• 제목/요약/키워드: elastohydrodynamic lubrication

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프로파일링을 한 로울러의 EHL 해석

  • 박태조
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1996년도 제23회 학술대회
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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.

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표면 거칠기를 고려한 볼 조인트 접촉의 미세 탄성유체윤활 해석 (Micro-EHL Analysis of a Ball Joint Contact with Surface Roughness)

  • 김태종
    • Tribology and Lubricants
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    • 제19권3호
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    • pp.123-132
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    • 2003
  • The effect of surface texture on elastohydrodynamic lubrication (EHL) point contact of a ball Joint mechanism in small reciprocating compressors is studied numerically by using multigrid method. Pressure and film thickness profiles have been calculated for surface roughness with waviness of different orientations and transverse ridge and dent at minimum and maximum Hoes M parameter conditions. The influence of the amplitude and the wavelength of the surface roughness was also studied. Results show that the oblique waviness with orientation angle of 30$^{\circ}$generates the smallest minimum film thickness as compared with those of longitudinal, transverse, and other oblique roughness. The influence of transverse waviness on the minimum film thickness is smaller than for the longitudinal waviness case.

타원접촉의 탄성유체윤활 제1보-윤활유의 유입방향이 Hertz 접촉타원의 장축방향인 경우 (An Elastohydrodynamic Lubrication of Elliptical Contacts Part I: Direction of Lubricant Entrainment Coincident with the Major Axis of the Hertzian Contact Ellipse)

  • 박태조;현준수
    • Tribology and Lubricants
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    • 제14권4호
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    • pp.58-63
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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. The results showed that 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.

왕복동형 압축기 볼 조인트 접촉의 탄성유체윤활 해석 (EHL Analysis of the Ball Joint Contact in a Reciprocating Compressor)

  • 김태종
    • Tribology and Lubricants
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    • 제19권2호
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    • pp.85-93
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    • 2003
  • In this study, a multigrid multi-integration method has been used to solve the steady-state, elastohydrodynamic lubrication (EHL) point contact problem of a ball joint mechanism used in small reciprocating compressors. Pressure and film thickness profiles have been calculated at minimum and maximum Moes M parameter conditions during one revolution of crankshaft. The effects of various lubricant viscosities, loads, ball velocities, elastic modulli, and radii of curvature on the calculated pressure distribution and film thicknesses have been investigated. The results indicate that the viscosity of lubricant, the sliding velocity of ball, and the reduced radius of curvature have considerable effects on the minimum and central film thicknesses. Solutions obtained with the multigrid analysis are compared with results calculated according to the Hamrock & Dowson relations for the minimum and central film thicknesses.

한계전단응력형태의 Bair & Winer 리올로지 모델을 사용한 선접촉 탄성유체윤활해석 (Elastohydrodynamic Lubrication of Line Contacts Incorporating Bair & Winer's Limiting Shear Stress Rheological Model)

  • 이희성;양진승
    • Tribology and Lubricants
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    • 제14권1호
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    • pp.85-93
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    • 1998
  • The Bair & Winer's limiting shear stress rheological model is incorporated into the Reynolds equation to successfully predict the traction and film thickness for an isothermal line contact using the primary rheological properties. The modified WLF viscosity model and Barus viscosity model are also adapted for the realistic prediction of EHD tractional behavior. The influences of the limiting shear stress and slide-roll ratio on the pressure spike, film thickness, distribution of shear stress and nonlinear variation of traction are examined. A good agreement between the disc machine experiments and numerical traction prediction has been established. The film thickness due to non-Newtonian effects does not deviate significantly from the fdm thicknesss with Newtonian lubricant.

Lundberg형 프로파일의 원통형 로울러의 탄성유체윤활 해석 (Elastohydrodynamic Lubrication Analysis of a Lundberg Profile-type Cylindrical Roller)

  • 박태조
    • Tribology and Lubricants
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    • 제29권6호
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    • pp.353-359
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    • 2013
  • The rollers and/or races in cylindrical and tapered roller bearings should be profiled to relieve high edge stress concentrations caused by their finite lengths and misalignment. In this study, a numerical analysis was performed to investigate the elastohydrodynamic lubrication (EHL) of a Lundberg profile-type cylindrical roller. A finite difference method with fully nonuniform grids and the Newton-Raphson method were used to present detailed EHL pressure distributions and film shapes, as well as the variations in the minimum and central film thicknesses with the profile modification coefficient. In the Lundberg profile, the maximum pressure and minimum film thickness always occurred near the edges. Proper modification of the Lundberg profile considerably increased the minimum film thickness.

