• Proceedings of the KSR Conference
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• 2004.06a
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• pp.720-725
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• 2004

We proposed new arc-type wheel profiles to improve severe flange wear of conventional wheel profile coned 1:40. We designed many candidate wheel profiles and analyzed the geometric characteristics, dynamic performance and stress at contact points to draw out the final profiles. From the analysis result, we chose two cases of profiles and applied to wheels of test train. Tests carried out in service line to analyze the dynamic performance and verify the wear reduction for two cases of profiles. Test results shows the equal level of dynamic performance and the improvement of wheel flange wear compared with the conventional wheel profile.

• Tribology and Lubricants
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• v.6 no.1
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• pp.82-88
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• 1990

In order to investigate tribological effects of coatings on different places on tool wear, commercial quality coated inserts were tested in production speed machining after the coatings on clearance or rake face of coated tools were selectively removed. The experimental results demonstrated that the primary role of coatings in tool wear was the reduction of the thermochemical adhesion between the tool material and workpiece. And the coating on rake face was observed to retard the progress of flank wear. In case of machining carbon steel, multicoated tools showed the most favorable results for considering the notch wear.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.59-64
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• 2002

Recently the applications of high speed machining are increasing due to the need for high performance and high accuracy machining and machining for difficult-to-cut material. However, the high speed machining also accompanies some problems: the product quality can be degraded due to the tool wear and the product cast can go up due to frequent tool replacements. Therefore, it is necessary to develop a technique of quantitative tool wear measurement to determine the precise timing for tool replacement. In this respect, this study suggests a reliable technique far the reduction of error components by developing a system using a CCD camera and an exclusive jig to be able to precisely measure the size of tool wear in flat end mill for high speed machining.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.369-376
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• 2003

The purpose of this work is to general approach to numerically simulating wear in rolling and sliding contact area between wheel and rail interface based on the analysis of dynamics characteristics with general MBS package. A simulation scheme is developed that calculates the wear at a detailed and various level. The estimation of material removal follows Archard's wear equation which states that the reduction of volume is linearly proportional to the sliding distance, the normal applied load and the wear coefficient and inverse proportional to hardness. The main research application is the wheel-rail contact of Korea High Speed Railway.

• Tribology and Lubricants
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• v.35 no.6
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• pp.362-368
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• 2019

In this study, mechanical and tribological properties were investigated by varying the process temperature (50, 100, 125 and 150℃) to reduce internal stress. The internal stress reduction by thermal dissociation ta-C coating film with increasing temperature is confirmed through the curvature radius of the ta-C coating according to the temperature of the SUS plate. As the coating temperature increased, the mechanical properties (hardness, modulus, toughness) deteriorated, which is in agreement with the Raman analysis results. As the temperature increased, the sp² phase ratio increased owing to the dissociation of the sp³ phase. The friction and wear properties are related to the process temperature during ta-C coating. Low friction and wear properties are observed in high hardness samples manufactured at 50℃, and wear resistance properties decreased with increasing temperature. The contact area is expected to increase owing to the decrease of hardness(72 GPa to 39 GPa) and fracture toughness with increasing temperature which accelerated wear because of the debris generated. It was confirmed that at process temperature of over than 100℃, the bond structure of the carbon film changed, and the effect of excellent internal stress was reduced. However, the wear resistance simultaneously decreased owing to the reduction in fracture toughness. Therefore, in order to increase industrial utilization, optimum temperature conditions that reduce internal stress and retain mechanical properties.

• Journal of the Korean Society for Railway
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• v.7 no.2
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• pp.130-136
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• 2004

The rolling-stocks on conventional line have suffered wheel problems due to the incompatibility between wheel and track condition. Especially, The 1:40 coned wheel profile's wear is very severe and these increase wheel maintenance cost. Thus we designed several arc-type wheel profiles coned 1:/20 to reduce the wheel flange wear and analyzed the dynamic performance of designed profiles. Tests carried out in service line to analyse the dynamic performance and verify the wear reduction for two cases of profiles. Test results shows the equal level of dynamic performance and the improvement of wheel flange wear compared with the conical wheel profile coned 1:40.

