• Title, Summary, Keyword: Friction coefficient measurements

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A Study on the Application of Runway Friction Measurements (활주로 마찰계수 측정 및 적용에 관한 연구)

  • Noh, Kun-Soo
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.24 no.3
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    • pp.62-68
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    • 2016
  • According to the accident/incident reports of aircraft runway overruns and excursions, it generally shows runway friction reduction and aircraft braking capability deterioration are the basic causes due to adverse weather. Although surface of paved runway gets wet, it also should give good friction capability. If runway surface is worn due to long time usage and friction capability is reduced due to rubber accumulation or weather conditions(snow, rain, ice etc.), airport authorities should rapidly measure friction coefficient and give them to relevant persons through aeronautical information system and support safe takeoff and landing. Operation wise, these information of friction coefficient reduction should be lead to aircraft performance adjustments, but the data from manufacturer(performance manual) are airplane braking coefficient and the data from airport authorities are vehicle measured braking coefficient. But these two data are considered as the same meaning although the definite relationship between them is not clarified yet. So I am trying to search for the technical background of these two data and suggest reasonable method to use them efficiently.

Design of an Haptic Tactile Interface (HTI) with Friction Coefficient Measurements

  • Winter, Christophe;Perriard, Yves
    • Journal of international Conference on Electrical Machines and Systems
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    • v.2 no.4
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    • pp.436-440
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    • 2013
  • An haptic tactile interface (HTI) is presented with its modeling. Its design is dedicated to perform friction coefficient measurement to characterize reachable feelings with that kind of interface. Friction measurements are presented and discussed.

Friction correction for model ship resistance and propulsion tests in ice at NRC's OCRE-RC

  • Lau, Michael
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.3
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    • pp.413-420
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    • 2018
  • This paper documents the result of a preliminary analysis on the influence of hull-ice friction coefficient on model resistance and power predictions and their correlation to full-scale measurements. The study is based on previous model-scale/full-scale correlations performed on the National Research Council - Ocean, Coastal, and River Engineering Research Center's (NRC/OCRE-RC) model test data. There are two objectives for the current study: (1) to validate NRC/OCRE-RC's modeling standards in regarding to its practice of specifying a CFC (Correlation Friction Coefficient) of 0.05 for all its ship models; and (2) to develop a correction methodology for its resistance and propulsion predictions when the model is prepared with an ice friction coefficient slightly deviated from the CFC of 0.05. The mean CFC of 0.056 and 0.050 for perfect correlation as computed from the resistance and power analysis, respectively, have justified NRC/OCRE-RC's selection of 0.05 for the CFC of all its models. Furthermore, a procedure for minor friction corrections is developed.

A study on the frictional characteristics of wet-clutch friction materials in accordance with compositions (습식클러치용 마찰재의 조성별 마찰특성에 관한 연구)

  • 강전익;한홍구;권오관
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.4
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    • pp.56-65
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    • 1990
  • Wet-friction materials have been widely used for clutches and brakes of automotives over past several decades. In order to enhance its performance, its friction behaviour should be fully understood. It is, however, still not at hand and therefore an attempt was made to have some more understanding of friction behaviour of wet-friction materials. Measurements of coefficient of friction were made with the variation of lubricants, lub. temperature, sliding velocity, and contact pressure. In addition, the effects of both the viscosity of lubricants and the porosity of materials on the coefficient of friction were also investigated. It can be concluded that the coefficient of friction is decreased as the concentrations of the resin and inorganic fillers are increased, and it tends to decrease with the increase in the lubricant temperature and sliding velocity.

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The Evaluation for Slip Risk of Various Hospital's zones (병원 내 다양한 구역의 미끄럼 위험성 평가 연구)

  • Kang, Hyun-Su;Park, Peom
    • Journal of the Korea Safety Management & Science
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    • v.18 no.3
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    • pp.81-89
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    • 2016
  • Floor slipperiness is a leading cause in slip and fall accidents which are a major source of occupational injuries in Korea. Researchers have estimated the slip and fall related accidents rank number one or two in number of the injured. The objectives of this study were to find the field contamination effect and improvement countermeasure. Slipping and falling are common accidents in large public facilities, especially facility which vulnerable adults generally use as like hospital. So, we measured the coefficient of friction of several floors on the floor in hospital, under dry and wet using BOT-3000. The results of the coefficient of friction measurements showed that floor type and surface conditions were all significant factors affecting the coefficient of friction. The most surprising finding of this study was that there were significant friction improvement when the floors were properly cleaned with cleaning equipments.

