• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.111-116
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• 2004

Li-complex and urea type greases (each 10 species) which were furnished by Chang-Am LS, analyzed anti-wear performance into fretting wear tester & four-bail wear tester. from the results of fretting wear test, the wear volume of Li-complex greases are $4.6\~8.9mg\;and\;8.3\~14.4mg$ with the test of urea greases. The anti-wear performance for 4-ball wear test of greases produced results around 0.5mm at the value of WSD. The grease life performance were evaluated by SKF-ROF Grease Tester and wheel bearing life tester. From the results of SKF-ROF tester, the life performance evaluated by whole working time produced results $50\~300hr$ with the Li-complex greases and 100-1000hr with the urea greases. That is to say, in spite of severe condition at the higher of $10^{\circ}C$ reaction temp, the life performance with Urea type greases are much superior to Li-complex type greases. Prior to wheel bearing life tester, the grease selected performance evaluation(=anti-wear test) are tested by wheel bearing tester. In this results, we can confirm results those are similar with SKF-ROF tester. In this study, we can draw two major conclusions, one is that Li-complex greases are superior to urea greases with anti-wear properties and the other is that urea greases are much superior to Li-complex greases with life performance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.44-44
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• 1998

It was observed that the friction coefficient decreased with increasing Si concentration in the l ilms. Furthermore, the friction behavior became more s때ble even when very small amount of S Si of less than 0.5 at. % was incorporatA:회 By analyzing the composition of the debris f formed, we could show that the low and stabilized friction coefficient is in마nately relatA:었 w with the formation of the Si rich oxide debris. These result supports the mechanism that the h hydrated silica debris is the reason for low friction coefficient in humid environment. Second e evidence of the role of Si rich oxide debris could be found in the triOO-chemical reactions d during initial stage of triho-test. When the Si concen$\sigma$ation was less than 5 at.%, initial t transient period of high friction coefficient was commonly observed. Mter the transient period, m the friction coefficient becomes lower with increasing contact cycles. The initial $\sigma$ansient p peri여 becomes shorter and the starting and maximum friction coefficients in $\sigma$ansient 야,riod d decreased with increasing Si concentration. Composition of the debris on the wear scar s surface was analyzed by Auger spe따'Oscopy at v뼈ous stages in the initial transient period. W We observed that when the friction coefficient increased in earlier stage of the $\sigma$'ansient p period, iron and oxygen was observed in the debris. However, decrease in the 당iction c coefficient in the later stage of the transient period was associated with the formation of s silicon rich oxide debris. This result also supports the friction mechanism of Si-DLC films t that the formation of Si rich oxide debris results in low friction coefficient in ambient a atmosphere. atmosphere.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.313-323
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• 2003

The sliding wear behaviors of Zircaloy-4 nuclear fuel rod were investigated using two support springs with convex and concave shapes in room temperature air and water. The main focus is to compare the wear behavior of various test variables such as slip amplitude, environment, contact contours with different spring shape and a number of cycles. The results indicated that wear volume and maximum wear depth increased with slip amplitude in both air and water, but their trends tended to change according to the spring shapes and test environments. In air condition, the wear volume was controlled by wear debris behavior generated on worn surface. As a result, final wear volume and maximum wear depth decreased if a ratio of protruded wear volume to worn area $(D_p)$ would be saturated to specific value. This is because wear particle layer could accommodate large strain by accumulating and transforming wear particle layer. However, in water condition, metal-to metal contact was more dominant and wear volume was greatly affected by changed mechanical behavior between contact surfaces since wear debris should be generated after repeated plastic deformation and fracture. After wear test, worn surfaces were examined using optical microscope and SEM and details of wear mechanism were discussed using a ratio of wear volume to worn area $(D_e)$ at each test condition.

• 한국산업융합학회 논문집
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• 제22권1호
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• pp.47-54
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• 2019

An experimental study was conducted on the wear and friction responses in sliding tests of a micro-textured surface on laser pattern (LP) steel as reduction gear material in electric guided vehicle. In this research, the friction characteristics of laser pattern steel under different micro texture density conditions were investigated. The friction tests were carried out at sliding speeds of 0.06 m/s to 0.34 m/s and at normal loads of 2 to 10 N. Photolithography method was used to create the dimples for surface texturing purpose. Four different specimens having different dimple densities of 10%, 12.5%, 15%, and 20% were observed respectively. In this research, friction conditions as shown in Stribeck curve were investigated. Furthermore, the microscopic surface was observed using scanning electron microscope. It was found that the dimple density had a significant role on the friction characteristics of laser pattern steel conditioned as reduction gear material in an agricultural vehicle. The duty number showed that the friction condition was hydrodynamic regime. The best performance was obtained from 12.5% dimple density with lowest friction coefficient achieved at 0.018771 under the velocity of 0.34 m/s and 10N load.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.111-112
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• 2009

