• Elastomers and Composites
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• v.42 no.3
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• pp.159-167
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• 2007

Hydraulic actuators are used widely for industrial machinery. The seal made from elastomer is used as a core part of the actuator, NBR(nitrile butadiene rubber) materials with high quality of oil resistance and abrasion resistance is used widely, requiring excellent characteristic of sealing. According to applied circumstances, the actuators for industrial machinery are used under different temperature situations. In this study, three different kinds of NBR, which is Hs70, 80, 90 are determined as one of hydraulic materials. An experimental investigation is performed to confirm the non-linearity under different temperature ($-10^{\circ}C,\;20^{\circ}C,\;80^{\circ}C,\;100^{\circ}C$) situation, material constants for finite element analysis and plastic deformation in accordance with Load-unload.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1472-1474
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• 2003

연소방지재(난연테이프, 난연도료, 난연seal, 난연레진, 난연보드 등)란 지중 배전케이블, 접속재 및 통신케이블 등의 외피에 화재확산 방지를 위해 도포하여 사용하는 것으로서 화재 시 발포하거나 단열의 효과가 있어 케이블, 전선 등이 연소하는 것을 지연시킨다. 따라서 본 평가 기술에서는 수직불꽃시험, 산소지수, 저 염소시험, 발연농도, 케이블 허용전류저감률 등 주 재료시험에 대한 시험방법을 검토하고 시험에 적용하여 시험 시 문제점을 도출하여 시험방법을 정립하고자 한다.

• International Journal of Fluid Machinery and Systems
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• v.3 no.2
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• pp.102-112
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• 2010

Artificial heart pumps have attracted the attention of researchers around the world as an alternative to the organ used in cardiac transplantation. Conventional centrifugal pumps are no longer considered suitable for long-term application because of the possibility of occurrence of blood leakage and thrombus formation around the shaft seal. To overcome this problem posed by the shaft seal in conventional centrifugal pumps, the magnetically suspended centrifugal pump has been developed; this is a sealless rotor pump, which can provide contact-free rotation of the impeller without leading to material wear. In Europe, clinical trials of this pump have been successfully performed, and these pumps are commercially available. One of the aims of our study is to numerically examine the internal flow and the effect of leakage flow through the gap between the impeller and the pump casing on the performance of the pump. The results show that the pressure head increases compared with the pump without a gap for all flow rates because of the leakage of the fluid through the gap. It was observed that the leakage flow rate in the pump is sufficiently large; further, no stagnant fluid or dead flow regions were observed in the pump. Therefore, the present pump can efficiently enhance the washout effect.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.97-105
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• 1989

This study was conducted to evaluate and compare the apical leakage among the retrograde filling materials; retrograde filling with non-zinc amalgam, cavity varnish and non-zinc amalgam, z.o.e cement, Glass Ionomer cement, scotch bond and silux. Sixty single rooted teeth were divided into six groups and each tooth was individually prepared for its particular group. The specimens were incubated at $37^{\circ}C$ for 24 hrs and then were infiltrated by 2% methylene blue for 7 days. Apical leakage was evaluated by measuring the degree of dye penetration between the filling material and the canal wall. The results were as follows: 1. The scotch bond and silux group showed the least amount of apical leakage and the control group showed the greatest amount of apical leakage. 2. The groups retrofilled with cavity varnish and amalgam, glass-Ionomer cement, scotch bond and silux showed significantly good apical seal than control group. 3. The groups retrofilled with glass Ionomer cement, scotchbond and silux showed significantly good apical seal than the groups retrofilled with Amalgam and Zinc oxide eugenol cement.

