• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.769-775
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• 2016

Currently, dental implants are widely used as artificial teeth due to their good chewing performance and long life cycle. Generally, a dental implant consists of an abutment as the upper part and a fixture as the lower part. When chewing forces are repeatedly applied to a dental implant, a gap is often generated at the interfacial surface between the abutment and the fixture, and it results in some deterioration such as loosening of the fastening screw, dental retraction and fixture fracture. To enhance the sealing performance for coping with such problems, this study proposes a new sealing-type abutment having a number of grooves along the conical surface circumference, and it carries out finite element analysis in consideration of the external chewing force and pretension between the abutment and the fixture. The result shows that the proposed sealing-type abutment shows an enhanced sealing performance in terms of the contact pressure in comparison with a conventional abutment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.407-412
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• 2017

This paper introduces a biocompatible packaging system for implantable medical device having a hermetic sealing, such that a perfect physical and chemical isolation between electronic medical system and human body (including tissue, body fluids, etc.) is obtained. The hermetic packaging includes an electronic MEMS pressure sensor, power charging system, and bluetooth communication system to wirelessly measure variation of capacitance. The packaging was acquired by Quartz direct bonding and $CO_2$ laser welding, with a size of width $ 6cm{\times}length\;10cm{\times}lheight\;3cm$. Hermetic sealing of the packaged system was tested by changing the pressure in a hermetic chamber using a precision pressure controller, from atmospheric to 900 mmHg. We found that the packaged system retained the same count or capacitance values with sensor 1 - 25,500, sensor 2 - 26,000, and sensor 3 - 20,800, at atmospheric as well as 900 mmHg pressure for 5 hours. This result shows that the packaging method has perfect hermetic sealing in any environment of the human body pressure.

• Tribology and Lubricants
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• v.20 no.5
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• pp.231-236
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• 2004

Sulfur Hexafluoride, S $F_{6}$ is widely used for leak detection and as a gaseous dielectric in transformers, condensers and circuit breakers. S $F_{6}$ gas is also effective as a cleanser in the semiconductor industry. This paper presents a numerical study of the sealing force of disk type seal in S $F_{6}$ gas safety valve. The sealing force on the disk seal is analyzed by the FEM method based on the Taguch's experimental design technique. Disk seals in S $F_{6}$ gas safety valve are designed with 9 design models based on 3 different contact length, compressive ratio and gas pressure. The calculated results of Cauchy stress and strain showed that the sealing characteristics of Teflon $^{ }$PTFE is more effective compared to that of FKM(Viton), which is related to the stiffness of the materials. And also, the contact length of the disk seal is important design parameter for sealing the S $F_{6}$ gas leakage in the safety valve.afety valve.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1188-1196
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• 2004

In this paper a determination of the optimal segment sealing material for a tunnel under the Han river between the Sungsoo-dong, Sungdong-Gu and the Chungdaw-dong, Kangnam-Gu in the Bundang railway. The geological investigation results show that some fractured zones exist loca]]y under the northern boundary of the Han river bed, but the other regions consist mostly of hard rocks of good Quality in the tunnel excavation level. Also, a hign water pressure of $5kgf/cm^2$ and a flash inflow of river water due to old boring holes are expected during tunnel excavation. A combined type sealing material of EPDM gasket with expansional rubber is selected as a optimal segment sealing material for the Han river tunnel considering the geological and site conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.361-370
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• 2003

In this study, the performance of water tightness of water expansional sealing material and gasket was evaluated. The water tightness test was performed varying the type of inner pressure condition, for which the water expansional sealing material was inundated for 5 days to evaluate the ability of water tightness. In order to carry out this test, we made use of two types of water expansional sealing material; general type and combined type with non-expansional rubber. In the case of gasket, EPDM gasket and complex gasket sticked to the water expansional sealing material were applied. The performance of water tightness depended on the construction defect and the deformation of segment. The construction defect and segment deformation were generally expressed by gap and offset of the construction joint. The results, of tests showed that the performance of water tightness was largely influenced by the gap between segments. Management criteria of gap and offset were proposed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.1
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• pp.21-28
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• 2015

