• Title/Summary/Keyword: Hydrodynamic Friction

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Development of Piston-Ring Assembly Friction Force Measuring System (피스톤-링 결합체 마찰력 측정시스템의 개발)

  • 윤정의;김승수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.2 no.3
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    • pp.94-104
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    • 1994
  • In order to improve engine performance and its reliability it is very important to find the friction force between piston-ring assembly and cylinder wall in engine operating conditions. A new system was developed for the piston-ring assembly friction force measurement. This system had a relatively high fundamental frequency at 884 Hz and a fine resolution of 0.5N in friction force measurement. Comparing with existing floating liner systems this systems required small installation space and at the same time alleviated the system noise problem induced by the thrust and slap impulse forces.

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The friction characteristics at vane tip of vane pump for power steering system (Power Steering용 베인 펌프의 베인 선단부에서의 마찰특성)

  • 박운성;정석훈;오석형;정재연
    • Tribology and Lubricants
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    • v.11 no.3
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    • pp.48-53
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    • 1995
  • In this paper, the friction characteristics of contact region between vane tip and camring is studied using a modeled experimental device. The contact region is under the influence of variable loads with the amplitude of hundreds of Newton and frequency of tens of Hz. The condition of lubrication between vane and disk is modeled after the actual condition between vane and camring. The coefficient of friction is obtained by measuring the frictional forces in the contact region between camring and vane. The friction characteristics of the actual oil hydraulic vane pump is estimated on the basis of coefficient of friction. The analysis of frictional characteristics shows us that the lubrication condition of vane tip is that of transition regime between hydrodynamic lubrication and mixed lubrication.

The Frictional Modes of Barrel Shaped Piston Ring under Flooded Lubrication (윤활유가 충분한 배럴형 피스톤-링의 마찰모드)

  • 조성우;최상민;배충식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.3
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    • pp.56-64
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    • 2000
  • A friction force measurement system using the floating liner method was developed to study the frictional behavior of piston rings. The measurement system was carefully designed to control the effect of the piston secondary motion and the temperature of cylinder wall and oil. The friction force between the barrel shaped piston ring and the cylinder liner, was measured under the condition of flooded oil supply. The measured friction forces were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(midstroke and dead centers). The modes could be identified on the Stribeck diagram of the friction coefficients and the dimensionless number of ㎼/p, where the friction coefficients are evaluated at near the midstroke and dead centers.

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Friction and Electrical Characteristics of Oil-impregnated Sintered-Metal Bearing with Grooves (그루브를 가진 함유소결베어링의 마찰 및 전기적 특성)

  • 정광섭;김병주;송무석;이영제
    • Tribology and Lubricants
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    • v.13 no.3
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    • pp.108-114
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    • 1997
  • The electrical and frictional properties of new sintered-metal bearing (S-bearing) with varying loads and speeds were measured. Also those were compared with the same products(J-bearing) made in Japan and the conventionally used ball bearing. The test results show that the frictional values of S-bearing are less than those of J-bearing, and that S-bearing operates in full-hydrodynamic lubrication regime. The values of rating current, starting time and jitter reveal that S-bearing is superior to J-bearing as well as ball bearing.

Characteristics of Herringbone-Grooved Hydrodynamic Bearing and Scanner Motor for Laser Beam Printer (레이저 프린터에 사용되는 빗살무늬 유체동압 베어링과 스캐너 모터의 특성)

  • Jeong, Seong-Hun;Lee, Yeong-Je;Jeong, Dae-Hyeon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.1 s.173
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    • pp.269-274
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    • 2000
  • Frictions and electrical contact voltages of the herringbone-grooved hydrodynamic bearing(HHB) were 9, measured to use in a laser scanner motor. This bearing with varying loads, speeds, oil viscosity, and radial clearances successfully operated up to 28,000rpm and 0.5N. Experimental results under various environments confirmed that this bearing had excellent performance with low friction force, and operated without contact between shaft and sleeve.

