• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.335-340
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• 2008

Cutting performance and wear behavior were studied with the diamond micro-blade of Cu/Sn bond materials containing various amount of lubricant materials such as graphite and $MoS_2$. Measurement of instantaneous electric power consumption for cutting glass workpiece at the constant velocity was conducted and proposed as a method to assess cutting efficiency. The energy consumption of micro-blade for glass cutting decreased with the content of graphite and $MoS_2$ while wear amount of blade in volume increased with the amount of lubricant addition during the dicing test. It is because that hardness, flexural strength, and fracture toughness ($K_{IC}$) reduced with the amount of lubricant addition. Blades with $MoS_2$ additive showed higher mechanical properties than those with graphite additives when the same amount of the lubricant additive in wt.% was added. Due to the lower density of graphite than $MoS_2$, higher volume fraction of graphite could result in stronger effect on lowering electric power consumption by reducing the friction between blade and work piece however increasing wear rate due to the reduction in strength and fracture toughness. Adhesive wearing mode of micro blade could be remarkably improved by the addition of graphite as well as $MoS_2$.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.123-134
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• 2012

A typical cooling system of an engine relies on a water pump that circulates the coolant through the system. The pump is typically driven by the crankshaft through a mechanical link with engine starting. In order to reduce the friction and warm-up time of an engine, the clutch-type water pump (CWP) was applied in 2.0 liter diesel vehicle. The clutch-type water pump can force cooling water to supply into an engine by the operation of an electromagnetic clutch equipped as the inner part of pump system. The onset of CWP is decided by temperature of cooling water and engine oil. And, the control logic for an optimal operation of the clutch-type water pump was developed and applied in engine and vehicle tests. In this study, the warm-up time was measured with the conventional water pump and clutch-type water pump in engine tests. And the emission and the fuel consumption were evaluated under NEDC mode in vehicle tests. Also, tests were carried out for the various temperature conditions starting the operation of CWP. From the results of the study, the application of CWP can improve the fuel consumption and $CO_2$ reduction by about 3%.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.396-401
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• 2015

A door checker holds a car door at several opening angles and limits the maximum door opening, so that the door does not bump against to passengers. Recently, the performance of door checker becomes more important as the feeling of door opening and closing effects on the quality of a car. However, some of door checkers make squealing noise when they are used for ages, which causes consumer's complaints as well as decreasing commercial value of the product. In this study, after various experiments for the noise, we concluded that the major reasons of the noise are acceleration of wearing and loss of lubricant due to impurities in working parts. Therefore, we developed a new mechanism of door checker which can resolve the major reasons of the noise. The developed mechanism is effective to prevent inflow of impurities and loss of lubricant by locating working parts in the case. We also proved that the developed mechanism does not make any noise after the test of 50,000 times of operations.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.259-266
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• 2020

Magnetic gears have the same characteristics as mechanical gears, and each rotor does not come in contact, which is advantageous over mechanical gears in friction noise, heat generation, and maintenance. In addition, when the rotor using the coil-winding is applied, it is possible to control the output of the gear as well as to cut off its own drive in the emergency situation and to change its gear ratio. So the application of the magnetic gear is infinite. However, when the coil-winding rotor is used, cogging torque due to the attraction force between the permanent magnet and the iron core appears, which leads to an increase in the torque ripple component causing the rotor vibration. Therefore, in this paper, various shapes of the coil-winding rotor are analyzed to reduce the torque ripple of the rotor, and the optimum shape for reducing the torque ripple of the magnetic gear is presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1630-1637
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• 2008

Jeju-do is a island formed by the volcanic activity and has more than 360 volcanic cones distributed widely along the long axis of the elliptically shaped island. The volcanic cones consist mainly of scoria, so called "Song-I" in the local dialect. In this study the chemical and soil mechanical properties of scoria being very different from those of the inland were investigated with the various tests. In the sieve-passing test the particle size of scoria had more than 10 of uniformity coefficient and gradation coefficient of 1 ~ 3, showing relatively homogenous distribution. Based on the uniformity classification, scoria was assorted into GW. In the large scale direct shear tested for measuring the mechanical strength of scoria the internal friction angle of red scoria was $37^{\circ}$ and that of black scoria was $36^{\circ}$. This indicated that there was no difference in the mechanical strength between two types of scoria. On the other hand, red and black scoria had $1.24{\times}10^{-3}$ to $3.55{\times}10^{-2}$ cm/sec of k values for the static water level permeability, thus being classified into a coarse or fine sand as compared with that representing the saturated soil. They also had 1.411 to $1.477\;g/cm^3$ of notably low $r_{dmax}$ values for the compaction test as compared with common soil, which was considered to be due to their low specific gravity and high porosity. In conclusion, the soil mechanic properties of scoria obtained from this study are thought to be very helpful for reducing lots of trial and error happening in the civil engineering construction.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.18-23
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• 2016

