• 대한기계학회논문집A
• /
• 제24권4호
• /
• pp.824-829
• /
• 2000

The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.

• Design & Manufacturing
• /
• 제6권1호
• /
• pp.24-28
• /
• 2012

Friction and wear affect all processes involved in the extraction of materials and their conversion into finished products in the die applications such as drawing, extrusion etc. Originating phenomenon from the contact surface between the tool and workpiece, they are usually a hindrance to materials process operations which usually result in damaging the tools, increasing energy consumption, the contamination of processed material by wear particles and also some problems associated with technologies to control friction and wear. The most well established method to control friction and wear is by the application of lubricant such as fluorocarbon. Besides, a surface technique so-called surface modification can be applied to solve the tribology problems of the die applications for both the economical and ecological reasons. In this article, we applied DLC(diamond-like carbon) thin film on alumina ceramic for HT test using the PIID(plasma ion immersion deposition), 4 groups of test specimens were tested up to $200^{\circ}C$ which is a little higher than the normal working temperature of die application. Pin-on-disc tribo-tester was used to test the friction and surfaces were characterized by SEM and EDS and else, the morphology changes of DLC coatings were studied. The present work indicated that the DLC had a great potential to reduce the friction and wear in the alumina die application without lubricants.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 제35회 춘계학술대회
• /
• pp.215-225
• /
• 2002

In order to enhance the thermal stability of binder materials of bonded type solid lubricants, several combinations of metal-alkoxide based sol-gel materials such as methyltrimethoxysilane(MTMOS), $titaniumisopropoxide(Ti(Opr^{j})_{4})$, $zirconiumisopropoxide(Zr(Opr^{j})_{4})$ and $aluminumbutoxide(Al(Obu^{t})_{4})$ were chemically modified by epoxy-, acrylic- and fluoro-silane compounds, respectively, in this work. Friction and wear characteristics of these hybrid ceramic materials were tested with a micro tribe-tester where a reciprocating steel ball slid on a test material, and the tribological property was also evaluated with respect to both heat-curing temperature and tile time. Test results generally showed that hybrid ceramic materials modified by epoxy-silane compounds had a low friction compared to others. And the higher heat-curing temperature and the longer heat treatment time resulted in the higher friction and the lower wear. IR spectroscopic analyses revealed that it was caused mainly by the increased metal oxide content in hybrid ceramics when the heat-curing temperature was over $320^{\circ}C$.

• 한국안전학회지
• /
• 제19권2호
• /
• pp.1-5
• /
• 2004

Al-brass is the raw material of mnufacturing tubes for heat exchanger of vessel where seawater is used to coolant because it has high level of heat coductivity and excellent mechanical properties and high level of corrosion resistance due to cuprous oxide($Cu_2O$) layer against seawater. However, damage of Al-brass tubes for heat exchanger of vessel is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment. In this study, to investigate on the effect of stress on the polarization characteristics of Al-brass. At the stress of 0% and 95% yield strength by constant displacement tester, in 3.5% NaCl + 0.1% $NH_4OH$ solution, the polarization tests were carried out. And thus open circuit potential, corrosion current density, anodic polarization, cyclic polarization and dezincification behavior of Al-brass are investigated.

• 한국가스학회지
• /
• 제13권4호
• /
• pp.40-45
• /
• 2009

MSDS 자료의 적정성을 고찰하기 위해 크실렌 이성질체에 대해 Pensky-Martens 밀폐식(ASTM D93), Setaflash 밀폐식(ASTM D3278), Tag 개방식(ASTM D1310), Cleveland 개방식(ASTM D92) 장치 등을 이용하여 인화점을 측정하였으며, 또한 최소자연발화온도는 ASTM E659-78장치를 사용하여 측정하고, 문헌값들과 한국산업안전보건공단의 MSDS 자료와 비교하였다. 그 결과, 측정된 인화점과 최소자연발화온도는 이들과 차이를 나타내어 안전의 목적을 위해 연소특성치 고찰이 필요함을 알 수 있었다.

