• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.50-55
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• 2003

Tribological testing of DLC films was conducted using a rotating type ball on a disk friction tester in a dry chamber. This study made use of four kinds of mating balls that were made with stainless steel but subjected to diverse annealing conditions in order to achieve different levels of hardness. In all load conditions using martensite mating balls, the test results demonstrated that the friction coefficient was lower when the mating materials were harder. The high friction coefficient found in soft martensite balls appeared to be caused by the larger contact areas. The wear track on the mating balls indicated that a certain amount of material transfer occurs from the DLC film to the mating ball during the high friction process. Raman Spectra analysis showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

• Tribology and Lubricants
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• v.9 no.2
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• pp.56-62
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• 1993

Al-Pb-Cu and Al-Si-Pb-Cu bearing alloys were produced by forced-stirring method and water-cooled copper mold casting to investigate the effect of the precipitation hardening on the wear properties. Sliding of produced alloy pin against a steel disc were performed under various applied loads. Lowering the wear rate and material transfer phenomena were explained by the strengthening of $\theta'$ precipitates on AI matrix. The transmission electron microscope observation reveals the role of the precipitates in the alloys with Cu. The movement of dislocations was hindered by precipitates which resulted in the reduction of plastic deformation at the worn surfaces.

• KSTLE International Journal
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• v.3 no.1
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• pp.38-42
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• 2002

Diamond-like Carbon(DLC) films were deposited on Si wafers by an RF-plasma-assisted CVD using CH$_4$gas. Tribological tests were conducted with the use of a rotating type ball on a disk friction tester with dry air. This study made use of four kinds of mating balls that were made with stainless steel but subjected to different annealing conditions in order to achieve different levels of hardness. In all load conditions, testing results demonstrated that the harder the mating materials, the lower the friction coefficient was. The friction coefficients were fecund to be lower with austenite mating balls than with fully annealed martensite balls. Conversely, the high friction coefficient found in soft martensite balls appeared to be caused by the larger contact area between the DLC film and the ball. The wear tracks on DLC films and mating balls could prove that effect. Measuring the wear track of both DLC films and mating balls revealed a similar tendency compared to the results of friction coefficients. The wear rate of austenite balls was also less than that of fully annealed martensite balls. Friction eoefficients decrease when applied leads exceed critical amount. The wear track on mating balls showed that a certain amount of material transfer occurs from the DLC film to the mating ball during a high friction process. Raman Spectra analysis Showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

• Journal of the Korea Fashion and Costume Design Association
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• v.20 no.2
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• pp.47-62
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• 2018

This study examined recycled fashion design utilizing natural images for application to recent trends. This study is significant in that it presents the possibility of the development of recycled women's wear design by reflecting the characteristics and expressions of natural images and using denim material, which is the most common clothing material for everyday life. The results of this study are summarized as follows. First, five types of women's clothing was produced, pursuing a natural design with a soft and feminine silhouette. Second, the colors used were blue and white, which could represent nature. Third, as for materials, this study used clothing that was to be thrown away: four pairs of denim pants and two denim dresses. This study chose denim cloth, with its great value for reuse, because of the characteristics of the strong and durable fiber, because everyone has more than one article of clothing made from denim and because it can be easily sourced. Fourth, for textile motifs, this study expressed a peaceful natural scenery with tropical animals and plants. In addition, this study further emphasized natural images using transfer media printing. This study has significance in that it presented the possibility of recycled fashion design and expanded the range of utilization using transfer media printing, a dyeing treatment to reduce the environmental burden.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.50-56
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• 2008

The tubes in heat exchanger are typically made of copper alloy, stainless steel, carbon steel, titanium alloy material. Type-439 ferritic stainless steel is ferromagnetic material, and furnish higher heat transfer rates than austenitic stainless steels and higher resistance to corrosion-induced flaws. Ferritic stainless steel can be found in low-pressure(LP) feedwater heaters and moisture separator reheaters(MSRs) in turbine system. LP feedwater heaters generally utilize thin wall Type-439 stainless steel tubing, whereas MSRs typically employ a heavier wall tubing with integral fins. Service-induced damage can occur on the O.D(outside diameter) surface of Type-439 ferritic stainless steel tubing which is employed for MSRs tubing, and the most typical damage mechanism is vibration-induced tube-to-TSP(tube support plate) wear and fatigue cracking. The wear has been reported that occurs mainly on the OD surface. Accordingly, in this study, we have evaluated the flaw sizing capability of magnetic saturation eddy current technique using magnetic saturation probe and flawed specimen.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.406-413
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• 2000

