• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.94-101
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• 2009

The physical properties of artificial aggregates made from clay and inorganic wastes with poor plasticity depends largely on forming method. The artificial aggregates composing of coal fly ash, stone sludge and clay were fabricated using 4 different forming methods and those physical properties were comparatively analyzed. The surface of aggregates made through the extrusion forming process was dense and smooth but was rough for the aggregates obtained by crushing a tile-shaped green body. The aggregates made by pelletizing process had a weak green strength and bumpy surface. The shell generated at surface during a high temperature sintering process induced the most aggregates to be bloated due to a dense shell. But the aggregates made through pelletizing process with dense surface layer showed no significant change in bulk density with sintering temperatures. The water absorption of aggregates decreased with sintering temperature, and that of pelletized specimen was standing $1.8{\sim}2.2$ times higher than that of made by other forming methods. It is concluded that the aggregates having various properties could be fabricated from one batch by using different forming methods.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.523-527
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• 2008

In this study, mechanical properties of Alloy 718 welded after forgings for jet propulsion component was investigated. Hot-forged and machined work-pieces($230mm\times70mm\times15mm$) which have different grain sizes are welded by electron beam welding technique. After welding, the components were solution heat-treated and aged. Samples were sectioned to analyze the microstructural evolution and formation of micro-crack. It was found that HAZ grain boundary liquation crack generally initiates in the coarse grains rather than the fine grains. Needle-like phases with high Nb contents were found at the outer part near the base metal. Vickers hardness and tensile tests were carried out at room temperature and at $649^{\circ}C$. The tensile properties of electron beam welding specimens exhibited around 100MPa and 10% decrease in strength and elongation, respectively.

• Journal of Korean Dental Science
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• v.8 no.1
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• pp.28-35
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• 2015

Purpose: To investigate the influence of crown margin design on the stress distribution and to localize critical sites in maxillary canine under functional loading by using three dimensional finite element analysis. Materials and Methods: The bite force of 100 N, 150 N, and 200 N was applied with an angulation of $45^{\circ}$ to the longitudinal axis of tooth. Six models were restored with IPS e.max (Ivoclar Vivadent, Schaan, Liechtenstein) with a different margin design. With lingual ledge and various thicknesses, three different core ceramics were designed in each model. Result: In the core ceramic, the maximum tensile stresses were found at the labiocervical region. In the veneering ceramic the maximum tensile stresses were found at the area where the force was applied in all models. Conclusion: Shoulder and chamfer margin types are acceptable for all-ceramic rehabilitations. A ledge on the core ceramic at cervical region may affect the strength of all-ceramic crowns.

• Journal of the Korean Ceramic Society
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• v.25 no.4
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• pp.364-372
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• 1988

The mechanical properties and microstructure of ceramics of the system Al2O3-ZrO2-Y2O3 sintered at 1$650^{\circ}C$ for 2h after powder preparation by the precipitation method from Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were investigated. The Al2O3-ZrO2-Y2O3 ceramics sintered at 1$650^{\circ}C$ for 2h after mixing alpha-Al2O3 and ZrO2-Y2O3 powders, both were separately precipitated and calcined, were found to have the relative density higher than 97.5% so that the strengthening and toughening mechanisms could be explained mainly as the stress-induced phase transformation. On the other hand, the sintered bodies prepared by co-precipitating the three starting materials were measured to have the relative density lower than 85% so that the degradation of strength were observed above 15 vol% ZrO2 contents due to the high porosity by which the effect of stress-induced phase transformation was assumed to be depressed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.7-13
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• 2015

The production processes were reviewed through the injection analysis of the shift lever as a core component of an auto lever installed in the automatic transmission of cars. The injection analysis was carried out for the shift lever and rod among the components in a shift lever module. The shift lever and rod are designed for injection molding with the insertion of a tube, a pin cable plate, and a steel rod for securing the strength of the product. The charging time, failure of injection molding, weld line, air trap, and deformation were reviewed according to this insert. Analyses on various gate positions were carried out for reviewing the cultivation and deformation of fiber around major components, such as the generation section of manipulation feeling and assembly section, so that optimal gate conditions might be reviewed and reflected in the mold design. Finally, we plan to compare the analysis results with the production of trial products.

