• Journal of Welding and Joining
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• v.17 no.5
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• pp.69-76
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• 1999

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of upset pressure on friction weldability. Under the condition of friction time 0.8sec, upset pressure 150MPa, the tensile strength and Charpy impact value of the friction welded joint were 336MPa, $400KJ/m^2$ respectively. And highest temperature of the weld measured was below $800^{circ}K$ which is very lower than melting point of Cu($1356^{circ}K$). Under the same conditions, W grains picked up in Cu matrix from Cu-W profitably affected on these mechanical fracture, and were dispersed in Cu by plastic flow during brake time.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.56-64
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• 2000

A friction force measurement system using the floating liner method was developed to study the frictional behavior of piston rings. The measurement system was carefully designed to control the effect of the piston secondary motion and the temperature of cylinder wall and oil. The friction force between the barrel shaped piston ring and the cylinder liner, was measured under the condition of flooded oil supply. The measured friction forces were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(midstroke and dead centers). The modes could be identified on the Stribeck diagram of the friction coefficients and the dimensionless number of ㎼/p, where the friction coefficients are evaluated at near the midstroke and dead centers.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.779-786
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• 2002

The Friction Brake Pad of High Speed Train is the most important parts in brake system, which is usually made of Cu-based Sintered friction material. This study has been carried out about the formulation effects of sintered friction material and made lots of sample brake pads. Then, we have done the performance test of the developed product by using full scale inertia Dynamo-meter. This performance test (braking speed 300km/h) was conducted as GEC Alsthom Standard test procedure and High Speed Brake Test (braking speed 350km/h) was done at "Poli" in Italy. The friction properties of this product was almost identical with the brake pad which is currently used to TGV. And the temperature of brake disk on braking speed 350Km/h was a little higher.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.1
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• pp.62-66
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• 2015

In this paper, a fretting testing machine is developed using ball-on-flat test apparatus. Precise micro-slip motion is produced by a linear stage. A relative displacement between a ball and a flat specimen is measured with a laser displacement sensor. Dry friction tests are conducted with AISI 52100 steel balls and cold-rolled high strength steel plates at room temperature and ambient humidity. The evolution of the kinetic friction coefficient is determined. Comparison between measured friction coefficients and those found in the literature is then carried out. Fretting tests with an electro-deposited coating are employed at an amplitude of 0.05 mm. Slip regime is identified with slip ratio. It is demonstrated that a developed testing machine allows determining the friction coefficient under fretting condition.

• Journal of Energy Engineering
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• v.7 no.2
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• pp.163-171
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• 1998

Degradation of polymer additives is enhanced at higher temperature of the test solutions. The degradation of Co-polymer solution was investigated experimentally in a closed loop at the temperature of 6$0^{\circ}C$ and 8$0^{\circ}C$ with various polymer concentrations of 100, 200, 400, 600 ppm in order to see the effect of temperature and polymer concentration with time. The degradation effect were found to be more dependent on temperature than mechanical shear. The friction factor versus Reynolds number curves show that in the range of Reynolds number number 50,000~150,000 the friction was decreased as Reynolds number increased and the friction of solution at low temperature approached to Virk's maximum drag reduction asymptote. For constant flowrates and temperatures the degradation effect was found to be less likely in higher polymer concentration. For constant flowrates and polymer concentrations the degradation rates are affected mainly by temperature. At the temperature of 8$0^{\circ}C$ and polymer concentration of 100 ppm, drag reduction effect was disappeared after 4 hours. However, this thermal degradation could be avoided with additional materials such as surfactants which are supposed to enhance the bonding forces between polymer molecules.

• Journal of the Korean Wood Science and Technology
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• v.14 no.2
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• pp.13-20
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• 1986

The effect of heat treatment on the dynamic viscoelasticity of the woods of Picea sitchensis and Paulownia coreana which have been for musical instruments was investigated. The treatment was made in a temperature range of 60-180$^{\circ}C$ for periods of 3 hours to 24 hours. The results obtained are summarized as follows: Moisture absorption decreased with increasing temperature. Dynamic Young's modulus decreased with increasing temperature and hours. Dynamic viscoelasticity decreased with increasing moisture content, but internal friction increased with increasing amount of moisture content.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.50-55
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• 1986

Characteristics of the flow and heat transfer in a channel of 37 rods are investigated numerically. The flow is taken to be a fully developed incompressible laminar flow and it has an uniform temperature profile at the inlet and flows down through the channel of constant wall temperature. A boundary-fitted coordinate system is used for the complex geometry. Calculation is initiated by calculating the developed flow profile and then proceeds to temperature development. Through the calculation the details of the flow and temperature distribution characteristics are found, and discussion is made on the mechanism of the transport phenomena in the complex geometry in terms of wall shear stress distribution, non-dimensionalized velocity, friction factor, Nusselt number distribution, Reynolds number, and porosity. Also the effects of the eccentricity in rod configuration are analyzed and its importance is emphasized.

• Coupled systems mechanics
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• v.4 no.3
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• pp.237-249
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• 2015

In the gear meshing process, gear temperature field concerns the meshing surface friction, the friction heat depends on the contact pressure, the contact pressure is affected by the elastic deformation of gears and the temperature field caused by the thermal deformation, so the temperature field, stress field and displacement field should be mutual coupling. It is necessary to consider in meshing gear pair in the operation process of thermodynamic coupling contact stress (TCCS) and thermodynamic coupling deformation (TCD), and based on thermodynamic coupling analysis (TCA) of gear teeth deformation.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.122-125
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• 2003

We investigated the effect of the abrasive and additive concentrations in Nano ceria slurry on the pad surface temperature under varying pressure through chemical mechanical polishing (CMP) test using blanket wafers. The pad surface temperature after CMP increased with the abrasive concentration and decreased with increase of the additive concentration in slurries for the constant down pressure. A possible mechanism is that the additive adsorbed on the film surface during polishing decreases the friction coefficient, hence the pad surface temperature gets lower with increase of the additive concentration. This difference of temperature was more remarkable for the higher concentration of abrasives. In addition, in-situ measurement of spindle motor was carried out during oxide and nitride polishing. The averaged motor current for oxide film was higher than that for nitride film, which means the higher friction coefficient.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.53-61
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• 1997

The performance characteristics of magnetic fluid seals are studied numerically as a function of working gap, pole width, angle of pole sharpening, and shaft speed. The temperature distribution of a magnetic fluid seal with multiple tooth is investigated as a function of the contact fraction of magnetic fluids at the periphery of pole tooth using a finite element method. The most significant design parameter of a magnetic fluid seal is the working gap between the pole pieces and the rotating shaft. The result shows that with increasing the working gap, the friction torque decreases radically. The practical working gap for the pole pieces with triangular tooth zone profile is 0.2-0.4mm. The FEM results indicate that the optimal filling of a magnetic fluid between the pole pieces and the shaft is very important due to the accumulations of nonuniform friction heating within the pole pieces, which may interfere the magnetic circuit flow.