• Title/Summary/Keyword: elastohydrodynamic lubrication

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Friction Force Measurement of Elastohydrodynamic Lubrication with Viscosity Index Improvers (탄성유체윤활 영역에서 점도지수 향상제의 첨가량에 따른 마찰력 측정연구)

  • Kong, Hyun-Sang;Jang, Si-Youl;Park, Kyoung-Kuhn
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.05a
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    • pp.267-271
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    • 2002
  • Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the characteristics of a certain lubricant, it is also important to get the information of traction force as well. In this work, we developed the device for measuring friction force of ehl contact condition together with the film thickness. To verify the validity of the measuring system, the friction force and film thickness under ehl condition are measured with the variation of additive ratios of viscosity index Improvers.

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A Study on the Elastohydrodynanic Lubrication Analysis and the Modification of the Roller Profile in the Cam-Roller of the Valve Mechanism for a Marine Diesel Engine (박용디젤기관 밸브기구용 캠-롤러 사이의 탄성유체윤활해석 및 롤러 형상 수정에 관한 연구)

  • 구영필;강민호;이득우;조용주
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.11a
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    • pp.121-128
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    • 1999
  • In this study, a numerical procedure to analyze 3-dimensional unsteady elastohydrodynamic lubrication was developed. The procedure was applied to the actual cam and roller follower of the valve mechanism for a marine diesel engine. The pressure distribution between the cam and roller follower was calculated for the several cam rotating angles. The pressure spike is shown near the roller edge and it is getting higher as the external load is increased. The roller profile for reducing the pressure spike was suggested by the Hertzian contact analysis.

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Elastohydrodynamic Lubrication of a Profiled Cylindrical Roller (II) (프로파일링을 한 원통형 로울러의 탄성유체윤활 (II))

  • 박태조;김경웅
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.1975-1981
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    • 1991
  • A new numerical solution of the elastohydrodynamic lubrication(EHL) problem of an axially profiled cylindrical roller is presented. A finite difference method and the Newton-Raphson method are used to solve the nonlinear system equations. A non-uniform grid system is adopted to reduce the number of grid points and to obtain accurate solution. For two different types of profiles which have similar elastostatic pressure distribution, the EHL results show large differences. Especially the difference in film shape is larger than in pressure distribution. Therefore, the magnitude of the minimum film thickness should be a major criteria to design the axial profile of the roller. Variations of the minimum film thickness with dimensionless parameters show considerably different behavior from those of infinite solution and show a good agreement with the experimental data in literatures. Present numerical scheme can be used generally in the analysis of three-dimensional EHL problem.

Monochromatic Image Analysis of Elastohydrodynamic Lubrication Film Thickness by Fringe Intensity Computation

  • Jang, Siyoul
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1704-1713
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    • 2003
  • Point contact film thickness in elastohydrodynamic lubrication (EHL) is analyzed by image processing method for the images from an optical interferometer with monochromatic incident light. Interference between the reflected lights both on half mirror Cr coating of glass disk and on super finished ball makes circular fringes depending on the contact conditions such as sliding velocity, applied load, viscosity-pressure characteristics and viscosity of lubricant under ambient pressure. In this situation the film thickness is regarded as the difference of optical paths between those reflected lights, which make dark and bright fringes with monochromatic incident light. The film thickness is computed by numbering the dark and bright fringe orders and the intensity (gray scale image) in each fringe regime is mapped to the corresponding film thickness. In this work, we developed a measuring technique for EHL film thickness by dividing the image patterns into two typical types under the condition of monochromatic incident light. During the image processing, the captured image is converted into digitally formatted data over the contact area without any loss of the image information of interferogram and it is also interpreted with consistency regardless of the observer's experimental experience. It is expected that the developed image processing method will provide a valuable basis to develop the image processing technique for color fringes, which is generally used for the measurement of relatively thin films in higher resolution.

An Analysis of Elastohydrodynamic Lubrication of Elliptical Contacts : Part II (타원접촉의 탄성유체윤활해석 : 제2보)

  • 박태조;현준수
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.06a
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    • pp.182-188
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    • 1999
  • A theoretical study of elastohydrodynamic lubrication of elliptical contacts with both rolling and spin has been carried out. A finite difference method and the Newton-Raphson method are applied to solve the problem. The velocity vectors resulting from combined spin and rolling/sliding motion lead to asymmetric pressure distributions and film shapes. Film contours and variations of the minimum and central film thicknesses are compared with various spin-roll ratios. At high spin-roll ratios the minimum film thickness is considerably reduced, whereas the central film thickness decreases less dramatically, The present numerical scheme can be used in the analysis of general elliptical contact problems.

