• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.51-58
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• 2006

The necessities for heightening fuel efficiency as well as lightweight design, lead to an increase of the use of aluminum alloys in the automobile industry. Extruded aluminum profile channels are used widely for the design of frame parts as lightweight assemblies, especially if a high stiffness is needed. While many applications can be realized with forming of hollow square-sectioned extruded profiles such as a stretch bending and a hydro-forming, some applications demand the use of a press bending which can be hardly found in the previous study. In this study, by introducing the use of a press bending into car sub-frames, the demands for higher accuracy as well as higher flexible method than the conventional methods will be satisfied. With respect to the design of sub-frames, the process planning was performed from the shape of a sub-frame product. The designed processes were analyzed by the commercial FEM code, DEFORM-3D. Forming dies for the each process were designed and prototypes of sub-frames were manufactured by the verified farming process. In addition, some of the important features of design parameters in the press bending were reviewed.

• Transactions of Materials Processing
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• v.22 no.6
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• pp.317-322
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• 2013

A radio frequency(R/F) switch connector is widely used in wireless devices such as mobile phone and navigator to check defects of the circuit board of product. The R/F switch connector shell plays a role in protecting the switch connector. Previously, this part was machined using a turning, which is time-consuming and has poor material utilization. Furthermore, the workpiece material of brass containing lead that has excellent machinability has environmentally regulated during recent years. The purpose of the current study was to develop the connector shell by forming through progressive dies including embossing, burring and forging process in order to achieve higher productivity and dimensional accuracy without tool failure. To accomplish this objective, a strip layout was designed and finite element (FE) analysis was performed for each step in the process. Try-out for the connector shell was conducted using progressive die design based on FE-analysis results. Dimensional accuracy of developed part was investigated by scanning electron microscopy. The result of the investigation for the dimensions of the formed connector shell showed that the required dimensional accuracy was satisfied. Moreover, productivity using the progressive die increased four times compared to previous machining process.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.45-53
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• 2009

Die casting process of Mg alloys for high temperature applications was studied to produce an engine oil pan. The aim of this paper is to evaluate die casting processes of the Aluminium oil pan and in parallel to apply new Mg alloy for die casting the oil pan. Temperature distributions of the die and flow pattern of the alloys in cavity were simulated to diecast a new Mg alloy by the flow simulation software. Dies have to be modified according to material characteristics because melting temperature and heat capacity are different. We changed the shape and position of runner, gate, vent hole and overflow by the simulation results. After several trial and error, oil pans of AE44 and MRI153M Mg alloys are produced successfully without defect. Sleeve filling ratio, cavity filling time and shot speed of die casting machine are important parameter to minimize the defect for die casting Magnesium alloy.

• Journal of Powder Materials
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• v.7 no.1
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• pp.42-49
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• 2000

Densificationbehavior of conventional austenitic stainless steel powder compacts was studied by comparing the relative density of sintered compact(Ds)with that of green compacts(Dg)prepared with various catbon contents and P/M process. Dg of 304and 316 powders by warm compaction under pressure of 686 MPa at heating temperature of powder(553K) and dies (573K) were 80% and 81%, repectively, whichwere 2 and 3% higher than those of conventional green compacts at the same pressure. Ds of 304 compacts sintered at 1373K in H2 gas has the same value of 84% max. regardless of compacting temperature, and Ds of 316 compacts at the same sintering conditions were 80% by conventional compaction and 83% by warm compaction. Oxygen contents of 304 and 316 sintered compacts were increased 1.43∼2.94% and 0.010∼0.921% higher than those of raw powders and warm green compacts, respectively. In other case, Ds of 316 compacts sintered at 1573K in vacuum had the same value of 86%max. And Ds of 316 compacts at the same sintering conditions were 83% and 86% by conventional and warm compaction, respectively. Oxygen contents of 304 sintered compacts were 0.321% and 0.360%, and in case of 316, they were 0.419% and 0.182% by the respective compating condition. With carbon additions in the range 0.1∼0.6% Ds increased to the extent of 86∼89% in 304 sintered compacts, and to 82∼84% and 85∼87% in 316 according to different two compacting peocesses compared to those of sintered compacts without carbon addition.

• Design & Manufacturing
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• v.12 no.1
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• pp.18-25
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• 2018

Both injection and injection molding dies have evolved into advanced technology. Product quality is also evolving day after day. Therefore, the conditions of the injection mold and the injection conditions are becoming important. In order to improve the quality of the product, the Hardware part of the mold has developed as an advanced technology, and the Software part has also developed with advanced technology. This study deals with the cooling part, which is part of the hardware. In addition to fluid cooling, which is commonly used in the industry, by using gas cooling identify the phenomena that appear on the surface of the product and the critical point strain of the product to find the optimal cooling. Electronic parts and automobile parts whose surface condition is important, the cooling process is important to such a degree that they are divided with good products and defective products according to the cooling process at the time of injection. By controlling this important cooling and reducing the injection time with additional cooling, the product quality can be increased to the highest production efficiency. In addition, high efficiency can be achieved without additional investment costs. This study was conducted to apply these various advantages in the field.

