• Title/Summary/Keyword: Friction Coefficient

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Analysis of Friction Coefficient Dependent on Variation of Steel Grade and Reduction Ratio in High Temperature Rolling Process (고온압연공정에서 강종 및 감면율 변화에 따른 마찰계수 변화 분석)

  • Her, J.;Lee, H.J.;Na, D.H.;Lee, Y.
    • Transactions of Materials Processing
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    • v.18 no.5
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    • pp.410-415
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    • 2009
  • Experimental and numerical studies were performed to examine the effect of material temperature and reduction ratio on friction coefficient during hot flat rolling. We carried out a single pass pilot hot flat rolling test at the temperatures range of $900{\sim}1200^{\circ}C$ and measured the spread of deformed material while reduction ratio varied from 20% to 40%. Materials used in this study were a high carbon steel and two alloy steels. The dimension of specimen used in hot rolling experiment was $50mm{\times}50mm{\times}300mm$. We performed a series of finite element simulation of the hot rolling process to compute the friction coefficient change in terms of steel grade and reduction ratio. Results showed that temperature dependency of friction coefficient is not noteworthy but the effect of reduction ratio on friction coefficient is quite large. For high carbon steel, friction coefficient at reduction ratio of 30% is lower than that at that of 20%. Meanwhile friction coefficient at reduction ratio of 40% was one and half times large compared with that at that of 20%. The effect of steel grade on friction coefficient was significant when reduction ration was large, e.g., 40%.

Frictional behaviour of epoxy reinforced copper wires composites

  • Ahmed, Rehab I.;Moustafa, Moustafa M.;Talaat, Ashraf M.;Ali, Waheed Y.
    • Advances in materials Research
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    • v.4 no.3
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    • pp.165-178
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    • 2015
  • Friction coefficient of epoxy metal matrix composites were investigated. The main objective was to increase the friction coefficient through rubber sole sliding against the epoxy floor coating providing appropriate level of resistance. This was to avoid the excessive movement and slip accidents. Epoxy metal matrix composites were reinforced by different copper wire diameters. The epoxy metal matrix composites were experimentally conducted at different conditions namely dry, water and detergent wetted sliding, were the friction coefficient increased as the number of wires increased. When the wires were closer to the sliding surface, the friction coefficient was found to increase. The friction coefficient was found to increase with the increase of the copper wire diameter in epoxy metal matrix composites. This behavior was attributed to the fact that as the diameter and the number of wires increased, the intensity of the electric field, generated from electric static charge increased causing an adhesion increase between the two sliding surfaces. At water wetted sliding conditions, the effect of changing number of wires on friction coefficient was less than the effect of wire diameter. The presence of water and detergent on the sliding surfaces decreased friction coefficient compared to the dry sliding. When the surfaces were detergent wetted, the friction coefficient values were found to be lower than that observed when sliding in water or dry condition.

Estimation of the Maximum Friction Coefficient of the Rough Terrain to Control the Mobile Robots (주행로봇 제어를 위한 험지의 최대마찰계수 추정)

  • Kang, Hyun-Suk;Kwak, Yoon-Keun;Choi, Hyun-Do;Jeong, Hae-Kwan;Kim, Soo-Hyun
    • Journal of Institute of Control, Robotics and Systems
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    • v.14 no.10
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    • pp.1062-1072
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    • 2008
  • When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the traversabilities, wheel-terrain maximum friction coefficient can indicate the index to control wheel-terrain traction force or whether mobile robots to go or not. This paper proposes estimating wheel-terrain maximum friction coefficient. The existing method to estimate the maximum friction coefficient is limited in flat terrain or relatively easy driving knowing wheel absolute velocity. But this algorithm is applicable in rough terrain where a lot of slip occurred not knowing wheel absolute velocity. This algorithm applies the tire-friction model to each wheel to express the behavior of wheel friction and classifies slip-friction characteristic into 3 major cases. In each case, the specific algorithm to estimate the maximum friction coefficient is applied. To test the proposed algorithm's feasibility, test bed(ROBHAZ-6WHEEL) simulations are performed. And then the experiment to estimate the maximum friction coefficient of the test bed is performed. To compare the estimated value with the real, we measure the real maximum friction coefficient. As a result of the experiment, the proposed algorithm has high accuracy in estimating the maximum friction coefficient.

