• Journal of Korea Foundry Society
• /
• 제17권2호
• /
• pp.195-206
• /
• 1997

AC8A matrix composites reinforced with Ni-aluminide were fabricated by squeeze casting process, and the characteristics and nature of the growth of Ni-aluminide phases at the interface between nickel and aluminurn were investigated. In the as-cast composites, the reaction layer between Ni skeleton and aluminum matrix was found to be $NiAl_3$, regardless of the casting temperatures and the kinds of preforms. During high temperature solution treatment the $NiAl_3$ layer grew and formed new $Ni_2Al_3$ layer. Because of presence of the porosity formed by Kirkendall effect at the interface between $NiAl_3$ and aluminum matrix, the tensile strength of composites was inferior to that of AC8A matrix alloy. However, the composites exhibited superior wear resistance due to the formation Ni-aluminide intermetallic phases. Composite A, of which Ni skeleton was fully transformed into Ni-aluminide, shows better wear resistance than that of composite B which still possessed some unreacted Ni skeleton.

• Proceedings of the SAREK Conference
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.899-903
• /
• 2009

Recently, research and development of the linear compressor are being active. The reason is that the one has not only higher efficiency than reciprocating type, but also lower noise. But because the dicharge valve of linear compressor is operated in high pressure and temperature circumstance, it is important to prevent leakeage. In this paper three other plastic reinforced composite materials were used. Those are TPI, PEEK and PEK which were containing other volume and kind of carbon fibers. First, for assessing mechanical properties, we measured the hardness and the heating property of the trst sepecimen by the microvickers hardness tester and the differential scanning calorimeter respectively. Finally, through FALEX tester, we could know the characteristics of the wear proving the results of before-conducted experiments.

• Korean Journal of Human Ecology
• /
• 제24권2호
• /
• pp.285-295
• /
• 2015

To identify optimized thermal properties of mold brassiere cup for improved thermal comfort during summer, we compared the thermal resistance and the water vapor permeability of Polyurethane (PU) foam, 3D spacer fabric and the two combined materials of the PU foam and the 3D spacer fabric. Four experimental mold brassieres were made of the materials for wearing test. Six women in their twenties evaluated the wearing sensation in the hot and humid environment. The changes in microclimate temperature and humidity while wearing test brassiere cups were measured. Results indicate that thermal resistance increased as more PU foam were combined, while the water vapor permeability was higher as the content of the 3D spacer fabric increased at thickness of 18mm and over. However, in the wear test, the PU foam brassiere was the most preferred in all ambient conditions due to its soft, flexible and smooth texture, despite its high thermal resistance and low water vapor permeability. This indicates that the textures of mold foams are more dominant properties than thermal properties for mold foams in determining the wear comfort of mold brassieres.

• Analytical Science and Technology
• /
• 제6권2호
• /
• pp.181-195
• /
• 1993

The purpose of this research is to improve the density and the hardness of the SUS alloys for wear resistant materials. The dependence of the density, shrinkage ratio and hardness of various alloys on the sintering temperature and composition were examined. Alloys added with 3% Ti shows the most proper sintering properties of shrinkage ratio and the hardness which is enough to substitute for existing high price materials.

• Elastomers and Composites
• /
• 제59권1호
• /
• pp.8-16
• /
• 2024

As regulations on greenhouse gas emission have strengthened globally, the demand for improved fuel efficiency in automobiles continues to rise. In response, the tire industry is actively conducting research to improve fuel efficiency by enhancing tire performance. In this study, silica-filled epoxidized natural rubber (ENR)/butadiene rubber (BR) blend compounds were manufactured according to ENR types and silica contents, and their physical properties and vulcanizate structure were evaluated. ENR-50, which has a higher epoxide content than ENR-25, exhibited stronger filler-rubber interaction, resulting in superior abrasion resistance. In addition, because of its high glass transition temperature (T_g), the wet grip performance of ENR-50 improved, even though the rolling resistance increased. Increasing the amount of silica had little effect on the abrasion resistance due to the increase in filler-rubber interaction and decrease in toughness. In addition, ENR-50 exhibited better wet grip performance; however, the rolling resistance increased. The results indicated that truck bus radial (TBR) tire tread compounds can be designed by applying ENR-50 to improve wear resistance and wet grip performance. In addition, by applying ENR-25 and reducing the silica contents improve fuel efficiency.

