• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.262-270
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• 1988

A numerical solution of the elastohydrodynamic lubrication problem for an axially profiled cylindrical roller is presented. The problem is analyzed using finite difference method and Newton-Raphson method. The effect of side leakage and compressibility of lubricants are considered and axially nonuniform grid is constructed over the computation zone. Isobars, contours and section graphs show pressure variation and film shape. Contours plot is very similar to the previously reported experimental observations based upon optical interferometry. The maximum pressure and the minimum film thickness occur near the start of the profiling. The method used makes it possible to design an optimum axial profile of the roller to increase the life of rolling bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.275-282
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• 2004

The engine bearing transmits the powers from cylinder to crankshaft with small clearance between con-rod and crankpin. The minimum oil film thickness is a significant parameter in the operation of bearing. The contact pressure of bearing should be considered for the reason that elastic deformation of bearing be caused by contact pressure of bearing. There are important factors which are maintaining of minimum oil film thickness expecting of the length of maximum and minimum oil film thickness with changing of the loads to keep running normally. Furthermore, this study is very crucial to develop the design of engine bearing and crankshaft system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.05a
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• pp.30-35
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• 1996

An elastohydrodynamic lubrication (EHL) analysis for an axially crown profiled cylindrical roller is carried out using a finite difference method and the Newton-Raphson method. Variations of the minimum film thickness with dimensionless parameters show considerably different from those of infinite solutions.

• Journal of the KSME
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• v.29 no.3
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• pp.261-269
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• 1989

볼 베어링의 성능에 중요한 영향을 미치는 볼 베어링 특유의 기하학적 형상, 탄성론에 근거한 볼과 궤도륜 사이의 접촉역학 및 구름접촉을 위한 탄성 유체윤활이론을 소개한 후, 축방향 하 중하에서 고속으로 회전하고 있는 볼 베어링의 해석방법을 기술하였다. 소개된 해석 방법이 완박한 것은 아니며, 보다 엄밀한 해석을 위하여 마찰열에 의한 온도상승의 영향을 고려하여야 할 것이다. 또한 해석 결과를 얻기 위하여 효율적인 수치 계산법을 적용한 볼 베어링 해석을 위한 결과를 얻기 위하여 효율적인 수치 계산법을 적용한 볼 베어링 해석을 위한 전용 소프트 웨어를 개발하여야 한다. 외국에서는 이와 같은 컴퓨터 프로그램이 사용되고 있으나, 우리도 독자적으로 전용 소프트웨어를 개발함으로써, 외국의 소프트웨어를 도입하였을 때의 한계를 피 하고, 다양한 응용예마다 가장 효율적인 해석을 할 수 있는 유연성을 가질 필요가 있다고 생각 한다. 구조물 최적설계를 위하여 유한요소 해석 프로그램을 이용하듯이, 이와 같은 전용 해석 소프트웨어를 사용하여 볼 베어링의 최적설계를 할 수 있을 것이다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1355-1364
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• 1994

This paper analyzes the running mechanism of flexible and thin foil above rotating protrusion through a numerical simulation. The scope of analysis is confined to the phenomena of elastohy-drodynamic lubrication between the stationary and rotary drums with a running protrusion and thin foil. This mathematical model is based on the modified Reynolds equation and the equation of plate, considering the geometry of protrusion, running direction of protrusion, and the effect of geometric nonlinearity. Finite element method is adopted as a numerical simulation technique to solve the avobe coupled nonlinear equations. In numerical analysis, the effects of the scanning angle in Reynolds equation and the nonlinear term in plate equation are evaluated. Furthermore, the simulation is applied to the situation that thin foil is located in the entire drums (stationary and rotary drums).

