• Title, Summary, Keyword: Boundary Friction

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Characteristics of friction and wear of the metals in boundary lubrication (경계윤활 상태에서의 금속재료의 마찰 및 마멸 특성)

  • 류종관;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.256-262
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    • 1998
  • Many lubricated systems experience boundary, lubrication condition during operation. However, the friction and wear characteristics of boundary lubrication are not clearly understood. In this work the factors which affect the friction and wear between boundary lubricated metallic surfaces are investigated. Experiments were performed on atuminium, copper, and SM45C with bearing ball using a pin-on disk type tester. The experimental conditions were determined by Taguchi experimental method. From the experimental results, the major factors that influence the friction and wear characteristics of boundary lubrication could be identified.

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An Experimental Study for the Effect of Friction Modifier Added in Fuel on the Engine Friction and Fuel Economy (연료 주입형 마찰 조정제가 엔진 마찰 및 연비에 미치는 영향에 대한 실험적 연구)

  • 조명래;강경필;오대윤;최재권
    • Tribology and Lubricants
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    • v.18 no.2
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    • pp.133-137
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    • 2002
  • This paper reports on the effect of fuel additive friction modifier on the engine friction and fuel consumption. The test of engine friction and fuel consumption is performed for the each oils and fuels. The TFA4724 friction modifier is added in test oil and fuel. The test results show that total engine friction is a decrease of 0.7-2.0% compared with base fuel, and fuel consumption is improved by 0.3%. The amount of friction reduction corresponds to that of boundary friction loss term in ring-pack friction losses. From the results, it is thought that the additive friction modifier in the fuel is effective to reduce the boundary friction in ring-pack.

Major Factors that Affect Friction and Wear of Metals in Boundary Lubrication (경계윤활 상태에서의 금속재료 마찰 및 마멸에 영향을 미치는 주요인자)

  • 류종관;이홍철;김대은
    • Tribology and Lubricants
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    • v.15 no.2
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    • pp.171-177
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    • 1999
  • Many lubricated systems experience boundary lubrication condition during operation. However, the friction and wear characteristics of boundary lubrication are not clearly understood. In this work the factors which affect the friction and wear between boundary lubricated metallic surfaces are investigated. Experiments were performed using a pin-on-disk type tester with pure aluminum, pure copper, and SM45C steel as the disk material and steel, stainless steel and bearing ball as the ball. The experimental conditions were determined according to the Taguchi experimental method. From the experimental results, the major factors that influence the friction and wear characteristics of boundary lubrication could be identified.

Control of Shock Wave/Boundary-Layer Interactions Using S-Shaped Mesoflaps (S-자형 플랩을 이용한 충격파와 경계층 간섭현상 제어에 관한 연구)

  • Lee Yeol
    • Proceedings of the KSME Conference
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    • pp.159-160
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    • 2002
  • New S-shaped aeroelastic mesoflaps are utilized to control normal shock/boundary-layer interactions. New generation of the mesoflaps is designed f3r a better rigidness and a good flow uniformity across the ulteractions. ,Major advantages of the mesoflap system can be a better total pressure recovery downstream of the interactions due to the lambda shock structure over the flap system, and a rehabilitation of the thickened boundary layer due to bleeding through a cavity underneath the flap system. Skin friction has been measured downstream of the interactions, using the laser interferometer skin friction (LISF) meter, which optically detects the rate of thinning of an oil film applied to the test surface. Various flap-thicknesses of the S-shaped mesoflap arrays are tested, and the results are compared to the solid-wall reference case. Overall, not much difference in the level of skin friction is noticed for the S-shaped flap arrays of various thicknesses, and its level is lower than the skin friction downstream of the solid-wall interaction

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Friction of component coatings in lubricated contact

  • Jacobson, Staffan;Hogmark, Sture
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.133-134
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    • 2002
  • The use of low friction wear resistant coatings for machine components is rapidly increasing. These components may operate in any lubrication regime, and less frequently even unlubricated. When run unlubricated it is easy to see the beneficial effect of a low friction coating. However, it has frequently been shown that the coating may also be very beneficial under boundary and mixed lubrication conditions. The present digest briefly presents a few interesting aspects of the use of low friction coatings in lubricated contact illustrated by selected experimental results.