Dichromatic 투사광선에 따른 나노 미터 해상도의 점접촉 유막 두께 측정 연구 (Study on the Measurement Technology of Fluid Film Thickness with Nanometer Scale by Dichromatic Incident Light)

  • 공현상;장시열
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2003년도 춘계학술대회 논문집
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    • pp.686-689
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    • 2003
  • Many technologies are applied to the measurement of elastohydrodynamic lubrication (EHL) film thickness. In particular, optical in-situ interferometric method has many advantages in making the actual contact behaviors realized with the experimental apparatus. Careful selection of incident lights greatly enhances the fringe resolution up to nanometer scale by using image processing technology. In this work, it is found that dichromatic incident light can provide much finer resolution of EHL film thickness than monochromatic incident light, because it has much more variables of color components to be discriminated among the wavelengths of colors according the variations of EHL film thickness. Some simulated interferometric images are shown how the film thickness is resolutionized in nanometer scale

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타원접촉의 탄성유체윤활 : 제2보 - 스핀운동의 영향 (An Elastohydrodynamic Lubrication of Elliptical Contacts : Part II - The Effect of Spin Motion)

  • 박태조
    • Tribology and Lubricants
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    • 제23권2호
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    • pp.49-55
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    • 2007
  • A numerical analysis of elastohydrodynamic lubrication of elliptical contacts with both rolling and spinning has been carried out. A finite difference method with non-uniform grid systems and the Newton-Raphson method are applied to solve the problems. The velocity vectors resulting from combined spinning and rolling/sliding motion lead to asymmetric pressure distributions and film shapes. Pressure distributions, film contours and variations of the minimum and central film thicknesses are compared with various spin-roll ratios. Reduction of the minimum film thickness under spinning is remarkable whereas the central film thickness is relatively less. The spin motion have large effect on variations of the minimum film thickness with load parameter which are small in pure rolling/sliding cases. Therefore present numerical scheme can be used in the analysis of general elliptical contact EHL problems and further studies are required.

표면 거칠기를 고려한 볼베어링의 탄성유체윤활 (EHL Analysis of Ball Bearing Considering Surface Roughness)

  • 이향;조용주
    • Tribology and Lubricants
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    • 제29권4호
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    • pp.228-234
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    • 2013
  • This paper presents analysis of elastohydrodynamic lubrication (EHL) of ball bearings, in which surface roughness is considered. A lot of time is required to obtain a solution in the case of EHL analysis where surface roughness is considered, because the analysis requires a variety of analytic nodes. To save time, we use the full approximation scheme (FAS) among multilevel methods. We analyze the results of EHL and contact analyses in terms of pressure. We also compare the results for smooth and rough surfaces with respect to film thickness. We confirm that the film pressure decreases as compared to contact pressure because of the presence of lubricants between the ball and the raceway. Furthermore, in the case when surface roughness is considered, the film pressure increases because of contact asperities. Therefore, surface roughness should be considered when designing ball bearings.

유압 베인 펌프에서의 탄성유체윤활 해석 (Elastohydrodynamic Lubrication Analysis in Hydraulic Vane Pump)

  • 박태조
    • 드라이브 ㆍ 컨트롤
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    • 제10권3호
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    • pp.7-13
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    • 2013
  • Hydraulic vane pumps are widely used in various hydraulic systems because of its compactness and light weight. It is well known that the vanes and cam ring are separated by very thin liquid films which result in the EHL state. Contrary to the case of cylindrical roller bearings, the inlet and side boundary pressures are much higher than the atmospheric pressure. In this paper, a numerical solution of the EHL of finite line contacts between the cam ring and vane tip with profiled ends is presented. Using a finite difference method with non-uniform grids and the Newton-Raphson method, converged solutions are obtained for moderate load and material parameters. The EHL pressure distribution and film shape are considerably affected by pump delivery pressure and the side boundary condition applied. Both the maximum pressure and the minimum film thickness always occurred near the edge regions. The present results can be used in the design of optimum vane profile in hydraulic vane pump.