• Corrosion Science and Technology
• /
• 제11권6호
• /
• pp.275-279
• /
• 2012

Ni-W alloy deposits have lately attracted the interest as an alternative surface treatment method for hard chromium electrodeposits because of higher wear resistance, hardness at high temperature, and corrosion resistance. This study deals with influences of process variables, such as electodeposition current density, plating temperature and pH, on the internal stress of Ni-W nanocrystalline deposits. The internal stress was increased with increasing the applied current density. With increasing applied current density, the grain size of the deposit decreases and concentration of hydrogen in the deposit increases. The subsequent release of the hydrogen results in shrinkage of the deposit and the introduction of tensile stress in the deposit. Consequently, for layers deposited at high current density, cracking occurs readily owing to high tensile stress value. By increasing the temperature of the electrodeposition from $60^{\circ}C$ to $80^{\circ}C$, the internal stress was decreased. It seems that an increase in the number of active ions overcoming the activation energy at elevated temperature caused a decline in the concentration polarization and surface diffusion. It decreased the level of hydrogen absorption due to the lessened hydrogen evolution reaction. Therefore, the lower level of hydrogen absorption degenerated the hydride on the surface of the electrode, resulting in the reduction of the internal stress of the deposits. By increasing the pH of the electrodeposition from 5.6 to 6.8, the internal stress in the deposits were slightly decreased. It is considered that the decrease in internal stess of deposits was due to supply of W complex compound in cathode surface, and hydrogen ion resulted from decrease of activity.

• Journal of the Korea Society of Computer and Information
• /
• 제27권12호
• /
• pp.239-249
• /
• 2022

This study attempted to categorize the motivation for participation in leisure sports and analyze the difference in consumer demand for leisure sports wear according to the type. As a result of the analysis, the functionality of the preferred material consisted of movement, comfort, and body temperature maintenance. When purchasing, the factors to consider were extracted such as basic emphasis, emphasis on flaunting, and emphasis on practicality. The improvement requirement was composed of basic function improvement and various function additional factors, and the purchase satisfaction factor was composed of three factors: brand, practicality, design, and functionality. Motives for participation in marine leisure sports were grouped into mania, leisure, and health types. As for the functionality of the preferred material, the mania type and leisure type preferred movement, comfort, and body temperature maintenance functionality over the health type. As for the factors to consider when purchasing, the mania type and leisure type had higher consideration for the factors of basic emphasis, ostentation, and practicality than the health type. In the improvement requirements, both basic function improvement and various function additions had the highest mania type and the lowest health type. In terms of purchase satisfaction factors, practicality and brand were found to have a high leisure type, and functional factors were found to have a high mania type. For the enthusiastic group, it is thought that product development should focus on functionality and additional functions, and health types should be focused on design and utilization.

• Journal of Powder Materials
• /
• 제16권1호
• /
• pp.56-62
• /
• 2009

The degree of WC decomposition and hardness of thermally sprayed WC-Co coatings are important factors determining the wear resistance of the coatings. In order to minimize the degree of decomposition and to increase hardness, the effects of processing parameters of high velocity oxyfuel(HVOF) spraying on various characteristics of nanostructured WC-12Co coating have been evaluated by an experimental design method. The HVOF sprayed WC-12Co coatings consisted of various carbide phases including WC, $W_2C$ and $W_3Co_3C$, with a much reduced carbon content. The degree of WC decomposition and decarburization was affected by changing barrel length and spray distance. The hardness of WC-Co coatings was strongly related to droplet temperature at substrate, and increased with increasing fuel addition and/or decreasing spray distance. The effective control of processing parameters was discussed in detail for manufacturing a high performance WC-Co coating.

• Journal of the Korean Society of Safety
• /
• 제23권4호
• /
• pp.25-29
• /
• 2008

Recently, new functionally graded material(FGM) that has a spatial variation in composition and properties is developed because of its good quality. This material yields the demands for resistance to corrosion and high temperature in turbine blade, wear resistance as in gears and high strength machine parts. Especially coating treatment in FGM surface brings forth a mechanical weak at the interface due to discontinuous stress resulting from a steep material change. It often, leads cracks or spallation in a coating area around an interface. The behavior of propagation cracks in FGMs was here investigated. The interface stresses were reduced because of graded material properties. Also graded material parameter with exponential equation was founded to influence the stress intensity factor. And the resistance curve with FGM coating was slightly increased.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1458-1462
• /
• 2003

High temperature and high pressure heavy water flows through the pipes in atomic power plants. The curved parts of pipes are critical parts in that they change the direction of steam flow, and these parts are especially affected by severe wear. Therefore, most pipes in atomic power plants are tested by non-destructive examination by workers who use ultrasonic sensors to measure the wall thickness of pipes. But not only are these pipes located in a very dangerous environment, but the space is also very limited. For the safety of workers, it is necessary to design a device that uses a mobile robot that can inspect curved pipes. This paper presents the design and construction of a small device that can generate the necessary contact forces between ultrasonic sensors and pipe walls in a limited space. And a mobile robot is used in place ortho worker for successful non-destructive examination.