Dynamic Behavior and Lubrication Characteristics of a Reciprocating Compressor Crankshaft by n Finite Bearing Model (유한 베어링 모델링을 이용한 왕복동형 압축기 크랭크축의 동적 거동 및 윤활특성 해석)

  • 김태종
    • Tribology and Lubricants
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    • v.18 no.6
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    • pp.402-410
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    • 2002
  • In this study, a hydrodynamic analysis of the reciprocating compressor crankshaft considering a finite bearing modelling of the journal bearings used in small refrigeration compressors is performed. In the problem formulation of the compression mechanism dynamics, all corresponding hydrodynamic forces and moments are considered using the finite bearing analysis in order to determine the crankshaft trajectory at each step. The solution of the Reynolds' equation is determined numerically using a finite difference method and a Newton-Raphson procedure was employed in solving the dynamic equations of the crankshaft. The crankshaft orbits fur the finite bearing model and short bearing theory were used to compare the effect of the hydrodynamic farces of the journal bearings on the dynamic and lubrication characteristics of the crankshaft-journal bearing system. Results show that the finite bearing model for the journal bearings must be considered in calculating for the accurate dynamic characteristics of the reciprocating compressor crankshaft.

TWO-PHASE WAVE PROPAGATIONS PREDICTED BY HLL SCHEME WITH INTERFACIAL FRICTION TERMS (계면마찰항을 고려한 이상유동에서 파동전파에 대한 수치적 연구)

  • Yeom, G.S.;Chang, K.S.;Chung, M.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.115-119
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    • 2009
  • We numerically investigated propagation of various waves in the two-phase flows such as sound wave, shock wave, rarefaction wave, and contact discontinuity in terms of pressure, void fraction, velocity and density of the two phases. The waves have been generated by a hydrodynamic shock tube, a pair of symmetric impulsive expansion, impulsive pressure and impulsive void waves. The six compressible two-fluid two-phase conservation laws with interfacial friction terms have been solved in two fractional steps. The first PDE Operator is solved by the HLL scheme and the second Source Operator by the semi-implicit stiff ODE solver. In the HLL scheme, the fastest wave speeds were estimated by the analytic eigenvalues of an approximate Jacobian matrix. We have discussed how the interfacial friction terms affect the wave structures in the numerical solution.

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Study on the Rotating Motion of a Piston Pin of Full Floating Type (비고정식 피스톤 핀의 회전운동에 관한 연구)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.23 no.3
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    • pp.95-102
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    • 2007
  • In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. Moreover, the lead removal from the bush material has strongly reduced the capability of the anti friction material to accept asperity contacts. In this paper, before trying to find the pressure distributions on the oil film of piston pin bearings by the unsteady two dimensional thermohydrodynamic lubrication analysis in order to do the optimum design of the bearings of piston pin, it will be investigated the tendancy of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress.

Mixed Lubrication Analysis of Cam/Tappet Interface on the Direct Acting Type Valvetrain System

  • Cho, Myung-Rae;Shin, Heung-Ju;Han, Dong-Chul
    • Journal of Mechanical Science and Technology
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    • v.15 no.6
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    • pp.685-692
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    • 2001
  • This paper reports on the mixed lubrication characteristics between the cam and the tappet contact surface of direct acting type valve train systems. First, the dynamic characteristics are solved by using the lumped mass method to determine the load conditions at the contact point. Then, the minimum oil film thickness is calculated with consideration of elastohydrodynamic line contact theory and the friction force is obtained by using the mixed lubrication model which separates the hydrodynamic and the boundary friction. Finally, the average surface temperatures are calculated by using the flash temperature theory. The results show that, there are some peaks in the friction force due to the asperity contact friction, and flash temperature at the position of minimum oil film thickness. It is thought that there is a relationship between the surface temperature and cam surface wear, and therefore, the analysis on the worn cam profile has been performed.

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A Study on the Numerical Friction Model for Extrusion (압출성형을 위한 마찰수식 모델에 관한 연구)

  • Oh P. K.
    • Transactions of Materials Processing
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    • v.14 no.1 s.73
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    • pp.14-20
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    • 2005
  • To carry out perfectly the forming analysis of the extruding products, it is necessary that the friction boundary condition between dies and blanks should be worked out the accurate numerical friction models. But, the existing numerical models of the extrusion may be large different from the actual conditions. In this study, accurate analysis of the extrusion forming for the variation of pressure and velocity should be subjected. It is to develop the accuracy of the numerical friction models and potentialize to apply for the high speed forming work in the extrusion. Therefore, the results should improve the accuracy, cause the energy saving for the extrusion and finally expand the applying areas of the results.