• Title, Summary, Keyword: Friction Force

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A Study on the Characteristics of Stick-slip Friction in CMP (CMP에서의 스틱-슬립 마찰특성에 관한 연구)

  • Lee, Hyunseop;Park, Boumyoung;Seo, Heondeok;Park, Kihyun;Jeong, Haedo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.18 no.4
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    • pp.313-320
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    • 2005
  • Stick-slip friction is one of the material removal mechanisms in tribology. It occurs when the static friction force is larger than the dynamic friction force, and make the friction curve fluctuated. In the friction monitoring of chemical mechanical polishing(CMP), the friction force also vibrates just as stick-slip friction. In this paper, an attempt to show the similarity between stick-slip friction and the friction of CMP was conducted. The prepared hard pa(IC1000/Suba400 stacked/sup TM/) and soft pad(Suba400/sup TM/) were tested with SiO₂ slurry. The friction force was measured by piezoelectric sensor. According to this experiment, it was shown that as the head and table velocity became faster, the stick-slip time shortened because of the change of real contact area. And, the gradient of stick-slip period as a function of head and table speed in soft pad was more precipitous than that of hard one. From these results, it seems that the fluctuating friction force in CMP is stick-slip friction caused by viscoelastic behavior of the pad and the change of real contact area.

Analysis of Nano-Tribophysics (Nano-Tribophysics 해석 기술)

  • 최덕현;황운봉
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.215-218
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    • 2003
  • Nano-scale experiments for adhesion force and friction force were performed with AFM/FFM. In macro-scale, the friction coefficient is constant without relating to the change of contact area. However, many papers have indicated that in nano-scale, the friction coefficient is related to the contact area. Contact area would increase with the normal force. Therefore, in this study, we analyzed the trend of the friction coefficient of Si(100) and Mica according to the normal force and then. the contact area was calculated by JKR-theory. Results showed the friction coefficient was constant under 180 nm$^2$ contact area and over 180 nm$^2$ contact area, it was degraded. Moreover. the friction coefficient was constant according to the adhesion force.

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A Study on Frictional Characteristics and Polishing Result of SiO2 Slurry in CMP (CMP시 SiO2 슬러리의 마찰 특성과 연마결과에 관한 연구)

  • Lee Hyunseop;Park Boumyoung;Seo Heondeok;Jung Jaewoo;Jeong Sukhoon;Jeong Haedo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.7
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    • pp.983-989
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    • 2005
  • The effects of mechanical parameters on the characteristics of chemical mechanical polishing(CMP) can be directly evaluated by friction force. The piezoelectric quartz sensor for friction force measurement was installed, and friction force could be detected during CMP process. Furthermore, friction energy can be calculated by multiplying relative velocity by integration of the friction force throughout the polishing time. $SiO_2$ slurry for interlayer dielectric(ILD) CMP was used in this experiment to consider the relation of frictional characteristics and polishing results. From this experiment, it is proven that the friction energy is an essential factor of removal rate. Also, the friction force is related to removal amount per unit length(dH/ds) and friction energy has corelation to the removal rate(dH/dt) and process temporature. Moreover, within wafer non-unifornity(WIWNU) is related to coefficient of friction because of the mechanical moment equilibrium. Therefore, the prediction of polishing result would be possible by measuring friction force.

Haptic Friction Display of a Hybrid Active/Passive Force Feedback Interface

  • An, Jin-Ung;Kwon, Dong-Soo
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1673-1678
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    • 2005
  • This paper addresses both theoretical and experimental studies of the stability of haptic interfaces during the simulation of virtual Coulomb friction. The first objective of this paper is to present an analysis of how friction affects stability in terms of the describing function method and the absolute stability theory. Two different feedback methods are introduced and are used to evaluate the analysis: an active force feedback, using a motor, and a passive force feedback, using controllable brake. The second objective of this paper is to present a comparison of the theoretical and experimental results. The results indicate that the sustained oscillations due to the limit cycle occur when simulating friction with an active force feedback. In contrast, a passive force feedback can simulate virtual friction without the occurrence of instability. In conclusion, a hybrid active/passive force feedback is proposed to simulate a highly realistic friction display.

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The Characteristics of Friction in Direct Acting OHC Valve Train System (직접 구동형 OHC 밸브 트레인 시스템의 마찰 특성)

  • 한동철;조명래
    • Tribology and Lubricants
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    • v.14 no.1
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    • pp.23-27
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    • 1998
  • The characteristics of friction in direct acting OHC vane train system have been investigated by the comparison of experimental and theoretical results. A modified friction model was presented to calculate the friction force at cam/tappet contact. A simple experimental system was evaluated to measure the friction force and the camshaft driving torque. The friction force was measured by using the dynamic loadcell. Good agreement was found between theoretical and experimental results in friction force, but there was a little difference in driving torque.

