• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.117-129
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• 2023

Hydrogen embrittlement of a pipe is an important factor in hydrogen transport. To characterize hydrogen embrittlement, tensile and fracture toughness tests should be conducted. However, in the case of hydrogen-embrittled materials, it is difficult to perform tests in hydrogen environment, particularly at low temperatures. It would be useful to develop a methodology to predict the fracture toughness of hydrogen-embrittled materials at low temperatures using more efficient tests. In this study, the fracture toughness of API X52 steels in hydrogen at low temperatures is predicted from numerical simulation using coupled finite element (FE) damage analyses with FE diffusion analysis, calibrated by analyzing small punch test data.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.46-56
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• 2013

The test facility with hot-air supply system is required to develop transpiration cooling materials and experimentally evaluate its performance. In the study, the facility consists of an arc-plasma generator, plenum chamber suppling cold air, and test section was designed and an internal flow analysis was executed. From CFD results, it was confirmed that the designed plenum chamber thermally safeties and ideally mixes with plasma gas and cold air in the chamber. In addition, validity of design for supplying homogeneous flow to the test section was confirmed by this analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.298-304
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• 1995

유동이 있는 경우 발생하는 소음에 대한 실험적 연구는 풍동과 무향실이 결합된 음향풍동에서 수행될 수 있다. 이러한 음향풍동은 팬, 수축부, 수집부, 확산부 그리고 무향실에 주의해서 설계되어야 하고 특히 각 부분에서 발생할 수 있는 이차소음을 최소화하도록 설계되어야 한다. 최종적으로 소음기와 흡음재를 이용해서 팬소음과 이차소음의 전파를 줄인다. 본 음향풍동은 개방형 흡입식(open suction type)으로 시험부에서 유속 62.8m/s, 난류강도 0.1%이하, 배경소음 50-55dB 이하로 설계되었다. 이러한 조건을 만족시키기 위하여 하니콤과 6장의 스크린이 있는 정체실과, 21:1의 수축비를 갖는 수축부를 이용하여 난류강도를 낮추고, 흡음재와 90도 각도의 모서리 그리고 공명형과 소산형 소음기로 소음의 전파를 줄였다.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2687-2689
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• 2003

국내 LNG/LPG 누출을 관리할 수 있는 유무선 복합 종합관리시스템을 개발하였다. 이 시스템은 무선가스누출 탐지 및 제어부, 유선가스누출 탐지 및 제어부, 종합관리 시스템부로 구성되며, 특징으로는 무선가스누설 제어부 : 통신속도 1200bps, 유선가스누설 제어부 : 내부통신속도 9600 bps, IEEE 802 양방향 통신 방식, 최대전송속도 25 Mbps, 군 관리기능(server to server). 자체진단기능 등이다. 본 시스템을 가스공사 연구개발원 내에 운영되고 있는 CNG 및 LCNG 충전에 설치 운영하여 성능시험을 거친 결과, 현재까지 기존의 외국제품과 동등한 성능을 보이고 있으며 단가면에서도 2/3정도로 경쟁력을 가지고 있다. 보다 장기적인 현장적용 시험을 통해 성능 및 장기안정성 등이 확립되면 국내시장뿐만 아니라 수출을 통한 국제시장 점유도 기대할 수 있을 것이다.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.41-47
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• 2010

The effect of PCB and BGA pad designs was investigated on the mechanical property of Pb-free solder joints. The mechanical property of solder joint was tested by three different test methods of drop impact tests, bending impact test, and high speed shear test. Two kinds of pad design such as NSMD (Non-Solder Mask Defined) and SMD (Solder Mask Defined) were applied with the OSP finished Pb-free solder (Sn-3.0Ag-0.5Cu, Sn-1.2Ag-0.5Cu). in the drop impact test and bending impact test, the characterized lifetime showed the same tendency, and SMD design showed better mechanical property of solder joint than NSMD regardless of test method, which was due to the different crack path. The fracture crack on SMD pad was propagated along the intermetallic compound (IMC) layer of solder joint, while the fracture crack on NSMD pad propagated through upper edge of land which shields pattern. In the high speed shear test, pad lift occurred on the solder joint of NSMD. SMD/SMD combination of pad design consequently illustrated the best mechanical property of BGA/PCB solder joint, followed by SMD/NSMD, NSMD/SMD, and NSMD/NSMD.