• The KSFM Journal of Fluid Machinery
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• v.8 no.6 s.33
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• pp.40-46
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• 2005

Because of design and manufacturing costs, it is important to predict an expected life of bellows with component stresses of bellows as its design factors and material characteristics. In this study, numerical analyses are carried out to elucidate the thermal and flow characteristics of the bellows-seal gate and globe valves for high temperature (max. $600^{\circ}C$) and for high pressure (max. $104 kgf/cm^2$) conditions. Using commercial codes, FLUENT, which uses FVM and SIMPLE algorithm, and ANSYS, which uses FEM, the pressure and temperature fields are graphically depicted. In addition, when bellows have an axial displacement, thermal stress affecting bellows life is studied. The pressure and temperature values obtained from the flow analyses are adopted as the boundary conditions for thermal stress analyses. As the result of this study, we got the reasonable coefficients for valve and thermal stress for bellows, compared with existing coefficients and calculated values.

• Transactions of Materials Processing
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• v.22 no.8
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• pp.442-449
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• 2013

The solenoid valve case of an 8-speed automatic transmission plays a role in maintaining the valve seal, which prevents an inflow of foreign substances into the transmission. The seal increases the reliability of the automatic transmission's performance. As a solution to pollution-related problems and to reduce fuel consumption, transmissions are being made with more gears to work more economically and have reduced fuel consumption. These newer transmission require greater dimensional tolerances and need to be manufactured with more precision. In the current study, the design of a multistage drawing considering both the product's height and limit draw ratio (LDR) of the material was performed using both a theoretical analysis and the expertise of industrial experts. The finite element modeling (FEM) simulation was performed using the commercial software, PAM-stamp, and tests of the dimensional measurements for a prototype were performed to verify the optimal progressive process.

• Food Science of Animal Resources
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• v.21 no.3
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• pp.235-245
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• 2001

This study was conducted to evaluate the usefulness of Second-Heat-Seal film(SHS) as an alternative material to PVDC/EVA shrink film(VSP) being currently used by domestic meat packer for vacuum-packaging of fresh meat. The samples from pork loin and beef striploin and round were stored at 2$^{circ}C$ for 5 weeks and measured for the changes of microbial counts, color, pH, volatile basic nitrogen(VBN), purge loss and sensory parameters. The pork loins packed with SHS showed higher spermine contents during the whole storage period at 2$^{circ}C$, and lower counts in total microbes and lactic acid bacteria after 28 days storage at 2$^{circ}C$ than those packed with SHS tended to be lower than those packed with VSP over the storage time. Nevertheless, no significant differences were observed between two packaging treatments in the other quality parameters evaluated. It is therefore concluded that SHS film might have a possibility to substitute for VSP film for vacuum-packaging of fresh meat at least from a materials point of view.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.8
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• pp.661-668
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• 2016

Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.56-61
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• 1994

Magnetic fluid is ferromagnetic material in liquid state, so the surface configuration of magnetic fluid affects the magnetic field, and vice versa. To analyze the devices with magnetic fluid, the magnetic field equations and hydrodynamic equation should be solved simultaneously. This paper presents the numerical algorithm to obtain the surface configuration of fluid under the influence of gravity, pressure and magnetic field without conventional sim¬plified assumption. The algorithm consists of nonlinear finite element method and ferro-hydrodynamics, such as Poisson equations and Bernoulli equations, respectively The simulated configurations of fluid are compared with experimental results, and the influence of the amount of fluid and pole piece shape on the seal capacities are analyzed.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.453-458
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• 2020

In this study, ethylene-propylene-diene monomer (EPDM) rubbers reinforced with various particle size of carbon black were prepared and tested. We followed recently published CSA/ANSI CHMC2 standard "the test methods for evaluating material compatibility in compressed hydrogen applications-polyemr". Measurement of change in hardness, tensile strength and volume were performed after exposure to maximum operating pressure, 87.5 MPa, for 168 hours (1 week). Once EPDM was exposed to high-pressure hydrogen, the samples experience volume increase and degradation of the physical properties. Also, after the dissolved hydrogen was fully eliminated from the specimens, the hardness and the tensile properties were not recovered. The rubber reinforced with smaller sizes of carbon black particles showed less volume expansion and decrease of physical properties. As a result, smaller particle size of carbon black filler led to more resistance to high-pressure hydrogen.