in marine environments, such as ships, offshore structures or sub-structures in wind power generation facilities are prone to corrosion. In this study, the corrosion fatigue crack propagation characteristics due to the environmental load are examined by experiment at -1050 mV vs. SCE, which is equivalent to the anti-corrosion potential of zinc anodes that are widely used as sacrificial anodes. In this study, for this purpose, an experimental study is conducted on the effect of cathodic protection on the propagation of fatigue cracks in the seawater environment under the condition of -1050 mV vs. SCE, considering the wave period in synthetic seawater. Cathodic protection prevents corrosion; however, excessive protection generates hydrogen through chemical reactions as well as calcareous deposits. The fatigue crack propagation rate appeared to be faster than the rate in a seawater corrosion environment at the early stages of the experiment. As the crack length and stress intensity factor K increased, the crack propagation rate became slower than the fatigue crack propagation rate in seawater. However, the crack growth rate was faster than that in the atmosphere.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.177-181
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• 2019

The purpose of this study was to investigate the degree of blocking of blue light of the tips and goggles of the curing light during the dental treatment using the blue light of the light curing. The light curing tips and goggles were placed on a UV-Vis spectrometer and the results of light transmission were analyzed. Comparative analysis. As a result, all four types of light curing tips used in the analysis showed excellent blue light blocking effect. In the case of safety goggles, red-type goggles showed blue light transmittance similar to those of light curing than yellow-type goggles. As a result, it is recommended that the attachment of the light curing with high degree of blue light blocking and the wearing of safety glasses are necessary to protect the eyes. This behavior is thought to reduce persistent irritation and fatigue in the eyes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.701-709
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• 2000

As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. Recasting the load vs. fatigue life relationships experimentally obtained, we predicted the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot. We therefore attempt to evaluate the effectiveness and validity of $K_e$ in predicting the fatigue life of auto seat belt anchor panel. We first establish finite element models reflecting the actual mechanical behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we then obtain the effective crack driving parameter $K_e$ composed of its ductility -dependent modal components. It is confirmed that the $K_e$ concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.979-986
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• 2016

The tripod shafts of constant-velocity joint are used in both the trains KTX and KTX-sanchon. It is an important component that connects the motor reduction unit and the axle reduction unit in a power bogie. The tripod shaft not only transmits drive and brake torque in the rotational direction, but also slides in the axial direction. If the drive system is loaded with an excessive torque, the fuse part of the shaft will be fractured firstly to protect the other important components. In this study, a rig was developed for conducting torsion tests on the tripod shaft, which is a type of mechanical fuse. The tripod shafts were subjected to torsional fracture test and torsional fatigue test on the rig. The weak zone of the tripod shaft was identified, and its fatigue life was predicted using finite element analysis (FEA). After analyzing the FEA results, design solutions were proposed to improve the strength and fatigue life of the tripod shaft. Furthermore, the deterioration trend and time for failure of the tripod shaft were verified using the hysteresis loops which had been changed with the advancement of the torsional fatigue test.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.195-195
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• 1994

병원별 총 추적기간은 602-4,137 인년 이었으며, 병원별 대상자 1인당 추적일수의 중앙값은 34.5-61일 이었다. 병원별 추적 완료율도 35.3-92.3%로 다양하게 나타났다. 대상자중 칼슘차단제의 혈관확장효과에 따른 부작용들의 8주간 누적 발생율을 보면, 안면홍조 23.3%, 두통 13.5%, 심계항진 13.3%, 어지러움 7.6%, 하지부종 6.6% 였다. 그 외 부작용으로는 변비 13예, 소화장애 8예, 오심 6예, 치은비대, 안면부종, 피로감이 각각 2예, 탈모증, 불면증, 허약감, 피부질환, 호흡곤란, 손발저림, 발한, 구강건조 등이 각각 1예 있었다. 안면홍조의 발생율이 남자(12.9%)보다 여자(29.9%)에서 높았으며, 투여한 약제에 따라서 Nitrendipine 34.0%, Nifedipine 26,6%, Nicardipine 17.8%, Amlodipine 12.2%로써 약제별로 차이가 있었다. 두통의 발생율은 40세 미만 32.8%, 40-54세 15,8%, 55세 이상 10.5%로써 연령이 증가할수록 발생율이 낮았다. 하지부종의 발생율도 남자(3.4%)보다 여자(8.6%)에서 높았으며, 투여한 약제에 따라서 Nitrendipine 15.2%, Nifedipine 10.0%, Amlodipine 2, 1%, Nicardipine 0%로써 약제별로 차이가 있었다. 안면홍조가 발생한 환자에서 약물을 계속 투여시 2주후에 63.5%, 4주후에 77.0% 6주후에 88.5%가 소실하여 최초 안면홍조가 발생한 환자중 11.5%에서만 증상이 남아있었다. 약물투여를 중단하게 된 사유는 안면홍조와 두통이 각각 15예, 심계항진 4예, 어지러움 2예, 변비 및 안면부종이 각각 1예로 나타났다.