• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.226-234
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• 2002

A systematic study of the role of transfer films on friction properties was performed with various temperatures in the brake system. An NAO friction material specimens containing 9 ingredients were tested using a pad-on-disk type friction tester A new method of measuring the transfer film thickness was developed by considering the electrical resistance of the transfer film using a 4-point probe technique. The properties of transfer film such as surface morphology and film distribution vaied according to the relative amount of graphite and magnesium oxide. By using SEM, it was possible to obtain information about the chemical composition of the transfer film. Results showed that there detected a threshold value of the relative amount of a two active materials to maintain a certiain thickness of a transfer film. Results also showed that formation of friction layer generated on the friction surface was strongly affected by chemical action of two ingredients during sliding due to chemical reaction of solid lubricants at different interface temperature. The results suggested that no apparent relationship between transfer film thickness and the average friction coefficient was founded and friction characteristics were affected more by the property of the solid lubricant and abrasive in the material.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.59-63
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• 2011

Friction damping is one of the attractive vibration control technique for space structures due to its simplicity and large damping capacity. However, passive approaches for friction damping have a limitation because energy is no longer dissipated at sticking. In order to overcome this problem, semi-active control methods to adjust normal force at frictional interface have been studied in previous researches. In this paper, two semi-active friction control method is compared by simulating SDOF model of truss structure. The first approach is on-off control to maximize rate of energy dissipation, whereas the second concept is variable friction force control to minimize amplitude ratio for each half period. The maximum friction force, control variable in on-off control method, is obtained to minimize 1% settling time, and is different from optimal friction force in passive control. Simulation results show that performance of on-off control is better than that of variable friction force control in terms of settling time and controlled friction force.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.273-279
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• 2000

Until recently performance requirements for automatic transmission fluids have continued to change to reflect the design changes of automatic transmission. The major purpose for these design changes is to improve the fuel economy and easy driving. To meet recent performance requirements fur automatic transmission the needs for special base oils Bike API Group III and IV base oils become larger. In this paper to evaluate the effects of base oils on performance of automatic transmission fluids formulated with API Group I,II,III and IV and Dexron III and Hereon Type additive package, Brookfield viscosity, oxidation test, SAE No.2 friction test and seal compatibility test were examined. From the test we knew that the use of Croup III and IV base oils in ATF has several benefits in low temperature viscosity, oxidation stability and SAE No.2 friction characteristics.

• Journal of Biosystems Engineering
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• 제30권4호
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• pp.195-201
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• 2005

The output of Stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, several kinds of combined wire screen meshes were used. The results are summarized as follows; The packed meshes with high mesh no. in the side of heater part of regenerator showed effective than the packed meshes with low mesh no. in the side of cooler part of regenerator. The temperature difference and pressure drop of the regenerator were not made by the specific surface area of wire screen meshes but by the minimum free-flow area to the total frontal area. Among the No. 150 single screen meshes, 200-60 combined meshes, the 200-150-100 combined meshes showed the highest in effectiveness.

• 한국해양공학회지
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• 제13권2호통권32호
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• pp.74-82
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• 1999

Nowadays, the crank shaft motor vehicle has become essential as the important component. The machining precision was asked for manufacturing the shaft. They could be unstable in the quality by the conventional are welding. Both in-process quailty control and high reliability of the weld are the major concerns in applying friction wlding to the economical and qualified mass-production. No reliable nondestructive monitoring method is avaliable at present to determine the real-time evaluation of automatic production quality control for bar-to-bar friction welding of the crank shaft of O.D 24mm for motor vehicle. This paper, so that, presents the experimental examinations and statistical quantitative analysis of the correlation between the cumulative counts of acoustic emission(AE) during plastic deformation periods of the welding and the tensile strength and other properties of the bar-to-bar welded joints of O.D. 24mm shaft as well as the various welding variables, as a new approach which attempts finally to develop real-time quality monitoring system for friction welding, resulting in practical possiblility of real-time quality control more than 100% joint efficiency showing good weld with no micro structural defects.

