• Tribology and Lubricants
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• 제33권4호
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• pp.153-167
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• 2017

The aim of this study is to find the change in trend in the eccentricities of two journal bearings supporting the crankshaft of a single cylinder engine and the degree of misalignment of the shaft. We analyze the change in oil film thickness considering the wear scar under mixed-elasto-hydrodynamic lubrication regime at potential wear regions. For this, we first calculate the central eccentricities of the two journal bearings by using the mobility method. Then we calculate the outer end eccentricity by using the geometry of the bearings. Further, the tilting angle and degree of misalignment of the shaft are calculated by using the eccentricities of the two bearings. We show that the eccentricity of bearing #1, on which higher load is applied, increases at the beginning of the start-up cycle and during the coast-down cycle. However, the eccentricity of bearing #2, on which lower load is applied, decreases at the beginning of the start-up cycle and increases during the coast-down cycle. From the results of the analysis of oil film thickness, we show that the mixed-elasto-hydrodynamic lubrication regime for a misaligned shaft is at the initial stages of the start-up cycle for both bearing #1 and #2 and at the final stage of the coast-down cycle for only bearing #1.

• 한국분말재료학회지
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• 제10권6호
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• pp.383-389
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• 2003

As in other areas of materials technology, the tendency towards light weight constructions becomes more and more important also for powder metallurgy. The development is mainly driven by the automotive industry looking for mass reduction of vehicles as a major factor for fuel economy. Powder metallurgy has to offer a number of interesting areas including the development of sintered materials of light metals. PM aluminium alloys with improved properties are on the way to replace ferrous pars. For high temperature applications in the engine, titanium aluminide based materials offer a great potential, e.g. for exhaust valves. The PM route using elemental powders and reactions sintering is considered to be a cost effective way for net shape parts production. Furthermore it is expected that lower costs for titanium raw materials coming from metallurgical activities will offer new chances for sintered parts with titanium alloys. The field of cellular metals expands with the hollow sphere technique, that can provide materials of many metals and alloys with a great flexibility in structure modifications. These structures are expected to be used in improving the safety (crash absoption) and noise reduction in cars in the near future and offer great potential for many other applications.

• 한국산학기술학회논문지
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• 제13권3호
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• pp.967-976
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• 2012

본 논문은 자동차 환경규제에 따른 CO2 감소 및 연비향상을 위하여 Stop&Go 기능을 적용한 소형 승용차에 대한 파워트레인 마운트 (Powertrain Mount) 의 진동 소음 최적화 방향을 제시하였다. 이를 위해 현재 "A" 차량에 적용중인 파워트레인 마운트 시스템을 분석한 후 다구찌 기법을 활용하여 파워트레인 마운트에 적용된 고무 동특성에 대한 다양한 변수를 제시하였고, 고무의 동특성 변수에 의해 만들어진 테스트 제품을 AHP(Analytic Hierarchy Process)기법을 적용하여 Stop&Go 기능에 적합한 진동 소음의 최적화 정도를 검증하였다. 이와 같은 시스템을 파워트레인 마운트의 초기 디자인 검증에 적용함으로써, 파워트레인 마운트의 고무 동특성에 대한 엔지니어링 노하우 (Engineering Know-How) 없이도 엔진의 움직임으로 야기되는 진동 소음의 문제점을 파악하고 이를 효과적으로 제어하는데 큰 역할을 할 것으로 예상된다.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.4002-4006
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• 2014

