• Title/Summary/Keyword: elliptical contacts

Search Result 10, Processing Time 0.025 seconds

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

  • 박태조;현준수
    • Tribology and Lubricants
    • /
    • v.14 no.4
    • /
    • pp.58-63
    • /
    • 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.

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
    • /
    • 1998.10a
    • /
    • pp.212-218
    • /
    • 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.

  • PDF

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
    • /
    • 1999.06a
    • /
    • pp.182-188
    • /
    • 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.

  • PDF

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

  • Park, Tae-Jo
    • Tribology and Lubricants
    • /
    • v.23 no.2
    • /
    • pp.49-55
    • /
    • 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.

Elastohydrodynamic Film Thickness in Elliptical Contacts with Rolling and Spinning (구름/스핀 운동을 하는 경우의 타원접촉 EHL 유막두께)

  • Park, Tae-Jo
    • Tribology and Lubricants
    • /
    • v.24 no.6
    • /
    • pp.355-361
    • /
    • 2008
  • In highly stressed machine elements such as angular contact ball bearings and toroidal type traction drives, the elastohydrodynamic lubrication of elliptical contacts with both rolling and spinning motion are occur. In this paper, a finite difference method with non-uniform grid systems and the Newton-Raphson method are applied to solve the problems. Pressure distributions, film contours and variations of the minimum and central film thicknesses are compared with various ellipticity parameter, dimensionless speed and load parameter. The results showed that the spinning motion has significant influence especially on the film shapes. Reduction of the minimum film thickness under spinning is remarkable whereas the central film thickness is relatively less. Especially variations of the minimum film thicknesses with rolling velocity, load and ellipticity ratio are a great different from those of pure rolling. Therefore present numerical scheme can be used in the analysis of general elliptical contact EHL problems and further studies are required.

Micro Ultrasonic Elliptical Vibration Cutting (II) Ultrasonic Micro V-grooving Using Elliptical Vibration Cutting (미세 초음파 타원궤적 진동절삭 (II) 타원진동 절삭운동을 이용한 미세 홈 초음파 가공)

  • Kim Gi Dae;Loh Byoung-Gook;Hwang Kyung-Sig
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.22 no.12 s.177
    • /
    • pp.198-204
    • /
    • 2005
  • For precise micro V-grooving, ultrasonic elliptical vibration cutting (UEVC) is proposed using two parallel piezoelectric actuators, which are energized by sinusoidal voltages with a phase difference of 90 degrees. Experimental setup is composed of stacked PZT actuators, a single crystal diamond cutting tool, and a precision motorized xyz stage. It is found that the chip formed in the process of UEVC is discontinuous because of the periodic contacts and non-contacts occurring between the tool and workpiece. It is experimentally observed that the cutting force in the process of UEVC significantly reduces compared to the ordinary non-vibration cutting. In addition, the creation of burr during UEVC is significantly suppressed, which is attributable to the decrease in the specific cutting energy.

An Evaluation of the Hamrock and Dowson's EHL Film Thickness Formulas (Hamrock과 Dowson의 EHL 유막두께식에 대한 평가)

  • 박태조
    • Tribology and Lubricants
    • /
    • v.12 no.3
    • /
    • pp.115-122
    • /
    • 1996
  • In this paper, a finite difference method and the Newton-Raphson method are used to evaluate the Hamrock and Dowson's EHL film thickness formulas in elliptical contact problems. The minimum and central film thicknesses are compared with the Hamrock and Dowson's numerical results for various dimensionless parameters and with their film thickness formulas. The results of present analysis are more accurate and physically reasonable. The minimum film thickness formula is similar with the Hamrock and Dowson's results, however, the central film thickness formula shows large differences. Therefore, the Hamrock and Dowson's central film thickness formula should be replaced by following equation. $H_{c} = 4.88U^{0.68}G^{0.44}W^{0.096}(1-0.58e^{-0.60k})$ More accurate film thickness formula for general elliptical contact problems can be expected using present numerical methods and further research should be required.

Elliptical EHL Contacts under Dynamic Loading Conditions in HERB Drive

  • Jang, Si-Youl;Park, Kyoung-Kuhn;Kim, Wan-Doo;Moon, Ho-Jee
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • 2002.10b
    • /
    • pp.89-90
    • /
    • 2002
  • Ball reducer (HERB Drive: High Efficient Wave Rolling Ball Drive) with waved grooves has many advantages over other types of reducers for high-reduction ratio, low noise and low energy loss, etc. The mechanism of force transmission is very similar to that of cam and follower in automobile valve train system especially in contact behaviors. In this study, we have investigated the traces of contact between ball and outer ring, and the dynamic contact behaviors of elastohydodynamic lubrication(EHL) with a certain reduction ratio. In order to verify the contact behaviors between ball and outer ring for the critical endurance lift, the contact velocity and load are computed for a cycle. During some intervals of a cycle, the contact velocity reverses its direction very suddenly. It is expected that changing the contact direction causes undesirable endurance performance because EHL film frequently col lapse at the moment of velocity reversal. From the computational investigation in this work, we hope to predict similar contact damages in other machinery due to this kind of contact behaviors, which is very typical in many contact phenomena.

  • PDF