• Title/Summary/Keyword: Friction speed

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A Study on Rolling Friction Characteristics of Magneto-Rheological Elastomer under Magnetic Fields (자기장 영향에 따른 자기유변탄성체의 구름 마찰 특성 연구)

  • Lian, Chenglong;Lee, Kwang-Hee;Kim, Cheol-Hyun;Lee, Chul-Hee
    • Tribology and Lubricants
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    • v.30 no.4
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    • pp.234-239
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    • 2014
  • Magneto-rheological elastomer (MR elastomer) is a smart material, because it has mechanical properties that change under a magnetic field. An MR elastomer changes its stiffness characteristics when the inner particles (iron particles) align along the direction of a magnetic field. There has been much research to make use of this characteristic to control vibration issues in various mechanical systems, such as for mounting systems in the automotive field, home appliances, etc. Furthermore, the friction and wear properties of MR elastomer have been studied, as these relate to the durability of the material needed to meet engineering requirements. Rolling friction (or rolling resistance) is one of these friction properties, but has not yet been studied in the context of MR elastomers. In this study, an MR elastomer is fabricated in the shape of a hollow cylinder to evaluate the rolling friction characteristic under a magnetic field. The test apparatus is setup and a strain gauge is used to calculate the rolling resistance under test conditions. Permanent magnets are used to supply the magnetic field during tests. The load and rolling speed conditions are also considered for the tests. The test results show that rolling friction characteristic has a different trend under different magnetic field, load, and rolling speed conditions. It is assumed that the stiffness change of an MR elastomer under a magnetic field has an effect on the rolling friction characteristic of the MR elastomer. For the future work, the rolling friction characteristics of MR elastomers will be controlled by adjusting the strength of the magnetic field using electromagnets.

Development of Friction Reduction Method between Piston Ring and Cylinder Liner (피스톤 링과 실린더 라이너에서의 마찰저감 기술개발)

  • 김완호;차금환;김대은;임윤철
    • Tribology and Lubricants
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    • v.14 no.4
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    • pp.37-43
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    • 1998
  • The friction loss between piston rings and cylinder liner is due to the tension of the piston rings. Lubricant is usually supplied to reduce the friction. However, the sliding speed of the piston varies during the reciprocating cycle and is very low near TDC(Top Dead Center)/BDC(Bottom Dead Center), where the hydrodynamic lubrication cannot be sustained. Since the lubrication regime is shifted from the hydrodynamic to the boundary lubrication near TDC/BDC, wear particles are easily generated so that the friction loss becomes bigger and bigger due to the plowing effect of wear particles. In this study, for the purpose of reducing the friction loss, an undulated surface is adopted to the cylinder liner to trap wear particles. The friction force variations, which are measured by strain gaged, show that the concept of undulated surface is one of the promising methods to effectively reduce the friction between piston rings and cylinder liner.

자동차에 사용되는 금속성 마찰재와 유기질 마찰재의 마찰 특성에 관한 연구

  • Jang, Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1997.04a
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    • pp.47-52
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    • 1997
  • Friction properties of two different types of automotive friction materials were studied. They were nonasbestos organic and semi-metallic friction materials. The two friction materials were tested using an inertia brake dynamometer to investigate friction stability, rooster tailing phenomena, temperature change of riction couples during drags and stops. Results showed that the level of the friction force is strong function of time, temperature, and speed regardless of the type of friction materials. The change of triction coefficient during braking (rooster tailing) was pronounced when the applied pressure was increased in the case of semi-metallic friction materials. This phenomena appears strongly dependent on the applied pressure, initial brake temperature and ingredients in the friction material.

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Tension Control Using On-Line Compensation of Friction Loss for Continuous Strip Processing Line (연속 공정 라인의 실시간 마찰손 보상을 통한 장력 제어 특성 개선)

  • Lee, Jeong-Uk;Choi, Chang-Ho;Hyun, Dong-Seuk
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.49 no.10
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    • pp.701-707
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    • 2000
  • This paper proposes a tension control to compensate friction loss using on-line friction torque observer for a continuous strip processing line. Friction loss of roller results in significant deviation of strip tension, accordingly it has an influence on the operation of other adjacent rolls. To avoid tension variation of the strip, a friction torque observer is designed in adjacent roll, which operates in speed control mode. The observed torque is added to the torque limit reference of the pay-off reel for on-line compensation of both friction loss and acceleration/deceleration torque at the same time. The simulation and experimental results show improvement of tension control performance by the proposed friction compensation method.

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The Welding Surface and Mechanical Characteristics in Friction Stir Welding for 5456-H116 Alloy (마찰교반용접에 의한 5456-H116 합금의 용접 형상과 기계적 특성)

  • Kim, Seong-Jong;Han, Min-Su;Jang, Seok-Ki
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.18 no.3
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    • pp.273-278
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    • 2012
  • The use of Al alloys instead of fiber-reinforced plastic(FRP) in ship construction has increased because of the advantages of Al-alloy ships, including high speed, increased load capacity, and ease of recycling. This paper describes the effects of probe diameter on the optimum friction stir welding conditions of 5456-H116 alloy for leisure ship, measured by a tensile test. In friction stir welding using a probe diameter of 5 mm under various travel and rotation speed conditions, the best performance was achieved with a travel speed of 61 mm/min. Using a probe diameter of 6 mm, rotation speeds of 170-210 rpm, and a travel speed of 15 mm/min produced a rough surface and voids because of insufficient heat input produced by the low rotation speed. At 500-800 rpm, chips were observed, although there were no voids, and the weld surface was excellent. However, at 1100-2500 rpm, many chips were produced due to excessive heat input. Heat effects were very evident on the bottom. For a travel speed of 15 mm/min, heat input caused by friction increased as the rotation speed increased. The mechanical characteristics were degraded by accelerated softening due to increasing heat input.