Self-assembly of organic molecules is formed spontaneously on surfaces by electrostatic interaction with substrate. This research has shown that the self-assembly improves safety and handling tractability of high-energetic materials (HEMs). According to the recent study, control of the specific crystal size for reducing the internal defects is mightily important, because the internal defects are a factor in unstability of HEMs. In turn, we performed self-assembly of organic molecules and HEMs by using nano-sized HEMs, which were produced by drowing-out or milling/crystallization. Surface modification efficiency was decided by size distribution, zeta-potential, friction sensitivity and electrostatic charge.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.223-227
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• 2014

The brake pad is one of the basic brake elements of a railway vehicle. It accomplishes braking action by friction between a pad and a brake disc. Because the brake pad must endure specified high pressure, the compressive strength is managed as the main performance factor. The standards for measuring the compressive strength of brake pads are KRS, KRCS, and KRT. These standards specify the size of the test piece for measuring compressive strength as $20mm{\times}10mm{\times}15mm$ ($W{\times}D{\times}H$). To reduce the uncertainty of the compressive strength, factors of uncertainty were analyzed. The results show that changing the dimensions of the cross section was useful to reduce the uncertainty. The uncertainty due to the new cross-sectional dimension shows the effectiveness of reducing uncertainty.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.47-59
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• 2008

Application of mechanically stabilized earth wall (MSEW) abutment has been rapidly increasing in United States of America, Pennsylvania since 2002. MSEW is effective for reducing construction cost and period compared to general concrete reinforced wall. In the paper, theoretical background and conventional criterion of MSEW abutment that is widely used abroad are analyzed. Based on the results, application of suitable MSEW abutment to domestic bridge type is examined. For the application of MSEW abutment in Korea, load interacting with upper shoe in domestic bridge types and structural analyses of beam seat and pile are investigated. As a result, all applications are possible except for PSC BOX Bridge that has heavy self-weight of girder. Through two and three dimensional numerical analyses, horizontal behaviour mechanisms between pile and MSEW were analyzed and field tests are also carried out for seven piles behind earth walls. From results of field tests, it is confirmed that an angle of internal friction of backfill material needs to be greater than 34 degree to use H-Pile as foundation of MSEW.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.911-915
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• 2017

Recently, there has been an increasing interest in the non-contact power transmission method of magnetic gears. Since there is no mechanical contact, noise caused by friction can be reduced, and even if a sudden large force is applied, the impact of the gear is close to zero. Further, since the power is transmitted by the magnetic flux, it has high reliability. However, there is a problem that a loss due to a magnetic field due to use of a magnetic flux. The loss caused by the magnetic field of the magnetic gear is a joule loss called eddy current loss. In addition, the eddy current loss in the magnetic gear largely occurs in the permanent magnet, but it is a fatal loss to the permanent magnet which is vulnerable to heat. Particularly, magnetic gears requiring high torque density use NdFeB series permanent magnets, and this permanent magnets have a characteristic in which the magnetic force decreases as temperature increases. Therefore, in this paper, the eddy current loss of the permanent magnet according to the permanent magnet attaching method is analyzed in order to reduce the eddy current loss of the permanent magnet. We have proposed a structure that can reduce the eddy current loss through the analysis and show the effect of reducing the loss of the proposed structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.411-417
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• 2013

The moment responses of electric pole foundations for a railroad were investigated using real-scale load tests. Large overturning moments were applied to two square rigid piles with a 1.1 m width and a 2.2 m embedded depth. Two different installation methods-with and without a form-were applied to evaluate the influence of the form work on the moment capacities of the foundations. The reduction of ground strength caused by the excavation without a form is more pronounce than the decrease of frictional strength due to the smooth concrete surface with a form. From the test results, it is found that the current design method which applies a proportional coefficient to consider the effect of a form work is not appropriate. When the normal and frictional stressed is considered separately, the effect of a form work can be estimated reasonably by reducing the friction angle between soil and foundation by 20%.