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Study on Tribological Characteristics of Machine Component in Boundary Lubrication (경계윤활에서 기계 부품 소재의 트라이볼로지적 특성에 관한 연구)

  • Kim, Myeong-Gu;Seo, Kuk-Jin;Nam, Jahyun;Kim, Dae-Eun
    • Tribology and Lubricants
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    • v.35 no.6
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    • pp.356-361
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    • 2019
  • The friction and wear between machine components directly influence the energy loss and failure in various machines. Therefore, there is always a demand for finding methods to reduce friction and wear. Of the possible methods, lubrication is a widely used method for reducing friction and wear. In the case of lubrication, it is important to analyze the tribological behavior in the boundary lubrication because most of friction and wear occurs in the boundary lubrication regime. Cast iron has been regarded as a good material for industrial applications due to the excellent mechanical properties and high productivity. Especially, nodular cast iron is a material that shows better mechanical properties and wear-resistance compared with cast iron due to inclusion of spheroidal graphite. In this work, we investigated the tribological characteristics of nodular cast iron with respect to different counter parts in boundary lubrication regime. Sliding tests were conducted with SUJ2, ZrO2, Si3N4 balls as counter parts using a pin-on-disk type tribotester. The results showed different friction and wear behaviors with different counter parts. The case of ZrO2 showed the lowest wear rate in specimen and no significant ball wear. In case of SUJ2, it showed similar wear rate with ZrO2 case in specimen and the highest friction coefficient. The case of Si3N4 showed the lowest friction coefficient, 33% lower than the case of SUJ2. It showed 16.9 times larger wear rate in specimen and 43% larger wear rate in ball compared to that of the SUJ2 case.

Characteristics of the major tribological parameters in boundary lubrication (경계윤활에서의 주요 Tribological 인자의 특성)

  • 류종관;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.82-90
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    • 1998
  • Machines that normally operate under fluid film lubricated condition also experience surface damage. This is largely due to the failure of the lubricant film which leads to boundary lubrication. Thus, it is important to have a good understanding of boundary lubrication behavior. In this paper the major tribological parameters that influence the boundary lubrication properties are evaluated. It is shown that disk roughness, hardness and normal load affect the friction and wear of metals in boundary lubrication. Also, the mechanism of surface damage is attributed to abrasion and wear particle interaction.

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Friction Characteristics of Piston Assembly (II) -Experiment- (피스톤계 마찰 특성 (II) -실험적 연구-)

  • Cho, Myung-Rae;Ha, Kyoung-Pyo;Kim, Joong-Soo;Oh, Dae-Yoon;Han, Dong-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.1
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    • pp.88-93
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    • 2003
  • The aim of this paper is to investigate the friction characteristics of piston assembly, which composed of ring pack and piston skirt. The friction force of piston assembly was measured by using the movable liner in the single cylinder engine, and the various parameters were tested. The friction force was suddenly increased at the expansion stroke due to higher cylinder pressure. The viscous friction was dominant at the mid stroke, but the boundary friction was dominant at the top and bottom dead centers. Through the experiment, we could validate previous theoretical study, and confirm that th e radial clearance and ring tension were very effective to reduce friction loss of piston assembly.

Skin friction measurements using He-Ne laser (He-Ne 레이저를 이용한 표면전단응력 측정에 관한 연구)

  • Choi, Seung-Ho;Lee, Yeol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.7
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    • pp.939-947
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    • 1997
  • An experimental study of the skin friction measurement in a turbulent boundary-layer has been carried out. The skin friction measurements are made using the laser interferometer skin friction (LISF) meter, which optically detects the rate of thinning of an oil applied to the test surface. This technique produces reliable skin friction data over a wide range of flow situations up to 3-dimensional complicated flows with separation, where traditional skin friction measurement techniques are not applicable. The present measured data in a turbulent boundary-layer on a flat plate using the LISF technique shows a good comparison with the result from the previous velocity profile techniques, which proves the validity of the present technique. An extensive error analysis is carried out for the present technique yielding an uncertainty of about .+-.8%, which makes them suitable for CFD code validation purposes. Finally the measurements of the skin friction in a separated region after a surface-mounted obstacle are also presented.

Experimental Study on Frictional Drag Reduction of Turbulent Flow by Polymer Solution Injection (폴리머 수용액 주입에 의한 난류마찰저항 감소에 대한 실험 연구)

  • 김형태;김덕수;김우전
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.3
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    • pp.9-15
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    • 2003
  • An experimental study has been carried out as a basic research for development of the friction drag reduction technology for ships by polymer injection. Experimental apparatus and procedures have been devised and prepared to measure the changes of the wall friction with injection of a polymer solution and basic experimental data on the friction drag reduction are obtained for a turbulent fiat-plate boundary layer and fully-developed channel flows. Variations of the friction drag reduction with some important parameters of polymer injection, such as the concentration of polymer solution, its injection flow rate and the measuring position downstream from the injection slot, are also investigated. Important experimental data and results obtained in the present study are presented. The amount of friction drag reduction up to 50% is observed.