• Journal of Technologic Dentistry
• /
• v.42 no.3
• /
• pp.298-305
• /
• 2020

Here, we studied the sports mouse guard as an oral device system, to minimize the sports related facial and dental injuries, jawbone fracture and brain injury, and by layering the hardened sheets for improving the activity performance and stable wearing. By pressuring and layering 2 soft- and 1 hard-layers of ethylene vinyl acetate (EVA) thermoplastic materials, for a category of martial art, record sports and leports, here we introduce a methodology for thickness control of layers to protect the teeth and oral structure. A personally customized mouse guard optimized for sports by layering a mixture of soft and hardened sheets is not easily detached during the sporting activity, easy to breathe through, comforts to wear, and also improves the sporting record. A designed EVA thermoplastic material for individual sports is used as the mouth guard, which is stably attached, easily removed, and convenient for breathing through the mouth.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.1
• /
• pp.144-149
• /
• 2012

The cutting characteristics of hardened aluminum alloy A17075-T6 were investigated during turning processing. Under variation conditions of cutting speed, depth of cut, and feed rate, the characteristics of cutting force, surface roughness, and machined texture were investigated. Surface roughness became worse in proportion to the increase of the feed rate. The thickness of material alteration layer which is derived from the effect of cutting force was the biggest when feed rate 0.148mm/rev. This research confirmed that the deformed layer is dominantly dependent on the variation of feed rate.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.209-212
• /
• 2004

Recent economic development caused a vast use of mineral resources in Korea. Consequently, a supply of poor quality course aggregate (poor particle shape as well as poor gradation) in construction material become a social problem. In this study, an effect of aggregate particle shape on property of concrete was evaluated. The flat and elongation ratio of crushed aggregate was controled to 8, 15, 25, 35, and $47\%$ in order to evaluate fresh concrete behavior as well as physical properties in hardened concrete. Test result shows a poor aggregate particle shape cause a significant increase in entrapped air in fresh concrete, while no significant effect on hardened concrete property, such as strength as well as stiffness. This increase in entrapped air, however, believed to cause a significant decrease in concrete durability.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.383-384
• /
• 2006

Fe-4Ni-0.5Mo-1Cu powder was selected as raw material, pressed and sinter-hardened at $1135\;^{\circ}C$ for 30 min with rapid cooling. The density varies in the range of $7.24-7.29\;g/cm^3$. Its fatigue properties have been tested in axial loading of alternating tensile/compressive stress at R=-1 with a servo-pulse pump. The fatigue endurance limit was measured to be 260 MPa. The microstructure showed more homogeneous bainite and martensite. Fractography displayed the fatigue cracks initiated from the pore areas near the surface. A non-typical ductile fatigue striation was found. More dimples occurred on fracture surface due to the plastic deformation, which can prohibit cracking propagation and improve its fatigue properties.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.09a
• /
• pp.114-120
• /
• 2005

High speed milling experiment on the hardened mold steel (CALMAX at hardness of HRc 55) is carried out using small diameter ball endmill. Tool lift and wear characteristics under the various machining parameters are investigated. Effect of dynamic runout on the wear of the tool is also studied. For most of the cases, catastrophic chipping of tool edge is not observed and uniformly distributed wear on the flank surface of the tool is obtained. It is found that lower rate of tool wear is obtained as the cutting speed is increased. Also, high pick feed rate is found to be more favorable in terms of tool wear and material removal rate.

• Journal of the Korean Society for Heat Treatment
• /
• v.8 no.1
• /
• pp.24-31
• /
• 1995

Heat flow equation and FEM have been used to calculate the hardening section of material in laser transformation hardening. SCM440 used as the diesel engine piston of vessel has been hardened by a $CO_2$ laser with the wavelength of $10.6{\mu}m$. The specimens were inclined from 0 to 70 degree to investigate the characteristics of laser hardening. The geometrical factor of heat flow equation affects the size of hardening area. The case width decreased with increasing travel speed and the case width increased with increasing inclined angle. Maximum case depth was achieved about 1.0mm and maximum hardness of laser hardened area was of 2.8 times than that of base metal. Experimental data show good agreement with the theoretical calculations for given laser hardening conditions.

• Proceedings of the KSR Conference
• /
• 1998.11a
• /
• pp.497-504
• /
• 1998

The manufacturing processes of the head hardened rails and the principles of the heat treatment for carbon steels are introduced in this paper, To get the good wear resistance of the rail, many kinds of microstructure had been developed for the rail head hardening. One of these is the tempered martensitic structure, which is very hard but brittle because of Quenching-Tempering Process. Another is the fine pearlitic structure by Slack Quenching. Now Banitic structure steels are emerging as a potential new material to replace eutectoid pearlitic steels for rail. The main reason of this change is due to the limitaion of pearlitic microstructure with regard to mechanical properties and wear resistances of railway rails.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.998-999
• /
• 2006

A new mathematical simulation technique for physico-mechanical properties of multi-component powder materials is proposed in this paper. The main advantage of the technique is that finite elements representing different components are placed into a common mesh and may exchange their properties. The output data are properties of material after sintering. The technique allows us to investigate the influence of each component of a material on the properties and distribution of properties inside the sample. The comparative analysis of materials with different compositions is based on simulation results that are well concordant with the results of the laboratory experiments.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.4
• /
• pp.76-82
• /
• 2018

3D formed Electrical Discharge Machining (EDM) and hole EDM were conducted for die and mold manufacturing with electrodes which were made by mechanical machining and wire EDM. It is difficult to machine the hardened material after heat treatment and quenching with traditional machining. The only method of machining hardened material is die-sinking EDM. In this research, hole EDM was conducted for heat-treated cold-worked tool steel (SKD11) for use as a die material. The EDM surfaces were analyzed by pulse-on time and peak current of EDM current, according to the machining conditions of EDM. The EDM surface profiles were affected by the peak current. The contribution of each factor is peak current (91.63%) and pulse-on time (0.93%). The best surface roughness was obtained with a $130{\mu}s$ pulse-on time and a 14.2 A peak current. With uniform EDM processing, the surface deteriorated with increasing pulse-on time and peak current. The thickness of the solidified layer induced by EDM was increased as the peak current, crater shapes, and erupted shapes of EDM surfaces were increased. Therefore, microcracking gaps induced by surface tension were increased.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.350-353
• /
• 2005

It is a feature of primary importance for a backing material for circular saw blades having teeth which are tipped with cermet, that the steel has not a too high hardenability in order that the backing material shall not be completely hardened through brazing, welding or grinding, etc. in connection with the finishing operation in the manufacturing of circular saw blade. It is believed that V-(2Mo+W) added steel from this point of view had best conditions. Using V-(2Mo+W) added backing steel, the tool failure can be effectively prevented due to superior damping performance.