• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.49-52
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• 2005

In the development of a propellant tank using liquid oxygen and liquid hydrogen, the improvement of microcrack resistance of carbon/epoxy composites is necessary for the application of a composite material to tank structures. In this research, two types of carbon/epoxy composites with different matrix systems were tested to measure interlaminar shear strength (ILSS), one of the material properties to evaluate fiber-matrix interface adhesion indirectly. Short beam specimens were tested inside an environmental chamber at room temperature(RT) and at cryogenic temperature( - 150 $^{\circ}C$) respectively. Results showed that the matrix system with large amount of bisphenol-A and CTBN modified rubber had good performance at cryogenic temperature.

• 한국가축번식학회지
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• 제26권2호
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• pp.119-124
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• 2002

본 연구는 돼지에서 동결정액을 이용한 번식능력을 개선하기 위한 동결정액 포장재료의 효과를 구명하기 위하여 실시하였다. 본 시험에는 축산기술연구소 종축개량부 (충남, 성환)의 인공수정센터에서 사육중인 종모돈이 사용되었다. 기존의 돼지 동결정액 포장방법인 maxi-straw 동결정액 포장방법과 5$m\ell$빈 cryogenic-vial 및 aluminum-pack 포장방법을 비교한 결과 cryogenic-vial로 포장하여 액체질소 상단 15cm에서 동결한 후 52$^{\circ}C$ water bath에서 190초 융해한 방법이 기존의 maxi-straw 방법과 비슷한 결과를 나타내었다. Cyogenic-vial 포장방법의 동결-응해 방법을 설정하기 위하여 융해시간을 달리하여 시험한 결과 액체질소 상단 15cm에서 동결하고 52$^{\circ}C$에서 190초 간 융해하였을 때 정자운동성이 120초 및 150초 응해시 보다 우수하였다 (P<0.05). 그러나 정상첨체비율은 응해시간 간에 차이가 없었다. 52$^{\circ}C$에서 45초간 응해 한 maxi-straw 포장방법과 52$^{\circ}C$에서 190초 융해한 cryogenic-vial 포장방법간에 정액성상을 비교한 결과 총정자운동성과 정자의 빠르기는 maxi-straw가 우수하였다 (P<0.05). 그러나 직진성과 정상첨체비율은 두 포장방법간에 차이가 없었다. 동결정액 포장방법별 인공수정시 번식성적은 maxi-straw 동결정액이 cryogenic-vial 동결정 액보다 수태율, 분만율, 그리고 산자수가 높았으나 통계적 유의차는 인정되지 않았다. 이상의 결과를 종합해 보면 cryogenic-vial 포장 방법의 동결 및 음해방법을 좀 더 연구개발하면 기존의 maxi-straw포장방법을 대체하여 실용화 할 수 있을 것으로 사료된다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.115-118
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• 2003

This research aims to measure mechanical tensile properties of CFRP composites for cryogenic tank material. Through the cryogenic chamber, tensile tests are peformed under cryogenic temperature for graphite/epoxy fabric specimen aged at $-150^{\circ}C$ for 30hrs with load and graphite/epoxy unidirectional specimen 3-cycled from RT to $-100^{\circ}C$ with load. For graphite/epoxy fabric specimen, tensile modulus showed to increase after aging at cryogenic temperature(CT) while to decrease after aging at room temperature(RT) and tensile strength is more decreased after CT-aged than at RT-aged. For graphite/epoxy unidirectional specimen, tensile modulus was almost not changed after 3-cycling but strength showed the trend of decrease as increase the number of cycling.

• 한국초전도ㆍ저온공학회논문지
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• 제26권1호
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• pp.20-24
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• 2024

Over the past four years, as the COVID-19 pandemic has struck the world, cold chain of COVID-19 vaccination has become a hot topic. In order to overcome the pandemic situation, it is necessary to establish a cold chain that maintains a low-temperature environment below approximately 203K (-70℃), which is the appropriate storage temperature for vaccines, from vaccine suppliers to local hospitals. Usually, cryocoolers are used to maintain low temperatures, but it is difficult for small-scale local distribution to have cryocooler due to budget and power supply issues. Accordingly, in this paper, a cryogenic TSU (Thermal storage unit) system for vaccination cold chain is designed that can maintain low temperatures below -70℃C for a long time without using a cryocooler. The performance of the TSU system according to the energy storage material for using as TSU is experimentally evaluated. In the experiments, four types of cold storage materials were used: 20% DMSO aqueous solution, 30% DMSO aqueous solution, paraffin wax, and tofu. Prior to the experiment, the specific heat of the cold storage materials at low temperature were measured. Through this, the thermal diffusivity of the materials was calculated, and paraffin wax had the lowest value. As a result of the TSU system's low-temperature maintenance test, paraffin wax showed the best low-temperature maintenance performance. And it recorded a low-temperature maintenance time that was about 24% longer than other materials. As a result of analyzing the temperature trend by location within the TSU system, it was observed that heat intrusion from the outside was not well transmitted to the low temperature area due to the low thermal conductivity of paraffin wax. Therefore, in the TSU system for vaccine storage, it was experimentally verified that the lower the thermal diffusivity of the cold storage material, the better low temperature maintenance performance.