• Laser Solutions
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• v.15 no.2
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• pp.15-20
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• 2012

A novel joining technology was developed to compensate the camber in polymers. The preheating laser beam circulates on the joining location and the accumulated heat serves to increase the flexibility of neighboring polymers. The temperature rises up to the glass transient temperature of the polymers and continually loading spring force closes the gap of camber. The irradiated laser was 808nm central wavelength and the power varied between 2Watt and 5Watt. The laps were adjusted between 3 and 10 and the optimum process parameters were 3Watt and 5 laps for the specific application. An FEM analysis was introduced to understand the mechanism of joining by the transient temperature distribution on the polymers. Thermocouples experiments were also tried to correlate the numerical analysis results and it showed the trend of heat accumulation in experiments.

• Restorative Dentistry and Endodontics
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• v.8 no.1
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• pp.97-106
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• 1982

The purpose of this study was to evaluate the effect of different polishing procedures on the surfaces of composite resins. Two-paste type comosite restorative resin (Hipol) was selected for this study. 70 cavities prepared on the plaster-stone dies, 6mm in diameter and 2mm in depth, was filled with composite resin according to the manufacturer's specifications and by polymerizing against mylar strips. The polymerized composite resin specimens were polished (surface finished) by using 6 polishing devices; white stones, diamond finishing points, 12-fluted carbide finishing burs, green stones, sand paper disks, and Quasite rubber disk after polished with sand paper disks and green stones. A profilometer (Bendix type) was used to record in microinches the surface roughness of each surface finished composite resin specimens. The results were as follows. 1. The best finished surface that can be obtained is a surface formed by the mylar matrix strip 2. The white stones produced the smoothest surface in the experimental group. 3. The green stones produced the roughest surface in the experimental group. 4. It was proved that the gradual use of finishing instruments from a rough one to fine ones reduced the surface roughness.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.1
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• pp.127-133
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• 1999

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the occlusal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination ($4^{\circ},\;8^{\circ},\;12^{\circ}$) of the upper first premolar. After 10 metal dies were made fir each group, the IPS Empress ceramic crowns were fabricated and each crown was cemented on each metal die with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results were : 1. The fracture strength of the ceramic crown with 2.5mm depth and $12^{\circ}$ inclination was the highest (630N). Crowns of 1.5mm depth and $4^{\circ}$ inclination had the lowest strength(378N). There were no significant differences of the fracture strength by axial inclination in same occlusal depth group. 2. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the margin, irrespective of occlusal depth.

• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.113-123
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• 1985

The purpose of this study was to evaluate the marginal fitness of collarless metal-ceramic crown formed with direct lift technique using wax compared with metal-ceramic crown with metal butt margin. Twenty crowns, ten were collarless metal-ceramic crowns and ten were metal-ceramic crowns with metal butt margins, were made and cemented on epoxy resin dies, and their marginal openings were measured on scanning electron microphotographic prints at x200 magnification. The results were as follows; 1. In the case of collarless metal-ceramic crowns, the mean marginal opeining was $43.78{\pm}17.67{\mu}m$, the mean maximum marginal opening was $52.81{\pm}19.81{\mu}m$, and the mean minimum marginal opening was $34.99{\pm}16.58{\mu}m$. 2. In the case of metal-ceramic crowns with metal butt margins, the mean marginal opening was $47.62{\pm}25.55{\mu}m$, the mean maximum marginal opening was $61.90{\pm}24.39{\mu}m$, and the mean minimum marginal opening was $34.86{\pm}24.92{\mu}m$. 3. There was no significant difference between two types of crowns at the 99% confidence level. 4. The marginal fitness of collarless metal-ceramic crown formed with direct lift technique using wax was clinically acceptable.

• Koreanishche Zeitschrift fur Deutsche Sprachwissenschaft
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• v.7
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• pp.105-125
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• 2003

Personal- und Reflexivpronomen stehen in einer komplementaren Beziehung zueinander. Die vorliegende Arbeit zeigt, welches von beiden Pronomen verschiedenen AcI-Konstruktionen jeweils richtig ist Vor allem stelle ich hier die These auf, dass Grammatik in erster Linie ein Regelwerk ist und dass dernzufolge $S\"{a}tze$ mit gleicher Struktur immer einheitlich und konsistent mit denselben Regeln $erkl\"{a}rt$ werden sollten: (1) a. Der Gefangen $l\"{a}sst$ den Polizisten auf ${\ast}sich_i/ihn_i$ achten. b. $Hans_i{\;}l\"{a}sst$ Maria zu $sich_i/{\ast}ihm_i$ kommen. (2) a. $Peter_i$ sieht Hans von ${\ast}sich_i/ihm_i$ betrogen. b. $Hans_i{\;}f\"{u}hlt$ die Freundin von $sich_i/{\ast}ihm_i$ weggezogen. Bei diesen Beispielen liegt der Verteilungsunterschied der Pronomina nicht an Grammatikregeln sondern am individuellen Sprachgebrauch. Ferner wird hier darauf hingewiesen, dass die AcI-Verben mit Ausnahme des Verbs lassen a1s 3-wertige Verben so wie die $S\"{a}tze$ in Beispiel (3) zu behandein sind D.h., die Struktur $f\"{u}r$ AcI-Konstruktionen sieht so aus wie (4b), nicht wie (4a). Betrachten wir dies noch einmal an einem Beispiel: (3) a. Ich sehe mich $m\"{u}de$ b. Ich $f\"{u}hle$ mich viel besser.