• Tribology and Lubricants
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• 제28권3호
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• pp.107-111
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• 2012

In this study, application feasibility of Magneto-rheological elastomer to friction control is investigated to identify the reciprocating friction and wear performance in applied magnetic field. Friction and wear of MR elastomerare measured by reciprocating tester by controlling the magnetic field. In the case of applied magnetic field, the coefficient of friction increases as both load and velocity increase. For the case of no magnetic field, the value of coefficient of friction hardly changes during the test. The amount of destruction is measured through cross section images of MR elastomer after tests. The depths of destruction are compared for MR elastomer with or without magnetic field. The results show that the depth of destruction of MR elastomer with magnetic field is deeper than without magnetic field. Based on the obtained results, optimal braking and driving performance can be achieved by controlling the coefficient of friction of MR elastomer, which can be applied to various industrial applications such as driving systems of automobiles and robots.

• Tribology and Lubricants
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• 제30권4호
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• pp.240-245
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• 2014

Low alloy heat resistant brake disk and sintered brake pad are applied to mechanical brake system for the speed-up of urban rapid transit. In this research, we analyzed how the frictional characteristics between brake disk and pad are influenced by the disk mass. At a high disk mass, the friction stability was the lower value as a result of the lack of tribofilm formation at the disk surface. Wear rates of friction materials showed the higher value at a low disk mass and wear rates of 10 mm and 15 mm showed the similar level. Average friction coefficient was the lower value at the 10 mm disk thickness and range of variation of average friction coefficient was also the smaller value at the 10 mm disk thickness. However, there were no significant changes in the friction coefficients under any of test conditions. Surface roughness of a disk showed the highest value at the 5 mm disk and surface roughnesses of 10 mm and 15 mm showed the similar level. As a result, friction characteristics of disk mass influenced the friction stability, as well as the wear rate of friction pad and disk, but not the friction coefficient.

• Journal of Biosystems Engineering
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• 제1권1호
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• pp.49-54
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• 1976

No reliable basic data were available on the kinetic friction coefficients between grains and frictional surfaces being used in grain handling equipments in Korea. In order to determine appropriate kinetic friction coefficient between three grains (Tongil, Jinheung, barley) and two surfaces at four levels of moisture content of grain, the laboratory tests using the newly designed experimental apparatus and strain gage measuring system were carried out, and the relationship among factors that affect kinetic friction coefficients of grains were analyzed. The results of this study are summarized as follows ; 1. Kinetic friction coefficient of samples being tested was dependent on surfaces and moisture content of grains . The ranges of them were 0.369-0.512 for Tongil variety , 0.347-0.469 for Jinheung variety, and 0.360-0.502 for barley, respectively. 2. There was a little difference of kinetic friction coefficients between two varieties of rice at the same testing conditions. Because the interaction had been large among treatments , each value of kinetic friction coefficient determined in this study should be used only for the corresponding conditions in this study . 3. Kinetic friction coefficients in creased linearly with increase in moisture content of grains and their regression equations were shown in Table.4. 4. Kinetic friction coefficients on a PVC surfaces was shown a little lower values than on the steel surfaces at various moisture levels, but especially in Jinheung and barley, a big difference was shown.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.44-49
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• 2001

Tube hydroforming is a relatively new technology in comparison with conventional stamping process. Thus, there is no large knowledge base to assist the product and process designers, especially from the friction point of view. This paper covers the topic f friction and lubrication with regard to tube hydroforming. It presents the fact that frictional characteristic can have an effect on the formability of specific components. It also presents the results of test about several lubricants which are used in practical press process. The presented concept describes the equipment which is required to determine the friction coefficient.

• 한국의류산업학회지
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• 제10권1호
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• pp.101-105
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• 2008

This study was concerned with the influence of reaction conditions on the surface friction properties of Syrene-Butadiene Rubber(SBR) sheet when it was chlorinated by chemical treatment method using the sodium hypochlorite and sulfuric acid. The results of this study were as follows. SEM photographs of chlorinated SBR surface showed uneven etching caused by the chlorination. In the FTIR spectra, the intensity of C=C peak of SBR was decreased with increasing the concentration of sodium hypochlorite. Otherwise there was no trace of C=C peak in spectrum of SBR treated with 5 wt% NaOCl with pH 0.1 for 90 seconds. EDX spectra showed that relative content of chlorine of SBR was increased with increasing the amount of sodium hypochlorite, and also affected with pH condition of acid solution. Friction angle and friction coefficient of SBR were influenced with concentration of sodium hypochlorite, but were not with pH condition of acid solution.