자동차 배출가스는 자동차에 의해 발생되는 일산화탄소, 탄화수소, 납 외에 사람의 건강 또는 생활 환경에 피해를 일으킬 염려가 있는 물질을 말한다. 배출가스를 감소시키기 위해서 다양한 기술을 개발하는 것도 중요하지만 현재 사용되어 지고 있는 요소를 분석하여 최적의 상태를 찾는 것도 중요한 사항이라 여겨진다. 본 연구는 냉각수에 함유되는 부동액이 배출가스에 영향을 미칠 수 있음에 착안하여 현재 국내에서 시판되고 있는 5개 회사제품의 부동액을 권고 수준의 양을 냉각수에 함유시켜 HC, NOx, $CO_2$ 배출량을 측정하고 배출가스에 미치는 영향을 파악하고자 하였다. 또한, 5개회사 부동액 제품에 대하여 냉각팬 구동시간과 NOx 배출량과의 상관관계를 살펴보고자 하였다. 엔진오일의 온도는 자동차 검사 규격에 맞도록 $90{\sim}93^{\circ}C$에 맞추었고, 수동기어를 사용하는 소형승용차의 검사 규격 속도 $40{\pm}2Km/h$에서 수행하였다. 실험결과 D사 부동액이 팬 작동시간이 가장 짧고, $CO_2$, NOx 배출량이 가장 적게 나타났다.

• 지식경영연구
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• 제17권2호
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• pp.27-50
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• 2016

Korean manufacturing industry have recently faced the catch-up of China in the mass commodity product, such as automotive, display, and smart phone in terms of market as well as technology. Accordingly, discussion on the importance of achieving catch-up in complex product systems (CoPS) has been increasing as a new innovation engine for the industry. In order to achieve successful catch-up of CoPS, we explored emerging technologies of CoPS, which are featured by the characteristics of radical novelty, relatively fast growth and self-sustaining, through the study of emerging technologies of gas turbine for power generation. We found that emerging technologies of the gas turbine are technologies for combustion nozzle and composition of electrical machine for increasing power efficiency, washing technology for particulate matter, cast and material processing technology for enhancing durability from fatigue, cooling technologies from extremely high temperature, interconnection operation technology between renewable energy and the gas turbine for flexibility in power generation, and big data technology for remote monitoring and diagnosis of the gas turbine. We also found that those emerging technologies resulted in technological progress of the gas turbine by converging with other conventional technologies in the gas turbine. It indicates that emerging technologies in CoPS can be appeared on various technological knowledge fields and have complementary relationship with conventional technologies for technology progress of CoPS. It also implies that latecomers need to pursue integrated learning that includes emerging technologies as well as conventional technologies rather than independent learning related to emerging technologies for successful catch-up of CoPS. Our findings provide an important initial theoretical ground for investigating the emerging technologies and their characteristics in CoPS as well as recognizing knowledge management strategy for successful catch-up of latecomers. Our findings also contribute to the policy development of the CoPS from the perspective of innovation strategy and knowledge management.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1496-1502
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• 2012

엔진에 장착된 자동차용 연료펌프는 외부 및 내부 로터로 구성되어 있으며, 내부 로터는 입구로부터 연료를 흡입하여 출구로 배출한다. 본 연구에서는 로터가 장착된 연료펌프의 성능을 평가하기 위해 해석 및 시험을 수행하였다. 입출구 포트 각도가 0, 15, $30^{\circ}$에서 컴퓨터 시뮬레이션을 통한 연료펌프의 유동 특성을 해석하였다. 가장 우수한 유동 특성을 가진 펌프를 결정한 후 진동 특성을 해석하였다. 그 결과 유량은 입출구 포트 각도가 $0^{\circ}$에서 191.0 LPH로 가장 우수하게 나타났으며, 진동은 0.866 $^m/s^2$으로 계산되었다. 진동 시험 결과를 통해 연구된 펌프가 기존의 펌프에 비해 작은 진동을 가지고 있음을 알 수 있었다. 그리고 두 펌프의 고유진동수들은 거의 일치하였다. 따라서 연구된 펌프의 성능이 우수하다는 것을 알 수 있었다.

