• 한국정밀공학회지
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• 제28권5호
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• pp.537-542
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• 소성∙가공
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• 제17권1호
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• pp.59-67
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• 2008

This paper is concerned with the development of multi-action die or multiple sliding die for the forming process of serrated sheets. Serrated sheets is used as a toothed or serrated seal for securing together overlapping portions of steel or plastic strapping ligature and have been produced conventionally in several methods such as rolling and indentation. Recently, longitudinally oriented thermoplastic materials have been widely used in the strapping industry, while such materials are quite slippery. Provided projections on a seal biting into the strap should overcome the slipperiness and also the tooth configuration must be closely controlled to avoid too much transverse penetration of the strap which could result in the shredding of the strap when it is placed under tension. The seal includes a central portion with a plurality of teeth which bite into one strap portion and a pair of reversely bent legs with a plurality of teeth which bite into the other strap portion. Forming processes applicable for serrated sheets have reviewed in qualitative sense to find possibility in terms of applicability of one of existing processes to the serrated sheet forming process. Existing seal products have been analyzed with enlarged picture of strap contacting surface of the seal by microscope. Based on the analyses of the existing forming processes and seal products, a new forming process is proposed for serrated sheets. The proposed process requires a multislide die which enables inclined indentation or cut-in into the seal material as well as scratching processes sequentially in a single action press.

• 공업화학
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• 제9권4호
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• pp.608-613
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• 1998

본 연구의 목적은 순수 카본블랙과 이중상 구조의 카본블랙 (DPCB)이 함유되어 있는 고무조성물의 물리적 특성에 대하여 조사하였다. DPCB는 FT-IR분석결과 1100~1200 파장에서 실리카 표면에 존재하는 Si-O 피크를 나타냈다. DPCB와 유기 실란커프링제 (Si69)를 함유하는 고무조성물의 가황속도는 순수 카본블랙을 함유한 고무조성물에 비해 지연되었다. Si69를 함유한 DPCB의 300% 모듈러스와 상호작용계수 ($a_f$)는 순수 카본블랙보다 높게 나타났으며, 내마모특성 지표인 피코 무게감소량은 일정하게 나타났다. DPCB의 $0^{\circ}C$에서의 tan ${\delta}$는 DPCB 50 phr 기준 실란커플링제를 2.0% 사용한 수준에서 순수 카본블랙보다 우수하였으며, $60^{\circ}C$에서의 tan ${\delta}$는 실란커프링제의 사용량이 증가 할수륵 감소하였다. 결국 본 연구에 사용된 DPCB는 일정한 마모저항을 유지하면서 회전저항을 개선하는데 적합하다고 생각한다.

• 전기화학회지
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• 제8권1호
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• pp.1-5
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• 2005

높은 비표면적을 갖는 carbon과 유기용매 전해질 사이의 계면에서 생기는 전기이중층용량을 기본으로 작동하는 전기이중층 캐패시터는 IC memories, microcomputer 등으로 폭 넓게 사용되며 maintenance-free의 영구적인 back-up용 전원으로 넓게 사용되고 있다 EDLC에 사용되는 전해질은 이온 전도도가 높아야 하고 사용되는 온도 범위가 넓어야 한다. 그리고 고전압을 인가했을 때 전해질이 전기화학적으로 안정해야 한다. 본 실험에서는 고전압에서 안정적인 액상 유기계 전해질을 사용하여 전기이중층캐패시터의 전기화학적 특성을 확인하였다. Paste rolling법으로 제조된 탄소전극과 $1M-LiPF_6$ in PC-GBL-DEC (volume ratio 1:1:2)의 유기용매전해질을 사용한 전기이중층캐패시터가 64F/g의 우수한 비축전용량을 발현하였다

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1109-1116
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• 2009

건축기술의 발달로 유리가 벽의 구조로 일반화도어 건축되고 있으며, 기존 벽의 역할인 수직 하중을 지탱하는 역할이 없어지게 되었다. 기능과 아름다운 면을 강조하게 되어 벽이 커튼의 역할만 하게 되어, 객차 실내 유리창에 접근시 차가운 느낌으로 불쾌감을 유발 한다. 그리고 유리창 아래에 바닥 난방을 했음에도 유리창에 외풍 발생으로 결로 현상이 발생하며, 즉 유리창 주변에 물방울이 발생(곰팡이 발생 원인)하여 겨울철 난방 에너지와 여름철 외부 온열이 유리를 통해 이동 하게 된다. 그러므로 에너지효율 감소에 절대적으로 영향을 준다. 객차에 발열 유리시스템을 적용하면 유리창 표면에는 냉기의 확산이 방생 하지 않으며, 객차의 실내 냉 난방시 에너지 절감 효과가 있다.

• 반도체디스플레이기술학회지
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• 제7권4호
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• pp.29-33
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• 2008

Rapid increase of integrity for recent semiconductor industry highly demands the development of removal technology of contaminated particles in the scale of a few microns or even smaller. It is known that the surface cleaning technology using $CO_2$ snow has its own merits of high efficiency. However, the detailed removal mechanism of particles using this technology is not yet fully understood due to the lack of sophisticated research endeavors. The detachment mechanism of particles from the substrates is known to be belonged in four types; rebounding, sliding, rolling and lifting. In this study, a modeling effort is performed to explain the detachment mechanism of a contaminant particle due to the rebounding caused by the vertical collision of the $CO_2$ snow. The Hertz and Johnson-Kendall-Roberts(JKR) theories are employed to describe the contact, adhesion and deformation mechanisms of the particles on a substrate. Numerical simulations are followed for several representative cases, which provide the perspective views on the dynamic characteristics of the particles as functions of the material properties and the initial inter-particle collision velocity.

