• Tribology and Lubricants
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• 제24권3호
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• pp.133-139
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• 2008

In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. In this paper, it will be investigated the tendency of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress. Finally, the pressure distributions on the oil film of piston pin bearings will be found by two-dimensional lubrication analysis in order to help the optimum design of the bearings of piston pin. Specially, it is investigated the effects on the film pressure distribution due to the change in maximum combustion pressure.

• 소성∙가공
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• 제7권2호
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• pp.114-126
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• 1998

A plasticity theory applicable to the powdered metal compaction is briefly summarized and its varia-tional form for the finite element analysis is described. The compaction processes of axisymmetric solid cylinder are simulated. For the analysis of the friction effect on compaction process the investigations were performed for different compact geometries. Efforts are focused on the transmitted pressure through the compact and density distributions within the compacts. Numerical results show that :(1) the friction coefficient could be selected simply from the transmitted force data by the single acting compaction test and the simulated results ; and (2) density variations within the compacts rely on the compact geometry such as height to diameter ration and the frictional condition between compact and dies.

• 한국기계가공학회지
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• 제9권2호
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• pp.40-46
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• 2010

The purpose of this study is to show the friction and wear characteristics on the vapor deposited coating layers on the SCM415 steel. In this research, frictional wear characteristic of coating materials such as TiAlN+WC/C Multilayer Coating was investigated under room temperature, normal air pressure and nothing lubricating condition. Therefore this study carried out research on the friction coefficient, micro hardness(Hv), roughness, EPMA on the vapor deposited coating layers on the SCM415 steel. As the wear experimental result, the coefficient of friction decreased according to experimental load increases.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.304-310
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• 2001

Flow pulsation often causes vibration and noise in piping systems and therefore has been a troublesome concern for fluid system engineers. According to frequency increase in this paper under the influence wave form of velocity in springly flow and viscosity are drop coefficient of viscosity become increase so that impedance and resistance. The transient variations of flow rate are measured by a modified impedance tube method which is realized by virtue of the present analytical technique. At pipe line in order to eliminate vibration, confirm happened intermittently impedance characteristics. We make a test and frequency analysis and have to minimize obstructive component at hydraulic circuit.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.24-27
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• 2001

Friction between the sheet and tools is one of the important factors affecting the sheet metal forming. Therefore, the clarification of the friction is essential to improve the formability of the sheet. In order to find the effect of material property and lubricant viscosity on the frictional characteristics, tensile test, surface roughness test and friction test are performed. The results showed that friction characteristics are mainly influenced by the surface roughness and lubricant viscosity. A mathematical model of the friction is developed for calculating friction coefficient in terms of surface roughness and lubricant viscosity. The validity and accuracy of the mathematical model of the friction are verified through the experiment and FEM analysis.

• Steel and Composite Structures
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• 제2권4호
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• pp.247-258
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• 2002

The high-temperature material properties of steel are very important to the fire resistance analysis of high-strength bolt connections. This paper reports on the results of the experimental studies on the high-temperature properties of 20 MnTiB steel which is widely used in high-strength bolts, and the friction coefficient of 16Mn steel plates at elevated temperature which is a necessary parameter for bolted frictional connection analysis. The test data includes yield strength, limit strength, modulus of elasticity, elongation and expansion coefficient of 20MnTiB steel at elevated temperature, and the friction coefficients between two 16Mn steel plates under elevated temperatures and after cooling. Based on the data from the tests, the mathematical models for predicting the mechanical properties of 20MnTiB steel and friction coefficients of 16Mn steel plates have been established.

• Tribology and Lubricants
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• 제24권2호
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• pp.55-62
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• 2008

In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. In this paper, it will be investigated the tendency of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress. Finally, the pressure distributions on the oil film of piston pin bearings will be found by two-dimensional lubrication analysis in order to help the optimum design of the bearings of piston pin. Specially, it is investigated how the changes in combustion pressure at exhaust and intake stroke and the pressure-viscosity index effect on the film pressure distribution.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.417-422
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• 2000

In prestressed concrete structures, determining serviceability and safety it is important to exactly calculate effective prestress force acting on structures. for the determination of effective prestress force, friction loss of the prestressing tendon should be decided exactly, but it is very difficult to measure the exact prestress force on the site and there is no actual field data. Therefore the friction loss coefficient recommended by the specification is not verified. in this paper, the friction loss standard PSC-Beam will be investigated, and is will be found what kind of relationship between the specification and the site. The results from this study can be summarized as follows. For jacking at both ends, actual intial prestress force in the center section of PCS-Beam was about 1.61% larger than theoretical initial prestress force and for hacking at one end, actual initial prestress force was approximate 4.9% lower than theoretical initial prestress force. Thus, for the exact calculation of friction loss, friction coefficient should be modified according to jacking methods.

• 한국기계가공학회지
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• 제7권4호
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• pp.62-67
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• 2008

In this research, we developed a pilot wire-drawing machine as well as wire end-pointing roller. Using these machines, we performed a pilot wire-drawing test at different coating material and lubricant when the reduction ratio is 10 %. To inversely compute the friction coefficient between the coating layer of wire and the surface of die for a specific lubricant, we carried out a series of three dimensional finite element analysis. Results show that the drawing force is varied with the coating material of wire at the same reduction ratio and lubricant. It is noted that the frictional coefficient in drawing is dependent on the coupled property of coating material and lubricant, indicating the best coating material for a given lubricant.

• 오토저널
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• 제2권1호
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• pp.32-38
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• 1980

In the case of a automobile marking skid on road for a period of braking, in general, the automobile velocity just before rapid braking can be obtained by evaluating the coefficient of friction between tires and road. Up to now, the coefficient of friction has been derived from mean velocity measured by a time watch, but the automobile velocity obtained in this manner would be deviated from actual value considerably, due to errors arising from not only measuring time but other various factors. In this paper the presumption method of automobile velocity by accelerometer is presented so as to improve the accuracy of measurement, and to determine the velocity readily. The results obtained in this experiment show that the frictional coefficients between tires and road under the given experimental conditions are considered to take linear relation over the fixed velocity limits 30km/h to 50km/h while for the same limits of velocities the coefficients of friction by the time watch method are not valid ar low velocity range. It will be seen that the former is simple and reliable whilst the latter is cumbersome and unreliable.