• Title/Summary/Keyword: sliding contact

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Thermoelastic Instability of the Layer Sliding between Two Non-conducting Half-planes (비전도 반평판 사이에서 미끄럼 운동하는 평판 층의 열탄성 불안정성)

  • 하태원;조용구;김흥섭;이정윤;오재응
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.483-488
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    • 2003
  • Frictional heating in brakes causes thermoelastic distortion of the contacting bodies and hence affects the contact pressure distribution. The resulting thermo-mechanical coupling can cause thermoelastic instability (TEI) if the sliding speed is sufficiently high, leading to non-uniform heating called hot spots and low frequency vibration known as hot judder. The vibration of brakes to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness ${\alpha}$ slides with speed V between two half-planes which are rigid and non-conducting. The advantage of this properly simple model permits us to deduce analytically the critical conditions for the onset of instability, which is the relation between the critical speed and the growth rate of the interface temperature and pressure. Symmetrical component of pressure and temperature distribution at the layer interfaces can be more unstable than antisymmetrical component. As the thickness ${\alpha}$ reduces, the system becomes more apt to thermoelastic instability. Moreover, the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with low critical speed, it might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.

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Dependence of Sliding Friction Properties on the Angle of Laser Surface Texturing for a Grooved Crosshatch Pattern Under Grease Lubrication (그리스 윤활하에서 레이저 표면 텍스쳐링된 그루브 빗살무늬 패턴의 사잇각에 따른 미끄럼 마찰특성 평가)

  • Kong, Minseon;Chae, Younghun
    • Tribology and Lubricants
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    • v.38 no.6
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    • pp.261-266
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    • 2022
  • Notably, laser surface patterning facilitates tribological applications under lubricated sliding contacts. Consequently, a special pattern that can reduce the coefficient of friction under contact is considered necessary for improved machine efficiency. However, inappropriate pattern designs produce higher friction coefficients and cannot reduce friction. In this study, we use cast iron pins as specimens to investigate their friction and wear characteristics. Moreover, we experimentally investigate the correlation between the friction reduction effect and the design of groove crosshatch patterns fabricated with various angles and widths. We conduct a friction test using a pin-on-disc type tribometer under grease lubrication to study the friction reduction effect of the specimens, and we observe that the average coefficient of friction changes with the crosshatch angle and width. The experiment reveals that grooved crosshatch specimens with a crosshatch angle of 135°maximize friction reduction. The coefficient of friction of the groove specimens with a width of 120 ㎛ is lower than that of the specimens with a width of 200?. The friction reduction effect of the width of the groove is attributed to the density of the groove pattern. Thus, grooved crosshatch patterns can be designed to maximize friction reduction, and the friction property of a grooved crosshatch pattern is found to be related to its width and angle.

Evaluation of Wear in Inconel 600 Tools in Superplastic Forming of Ti6Al4V Sheet (Ti6Al4V 판재의 초소성 성형공정에서 Inconel 600 금형 마모 평가)

  • J. Bang;J. Song;M. Kim
    • Transactions of Materials Processing
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    • v.33 no.2
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    • pp.112-117
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    • 2024
  • In this study, the friction and wear characteristics of Inconel 600 in the superplastic forming process of Ti6Al4V were evaluated through pin-on-disc tests. To achieve an efficient and systematic experimental design, the Taguchi method was employed. The wear track of the Inconel 600 pin showed scratches in the sliding contact direction, confirming that the wear mechanism is abrasive wear. Through sensitivity analysis such as ANOVA and Main effects, it was confirmed that both normal force and sliding distance have a significant impact on the wear. Changes in sliding velocity and distance did not affect the friction coefficient, which remained relatively constant at approximately 0.380. The wear prediction model for Inconel 600 in the superplastic forming of Ti6Al4V was constructed, which can be utilized as a guideline for the prediction and management of tool wear.

Finite Element Analysis of Contact Behavior Characteristics in LPG Filling Unit Depending on Multi-ball/Cylinder Rolling Friction Motions (LPG 충전기에서 다수 볼-실린더의 구름마찰운동에 따라 달라지는 접촉거동특성에 관한 유한요소해석)

  • Kim Chung-Kyun
    • Journal of the Korean Institute of Gas
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    • v.10 no.2 s.31
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    • pp.27-32
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    • 2006
  • In this paper, the contact stress and friction force between multi-balls and rolling friction contact surfaces of two cylinders have been presented using a finite element analysis. The multi-balls for a rolling friction motion may be contacted with a reciprocating mechanism of a parallel cylinder and a misaligned cylinder in a LPG filling unit. The FEM computed results indicate that SiC ceramic and SUS 304 balls show a high contact stress and friction force on the contact spot of rolling balls. But the PEEK balls show a low contact stress and friction loss due to a high flexibility of a PEEK polymer. In this study, we may recommend SiC and SUS 304 balls for high compressive loadings between a multi-ball and a cylinder contact mechanisms and PEEK balls for a low compressive force. And the misalignment between two cylinders should be restricted for a low contact stress and friction loss, especially.