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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AEBS Algorithm with Tire-Road Friction Coefficient Estimation (타이어-노면 마찰계수 추정을 이용한 AEBS 알고리즘)

  • Han, Seungjae;Lee, Taeyoung;Yi, Kyongsu
    • Journal of Auto-vehicle Safety Association
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    • v.5 no.2
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    • pp.17-23
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    • 2013
  • This paper describes an algorithm for Advanced Emergency Braking(AEB) with tire-road friction coefficient estimation. The AEB is a system to avoid a collision or mitigate a collision impact by decelerating the car automatically when forward collision is imminent. Typical AEB system is operated by Time-to-collision(TTC), which considers only relative velocity and clearance from control vehicle to preceding vehicle. AEB operation by TTC has a limit that tire-road friction coefficient is not considered. In this paper, Tire-road friction coefficient is also considered to achieve more safe operation of AEB. Interacting Multiple Model method(IMM) is used for Tire-road friction coefficient estimation. The AEB algorithm consists of friction coefficient estimator and upper level controller and lower level controller. The numerical simulation has been conducted to demonstrate the control performance of the proposed AEB algorithm. The simulation study has been conducted with a closed-loop driver-controller-vehicle system using using MATLAB-Simulink software and CarSim Vehicle model.

Computation of High Temperature Friction Coefficient of SCM435 Steel (SCM435 강의 고온마찰계수 계산)

  • Sung, J.U.;Cho, S.H.;Lee, H.J.;Lee, Y.
    • Transactions of Materials Processing
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    • v.20 no.3
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    • pp.243-249
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    • 2011
  • In this study, an approach designed to compute high temperature friction coefficients for SCM 435 steel through a pilot hot rolling test and a finite element analysis, is proposed. Single pass pilot hot flat rolling tests with reduction ratios varying from 20 to 40% were carried out at temperatures ranging from 900 to $1200^{\circ}C$. In the proposed approach, the friction coefficient is calculated by comparing the measured strip spread and the roll force with the simulation results. This study showed that the temperature and reduction ratio had a significant influence on the friction coefficient. As both material temperature and reduction ratio become higher, the friction coefficient increases monotonically. This finding is not in agreement with the Ekelund model, which is widely used in the analysis of the hot rolling process. In the present work, the friction coefficient at a reduction ratio of 40% was found to be 1.2 times greater than that at a reduction of 30%. This higher friction coefficient means that an increment of the roll thrust force is expected at the next stand. Therefore, a roll pass designer must understand this phenomenon in order to adjust the reduction ratio at the stands while keeping the driving power, the roll housing structure and the work roll strength within the allowable range.

An Experimental Study on The Friction Coefficient of Rubbers for Clutch Master Cylinder Cup-Seals (클러치 마스터실린더 컵-시일 고무의 마찰계수 실험 연구)

  • 이재천;임문혁;이병수;장지현;정용승;허만대;최병기
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.5
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    • pp.112-118
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    • 2003
  • The friction coefficients of the rubber for clutch master cylinder were experimentally measured in this study. The cylindrical rubber samples for primary cup-seal and secondary cup-seal were tested against the aluminum or the steel plates of master cylinder housing under the various conditions of brake oil temperatures and normal loads. Dry sliding friction coefficients were also measured under various load conditions. The test revealed following results. First, the friction coefficient under fluid lubrication condition in general decreases, as the oil temperature or normal load increases. Second, the steel plate of low surface roughness yielded comparatively low friction coefficient on the range of 0.30∼0.67. On the other hand, the aluminum plate of high surface roughness yielded high friction coefficient on the range of 0.31∼1.15. Third, the friction coefficient of dry surface contact decreases as the normal load increases. This is contrary to the general principle of friction coefficient between metal plates.