• 대한조선학회논문집
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• 제51권3호
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• pp.246-253
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• 2014

Liquid natural gas is stored and transported inside cargo tank which is made of specially designed cryogenic materials such as 9% Ni steel, Al5083-O alloy and SUS304 and so on. The materials have to keep excellent ductile characteristics under the cryogenic environment, down to -163oC, in order to avoid the catastrophic sudden brittle fracture during the operation condition. High manganese steel is considered to be the promising alternative material that can replace the commonly used materials mentioned above owing to its cost effectiveness. In line with this industrial need, the mechanical properties of the high manganese steel under both room and cryogenic environment were investigated in this study focused on its tensile and fatigue behavior. In terms of the tensile strength, the ultimate tensile strength of the base material of the high manganese steel was comparable to the existing cryogenic materials, but it turned out to be undermatched one when welding is involved in. The fatigue strength of the high manganese steel under room temperature was as good as other cryogenic materials, but under cryogenic environment, slightly less than others though better than Al 5083-O alloy.

• Journal of Mechanical Science and Technology
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• 제15권1호
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• pp.26-34
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• 2001

Most research to date concerning the cryogenic toughness of austenitic stainless steels has concentrated on the base metal and weld metal in weldments. The most severe problem faced on the conventional austenitic stainless steel is the thermal aging degradation such as sensitization and carbide induced embrittlement. In this paper, we investigate the cryogenic toughness degradation which can be occurred for austenitic stainless in welding. The test materials are austenitic stainless JN1, JJ1 and JK2 steels, which are materials recently developed for use in nuclear fusion apparatus at cryogenic temperature. The small punch(SP) test was conducted to detect similar isothermally aging condition with material degradation occurred in service welding. The single-specimen unloading compliance method was used to determine toughness degradation caused by thermal aging for austenitic stainless steels. In addition, we have investigated size effect on fracture toughness by using 20% side-grooved 0.5TCT specimens.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.347-351
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• 2004

The cryogenic test facility is developed for test of deep groove ball bearings, floating ring seals, materials (steel & copper) for High Pressure Turbopump of liquid rocket engine (LRE). The cryogenic bearing test is performed to evaluate the flow rate of cooling water and the load-carrying capacity of bearings. The cryogenic seal test is performed to evaluate the determination of magnitude of leakages through the seal, a time variation of this magnitude. The test of the materials Pair is performed to evaluate its fitness for operation in the liquid oxygen medium.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1057-1059
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• 2017

액체로켓엔진 개발에서 엔진 짐벌링 시 산화제라인의 벨로우즈 극저온 단열 방법을 연구하였다. 극저온 산화제의 열단열과 엔진구성품의 고온으로부터의 열차폐는 엔진 추진성능과 효율에 중요하다. 엔진 짐벌링중 고압배관과 재순환라인(예냉라인)이 단열부위로 기존의 극저온 단열과는 차별화된 디자인과 소재가 필요하다. 엔진 짐벌링중에 벨로우즈의 극저온 단열재가 열단열과 열복사를 고려하여 새로운 디자인으로 마찰력과 작동반경을 고려하여 PTFE소재의 단열재가 적용된다. 향후 엔진 시험을 통하여(짐벌링과 TVC) 새로운 벨로우즈 단열재가 향상되고 디자인 변경이 요구된다.

• 한국해양공학회지
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• 제27권1호
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• pp.74-79
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• 2013

In the context of the structural performance of an LNG hold, the mechanical characteristics of the insulation material are considered to be a critical design factor under cryogenic temperatures. This paper presents the thermal elasto-plastic behavior of the reinforced polyurethane foam (RPUF) adapted for the insulation material of a membrane-type LNG carrier via both experiments and numerical simulations realizing the cryogenic condition. The experiments are carried out to investigate the thermal transfer and thermal elasto-plastic deformation characteristics of an actual RPUF specimen. The heat transfer simulations based on the finite element method (FEM) include a forced convection analysis. The results of heat transfer analyses are compared with the experimental results. Reasonable cryogenic conditions for RPUF are reviewed based on both the analysis and experimental results.

• 한국초전도ㆍ저온공학회논문지
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• 제19권2호
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• pp.53-57
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• 2017

In superconducting power devices including power cables in which high temperature superconducting (HTS) tapes are utilized, a reliable electrical insulation should be achieved for its maximum performance. For an efficient design of HTS superconducting devices, a comparative evaluation of the mechanical and thermal propperties for various insulation materials at cryogenic temperatures is required. Especially, in the process of the property evaluation of the sheet-shaped insulation materials, anisotropy according to the machining direction should be considered because the mechanical and thermal properties are significantly influenced by the sample orientation. In this study, the cryogenic thermal and mechanical properties of various insulation material sheets such as PPLP, Cryoflex, Teflon, and Kapton were determined considering sample orientation. All samples tested at cryogenic temperature showed significantly higher tensile strength as compared with that of room temperature. The ultimate tensile strength at both temperature conditions significantly depended upon the sample orientation. The thermal properties of the insulation materials exhibited a slight difference among samples depending on the orientation: for the PPLP and Cryoflex, the CD orientation showed larger thermal contraction up to 77 K as compared to the MD one. MD samples in PPLP and Cryoflex showed a lower CTE and thermal contraction which made it more promising as an insulation material due to its comparable CTE with HTS CC tapes.