• Product Safety
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• s.184
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• pp.58-63
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• 2009

전기기기에 의해 감전재해는 전기기기의노출된 충전부에 직접 접촉하여 발생하는 경우와 전기기기의금속제 외함 등의 비충전부분이 절연열화 등의 원인으로 누전되었을 경우 접촉하여 발생하는 것이다. 본 고에서는 충전부(LivePart)로부터 인체감전 사고 방지를 방지하기 위하여, 충전부 직접 노출에 대한 안전성을 확보 및 이중구조에서 기초절연의 접촉에 대한 적합성 판단을 제시 하고자 한다.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.85-92
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• 2018

In order to use glued built up timber beam as a structural member for post and beam construction, it must be possible to manufacture long-span lumber. In this study, the researchers conducted a performance evaluation for longitudinal bonding of lumber (cross-section $89{\times}120mm$) made from larch. The specimens were prepared in six different forms using the longitudinal bonding method. The bonding strength of these specimens was tested through tensile strength tests and bending strength tests. The tensile strength test result of the longitudinally bonded parts was better than that of the double lap specimens. And, the tensile strength value of the scarf specimen was better than that of the hooked scarf specimen. The tensile strength of the GFRP (Glass Fiber Reinforced Plastic) rod insertion bonding specimen was 3.6 MPa, which was the highest. As for the bending strength test result of the longitudinally bonded part, the average MOR (modulus of rupture) of the specimen where a GFRP rod was inserted and bonded measured 29 MPa, while the specimens of other bonded parts showed a MOR no more than 11 MPa. Toughness destruction was observed in specimens where a GFRP rod was insertion-bonded. The rest of the specimens showed brittle destruction. The average MOR strength of the Rod + Lap specimen was 30.5 MPa, which was the highest among all longitudinally bonded specimens. The bending strength of the Rod + Lap specimens showed an effective strength that was 66% of that of the control group which were not longitudinally bonded.

• Journal of Korean Society of Steel Construction
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• v.12 no.2 s.45
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• pp.177-185
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• 2000

An experimental research to evaluate the slip coefficients of high-strength friction-type bolt connection of weathering steel plate has been performed in this paper. The test specimens with mill scale or shot blast had been exposed in open air during 3 and 6 months and cleaning of rust surface by hand brushing, power tool brushing and no cleaning was considered. The relaxation of bolt clamping force had also been measured during 600 hours. It was found that slip coefficients increased to the value over 0.6 with exposure except mill scale surface by power tool brushing. The relaxation of bolt tension force in exposed specimens also increased and maximum value reached to about 10%.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.496-499
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• 2008

공공부분 S/W사업은 분리발주가 원칙이고 일괄발주가 예외지만 현재 많은 공공부분 S/W사업은 일괄 발주 사업으로 진행되고 있다. 일괄발주는 SI업체가 S/W업체도 선택하여 입찰 및 개발하기 때문에 발주자가 원하는 품질 좋은 S/W를 선택할 수 없고, 발주자가 S/W를 업그레이드 및 확장할 때 SI업체에 의존하게 되는 단점이 있다. 이런 단점을 보완하고, S/W분리발주를 활성화시키기 위해 지식경제부(구 정보통신부)에서는 S/W분리발주 매뉴얼을 작성하여 보급 및 교육을 하고 있으며, 발주처에서는 품질이 우수한 S/W를 선택하기 위한 S/W분리발주 BMT를 공인된 시험기관인 한국정보통신기술협회(TTA) SW 시험인증센터에서 BMT를 실시하고 있다. 본 논문은 위협관리시스템(TMS) S/W분리발주 BMT를 공인된 국가 시험인증기관인 한국정보통신기술협회(TTA) SW시험인증센터에서 수행한 사례를 기술하였다

• Journal of Energy Engineering
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• v.25 no.4
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• pp.103-109
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• 2016

Polyethylene pipes has useful benefits which are anti-corrosive and flexible material, so it is used to gas pipes but also class 3 water pipes of nuclear power plant, process pipes of petrochemical plant and chemical plant. So the usage of polyethylene pipes is widely increased. But it has been limited for the usage of polyethylene, because it can not be directly detected to fusion joints by using non destructive evaluation. Polyethylene pipes are connected by two methods, one is butt fusion and the other is electrofusion. Butt fusion is widely used to connecting the pipes. It is proposed to method for determining the reliability of joints in this study that is detection of the melt flow zone at fusion joints. In this study, middle density polyethylene is used, outside diameter of the test specimen is 225mm and thickness is 20.5mm. Speed of ultrasonic of this test specimen is 2,200m/s. Test specimens were fabricated by varying the heating time which means from 0% to 130% applying time through heating plate to polyethylene for detecting melt flow zone. Also 4 additional test specimens were made, one was made that not scrapping attached surface of pipes but applying 100% of the proper heating time and the others were made to include of soil, gravel and vinly tape paper at fusion joints, that were also applied 100% of proper heating time. Ultrasonic testing to measure the melt flow zone of 20 test specimens was conducted by using 3.5MHz and 5.0MHz ultrasonic probes and melt flow zone measuring was conducted to three times at different point to one specimen. To differentiate the melt flow zone signal, post image processing was equally conducted to all test results and image levels, contrast, sharpen, threshold were adopted to all teat results and the test results were displayed gray scale. From the results, for the shorter heating times the reflection area of multiple echo have been increased, so the data was obtained from the position where it can be eliminated as much as possible. At 80% of proper heating time(168 sec.), the signal of melt flow zone was obtained clearly, so measuring could be conducted. From 7% of proper heating time(15 sec.) to shorter heating times. we could not obtain the signal because test specimen was not fused. From the result, we can verify that measuring of melt flow zone by using phased array ultrasonic imaging method is possible. And we can verify to complete and incomplete butt fusion by measuring the melt flow zone.