A Tsunami damper, which is installed on the outer wall of a nuclear power plant, is usually used as a ventilation window of the machine room, but can serve as a device for preventing flooding of the machine room when large waves flow over the outer wall. The sealing strip, which is inserted between the casing and the blades, plays an important role in maintaining a watertight environment. In this study, in order to ensure an effective watertight performance of the tsunami damper, FE analysis is conducted to compare the contact characteristics of sealing strips with three different section shapes. In the analysis, the casing and the blade of Tsunami damper are assumed to be rigid bodies; the sealing strip is assumed to be a flexible body. The stress, the strain, and the contact pressure are investigated to examine the sealing performance of each model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.610-614
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• 1996

Sealing of lubricat-air mixture in the high performance machining conte is one of most the important characteristics to carry out enhanced lubrication. High speed spindle requires non-contact type of sealing mechanism. Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Effect of geometry and leakage path are evaluated according to variation of sealing geometry, Velocity, pressure, turbulence intensity of profile is calculated to fina more efficient geometry and variables. This offers a methodological way of enhancement seal design for high speed spindle. The working fluid is regarded as two phases that are mixed flow of oil phase and air phase. It is more reasonable to simulate an oil jet or oil mist type high speed spindle lubrication. Turbulence and compressible flow model are used to evaluate a flow characteristic, This paper arranges a geometry of mostly used non-contact type seal and analyzes leakage characteristics to minimize a leakage on the same sealing area.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.10
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• pp.477-482
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• 2002

One of the key technologic requirements for rotary blood pumps is the sealing of the motor shaft. A mechanical seal, a journal bearing, magnetic coupling, and magnetic suspension have been developed, but they have drawbacks such as wear, thrombus formation, and power consumption. A magnetic fluid seal is durable, simple, and non power consumptive. Long-term experiments confirmed these advantages. The seal body was composed of a Nd-Fe-B magnet and two pole pieces; the seal was formed by injecting magnetic fluid into the gap (50${\mu}m$) between the pole pieces and the motor shaft. To contain the ferro-fluid in the seal and to minimize the possibility of magnetic fluid making contact with blood, a shield with a small cavity was attached to the pole piece. While submerged in blood, the sealing pressure of the seal was measured and found to be 31kPa with magnetic fluid LS-40 (saturated magnetization, 24.3 KA/m) at a motor speed of 10,000 rpm and 53kPa under static conditions(0mmHg). The specially designed magnetic fluid seal for keeping liquids out is useful for axial flow blood pumps. The magnetic fluid seal was incorporated into an intra-cardiac axial flow blood pump.

• Journal of the Korean Society of Safety
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• v.22 no.6
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• pp.27-34
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• 2007

Static or dynamic elastomeric O-ring seals are installed between joining parts, and play key roles of high pressure-tightening. Sealing performance and structural safety of the O-ring are dependent on groove design, plain diameter, squeeze and applications such as pressure and temperature. In this study, to solve O-ring problem squeezed and highly pressurized under laterally one-sided constrained condition, hyperelastic FE analyses are performed, and FE results are compared with measured ones by computer-aided tomography, deformed shape and extrusion depth of the O-ring. Through the comparisons, FE analysis technique was verified. In order to evaluate design sensitivity, Taguchi method was used to select FE analysis cases. Adjustment parameters are clearance gap, groove comer radius, plain diameter and squeeze. By means of verified FE analysis technique, it has been analysed how the parameters have effects on contact stress fields, internal stress fields, and extrusion depths. Sealing performance has been evaluated based on contact stress fields and contact widths, and structural safety on internal stress and strain, extrusion lengths.

• Design & Manufacturing
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• v.15 no.1
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• pp.32-40
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• 2021

Mold design for in-mold coating was carried out to achieve simultaneous injection molding and two-color coating for car gas cap cover. The developed mold includes one core and three cavities which are composed of a substrate cavity and two coating cavities. To provide a sealing edge for complete seal during the second coating, the first coated material was used at the boundary between the first coating and the second one, and injection molded substrate was used at the parting line. The materials used were PC/ABS for substrate and 2-component Polyurea for coating. Through experiments, it was found that the suggested sealing edges were effective for complete seal during the second coating. In cavity pressure traces, there were three peaks caused by mold closing, coating-material injection and cleaning-piston advancement inside the mixing head. The cavity pressure increased with decreasing coating thickness.