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The Study on the Wear-Corrosion Behavior of Ductile Cast Iron in the Acidic Environment (산성환경 중에서 구상흑연주철재의 마멸-부식거동에 관한 연구)

  • 임우조;박동기
    • Tribology and Lubricants
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    • v.18 no.4
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    • pp.299-304
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    • 2002
  • This paper reports the studies on the wear-corrosion behavior of ductile cast iron in the acidic environment. In atmosphere and variety of pH solution, specific wear rate and wear-corrosion characteristics of GCD 60 with various sliding speed and distance were investigated. And electrochemical polarization test of GCD 60 was examined in the environment of various pH values. The main results are as following : As the contact pressure increases, the critical velocity of specific wear rate becomes transient at low sliding speed. As pH value becomes low, wear-corrosion loss increases in the aqueous solution. As the corrosion environment is acidified, corrosion potential of GCD 60 becomes noble and corrosion current density increases.

SUPERLUBRICITY IN CARBON FILMS

  • Erdemir, Ali
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.163-164
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    • 2002
  • This paper describes a new carbon film that afford superlubricity (i.e, friction coefficients of 0.001- 0.005) and superlow wear rates (i.e., $10^{-11}-10^{-10}mm^3/N.m$) to sliding metallic and ceramic surfaces, when tested in inert test environments. The wear life of these films are more than 1000 km even under very high contact pressures (i.e., 1-3 GPa) and at a wide range of sliding velocities (i.e., 0.1 to 2 m/s). They are produced in a plasma enhanced chemical vapor deposition system at room temperature using highly hydrogenated gas discharge plasmas. Extensive research has shown that films grown in highly hydrogenated gas discharge plasmas (i.e., hydrogen-to-carbon ratio of 6 and above) provide superlow friction and wear coefficients. In full paper, specific conditions under which superlubricity can be achieved in carbon films will be discussed.and a mechanistic model will be proposed to explain the superlubricity of new carbon films.

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Robust control of a flexible manipulator with artificial pneumatic muscle actuators (유연한 공압인공근육로봇의 강건제어)

  • 박노철;박형욱;박영필;정승호
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.1704-1707
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    • 1997
  • In this work, position and vibratiion control of a two-link manipulator with one flexible link, which an unkoun but bounded payload mass and two pair of artificial muscle-type penumatic actuators, are investgated. A flexible link robot has advantages over a figid link robot in the sense that it is much safer when it cones into contact with its environment, including humans. Furthermore, for the sake of safety, it would be more desirabel if an actuator could deliver required force while maintaining proper compliance. An artificial muscle-type penumatic actuator is adequate for such cases. In this study, a controller based on singular perturbation method, adaptive and sliding mode contro, and .mu.-synthesis is developed. The effectiveness of the proposed control scheme is confirmed through simulations and experiments.

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Surgical Treatment of Transverse Mandibular Deficiency by using Split and Replantation of Corticocancellous Bone Graft (하악골 Malunion에 따른 Transverse Mandibular Deficiency에 대하여 split and Replantation of Corticocancellous Bone Graft를 이용한 외과적 교정술의 증례보고)

  • Kim, Chin-Soo
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.11 no.1
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    • pp.249-254
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    • 1989
  • Transverse mandibular deficiency is rare maxillomandibular malrelationship. Most of this malrelationship is considered to be caused by loss of bone substances. This can be corrected by subapical osteotomy, midsagittal vertical osteotomy, midline horizontal L sliding osteotomy, etc., case by case. In these cases, malrelationship after malunion of mandibular fracture, combination of vertical osteotomy and sliding autogenous cortical bone graft was used and favorable results were obtained. Advantages over previous traditional surgical methods were as follows : 1. This method provided easy access and good visibility. 2. It provided broad bone contact area, thus no other operation to obtain bone graft was needed. 3. There were little circumstances to extract teeth. 4. There were no difficulty in tongue movement after operation.

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Tribological Characteristics of MoS$_2$ Coatings in High Vacuum (고진공하에서의 $MoS_2$ 코팅의 트라이볼로지적 특성)

  • 권오원;김석삼;이상로
    • Tribology and Lubricants
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    • v.16 no.6
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    • pp.409-414
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    • 2000
  • The friction and wear behaviors of MoS$_2$ coatings were investigated by using a pin and disk type tester. The experiment was conducted by using silicon nitride as pin material and MoS$_2$-on-bearing steel as disk material under different operating conditions that include linear sliding velocities in the range of 22-66 ㎜/sec, normal loads varying from 9.8 N to 29.4 N, corresponding to maximum contact pressures of 1.18-2.83 GPa and atmospheric conditions of high vacuum, medium vacuum, ambient air. The results showed that low friction coefficient of the coating has been identified in high vacuum and that friction coefficient and wear volume increased with increasing normal load. Also at high load conditions, the friction coefficient and wear volume increased with increasing sliding velocity.

Tribological Characteristics with Purity Zirconia of Compression Ring Materials in Piston (피스톤 압축 링 재료의 지르코니아 순도에 따른 트라이볼로지 특성)

  • Oh, Seong-Mo
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.5
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    • pp.91-96
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    • 2006
  • The friction and wear properties of ceramics are very important in the applications to engineering ceramic parts such as seal rings, pump parts, automobile meter parts, and so on. In this study, the effects of each other purity on the mechanical and tribological properties of purity zirconia ceramics were investigated. Also in order to determine the effects of sliding distance, sliding speed, contact load, friction coefficient, the amount of worn out material at a certain time, and the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The results show that we obtained the good properties of friction coefficient and wear resistance at the purity 99.5% of zirconia. than this of the purity 95% were great at the wear amount of worn out material.