Diamond-like carbon (DLC) is a convenient term to indicate the compositions of the various forms of amorphous carbon (a-C), tetrahedral amorphous carbon (ta-C), hydrogenated amorphous carbon and tetrahedral amorphous carbon (a-C:H and ta-C:H). The a-C film with disordered graphitic ordering, such as soot, chars, glassy carbon, and evaporated a-C, is shown in the lower left hand corner. If the fraction of sp3 bonding reaches a high degree, such an a-C is denoted as tetrahedral amorphous carbon (ta-C), in order to distinguish it from sp2 a-C [2]. Two hydrocarbon polymers, that is, polyethylene (CH2)n and polyacetylene (CH)n, define the limits of the triangle in the right hand corner beyond which interconnecting C-C networks do not form, and only strait-chain molecules are formed. The DLC films, i.e. a-C, ta-C, a-C:H and ta-C:H, have some extreme properties similar to diamond, such as hardness, elastic modulus and chemical inertness. These films are great advantages for many applications. One of the most important applications of the carbon-based films is the coating for magnetic hard disk recording. The second successful application is wear protective and antireflective films for IR windows. The third application is wear protection of bearings and sliding friction parts. The fourth is precision gages for the automotive industry. Recently, exciting ongoing study [1] tries to deposit a carbon-based protective film on engine parts (e.g. engine cylinders and pistons) taking into account not only low friction and wear, but also self lubricating properties. Reduction of the oil consumption is expected. Currently, for an additional application field, the carbon-based films are extensively studied as excellent candidates for biocompatible films on biomedical implants. The carbon-based films consist of carbon, hydrogen and nitrogen, which are biologically harmless as well as the main elements of human body. Some in vitro and limited in vivo studies on the biological effects of carbon-based films have been studied [$2{\sim}5$].The carbon-based films have great potentials in many fields. However, a few technological issues for carbon-based film are still needed to be studied to improve the applicability. Aisenberg and Chabot [3] firstly prepared an amorphous carbon film on substrates remained at room temperature using a beam of carbon ions produced using argon plasma. Spencer et al. [4] had subsequently developed this field. Many deposition techniques for DLC films have been developed to increase the fraction of sp3 bonding in the films. The a-C films have been prepared by a variety of deposition methods such as ion plating, DC or RF sputtering, RF or DC plasma enhanced chemical vapor deposition (PECVD), electron cyclotron resonance chemical vapor deposition (ECR-CVD), ion implantation, ablation, pulsed laser deposition and cathodic arc deposition, from a variety of carbon target or gaseous sources materials [5]. Sputtering is the most common deposition method for a-C film. Deposited films by these plasma methods, such as plasma enhanced chemical vapor deposition (PECVD) [6], are ranged into the interior of the triangle. Application fields of DLC films investigated from papers. Many papers purposed to apply for tribology due to the carbon-based films of low friction and wear resistance. Figure 1 shows the percentage of DLC research interest for application field. The biggest portion is tribology field. It is occupied 57%. Second, biomedical field hold 14%. Nowadays, biomedical field is took notice in many countries and significantly increased the research papers. DLC films actually applied to many industries in 2005 as shown figure 2. The most applied fields are mold and machinery industries. It took over 50%. The automobile industry is more and more increase application parts. In the near future, automobile industry is expected a big market for DLC coating. Figure 1 Research interests of carbon-based filmsFigure 2 Demand ratio of DLC coating for industry in 2005. In this presentation, I will introduce a trend of carbon-based coating research and applications.