Modeling of the friction in the tool-workpiece system in diamond burnishing process

  • Maximov, J.T.;Anchev, A.P.;Duncheva, G.V.
    • Coupled systems mechanics
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    • v.4 no.4
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    • pp.279-295
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    • 2015
  • The article presents a theoretical-experimental approach developed for modeling the coefficient of sliding friction in the dynamic system tool-workpiece in slide diamond burnishing of low-alloy unhardened steels. The experimental setup, implemented on conventional lathe, includes a specially designed device, with a straight cantilever beam as body. The beam is simultaneously loaded by bending (from transverse slide friction force) and compression (from longitudinal burnishing force), which is a reason for geometrical nonlinearity. A method, based on the idea of separation of the variables (time and metric) before establishing the differential equation of motion, has been applied for dynamic modeling of the beam elastic curve. Between the longitudinal (burnishing force) and transverse (slide friction force) forces exists a correlation defined by Coulomb's law of sliding friction. On this basis, an analytical relationship between the beam deflection and the sought friction coefficient has been obtained. In order to measure the deflection of the beam, strain gauges connected in a "full bridge" type of circuit are used. A flexible adhesive is selected, which provides an opportunity for dynamic measurements through the constructed measuring system. The signal is proportional to the beam deflection and is fed to the analog input of USB DAQ board, from where the signal enters in a purposely created virtual instrument which is developed by means of Labview. The basic characteristic of the virtual instrument is the ability to record and visualize in a real time the measured deflection. The signal sampling frequency is chosen in accordance with Nyquist-Shannon sampling theorem. In order to obtain a regression model of the friction coefficient with the participation of the diamond burnishing process parameters, an experimental design with 55 experimental points is synthesized. A regression analysis and analysis of variance have been carried out. The influence of the factors on the friction coefficient is established using sections of the hyper-surface of the friction coefficient model with the hyper-planes.

Estimation of Tire-Road Friction Coefficient using Observers (관측기를 이용한 노면과 타이어 간의 마찰계수 추정)

  • 정태영;이경수;송철기
    • Journal of Institute of Control, Robotics and Systems
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    • v.4 no.6
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    • pp.722-728
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    • 1998
  • In this paper real-time estimation methods for identifying the tire-road friction coefficient are presented. Taking advantage of the Magic Formula Tire Model, the similarity technique and the specific model for the vehicle dynamics, a reduced order observer/filtered-regressor-based method is proposed. The Proposed method is evaluated on simulations of a full-vehicle model with an eight state nonlinear vehicle/transmission model and nonlinear suspension model. It has been shown through simulations that it is possible to estimate the tire-road friction from measurements of engine rpm, transmission output speed and wheel speeds using the proposed identification method. The proposed method can be used as a useful option as a part of vehicle collision warning/avoidance systems and will be useful in the implementation of a warning algorithm since the tire-road friction can be estimated only using RPM sensors.

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Development of Forward Slip Model in Hot Strip Mill (강판의 열간압연 선진율 예측모델의 개발)

  • 문영훈;천명식;이준정
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.7
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    • pp.1597-1603
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    • 1995
  • A prediction model on forward slip has been developed for presetting rolling speed of each finish mill stand in the continuous hot strip roduction. Those factors such as neutral point, friction coefficient, volume fractions undergoing width spread, shape of deformation zone at each side of entry and delivery of the rolls were taken into account. To reduce the speed unbalance between adjacent stands a refining method of adjusting friction coefficient has also been developed. On-line application of the model showed a good agreement in rolling speeds between the predictions and the actual measurements, and gave an outstanding improvement in the travelling stability of strip passing through the finishing mill train.

On the Instantaneous and Average Piston Friction of Swash Plate Type Hydraulic Axial Piston Machines

  • Jeong, Heon-Sul;Kim, Hyoung-Eui
    • Journal of Mechanical Science and Technology
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    • v.18 no.10
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    • pp.1700-1711
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    • 2004
  • Piston friction is one of the important but complicated sources of energy loss of a hydraulic axial piston machine. In this paper, two formulas are derived for estimating instantaneous piston friction force and average piston friction moment loss. The derived formula can be applicable for piston guides with or without bushing as well as for axial piston machines of motoring and pumping operations. Through the formula derivation, a typical curve shape of friction force found from several experimental measurements during one revolution of a machine is clearly explained in this paper that it is mainly due to the equivalent friction coefficient dependent on its angular position. Stribeck curve effect can easily be incorporated into the formula by replacing outer and inner friction coefficients at both edges of a piston with the coefficient given by Manring (1999) considering mixed/boundary lubrication effects. Novel feature of the derived formula is that it is represented only by physical dimensions of a machine, hence it allows to estimate the piston friction force and loss moment of a machine without hardworking experimental test.

Back-calculation of Skin Friction Coefficient ($\alpha$, $\beta$) on a Single Pile by Long-Tenn Field Monitoring (현장 계측 사례를 통한 단독 말뚝의 주면마찰계수($\alpha$, $\beta$ 계수) 역산정)

  • Ko, Jun-Young;Kim, Young-Ho;Choi, Yong-Kyu;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.26 no.11
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    • pp.99-110
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    • 2010
  • A fundamental study of the pile-soil systems subjected to negative skin friction in soft soil was conducted using the long-term field measurements. The emphasis was on the identification of the magnitude and distribution of skin frictions ($\alpha$ and $\beta$ coefficients) in bitumen coated and uncoated piles. A skin friction coefficient of instrumented piles is back-calculated by varying degrees of consolidation (U) of surrounding soils. It is shown that the bitumen coated pile is capable of reducing the negative skin friction up to almost 50 to 90 percents. Through comparisons with the existing friction coefficient values ($\alpha$ and $\beta$ coefficients), the calculated coefficients are within the appropriate range, and thus we can suggest basic materials to estimate the realistic pile behavior in the short-term and long-term analysis.