• 대한기계학회논문집B
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• 제36권7호
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• pp.759-765
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• 2012

1.7L 커먼레일 직접분사 디젤 엔진을 이용하여 1500rpm 3.9bar BMEP 조건에서 세가지 연소 전략에 따른 배기가스 배출 특성 및 탄화수소 종 분석을 수행하였다. 첫째 전략은 EGR 을 사용하지 않고 연료 분할 분사를 이용하는 방법(split injection), 둘째는 적절한 EGR 적용 및 단일 연료분사 방법(single-1)이며 셋째는 다량의 EGR 및 레일 압력 증대 등을 통한 저온디젤연소(single-2)이다. 본 실험 조건으로부터 split injection 방법과 single-1 방법은 PM-NOx 상반 관계를 보였고, single-2 방법은 PM-NOx 상관관계에서 벗어나 PM 및 NOx 동시 저감이 가능하였다. 탄화수소 종 분석 결과, THC 배출 경향과 동일하게 탄소번호에 관계없이 split injection 이 가장 적은 배출을 보였고, single-1 그리고 single-2 의 순서로 많이 배출하였다. 메탄, 아세틸렌 및 CO 의 THC 에 대한 비율은 공연비가 농후해 짐에 따라서 증가하였고 이는 공연비가 농후에 따른 연소 영역에서 산소 농도 감소로 열해리가 증가하였기 때문이다.

• 한국기계가공학회지
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• 제16권4호
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• pp.53-61
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• 2017

Turbocharger is a device for increasing the power of a vehicle engine. The control plate is the main component for fixing the vane of the turbocharger. Now, the control plate is made of austenite steel cutting after the casting process. It has excellent corrosion, heat resistance and mechanical characteristics of material. However, present the process is made by cutting after casting. when cutting is processed after casting, so materials, processing time, and processing energy are lost. Therefore, this study proposes a process to powder compact use of stainless steel Deklak2 and to minimize amount of cutting through net shape process. The mechanical properties of Deklak2 were verified by tensile test, hardness test and relative density measurement, and the governed equation was defined. Also, the curvature radius 1, 2 and the density, affects the shape, were selected as the design parameters, and the best process conditions was proposed through the Taguchi method and the evaluation of SN ratio. And then prototype molds were fabricated and compared with the results of the finite element analysis for the verification, and it was found that the tendency of relative density and dimension was coincided. Therefore, it was found that the amount of cutting can be minimized by only the net shape process after the sintering process and it can be applied to mass production.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1257-1263
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• 2010

함정구조물은 함내 엔진 및 프로펠러 추진력의 환경진동에 노출되어 있다. 일반적으로 함상구조물은 함상진동규격인 MIL-STD-167-1A 에 따라 개발되고 있으며, 장기간 사용을 목적으로 하는 함상구조물의 진동에 대한 피로수명은 해석적 접근법과 진동실험을 통해 반드시 평가되야 한다. 본 논문에서는 함상구조재로 사용된 주조 알루미늄합금인 A356 의 피로강도를 14 S-N 법으로 평가하고, 구조물의 작용응력은 함상진동규격에 준하는 주파수응답해석을 통해 분석되었다. 최대등가응력의 주파수는 최대실험주파수에서 나타났으며, 함상장비의 진동피로수명은 누적손상법에 의해 평가되었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.71-74
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• 2005

In manufacturing automotive parts, such as engine cradles, frame rails, subframes, cross-members, and other parts from circular tubes, pre-bending and pre-forming operations are often required prior to the subsequent tubular hydroforming process. During some pre-forming operations, the cross section of a bent circular tube is crushed into an oval-like shape to ensure proper geometry and sufficient clearance in the hydroforming dies. For such applications, the use of oval Instead of circular tubes could be an effective means of eliminating the pre-forming step. The oval tube could also be produced with less thinning and with less strain on the outside of the bend when controlled by a booster system without the use of mandrel. Hence, the understanding of the issues that occur in the bending of oval tubes is worthy of Investigation. This paper presents parametric studies on the bending of oval tubes without a mandrel. The finite element modeling technique is used to examine the deformation characteristics for both circular and oval tubes. In the simulations, the bending process parameters of bend radius, aspect ratio of the tube ovalness, and tube wall thickness are varied. Observations are made to obtain a hoop-buckle limit diagram in terms of a non-dimensional shape degradation factor. Suggestions based upon developed criteria are made on the acceptability of bend tubes suitable for hydroforming applications without the need ofa pre-forming step or the used of a mandrel.