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윤활유 부족 상태에서의 볼 베어링 유막 두께 변화에 대한 연구
정순비(SoonBi Jung),이보라(Bora Lee),유용훈(YongHun Yu),조용주(YongJoo Cho) 한국트라이볼로지학회 2017 한국윤활학회지(윤활학회지) Vol.33 No.3
In this study, we perform a numerical analysis to predict the film thickness and lubrication regions for a thrust ball bearing under different operating conditions. Film thinning and replenishment affect the film thickness in starved lubrication. As the inlet meniscus position is brought to the edge of the Hertz contact, the thin film thickness is calculated as starved equation. We use a film replenishment model to determine the recovery film thickness between rolling elements. We use a hydrodynamic model to describe film recovery, that results from the effects of surface tension. In this model, we consider the surface tension gradient in fluid depression as the driving force for fluid recovery. We use Fourier transform method to determine the time-dependent depth of depressed oil. We calculate the change in the central film thickness graphically by using the recovery equation in starved elastohydrodynamic lubrication(EHL) under operating conditions that include numbers of balls, sliding velocity, applied force, and ambient film thickness. We evaluate the degree of starvation by using the distance from the center of the contact area to the meniscus position. Parched lubrication, a phenomenon where the film thickness decreases consistently, occurs at the severe condition. We determine optimal values with respect to the numbers of balls, and sliding velocity. The investigation can contribute to the design operating conditions for proper lubrication.
유전자 알고리즘을 이용한 원판 캠의 비 유막두께 최적화
권순만(Soon-Man Kwon),김창현(Chang Hyun Kim),남형철(Hyoungchul Nam),신중호(Joong-Ho Shin) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.11
The rate of wear of cam followers in a valve train system is mainly a function of contact stress between the cam and the follower, sliding velocity and hydrodynamic film thickness between the two mating surfaces. The wear or surface fatigue can be reduced by maximizing the elastohydrodynamic film thickness. In this paper, an attempt has been made to estimate the optimal specific film thickness of cam-follower system quantitatively. A general TES polynomial function with real values of exponents is developed and genetic algorithm (GA) is used as optimization techniques for maximizing the minimum specific film thickness. The optimization programs enumerate values of the exponents for synthesis of cam displacement curves. The results show that the minimum film thickness can be increased considerably, e.g. approximately 7% in this paper.
박용엔진 크랭크 핀 베어링의 형상오차가 최소유막두께에 미치는 영향
하양협(YangHyup Ha),신인동(InDong Shin),이상민(SangMin Lee),이승준(SeungJun Lee),이득우(DeugWoo Lee) 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.5
?;?;Bearings of marine engines are operated under severe conditions because of dynamic load and low sliding speed. This paper deals with lubrication analysis of a crank pin bearing for a marine diesel engine. Journal center locus and oil film thickness are compared of crank pin bearing. In the past researches, journal bearings have been studied only about the surface of bearing. In addition to this conventional research, this paper analyzes the effect of roundness error of a journal and a bearing on the minimum film thickness. Numerical analysis has been studied by using Reynolds equation and also Half.Sommerfeld condition is applied as boundary condition. Futhermore, this study investigates the effect of roundness error change on the minimum film thickness. The results demonstrate that the bigger amplitude of roundness error yields, the lower minimum oil film thickness is. In comparison to previous research considered a journal and a bearing individually, the results considering a journal and a bearing together show that amplitude of roundness error of journal has very little effect on the minimum oil film thickness.
유전자 알고리즘을 이용한 원판 캠의 비 유막두께 최적화
권순만(Soon-Man Kwon),김창현(Chang Hyun Kim),남형철(Hyoungchul Nam),신중호(Joong-Ho Shin) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
During operation, cam-follower contacts experience a complex combination of cyclically-varying speed, load and geometry. The wear or surface fatigue can be reduced by maximizing the elastohydrodynamic film thickness. In this paper, an attempt has been made to estimate the optimal specific film thickness of cam-follower system quantitatively. A general TES polynomial function with real values of exponents is developed and genetic algorithm (GA) is used as optimization techniques for maximizing the minimum specific film thickness. The optimization programs enumerate values of the exponents for synthesis of cam displacement curves. The results show that the minimum film thickness can be increased considerably, e.g. approximately 7% in this paper.