• Fashion & Textile Research Journal
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• v.15 no.4
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• pp.523-532
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• 2013

This study investigates risk reduction behavior with risk perception in outdoor wear purchase situations. Data were collected via a questionnaire from 400 consumers between the ages of 20 to 50 residing in Seoul and Kyonggi-do. Data analysis were conducted with SPSS 20 program on the reliability test, factor analysis, cluster analysis, t-test, ANOVA, and Duncan's multiple range test. Factor analyses were employed for the participation motivation of mountain climbing activities, risk reduction behavior and risk perception. Five factors were for the participation motivation of mountain climbing activities (health and fitness, external ostentation, achievement and excitement, improvement of climbing skills, and society). Five factors were for risk perception (fashionability loss and social risk, time and convenience loss, economic risk, performance risk, and psychological risk). Five factors were for the risk reduction behavior (interpersonal information sources use, marketer-dominated information sources use, professional information sources use, pre-purchase deliberation/observation/experience, and brand dependence). Three clusters were identified based on the motivation of outdoor activities (the affiliation/display, the health/internal informativeness and low motivation). The participation motivation for mountain climbing activities were varied. Manufacturers should increase efforts to develop products with good qualities at a reasonable cost as well as establish new marketing strategies since the risk of product performance and economic efficiency in the purchase of outdoor wear was a significant consumer perception.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.16-19
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• 2005

There are about 13,000 freight cars in Korea. The holding amount of the freight cars are many more than the other types of cars. But the bogie structure has many friction parts, so three are many hold-ups for the maintenance problem on the spot. As seen in Fig. 1 friction parts are organized of 30 parts in case of welding structure bogie. Especially left-right positions of the axle box have severe problems for the wear, they occurs the reduction of maintenance period, a lowering of the running safety. Generally the thickness of wear plate is 4.5mm and attached to bogie by way of welding method. At the running situation the friction occurs in wear plate each other. Namely the role of the wear plate reduce the load from the carbody. So we need the wear plate fur low-wearing, adequate friction power.

• KSTLE International Journal
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• v.1 no.1
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• pp.12-20
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• 2000

Nano-wear and friction of carbon overcoated laser-textured and mechanically-textured computer hard disk were characterised after contact start/stop (CSS) wear test. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties and friction characteristics of the coating arising from the contact start/stop wear test These techniques include: the atomic force microscopy (AFM), the continuous nano-indentation test, the nano-scratch test, the time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and the auger electron spectroscopy (AES). It was shown that the surface roughness of the laser-textured (LT) bump and mechanically textured (MT) Bone was reduced approximately am and 7nm, respectively, after the CSS wear test. The elastic modulus and hardness values increased after the CSS test, indicating straining hardening of the top coating layer, A critical load was also identified fer adhesion failure between the magnetic layer and the Ni-P layer, The TOF-SIMS analysis also revealed some reduction in the intensity of C and $C_2$$F_59$, confirming the wear of lubricant elements on the coating surface.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.3
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• pp.121-130
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• 2017

NAND flash memory has advantages of non-volatility, little power consumption and fast access time. However, it suffers from inability that does not provide to update-in-place and the erase cycle is limited. Moreover, the unit of read/write operation is a page and the unit of erase operation is a block. Therefore, erase operation is slower than other operations. The AGC, the proposed garbage collection policy focuses on not only garbage collection time reduction for real-time guarantee but also wear-leveling for a flash memory lifetime. In order to achieve above goals, we define three garbage collection operating modes: Fast Mode, Smart Mode, and Wear-leveling Mode. The proposed policy decides the garbage collection mode depending on system CPU usage rate. Fast Mode selects the dirtiest block as victim block to minimize the erase operation time. However, Smart Mode selects the victim block by reflecting the invalid page number and block erase count to minimizing the erase operation time and deviation of block erase count. Wear-leveling Mode operates similar to Smart Mode and it makes groups and relocates the pages which has the similar update time. We implemented the proposed policy and measured the performance compare with the existing policies. Simulation results show that the proposed policy performs better than Cost-benefit policy with the 55% reduction in the operation time. Also, it performs better than Greedy policy with the 87% reduction in the deviation of erase count. Most of all, the proposed policy works adaptively according to the CPU usage rate, and guarantees the real-time performance of the system.