• Title/Summary/Keyword: 홀더

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The Effect of Compliance Structures Near the Mechanical Heart Valve on Valve Surface Erosion (기계식 인공 판막 주위의 유연성 구조가 표면 괴식에 미치는 영향)

  • Lee, Hwan-Sung;Hwang, Sung-Won;Sun, Kyung
    • Journal of Biomedical Engineering Research
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    • v.23 no.4
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    • pp.309-315
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    • 2002

  • Since the discovery, in the 1980s, of erosion-pit-induced fractures in implanted mechanical heart valves. cavitation on the surface of mechanical heart valves has been widely studied as a possible cause of pitting. Several factors, including peak dp/dt of the ventricular pressure. maximum closing velocity of the leaflet, and squeeze flow. have been studied as indices of the cavitation threshold. In the present study. cavitation erosion on the surface of a mechanical valve was examined by focusing on squeeze flow and the water hammer phenomenon during the closing period of the valve. In this study, we measures pressure wave forms near a valve and closing velocities of a disk, which were placed in a holder with and without compliance. In case of all holders, pressure drop of below vapor pressure expect at near the surface disk. It was also found that the closing velocity of the disk increased and that cavitation erosion was enhanced too. These results suggest that disk closing velocity during the closing phase has signifiant effects on pitting erosion.

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Post-cure Condition of a Silicone Rubber Material for a LCD Lamp Holder (LCD 램프홀더용 실리콘고무재료의 후가교 조건)

  • Ahn, Won-Sool;Lee, Joon-Man
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.7
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    • pp.1661-1667
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    • 2009

  • Post-cure characteristics of a silicone rubber material which is widely used for a LCD lamp holder were investigated using thermogravimetric analysis (TGA). Research was especially focussed on searching for the optimum post-cure conditions in relation to the practical operation environments. The results showed that incipient volatile temperature(Ti) during the process was considered as the most important factor and, thereby, post-curing for 2hrs at $250^{\circ}C$seemed to be a reasonable condition in the practical view-point. Arrhenius plot of shift factors which were empirically determined from the time-temperature-superposition-principle showed good linearity, exhibiting the post-cure mechanism might be proceeded through single mechanism with activation energy of 108.25kJ/mol.

  • https://doi.org/10.5762/KAIS.2009.10.7.1661 인용 PDF

Tightness of specimen sealing box in 20 L test chamber to evaluate building materials emitting pollutants (건축자재에서 방출되는 오염물질 평가 시 사용되는 20 L 시험챔버 시편홀더의 기밀성 개선)

  • Shin, Woo Jin;Lee, Chul Won;Kim, Man Goo
    • Analytical Science and Technology
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    • v.20 no.4
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    • pp.261-267
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    • 2007

  • The 20 L small chamber test method is to evaluate pollutants such as TVOC, formaldehyde emitted from building materials. This method was only designed to evaluate the surface emission of sample exposed in the chamber. In this method, building materials cut with a fixed standard size are fixed in a sample sealing box. The sample sealing box is put into the 20 L test chamber. This chamber is ventilated at a standard air change rate with purified air for 7 days then the sample from the chamber is collected and analyzed to measure the emission rate of TVOC and formaldehyde. In this method, however, if the sealing box does not guarantee airtightness, accurate evaluation for the building materials can not be achieved due to the pollutants emitted from edge of the sample so called, edge effect. This edge effect can be much greater when evaluating panels such as plywood, flooring due to their surface treatment. In this study, flooring was tested to check airtightness of the sample sealing box with analytic results between 1L and 20 L test chamber. Furniture materials like LPM coated one side surface treatment and MDF coated both sides surface treatment with LPM were tested to identify whether the improvement of the sample sealing box airtightness is possible with the comparison between existing and improved test method that low VOC emission tape was used to seal the sample edge. After 7 days, MDF TVOC emission rate was different according to the existence and nonexistence of tape. The emission rate of the existing test method was $0.009mg/m^2h$ and that of improved test method was $0.003mg/m^2h$. Relative standard deviation for the existing test method was $0.004mg/m^2h$ and relative standard deviation for the improved test method was $0.002mg/m^2h$ when the same sample was analyzed three times. The improved test method in this study using low VOC emission tape was effective and able to reduce the heterogeneous effect of the edge from the sample sealing box.

  • https://doi.org/10.5806/AST.2007.20.4.261 인용 PDF KSCI

Stamping analysis of automotive wheel disc (자동차용 휠 디스크 스탬핑 해석)

  • 김주성;민홍기
    • Journal of the korean Society of Automotive Engineers
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    • v.14 no.3
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    • pp.26-31
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    • 1992

  • 본 연구에서는 ABBAQUS/EXPLICIT CODE를 이용하여 자동차용 휠 디스크의 성형성을 파악하기 위한 모델링 방식과 컴퓨터 시뮬레이션의 결과인 스프링백, 잔류응력, 두께 변화, 변형률 등을 소개하기로 한다. 컴퓨터 시뮬레이션을 휠 디스크 스탬핑에 이용한 경우 스탬핑시 발생하는 여러현상을 쉽게 예측할 수 있으며, 또한 금형의 Geometry 결정 및 홀더와 펀치의 작용하중 등 금형 설계시 요구되는 데이타 확보가 매우 용이하다.

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