• Design & Manufacturing
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• v.6 no.1
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• pp.39-44
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• 2012

Hot tool steel, in general, has not been used as a material in hot forging. However such a hot tool steel is recently applied to forging materials by recent forging technology. DH32 is known as a kind of hot tool steels, which is developed for characteristics of excellent strength and toughness in high temperature. Feasibility of DH32 to hot forging material has been researched to develop the hot forging technology of a plunger used for a large-sized marine fuel pump. Hot compression experimental works were performed to investigate the hot strain characteristic of DH32 and with the experimental results FE simulations were also conducted for the design of forging processes and preform. It is found out through the hot compression experimental works that DH32 has a hot brittleness at more than $1150^{\circ}C$.

• Transactions of Materials Processing
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• v.22 no.1
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• pp.30-35
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• 2013

In this study, springback amounts of an S-rail are quantitatively compared according to the hardening model using a finite element simulation for the stamping process with high strength steels. For comparison of the hardening models, two types of hardening models were investigated. The two models were isotropic hardening and kinematic hardening. For the analysis with kinematic hardening, the Yoshida-Uemori model was selected. Five kinds of springback modes were measured at designated sections and a comparison was made between the experiment and the analyses with two types of hardening models. The analysis results show that the springback in the flange and the wall curl are predicted more accurately with a kinematic hardening model.

• Composites Research
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• v.18 no.6
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• pp.34-39
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• 2005

In this study, we analyzed the relation between physical/mechanical properties and ballistic properties for several engineering ceramics that were expected to use as armor material. After physical/mechanical measurement, we measured ballistic properties about KE(Kinetic Energy, L/D=10.7, tungsten heavy alloy) and HEAT(High Explosive Anti-Tank, K215) projectiles. Increasing Young's modulus/density, hardness/density and flexural strength/density ratios, ballistic properties were generally increased. Especially it appeared that the ballistic property about KE projectile was lineally increased, as HEL/density ratio increased.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.3122-3122
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• 2001

Documented quality control plays a vital role I the production of technical “Depth filter” sheets used in industries such as Beverage and pharmaceutical. Depth filter sheets which can be up to several millimeters thick are stacker in plate and frame filter systems. They are the core of stainless steel filter systems which can be up to several meters high. FT-NIR Spectroscopy has many potential applications in the whole production line of filter sheets. Raw materials such as different types of cellulose pads, white powdery fillers (e.g. Kieelgur, Perlite) or liquid chemicals such as wet-strength agents we, with the help of NIR, easy to identify. NIR can also determine physical parameters such as particle size, essential for the filtration behavior. FT-NIR can be used for the quality parameters of the final product. Moisture and permeability can be determined, and with the help of the speed of this NIR method it is possible to correct possible faults quickly in the production process. Waste production can be minimized which is good for both the product profitability and the environment. Further tests have shown that it is also possible to use NIR on-line in the production area, to check the concentrations and the homogeneity of the paper suspension consisting of cellulose fibres, fillers and additives.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.458-461
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• 2004

The column for Steel Framed Reinforced Concrete Structure (SFRCS) and the column for Reinforced Concrete Structure (RCS) could be the most common building structure. The increasing of the need for massive space hasaffected the size of building components for supporting the massive structure. However, the changing of components size makes inefficient space of building. Hence. to meet the need for acquiring efficient space comparing the budget and cost the new structure method, Concrete Filled Tube Steel (CFT), was developed. CFT is the structure for which steel tube instead of other materials such as wood for holding concrete is used. The most benefit of this one is to help in reducing the size of the building components and local buckling because of tube steel holding concrete. For this reason, this research will examine the probability of applying CFT on construction sites by using the concrete $(800kg/cm^2)$ especially for CFT through the data from the real size mock-up.