The friction and wear behaviors of Magnetron Sputtered MoS$_2$films were investigated by using a pin on disk type tester which was designed and manufactured for this experiment. The experiment was conducted by using silicon nitride (Si$_3$N$_4$) as a pin material and Magnetron Sputtered MoS$_2$on bearing steel (STB2) as a disk material, under operating conditions that include different surface roughness (Polishing specimen, Grinding specimen)(2types), linear sliding velocities in the range of 22, 44, 66mm/sec (3types), normal loads vary from 9.8N, 19.6N, 29.4N(3types), corresponding to contact pressures of 1.9∼2.7GPa and atmospheric conditions of high vacuum( 1.3${\times}$10$\^$-4/Pa), medium vacuum( 1.3${\times}$10$\^$-l/Pa), ambient air(10$\^$5/Pa)(3types). We investigated fracture mechanism in magnetron sputtered MoS$_2$films with Magnetron Sputtering method in each experiment.

• Textile Coloration and Finishing
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• v.30 no.4
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• pp.227-236
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• 2018

As consciousness of safety becomes an important social issue, the demand for protective clothing is increasing. Conventional flame-retardant cotton working wear has low durability, and working wear with m-aramid fibers are stiff, heavy, less permeable, and expensive. In this study, recycled m-aramid and cotton have been blended to produce woven fabric of different compositions to enhance high performance and comfort to solve aforementioned problems. The fabrics were analyzed according to constituents and various structural factors. Mechanical properties were measured using KES-FB system. The measured thermal properties are TGA, $Q_{max}$, TPP and RPP. Fabric with polyurethane yarn covered by m-aramid/cotton spun yarn is observed to have good wearability. The fabric of open end spun yarn showed more stiffness than that of ring spun yarn. The sample with the high count of yarn has more smooth surface. In addition, high m-aramid content fabric is considered to have relatively high stiffness when using as clothing. In TGA the fabric with higher m-aramid content showed more stable decomposition behavior. The fabric having rough surface showed lower heat transfer properties in $Q_{max}$. The influence of the fabric thickness was important in convection and radiant heat test.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.76-83
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• 1993

The vibration characteristics of radial tire are studied. In order to obtain theoretical natural frequency and mode shape, the plane vibration of a tire is modeled to that of circular beam. By using the Tielking method based on Hamilton's principle, theoretical results are determined by considering tension force due to tire inflation pressure, rotational velocity and tangential, radial stiffness. Modal parameters varying the inflation pressure are determined experimentally by using the transfer function method. Results show that material property and wear are parameter for shifting of natural frequency and damping.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.100-108
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• 2004

Contamination of environment induces the shortage of drinkables. In this trend, the leakage of water that occurs by breakage or erosion of rubber valve seats is serious problem. Rubber is apt to cause breakage between two materials when they contact with each other. The possible way to avoid leakage of water by damage and breakdown of rubber is to replace that with metal. Because of this reason, nowadays, rubber is being substituted with metal as valve seat materials for water works. In tribology, a severe from of wear is characterized by local, macroscopic material transfer, removal, or formation of surface protrusions when two solid surfaces experience relative sliding under load. One of the major problems in sliding of metals is galling due to bad surface quality. Experimentally, there are various elements which influence on incipient galling, such as hardness, surface roughness, temperature, load, velocity and external environments. This paper is aimed at verifying the galling tendencies according to hardness, surface roughness, load and velocity and showing how much effect the factors have on the galling tendencies.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.37-46
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• 2015

In this paper, the heat transfer characteristics of PCB (Printed Circuit Board) with cabon CCL (Copper Claded Layer) were studied through experiments and numerical analysis to compare of PCBs with conventional the FR-4 core and heavy copper cores. For study, samples are producted with HDI (High Density Interconnection) PCB of mobile phone with variations of thickness of core materials and grades of carbon material to evaluate heat transfer characteristics respectively. From this research results, heat transfer characteristics of the carbon core was rather low than heavy copper, but better than FR-4 core. In addition, even though the carbon and heavy copper core contributed on the heat transfer characteristics as their thickness increases, FR-4 cores disturbed heat transfer characteristics as it's thickness increases. Therefore, carbon core is recommendable to improve the heat transfer characteristics of the PCB because heavy copper core has much disadvantages such as increasing of wear of drill, the weight of PCB, and manufacturing cost by additional insulation materials for electrical insulation.