• 한국안전학회지
• /
• 제31권4호
• /
• pp.42-47
• /
• 2016

The combustible properties(flash point, explosion limit and autoignition temperature) are the important safety items which are considered in the typical MSDS(material safety data sheet). In this study, for the safe handling of n-butyl methacrylate(n-BMA) being used in various ways in the chemical industry, the flash point and the autoignition temperature(AIT) of n-butyl methacrylate was experimented. And, the lower explosion limit of n-butyl methacrylate was calculated by using the lower flash point obtained in the experiment. The flash points of n-butyl methacrylate by using the Setaflash and Pensky-Martens closed-cup testers measured $44^{\circ}C$ and $51^{\circ}C$, respectively. The flash points of n-butyl methacrylate by using the Tag and Cleveland open cup testers are measured $53^{\circ}C$. The AIT of n-butyl methacrylate by ASTM 659E tester was measured as $295^{\circ}C$. The lower explosion limit by the measured flash point $44^{\circ}C$ was calculated as 0.85 vol.%. It was possible to predict lower explosion limit by using the experimental flash point or flash point in the literature.

• 대한기계학회논문집A
• /
• 제27권10호
• /
• pp.1800-1808
• /
• 2003

This work deals with the electrical conductivity of dielectric on output parameters such as metal removal rate and surface roughness value of a carbon steel(SM25C) and sintered carbides cut by wire-electrical discharge machining(W-EDM). Dielectric has several functions like insulation, ionization, cooling, the removal of waste metal particles. The presence of minute particles(gap debris) in spark gap contaminates and lowers the breakdown strength of dielectric. And it is considered that too much debris in spark gap is generally believed to be the cause of arcing. Experimental results show that increases of cobalt amount in carbides affects the metal removal rate and worsens the surface quality as a greater quantity of solidified metal deposits on the eroded surface. Lower electrical conductivity of the dielectric results in a lower metal removal rate because the gap between wire electrode and workpiece reduced. Especially, the surface characteristics of rough-cut workpiece and wire electrode were analyzed too. Debris were analyzed also through scanning electron microscopy(SEM) and surface roughness tester. Micro cracks and some of electrode material are found on the workpiece surface by energy dispersive spectrometer(EDS).

• 대한기계학회논문집
• /
• 제16권4호
• /
• pp.658-666
• /
• 1992

본 연구에서는 고속, 연속장업으로 이루어지고 있는 스템핑 공정에서 금형과 강판간의 접촉-슬립에 따른 마찰 및 윤활특성의 성능을 평가할 수 있도록 한 원형단면 형상의 드로오비드 마찰실험장치를 활용하여 가압력, 윤활유 특성, 드로잉 속도와 강 판의 표면특성 등에 따른 자동차용 냉연강판과 도금강판의 마찰계수와 드로오비드 저 항력에 대한 테이터 베이스를 구축하고자 한다.

• 설비공학논문집
• /
• 제21권10호
• /
• pp.559-563
• /
• 2009

Performance of refrigerant oil at the thrust-bearing and at the journal-bearing of a scroll compressor is a significant factor. This paper presents the friction and anti-wear characteristics of nano oil with a mixture of a refrigerant oil and carbon nano particles. The characteristics of friction and anti-wear using nano-oil is evaluated using the disk on disk tester for measuring friction surface temperature and the coefficient of friction. The average friction coefficient of nano-oil was reduced by 60% compared to raw oil under 600 N and 1,000 rpm. It is believed that the interaction of nano particles between surfaces can be improved the lubrication in the friction surfaces. Worn surfaces of frictional specimen were also investigated by the optical and atomic force microscopy. Conclusively, it is expected that wear and friction coefficient of compressor can be reduced by alignment applying nano-oil as refrigerant oil.

• 비파괴검사학회지
• /
• 제22권2호
• /
• pp.125-131
• /
• 2002

본 연구에서는 3종류의 취성재료에 비커스 경도기를 사용하여 압축하중에 의한 신호특성과 잔류응력의 에너지 해방에 의하여 검출되는 신호특성을 조사하였다. 각 시험편에서 I영역과 III영역에서는 신호가 검출되었으나, 일정 하중이 유지되는 II영역에서는 음향방출 신호가 전혀 검출되지 않았다. 유리 시험편은 III영역에서 높은 진폭값을 가지는 신호가 검출되었고, $Al_2O_3$ 및 $Al_2O_3/SiC$ 시험편은 I영역에서 높은 진폭값을 가지는 신호가 검출되었다.