• Tribology and Lubricants
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• v.30 no.6
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• pp.364-369
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• 2014

To assess the wear behavior of rails against subway rail car wheels, we investigate the sliding wear behavior of pins derived from two types of rails (normal rails and heat-treated rails) against a disc derived from a subway rail car wheel, using a pin-on-disc-type tribometer. We base the sliding wear test conditions on the sliding conditions for wheel flange-rail gauge corner contact. We demonstrate the remarkable transition in the wear behavior of the pins derived from the rails, from severe wear to mild wear, as a function of the sliding distance. The wear rate of the heat-treated rail material in the running-in wear region is much lower than that of the normal rail material. Furthermore, the wear rates of the pins in the running-in wear region decrease with increasing hardness and with decreasing sliding speed. However, there is little difference between the heat-treated rail pin and the normal rail pin in the wear rate in the steady-state wear region. Stricter controls on the decarburized layer beneath the surface of rails are required to reduce the wear rate in the running-in wear region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1507-1519
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• 1997

This paper aims to clarify the effects of grinding conditions on bending strength in surface grinding of various ferrites with the resin bond diamond wheel. The main conclusions obtained were as follows. At a constant material removal rate, the strength improves with increased wheel depth of cut and decreased workpiece speed. It is desirable to grind at higher peripheral wheel speed and under the critical workpiece speed presented in this paper. Grinding the ferrite of higher brittleness, the wheel depth of cut limited to hold 50% of their inherent strength becomes lower. The effect of various grinding conditions on bending strength becomes more larger in the order of Sr, Mn-Zn and Cu-Ni-Zn. When using the diamond grain of the lower toughness, the bending strength becomes higher, and the wheel wear occurs faster. Considering both bending strength and wheel wear rate, the best concentration of wheel is 100. The ground surfaces exhibit that the fracture process during grinding becomes more brittle in the order of Sr, Mn-Zn and Cu-Ni-Zn.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.43-50
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• 2000

A CBN wheel was used for the highly efficient and precision grinding of the mold material(STD11). The grinding form accuracy by a CBN wheel is very excellent due to its low wheel wear, but grinding fragments resemble fine powders rather chips. A fine powders by this fragmentation can easily get attached to the wheel surface and therefore causing a loading. In order to prevent this fragmentation phenomena, the alumina stick is use to processing. Because the dressing with alumina stick should be interrupted for a processing, the automation of the processing and high productivity was very difficult. The investigation on the effect of Ultrasonic In-Process Dressing(ULID) on the grinding characteristics focuses in this Paper. This ULID method is that ultrasonic vibration in my Position of wheel is used to remove impurities on the wheel surface. Finally, the rate of surface roughness change in grinding by the ULID method was less than grinding without ultrasonic vibration. Loading phenomena by the ULID method were more prevented than grinding without ultrasonic vibration.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.319-323
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• 2002

Recently, new polishing system which was made by magnetic intelligent compound (MAGIC) was invented and, the study is going on for practical use the analysis of factors, that is, the kind of polishing grain, composition ratio of wheel elements, machining frequency, polishing pressure, which the main influence for polishing efficiency are the first step. In this study, analyzed influence of wheel raw material composition ratio on surface roughness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.4 no.3
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• pp.12-24
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• 1995

Various surface grinding experiments using resin bonded diamond abrasive wheels are carried out for tungsten carbide materials in order to minimize the damage on the ground surface and to purse the precise dimension compared to conventional grinding machine. When grinding quality is constant, theoretical grinding effect is changed according to the speed of workpiece. Accordingly, grinding forces, which are Fn, Ft, were analyzed for the machining processes of tungsten-carbide material to obtain optimum grinding conditions. Brief investigation is carried out to decrease the dressing efficiency of resinoid bonded diamond grinding wheel to grind tungsten-carbide. Truing is also carried out to provide a desired shape on a wheel or to correct a dulled profile. High quality in dimensional accuracy and surface are often required as a structural components, therefore 3-points bending test is carried out to check machining damage on the ground surface layer, which in one of sintered brittle material. From this experimental study, some useful machining data and information to determine proper machining condition for grinding of tungsten-carbide materials are obtained.

• Journal of Institute of Convergence Technology
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• v.6 no.2
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• pp.1-7
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• 2016

The rotating electrodynamic wheels can produce three-axial forces on the conductive target. The forces are linked strongly each other, and their magnitudes depend on the rotating speed of the wheel. However, the wheels can be used effectively as an actuating principle for transfer system of conductive material. The conductive material is a pipe with a constant cross-section or a conductive plate. In this paper, a few applications using the electrodynamic wheels as transferring means are introduced including the full description of the real hardware implementation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.82-85
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• 2000

Polymeric composite insulators are used for outdoor insulation. However, our knowledge about their long-term performance in an outdoor environment is still very limited. The electrical stress caused the surface of these insulators to become degradation. In order to evaluate the tracking resistance of polymer insulators, we performed the tracking wheel test which is recommended by CEA LWIWG-01. And the flashover voltage tests were conducted for understanding electrical characteristics after tacking wheel test. Also, these insulators are studied by characterization methods such as contact angle measurement, SEM, etc.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.43-47
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• 2002

In this study, through the experimental results of grinding ratio, grinding force and surface roughness with the obtained wear amount of diamond wheel and ceramic material during the grinding process, the following conclusions could be found. In the case of $Si_3N_4$, the wear of diamond wheel is large while the grinding force is stable and the range of change in surface roughness is small. for the case of $AL_2O_3$ and $ZrO_3$, while the wear of diamond wheel is getting smaller, the grinding force is increasing but the value of surface roughness is decreasing. For grinding with the vitrified bond wheel, it seems that the self-sharpening can be found for $Si_3N_4$ and the glazing effect of the cutting edge for $AL_2O_3$ and $ZrO_3$.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.162-167
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• 2002

An automotive wheel bearing is one of the most important components to guarantee the service life of a passenger car. The endurance life of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, temperature, loading conditions, bearing geometry, internal clearance and so on. In this paper, we analyze the relation between loads and deformations of wheel bearing units. On the basis of it, we calculate the endurance life of wheel bearing units and suggest a method to determine the initial contact angle to achieve a maximum endurance life with considering stress concentration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.670-673
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• 2002

Automotive wheel bearings are one of the most important components to guarantee the service life of a passenger car. The endurance life of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, temperature, loading conditions, bearing geometry, internal clearance and so on. In this paper, we analyze the relation between loads and deformations of wheel bearing units. On the basis of it we calculate the endurance life of wheel bearing units and analyze the contribution of bearing geometric parameters on the endurance life by using Taguchi method.