STUDY ON WELDABILITY OF CU (OFC) BY FRICTION STIR WELDING

  • Bang, Keuk-saeng;Lee, Won-bae;Yeon, Yun-mo;Jung, Seung-boo
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.522-527
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    • 2002
  • The microstructure and mechanical properties of friction stir welded OFC plates with 2mm in thickness were examined with the changing welding parameters such as welding speed, rotation speed in this study. The sounding welding conditions was acquired at the optimum welding conditions of the 41mm/min to 61mm/min of welding speed at 1250 rpm of rotation speed. The microstructure of weld zone was divided into four parts such as the base metal region (EM), thermal mechanical affected zone (TMAZ), heat affected zone (HAZ), stir zone (SZ). The grain size in the SZ and the width of weld nugget were increased with increasing welding speed. The hardness profiles of the base metal were distributed about 80HV. The HAZ is a slightly softened region of about 60~75 HV relative to the base metal. The hardness profiles of the SZ were higher than that of base metal. The tensile strength was increased with increasing welding speed. In case increasing rotation speed, tensile strength was decreased. The maximum tensile strength was about 220:MPa which was 110% of joint efficience of that of base metal at 41mm/min of welding speed, 1250rpm of rotation speed.

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HVOF Spray Coating of Co-alloy(T800) for the Improvement of durability of High Speed Spindle (초고속 회전체의 내구성향상을 위한 Co-alloy(T800)의 초고속 용사코팅)

  • Cho, Tong-Yul;Yoon, Jae-Hong;Kim, Kil-Su;Youn, Suk-Jo;Back, Nam-Ki;Park, Byung-Chul;Chun, Hui-Gon
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.6
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    • pp.32-37
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    • 2006
  • Micron size Co-alloy(T800) powder was coated on Inconel 718 by HVOF thermal spraying for the studies of the improvement of durability of high speed spindle by using Taguchi program for the parameters of spray distance, flow rates of hydrogen and oxygen and powder feed rate. The optimal coating process was determined by the studies of coating properties such as micro-structure, porosity, surface roughness and micro hardness. Friction and wear behaviors of coatings were investigated by sliding wear test at room temperature and $1000^{\circ}F(538^{\circ}C)$. At both room temperature and $538^{\circ}C$ the sliding wear debris and friction coefficients of the coating were drastically reduced compared with the surface of non-coated parent material. This shows that Co-alloy powder coating is highly recommendable for the durability improvement surface coating of high speed air-bearing spindle. At high temperature wear traces and friction coefficients of both coating and non-coating were drastically reduced compared with those of room temperature since the brittle oxides were formed easily on the surface, and the brittle oxide phases were attrited by the reciprocating sliding wear according to the complicated mixed wear mechanisms These oxide particles, partially melts and the melts play role as lubricant and reduce the wear and friction coefficient. This also shows that Co-alloy powder coating is highly recommendable far the durability improvement surface coating on the surface vulnerable to frictional heat such as high speed spindles.

A Long-Term Friction Test of Bridge Bearings Considering Running Speed of Next Generation Train (차세대 고속철 주행속도를 대비한 교량받침의 장기마찰시험법)

  • Oh, Soon-Taek;Lee, Dong-Jun;Jun, Sung-Min;Jeong, Shin-Hyo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.2
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    • pp.34-39
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    • 2016
  • Structural behaviour of PSC box bridge, on which KTX train runs, is analysed up to 500 km/h speed considering 12 stages track irregularity and interaction between bridge and vehicle. To evaluate wheel forces and rotations of vehicle, lateral wheel forces, derail factor and offload factor calculated on the track combining the bridge and 170 m normal track are compared with existing allowed limits. Maximum longitudinal displacement and accumulated sliding distance of the brige bearings for simply supported and 2 span continuous PSC bridges are presented by each running speeds. Long-term friction tests based on EN-1337-2 are conducted between PTFE and DP-mate plates. Finally, the long-term friction tests are proposed to consider the increasing speed of next generation high-speed train.

An Experimental Study of the Friction and Temperature characteristics of Engine Crankshaft Bearings (엔진 크랭크샤프트 베어링에 대한 마찰 및 온도 특성에 대한 실험적 연구)

  • 조명래;문회지;장인배;한동철
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1993.12a
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    • pp.57-62
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    • 1993
  • To increase the fuel economy, a reduction of friction loss is important in engines. Experimental investigations have been required for reducing the friction loss of crankshaft bearings. Hydraulic cylinder, and servo control ler system which modified the applied load, and test rig for the observation of the characteristics of engine crankshaft bearings were designed and fabricated. Experiment is performed. Friction torque, journal locus and circumferential temperature variations of crankshaft bearings were measured with appling load, revolution speed, and oil inlet temperature, etc.

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A Study on the Numerical Friction Model in the Drawing (인발가공에 있어서 마찰수식모델에 관한 연구)

  • 오박균
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.5 no.3
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    • pp.260-265
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    • 2004
  • In order to analyze the shaped drawing process, 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 drawing may be large different from the actual conditions. In this paper, accurate analysis of the drawing process should be subjected. It is to develop accuracy of the numerical friction models and potentialize to apply for the high speed forming work in the drawing process. Therefore, the results should improve the accuracy, cause the energy saving for the drawing process and finally expand the applying areas of the results.

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