• 한국철도학회논문집
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• 제18권4호
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• pp.289-300
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• 2015

철도 전동 소음은 철도에서 발생하는 대표적인 소음으로서 차륜과 레일의 음향 조도에 의해 가진 된 차륜 및 레일의 진동으로부터 발생한다. 철도 전동 소음 해석 시 레일 방사 소음은 자유 공간에 놓인 레일의 음향 방사 파워를 이용해 원거리에서 계산하므로, 일반적으로 소음원 모델에 지면 반사를 고려하지 않는다. 그러나 레일 주위의 근접 음장을 해석하고 저감 대책을 적용하기 위해서는 지면에 의한 음파의 반사를 고려해야 한다. 본 논문에서는 파수유한요소/경계요소법을 이용해 지면에 의해 발생하는 레일 소음의 변화와 그 특성을 살펴보았다. 해석은 먼저 레일이 강체 지면에 부착된 경우와 레일 패드 높이만큼 강체 지면에서 이격된 경우에 대해 방사효율을 구하고 그 결과를 비교하였다. 이를 통해 레일과 강체 지면의 이격 여부에 따라 레일 방사 소음에 크게 변화함을 확인하였다. 둘째로는 지면에 임피던스 경계조건을 부여하고 레일에서 방사되는 음향 파워 및 지향 특성의 변화를 살펴보았다.

• Elastomers and Composites
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• 제44권3호
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• pp.232-243
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• 2009

근래 고성능 친환경 타이어의 개발요구에 의하여 경제성(낮은 회전 저항)과 안전성(wet traction) 및 내마모성면에서 균형있는 특성을 가지는 타이어 트레드 고무의 합성 제조 기술이 중요하게 대두된다. 이를 위하여 다양한 기능성 용액중합 SBR의 개발과 함께 고무/충전제 간의 상호작용 증진 기술이 학술적으로나 산업적으로 활용되고 있다. 본 고에서는 기존의 카본블랙 고무와 함께 최근 green tire로서 각광 받는 실리카 충전 고무에서 충전제와 상호반응이 가능한 화학적 변성 SBR과 커플링제를 이용한 고성능 타이어 트레드 고무의 합성 제조 기술에 대하여 최근 연구 방향과 함께 작용 메카니즘에 대하여 고찰하였다.

• 해양환경안전학회지
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• 제7권3호
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• pp.17-28
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• 2001

The wheelhouse front glass of a Fore-Bridge-Ship (Ro-Ro Ship) was broken by the shipping of water in rough seas, and then the flooding of seawater into the wheelhouse caused the uncontrollable condition of the ship. The hull which was entered into the floating condition rolled severely, and the heavy rolling caused secondary damage such as the collapse of a lot of cargo. It was an incredible accident because the height of bow freeboard was about 2.5 times higher than the standard height of minimum bow freeboard regulated by the International Load Line Convention(1966). And it would be also difficult for navigators to imagine a great deal of seawater flooding into the wheelhouse because the front glass was positioned at about 20m height above the sea surface. In this paper, we carried out the evaluation for the safety navigation of the Fore-Bridge-Ship numerically against ship's speed and encountering angle to the wave in each sea state of rough sea, by using the integrated seakeeping performance index (ISPI) which is able to evaluate synthetically the safety operation of ships. And then the problem on the application of the past criteria proposed as the safety navigation of a merchant ship was clarified by inquiring the dangerousness of the shipping of water at her bow deck, which caused the breakage of the wheelhouse front glass.

• 한국조경학회지
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• 제31권1호
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• pp.66-77
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• 2003

The purpose of this study is to propose a standard putting green management program to prepare fast green suitable for international golf tournaments, and to conform whether the reported green speed model can be applied to the real field situations. The west course of Lakeside Country Club was selected for the case study. This study was initiated on August 1st, 2001 and continued through October 4th, 2001. The results are summarized as follows: 1. Following the long-term schedule, 'penncross' creeping bentgrass turf was mowed at 5.0mm(37days), 4.5mm(8days), 4.0mm(4days), 3.5mm(2days), 3.2mm(2days), 3.0mm(2days), 2.8mm(2days) and the mowing direction was changed daily. Variation of mowing height was reduced to a minimum range. Core aerification with deep tines was applied 19 days prior to the first practice round. Dry sand maintenance was top-dressed 2 times at 1.5mm/$m^2$ on the 17th day and 1.0mm/$m^2$ on the 10th day. Minimum irrigation was applied to keep the turf alive. During the tournament preparation week, dew on the putting greens was removed by using a sponge roller. Following the dew removal, the greens were cut once each morning at a height of 2.8mm. The mower used was the 21 inch working behind mower equipped with a tournament bedknife and 11 reel blades. Following the mowing, the peens were rolled with a light-weight roller in one direction in the morning. Rolling was used as a finishing technique to ensure that the surface was as smooth as possible, and to provide true ball roll and maximum green speed. In conclusion these management practices satisfied the daily green stimpmeter readings required for USGA championship play. 2. During the period of tournament preparation, no damage was observed on the green, but scalping in green edge appeared in about 0.39% of the total area of 18 greens in the west course.