• Tribology and Lubricants
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• v.2 no.2
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• pp.12-19
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• 1986

Using emulsion lubricant whose cooling effect and incombustibility are good and which is economical, I investigated lubricative mechanism and the behavior of scattered particles in the elastic fluid lubrication region with the line contact between rollers and plates and the light interference system. The results of the study are as follows: (1) The flow in the squeeze oil film is considered as comparatively wide clearance and narrow one, and in the former case the effect of the distribution of particles and the velocity on the flow. In the latter case, emulsion particles stay in the clearance an the oil film changes with the decrease of the oil film thickness. (2) In the wide clearance the velocity difference of the flow O/W or W/O emulsion is inverse proportional to the particle size. In the narrow clearance the distribution of the remained drops is different from one another and the scattered particles change more easily in O/W type than in W/O type. (3) At the beginning of the EHL the stagnation region with slow flowing velocity exists and the behavior at the region is different depending on the particle size. (4) By observing the dischromatic light interference line, emulsion oil passing through EHL region and the crack behavior at the beginning of EHL were found.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1989.06a
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• pp.22-28
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• 1989

유압베인펌프는 토출유량이 많고 소형으로 동력밀도는 높으나 토출압력면에스는 피스톤식 펌프에 뒤지기 때문에 발생압력의 고압화에 대한 연구가 계속되어 왔다. 유압장치의 경제적인 압력으로서 $300kgf/cm^2$가 제시되어 있는 가운데, 유압베인펌프의 고압화의 연구가 진행중에 있는 점, 또한 최근들어 에너지 절약의 일환으로 펌프의 수명연장 문제가 거론되어 지고 있는 점, 물에 타기 어려운 난연성유압 작동유를 사용할 경우 마찰증대 및 마모성능이 저하하는 점 등의 이유에서 유압베인 펌프의 마찰, 윤활문제가 중요시 되어지고 있다. 특히 펌프의 체적효율을 높이는 것과 마찰, 마모를 저하시키는 것과는 서로 상반된 관계에 놓여있기 때문에 문제의 해결에 어려움을 갖고 있다. 이와같은 모순을 해결하기 위해서는 베인과 캠링사이의 슬라이딩부분의 윤활상태를 파악하지 않으면 안된다. 그러나 베인의 선단부에는 10-20ms의 짧은 시간동안에 수백기압의 압력이 변화하기 때문에 지금까지 확실한 작용력의 파악이 어려워 이 분야의 윤활상태 파악에 관한 연구는 거의 이루어지지 않고 있다. 베인과 캠링간의 윤활상태를 윤활공학적 관점에서 보면 변동하중 상태에서의 슬라이딩 탄성유체윤활상태 또는 혼합윤활상태에 있는 것으로 판단되어지는데, 이와같은 여러가지 어려운 조건 때문에 윤활상태를 파악하는데, 어려운점이 뒤따르게 된다. 위와 같은 배경에 착안하여 본 연구에서는 유압베인펌프를 모델화하여 변동하중상태에서 실험이 가능한 장치를 제작, 사용하여 베인 선단 슬라이딩부분의 윤활상태를 파악하였다.

• Tribology and Lubricants
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• v.28 no.4
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• pp.153-159
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• 2012

Tapered roller bearings are widely used in high axial-load and radial-load applications. In this study, a numerical analysis is performed to study a finite line contacts EHL problem between a tapered roller and raceway in tapered roller bearings. Converged solutions are obtained for moderate load and material parameters using a finite difference method with non-uniform grids and the Newton-Raphson method. The contours and sectional plots of pressure distribution and film shape are compared. The pressure distribution and film shapes near both ends of the roller are very different from those in the central part and are transversely asymmetric. The maximum pressure and absolute minimum film thickness always occur at the small end of the roller.

• Tribology and Lubricants
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• v.25 no.5
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• pp.335-341
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• 2009

Elastohydrodynamic lubrication (EHL) analysis shows that film thickness is very flat in the contact area and pressure distribution is somehow similar to that of Hertzian 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.

• Tribology and Lubricants
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• v.25 no.6
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• pp.367-373
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• 2009

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.