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Qualitative Analysis of Film Thickness in Elastohydrodynamic Lubrication (탄성 유체 윤활에서의 유막 두께 측정에 관한 정성적 분석)

  • 최언진;장시열
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.06a
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    • pp.147-155
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    • 1999
  • The film thickness and shape of elastohydrodynamic lubrication is measured by optical interferometer, which is the most precise method for EHL film measurement. However the interpretation of the image pattern from optical viscometer is not easy for two-dimensional shape. A newly developed method of image processing makes it possible to evaluate the film thickness and shape in every point of contact region with two dimensional aspects. In this study, we captured film shape of EHL film from the monochromatic incident light with the Image processing method, which uses phase shift method, and obtained the image analysis method for gray level image in order to qualitatively evaluate film shapes.

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Study of the Friction Force Measurements According to the Rolling-Sliding Ratios under the Condition of Elastohydrodynamic Lubrication (구름-미끄럼 속도비에 따른 탄성유체윤활영역에서 유막두께와 마찰력 측정연구)

  • 장시열
    • Tribology and Lubricants
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    • v.20 no.5
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    • pp.225-230
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    • 2004
  • Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the tribological characteristics of a certain lubricant, it is also important to get the information of traction behaviors as well. In this work, we developed a device for measuring the friction force of ehl contact condition as well as the film thickness. To verify the validity of the measuring system, the friction forces and film thicknesses under ehl condition are simultaneously measured with the variations of additive ratios of viscosity index improvers which cause non-linear tendencies of film thickness to contact velocity.

An Analysis of Elastohydrodynamic Lubrication of Elliptical Contacts:Part I (타원접촉의 탄성유체윤활해석:제1보)

  • 박태조;현준수
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1998.10a
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    • pp.212-218
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    • 1998
  • This paper presents a study of the elastohydrodynamic lubrication of elliptical contacts where lubricant entrainment coincides with the major axis of the Hertzian contact ellipse. A finite difference method and the Newton-Raphson method are applied to analyze the problem. Film contours and pressure distributions are compared with the results for lubricant entrainment coincides with the minor axis. Variations of the minimum and central film thicknesses with the radius ratio are also examined. Therefore, the present numerical scheme can be used generally in the analysis of the EHL of elliptical contacts where the lubricant entraining vector did not coincide with either of the principal axis of the conjunction.

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Analysis of Line and Circular Contact Elastohydrodynamic Lubrication with Multigrid Multilevel Method (다중 격자 다중 차원법을 이용한 선접촉 또는 점접촉 탄성 유체 윤활 해석)

  • 장시열
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.11a
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    • pp.323-330
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    • 1999
  • The conventional analysis for the numerical computation of fluid film thickness with elastic deformation of contact region. is performed by Newton-Rephson method for its 18st convergence characteristics. However, both high load and relatively low sliding velocity frequently make it impossible for Newton-Rahpson method to get both converged and stable solutions. In particular, this method cannot provide converged Solution under the condition of high load above 1.0 GPa which frequently occurs in line contact of EHL problem. Multigird multi-level method for the solver of non-linear partial differential equation including solid deformation is preferred to Newton-Rshpson method for better convergence and stability and is applied to line contact EHL behavior in this study.

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n Analysis of Elastohydrodynamic lubrication in Line Contacts-the effect of temperature variation (유체 온도 변화를 고려한 선 접촉면사이의 탄성유체윤활 해석)

  • 서민호;임윤철
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.11a
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    • pp.364-373
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    • 2001
  • This paper describes the variation of lubricant's temperature effects on elastohydrodynamic lubrication. The Newton-Raphson technique was used to solve the simultaneous system of Reynolds and elasticity equations. To show effects of lubricant's temperature, average temperature across the oil film was calculated using the energy equation. Pressure distribution, film shape, and temperature distribution were obtained for fully flooded conjunctions, and various dimensionless speed parameters while load and material parameters were held constant. Minimum film thickness were obtained for various material properties while load and velocity were held constant. It is drawn that the thermal effects have a strong influence on a minimum film thickness under high rolling velocity and slip ratio.

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