Analysis of the Static Friction Coefficient of Contacting Rough Surfaces in Miniature Systems (거친 면 접촉의 정적 마찰계수 해석)

  • 김태종
    • Tribology and Lubricants
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    • v.19 no.4
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    • pp.230-236
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    • 2003
  • In applications such as MEMS and NEMS devices, the adhesion force and contact load may be of the same order of magnitude and the static friction coefficient can be very large. Such large coefficient may result in unacceptable and possibly catastrophic adhesion, stiction, friction and wear. To obtain the static friction coefficient of contacting real surfaces without the assumption of an empirical coefficient value, numerical simulations of the contact load, tangential force, and adhesion force are preformed. The surfaces in dry contact are statistically modeled by a collection of spherical asperities with Gaussian height distribution. The asperity micro-contact model utilized in calculation (the ZMC model), considers the transition from elastic deformation to fully plastic flow of the contacting asperity. The force approach of the modified DMT model using the Lennard-Jones attractive potential is applied to characterize the intermolecular forces. The effect of the surface topography on the static friction coefficient is investigated for cases rough, intermediate, smooth, and very smooth, respectively. Results of the static friction coefficient versus the external force are presented for a wide range of plasticity index and surface energy, respectively. Compared with those obtained by the GW and CEB models, the ZMC model is more complete in calculating the static friction coefficient of rough surfaces.

Variation of Friction Coefficient of Airport Runway Surface by Rubber Deposits (고무 퇴적물에 의한 공항 활주로 표면 마찰계수 변화)

  • Cheon, Sung-Han;Lim, Jin-Sun;Park, Joo-Young;Jeong, Jin-Hoon
    • International Journal of Highway Engineering
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    • v.12 no.3
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    • pp.131-137
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    • 2010
  • In this paper, overseas criteria and research results were reviewed to develop a rational criterion proper to domestic airport runways on measurement of friction coefficient and removal of rubber deposit. The friction coefficients of the runways of the Incheon International Airport were measured by the ASFT(Airport Surface Friction Tester) from August 2007 to July 2009 and the data at intensively landed points were analyzed. Variation of the friction coefficient due to accumulation and removal of tire rubber was analyzed and seasonal influence on the variation were investigated by pavement types. The friction coefficient steadily decreased over a long term despite periodical removal of the rubber deposits. The variation of the friction coefficient in summer was larger than other seasons and asphalt pavement was more sensitive to the seasonal influence than concrete pavement. The friction coefficient of the asphalt pavement with macro texture was even larger than that of early age concrete pavement with micro texture. The variation of the friction coefficient of the asphalt pavement due to the deposit and removal of the tire rubber was also larger than that of the concrete pavement.

Predicting Flow Resistance Coefficients in Water Supply Mains (주변환경을 고려한 상수관망의 관 마찰손실계수 산정)

  • 손광익
    • Water for future
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    • v.29 no.4
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    • pp.223-231
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    • 1996
  • For the most efficient operation of water mains, 124 head losses in domestic water supply steel mains were measured to provide the values of friction coefficient and the variable affecting the deterioration rate of Hazen Williams' and Darcy-Weisbach's friction coefficient. The experimental results show that pipe age is governing the friction coefficient of large mains (Diameter > 1100 mm). On the other hands, pipe age and pipe diameter are affecting the variation of carrying capacity for small mains (Diameter < 1100 mm). The friction coefficient of water mains in foreign countries is higher than that in Korea by about 5 to 10 in Hazen Williams' C value. The growing rate of roughness height of domestic water main is about 0.41 mm/year which is higher than the average of United States of America. So further study is required to find out what causes the serious deterioration rate.

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