• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.377-383
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• 2005

This paper deals with the flow characteristics of air-water two-phase flow in a vertical tube of 10mm I.D. and 600mm in length at an adiabatic condition. The obtained experimental data were covered with the liquid superficial velocity ranging from 0.095m/s to 2.56m/s. and the gas superficial velocity ranging from 0.032m/s to 21.08m/s. The effects of the gas and liquid superficial velocity on the flow pattern transitions, frictional pressure drop, and film thickness and gas-liquid interface roughness were also examined. It was found that the film thickness increased and the liquid film wave length was more longer with the liquid superficial velocity $j_L$ increasing at $j_G$ constant. It was also showed that the frictional pressure drops were experienced in three regions. namely increasing region(bubbly flow), decreasing region (Taylor bubble and slug flows) and re-increasing region (annular flow).

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.590-599
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• 2003

In this study. object transport method based on ultrasonic flexural vibration is presented. Ultrasonic vibration generates ultrasonic traveling waves on the surface of elastic medium. Objects are transported through the interaction with traveling waves propagating in medium. Two types of transport methods are studied： frictional drive and acoustic levitation. With frictional drive, objects are transported in contact with the beam in the opposite direction of wave propagation whereas with acoustic levitation, objects are acoustically levitated above the beam surface and transported in the wave propagation direction. Transport characteristics are experimentally investigated using objects of different shapes and sizes. The transition from acoustic levitation mode to frictional drive mode is also examined. and it is found to occur when the ratio of mass to area of an object exceeds the threshold ratio of mass to area. It is envisaged that this feasibility study will serve as a stepping-stone for ultrasonic vibration to become an effective industrial material handling device in the future.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.113-120
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• 1982

In the previously reported Part I, the experimental results in frictional machining that finished medium carbon steel SM 50 C under 6 kinds of liquid atmospheres by using ceramic tip as a frictional tool was described. The present study reports the experimental results that all the machining conditions are same in the Part I except tool material changed ceramics into tungsten carbide. The ceramic tool material is a stable oxide and a non-metallic material, but the tungsten carbide has the metallic characteristics that adhere to carbon steel at about 750.deg.C. The present study shows th comparison of the experimental results for the above 2 kinds of frictional tool material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.207-212
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• 2001

In this paper, dynamic stability and vibration characteristics of a flexible shoe in drum brake systems are investigated. The frictional force between the drum and the shoe is assumed as a distributed frictional force, while the shoe is modeled as an elastic beam supported by two translational springs at both ends and elastic foundations. Governing equations of motion are derived by energy expressions, and numerical results are calculated by finite element method. Through the numerical simulation, critical distributed frictional forces are calculated by changing the stiffness of two translational springs and elastic foundation parameters. It is also shown that the beam loses its stability by flutter and divergence depending on the stiffness of elastic supports and elastic foundation parameters. Finally, the time responses of the beam corresponding to their instability types are demonstrated.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.119-125
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• 2003

An experiment study on pressure drop was carried out for both an adiabatic and a diabatic two-phase flow with pure refrigerants R134a and Rl23 and their mixtures as test fluids in a uniformly heated horizontal tube. The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. The measured frictional pressure drop was compared to a few available correlations. Homogeneous model considerally underpredicted the present data for mixture as well as pure component in the entire mass velocity ranges employed in the present study, while Friedel correlation was found to satisfactorily correlate the frictional pressure drop data as compared to other correlation.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.88-93
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• 2005

Frictional heat generates when the brake shoes are in contact with wheel tread under high pressure for EMU's speed control, stopping, and deceleration. Such a frictional heat has a significant effect on the wheel tread. In order to analyze the characteristics of frictional heat and measure the amount of the generated heat, tests by using a brake dynamometer and for running vehicles are carried out. In addition, finite element analysis is performed to simulate the temperature distribution and thermal analysis of the brake shoes. Through the tests and the simulations, it is found that the problems by temperature increase at tread braking are verified.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1575-1578
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• 2005

As GA(Galvannealed sheet steel, GA) has good corrosion resistance, weldability and paintability as well as excellent stamping formability it's demand is rapidly increasing for automotive panel. But the layer of the Galvannealed sheet steel is easy to have a coating layer such as powdering and flaking in the press process because it is composed of Fe-Zn alloy. Therefore, the process condition is properly required to form the surface treated sheet steel. The frictional characteristics with dies are changed according to the annealing temperature, $505^{\circ}C,\;515^{\circ}C\;and\;540^{\circ}C$ during the process. To obtain the frictional characteristics of GA sheet steel in this study, on flat friction test is conducted. The friction coefficient is compared with the variation of pressure and velocity, viscosity of lubricant at the various galvannealed temperatures.

• Tribology and Lubricants
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• v.30 no.4
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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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1807-1818
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• 1991

The frictional characteristic of Zn-Ni electrogalvanized steel sheet was investigated by experimental procedures. To clarify the effect of surface property on the frictional characteristic of Zn-Ni coated steel sheet, Micro-hardness test, SEM analysis and X-ray diffraction analysis were carried out. Coefficients of friction for various stamping lubricant and Ni content in coated layer were measured by a draw bead friction test. The results show that frictional characteristic is very sensitive to Ni content of coated layer and depends on stamping lubricant. For Ni content less than about 11%, selection of proper lubricant is necessary to obtain low coefficient of friction in Zn-Ni coated steel sheet such as in case of cold rolled steel sheet.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.107-117
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• 2020

Open-ended steel pipe piles have outside frictional force and inside frictional resistance in which blocked soil acts on the inside of the steel pipe during installation. It is expected that the ultimate load will change depending on the inside and outside resistance. And, if the ground on which the piles were constructed is clay soil, it is predicted that it will have effect on the negative skin friction caused by the ground settlement. Therefore, in this study, the behavior according to the inside and outside resistance characteristics of steel pipe piles was analyzed numerically, and the frictional force distribution, axial load and settlements before and after the occurrence of ground settlement were calculated. As a result of the analysis, the inside frictional resistance had less influence than the outside frictional resistance. However, inside frictional resistance is considered to be one of the important factors considering the effect on the overall pile behavior, and both resistance factors need to be considered in the design process.