Effects of Blank Holding Force on the Friction Behavior in Sheet Metal Forming (박판성형 마찰거동에 미치는 블랭크 홀딩력의 영향)

  • Shim, J.W.;Keum, Y.T.
    • Transactions of Materials Processing
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    • v.16 no.5
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    • pp.381-385
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    • 2007
  • In order to examine the effect of the blank holding force on the friction behavior in the sheet metal forming, a sheet metal friction tester is designed and manufactured, which can measure friction forces in various forming conditions such as lubrication, die roughness, drawing speed, radius of die corner, blank holding force, etc., and the friction tests are performed, in which friction coefficients in various blank holding forces and pulling speeds are calculated using Coulomb's friction law. The friction test reveals that friction coefficient decreases as the blank holding force, the drawing speed and lubricant viscosity increase together or individually.

Effects of Blank Holding Force on Friction Behavior in Sheet Metal Forming (박판성형 마찰거동에 미치는 블랭크 홀딩력의 영향)

  • Shim, J.W.;Keum, Y.T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.394-396
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    • 2007
  • In this study, in order to see effect of the blank holding force on the friction behavior in the sheet metal forming, a sheet metal friction tester is designed and manufactured, which can measure friction forces in various forming conditions, such are lubrication, die roughness, drawing speed, radius of die corner, blank holding force, etc., and performed the friction test in which friction coefficients in various blank holding forces and pulling speeds are calculated using Coulomb's friction law. The friction test reveals that friction coefficient decreases maximum 30% as the blank holding force and the drawing speed are increased to 2.5kN and 1500mm/min, respectively.

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System Development for Providing Optimal Friction Force for Sorting Machine

  • Lee, Jeong-Wook;Lee, Woon-Sung;Kim, Jung-Ha
    • 제어로봇시스템학회:학술대회논문집
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    • pp.2555-2559
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    • 2003
  • In this study, we develop an automatic sorting system, which is mostly affected by frictional forces between a veneer and friction-generating device. So we will make a suitable dynamic model and mechanism to control friction force using a AC servo-motor. We suggest Stick friction and Column friction model, which is occurred between roller and veneer and within veneers as well. A kind of sensor can get the velocity of roller and movement of roller vertical direction. We assume that the several things to simplify the complicate and difficult nonlinear friction phenomenon. And to create an optimal normal force, which can generate a suitable friction force, we control the movement of sorting roller and supporter as well. We introduce several results about a friction character and suggest the value of calibration of sorting roller movement and supporters as well.

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A Study of Tire Road Friction Estimation for Controlling Rear Wheel Driving Force of 4WD Vehicle (4WD 차량의 후륜 구동력 제어를 위한 구동시 노면마찰계수 추정에 관한 연구)

  • Park, Jae-Young;Shim, Woojin;Heo, Seung-Jin
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.5
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    • pp.512-519
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    • 2016
  • In this study, the tire road friction estimation(TRFE) algorithm for controlling the rear wheel driving force of a 4WD vehicle during acceleration is developed using a standard sensor in an ordinary 4WD passenger car and a speed sensor. The algorithm is constructed for the wheel shaft torque, longitudinal tire force, vertical tire force and maximum tire road friction estimation. The estimation results of shaft torque and tire force were validated using a torque sensor and wheel force transducer. In the algorithm, the current road friction is defined as the proportion calculated between longitudinal and vertical tire force. Slip slop methods using current road friction and slip ratio are applied to estimate the road friction coefficient. Based on this study's results, the traction performance, fuel consumption and drive shaft strength performance of a 4WD vehicle are improved by applying the tire road friction estimation algorithm.

A Novel Numerical Method for Considering Friction During Pre-stressing Construction of Cable-Supported Structures

  • Zhao, Zhongwei;Liang, Bing;Yan, Renzhang
    • International journal of steel structures
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    • v.18 no.5
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    • pp.1699-1709
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    • 2018
  • Suspen-dome structures are extensively used due to their superiority over traditional structures. The friction between cable and joints may severely influence the distribution of cable force, especially during the pre-stressing construction period. An accurate and efficient numerical method has not yet been developed that can be used for estimating the influence of friction on cable force distribution. Thus, this study proposes an efficient friction element to simulate friction between cable and joint. A flowchart for estimating the value of friction force is introduced. These novel numerical methods were adopted to estimate the influence of friction on cable force distribution. The accuracy and efficiency of these numerical methods were validated through numerical tests.