커넥팅로드 대단부 베어링의 단면 프로파일 변화가 동적하중지지력에 미치는 영향
한정흔(Jeongheun Han),장시열(Siyoul Jang) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Among the moving components in the engine system, connecting rod bearing is one of the components that needs very high durability, because it has the motions under highly fluctuating load and contacting speed. In spite of the highly fluctuating loads, it should keep a consistent fluid film in the gap between crank pin and big-end bearing by feeding the lubricant on the bearing surface. If the mechanism of keeping the fluid film over the contact area is not operated properly, the whole moving system of crankshaft and piston system will be collapsed. The periodic and fluctuating loads on the crank pin is analysed by the analysis of multibody dynamics of crankshaft-piston interactions as well as the lubrication mechanism which includes the elastic deformation of contacting surface (i.e. elstohydrodynamic lubrication) is computed. The computational method in this work simulates more realistic phenomena in the contacting behaviors of crank pin-connecting rod mechanism and it can provide the information to reduce the concentrated contact stress especially during the explosion period. From the computational results, clearance design in the big-end bearing is modified by enlarging cross-section profile in some region of bearing edge location. The developed design method is believed to keep the oil film thickness thick and reduce the wear rate of bearing surface for the durability of the engine.
비정상 상태의 선접촉 탄성유체윤활 유막두께 및 유막압력 특성연구
장시열(Siyoul Jang),조재철(Jae Cheol Cho) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.5
Elastohydrodynamic lubrication (EHL) analysis shows that film thickness is very flat in the contact area and pressure distribution is somehow similar to that of Hertz ian contact pressure except the outlet region with pressure spike. These typical patterns of EHL film thickness and pressure are the cases under the steady contact conditions of applied loads and speeds. However, many engineering contacts are rather under the conditions of varying loads and contact speeds, and therefore the predictions for endurance life and performance of machine elements with steady EHL analysis are not suitable in many occasions. This study shows the differences in film thickness formation and pressure distribution between steady and transient contact conditions in several contact cases.
장시열(Siyoul Jang),조재철(Jae Cheol Cho) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.6
Many research of elastohydrodynamic lubrication (EHL) has been performed under the condition of steady state loading. However, mechanical elements undergo severe high loads that are in the fluctuating modes of frequency and amplitude. Conventional numerical method for the circular contact of EHL study has the difficulty in making the film thickness and pressure of EHL converged in high loads of steady state as well as fluctuating loading conditions. In this work, multigrid multilevel method are used for the stable convergence of film pressure and thickness under the conditions of high as well as varying loads, and very stable solutions of film behaviors with elastic deformation are obtained. Several results of dynamic loading condition are shown and compared with those of steady state condition in the aspects of circular EHL film thickness and pressure.
접촉 스테이지 구동시 PR유체 유막 두께의 정성적 분석
김학수(Hak Su Kim),박준수(Jun Su Park),이덕재(Duck Jae Lee),신동혁(Dong Hyuk Shin),장시열(Siyoul Jang) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
The parallel contact mechanism between mold and target is the on of most important issues for the imprinting system. It is influenced by precision level of the imprinter, the waviness of mold and target and the stage motion for alignment. The uniformity of PR fluid thickness should be maintained for imprinting quality, and the ununiformity of PR fluid thickness is caused by unstable pressure distribution. In this study, we captured film shape of PR fluid film with the image processing method under several motions of contact stage. It is expected to get the information of pressure distribution by measuring the film thickness of PR fluid.
엔진오일의 저점도화에 따른 엔진 베어링의 유막거동에 관한 연구
김한구(Han Goo Kim),김청균(Chung Kyun Kim),이일권(Il Kwon Lee) 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.6
The purpose of this paper is analyzing oil film behaviors of engine bearing, when viscosity of engine oil is lowered for the purpose of fuel economy improvement. The friction loss power, the minimum oil film thickness and oil film pressure distribution for a engine bearing is analyzed using an AVL's EXCITE program. The computed results indicate that a close correlation has been found between the engine oil viscosity and the friction loss power. When the low viscosity engine oil is applied, its effect on the minimum oil film thickness is revealed as insignificant. Nevertheless, the low viscosity engine oil inevitably brings the reduction of the friction loss power. The lowering of engine oil viscosity causes the reduction of friction loss power which has a very close relation with the fuel economy. These results as the lowering of engine oil viscosity will be a important factor for improvement of the fuel economy in future.
UV 임프린트 공정에서 가압 변화에 따른 레진막 두께 형성 연구
신동혁(Dong Hyuk Shin),장시열(Siyoul Jang) 한국트라이볼로지학회 2009 한국트라이볼로지학회 학술대회 Vol.2009 No.11
The parallel contact mechanism between mold and target is the on of most important issues for the imprinting system. It is influenced by precision level of the imprinter, the waviness of mold and target and the stage motion for alignment. The uniformity of PR fluid thickness should be maintained for imprinting quality, and the ununiformity of PR fluid thickness is caused by unstable pressure distribution. In this study, we captured film shape of PR fluid film with the image processing method under several motions of contact stage. It is expected to get the information of pressure distribution by measuring the film thickness of PR fluid.