• 한국가스학회지
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• 제14권5호
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• pp.7-12
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• 2010

본 논문은 H빔과 강화 콘크리트에 의해 건설된 LNG 저장탱크의 외부탱크에 대한 응력 및 변위거동 안전성을 유한요소법으로 해석하였다. 외부탱크의 바닥면 콘크리트 구조물 중심부에 0.2g의 가진력을 가하였다. FEM 계산결과에 의하면, von Mises 최대응력은 돔루프 구조물의 가장자리 부근에서 발생하고, 최대변위 거동량은 돔루프의 중심부에서 형성되고 있음을 알 수 있다. 여기서 제시한 해석결과에 의하면, H빔의 개수가 증가할수록 집중응력과 변위거동량은 완만하게 증가한다는 사실이다. 이것은 강화 콘크리트 구조물의 강성도가 H빔의 강성도에 비해 대단히 높기 때문에 H빔의 개수가 돔루프의 안전성에 큰 영향을 미치지 못한다는 것이다. 따라서 0.2g 정도의 가진력을 가할 경우는 H빔의 자중량을 고려하여 개수를 60개 이하로 제한하는 것이 바람직하다.

• 한국가스학회지
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• 제13권4호
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• pp.27-32
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• 2009

본 본문에서는 헬멧의 정상부에 별도로 보강뼈대를 설치하지 않은 경우에 헬멧의 두께를 변수로 헬멧 구조물에 걸리는 응력과 변형거동 특성을 유한요소법으로 해석하였다. 헬멧은 현장 작업자의 안전성과 충격에너지 흡수력을 높일 수 있도록 제작해야 하고, 헬멧을 오랫동안 착용해도 불편함이 없어야 하며, 또한 머리와 목을 보호할 수 있어야 한다. FEM 해석결과에 의하면, 외부의 충격력이 헬멧의 꼭대기에 가해졌을 때 헬멧에 작용하는 최대응력과 최대변형은 하중이 작용하는 지점에서 발생하고, 최대응력은 헬멧모체 구조물의 초기파손을 일으키는 원인으로 작용하는 것으로 나타났다. 헬멧의 두께를 4mm에서 2mm로 줄이면, 충격에너지 흡수율은 급격하게 증가하지만 헬멧에 작용하는 최대응력은 열가소성 소재의 인장강도 54.3MPa을 많이 초과하므로 파손되었다할 수 있다. 따라서 헬멧의 강도안전을 확보하기 위해서는 헬멧의 정상부에 보강뼈대를 설치하는 것이 바람직하고, 헬멧모체 구조물의 두께를 보다 두껍게 설계할 필요가 있다.

• 한국가스학회지
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• 제17권1호
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• pp.73-80
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• 2013

본 연구에서는 유한요소해석법을 사용하여 V홈 오링의 밀봉거동과 내구 안전성에 관련된 변형률, 응력, 접촉법선응력 해석결과를 제시하고 있다. 밀봉거동과 내구 안전성에 관한 FEM 해석결과에 의하면, V홈 형상을 갖는 오링에 작용하는 최대변형률, 최대압축응력, 최대접촉법선응력은 기존의 오링에 비해 약 1.2배나 더 높게 나타났다. 이것은 오링이 두 개의 원형을 겹치도록 형성된 중간부에 V홈을 넣었기 때문에 가능한 것으로 판단되고, V홈 오링은 볼밸브, 압력용기, 가스기기의 밀봉을 하는데 매우 유용한 것으로 알려져 있다. 그리고, V홈 오링에서 가스압력을 높여도 압출에 의한 파손현상이 발생되지 않았는데, 이것은 V홈이 형성되어 있기 때문이다. 따라서, V홈 오링은 기존 오링에 비해 밀봉수명을 연장시킬 수 있다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.255-260
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• 2004

Recently, the technologies related to the swash plate type oil hydraulic piston pump are requiring extreme technologies to overcome the limit of high efficiency in cope with high speed and pressure, and are devoted to compact the unit, to gain low noise level, and to adopt electronic technologies, and the question regarding to maximize the mechanical efficiency, that is, to minimize the torque loss by minimizing the leakage loss in the relative sliding region but these are in trade-off relation that tribological responding is very difficult. Cylinder block-valve pate in high speed relative sliding motion has the characteristics that should be extremely controlled for the optimization of these leakage loss and mechanical efficiency, and pressure resistance designing of them is important for high pressure performance. But, studies on the stress analysis of these parts have not been performed briskly, so in this paper the stress distribution and the region where the highest displacement appears are described through the static stress analysis using CATIA V5. Through the future studies on these theme, it has the purpose of finding the suitable materials for the other parts as well as cylinder block and valve plate, in cope with high pressure operation through the stress analysis with the most similar conditions for the practical operation.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.350-354
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• 2004

In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15 N contact force in a reciprocal sliding motion of sliding distance of 10 mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP > Surefil > Compoglass > Z100 > Fuji II LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji ?LC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light source as curing unit for composite resin restorations.