• 소성∙가공
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• 제20권5호
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• pp.377-386
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• 2011

During stamping processes, the air trapped between sheet metal and the die cavity can be highly compressed and ultimately reduce the shape accuracy of formed panels. To prevent this problem, vent holes and passages are sometimes drilled into the based on expert experience and know-how. CAE can be also used for analyzing the air behavior in die cavity during stamping process, incorporating both elasto-plastic behavior of sheet metal and the fluid dynamic behavior of air. This study presents sheet metal forming simulation combined simultaneously with simulation of air behavior in the die cavity. There are three approaches in modeling of air behavior. One is a simple assumption of the bulk modulus having a constant pressure depending on volume change. The next is the use of the ideal gas law having uniform pressure and temperature in air domain. The third is FPM (Finite point method) having non-uniform pressure in air domain. This approach enables direct coupling of mechanical behavior of solid sheet metal and the fluid behavior of air in sheet metal forming simulation, and its result provides the first-hand idea for the location, size and number of the vent holes. In this study, commercial software, PAM-$STAMP^{TM}$ and PAM-$SAFE^{TM}$, were used.

• 한국전기전자재료학회논문지
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• 제27권8호
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• pp.535-540
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• 2014

Because of the development of LED technology, products due to high output and compact, the material with high thermal conductivity has been developed. Now that heat radiating part of the LED lamp is currently used for die casting of aluminum. The development of aluminum with excellent thermal conductivity is required. In this study, we measured the thermal properties and compared them while we produced the alloy by changing the component of die casting aluminum. From this study, the thermal conductivity and thermal resistance of the developed alloy were superior to die casting aluminum.

• Design & Manufacturing
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• 제2권4호
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• pp.54-61
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• 2008

Warpage, which is one of the molding trouble, acts as possible factor which results in defect in assembly. In this study, a mold was designed to produce specimens with rib parallel to flow direction, specimens with rib perpendicular to flow direction and specimens without rib. This work researched change of warpage according to injection molding condition such as injection pressure, packing pressure, packing time, resin temperature, mold temperature in non-crystalline resins(PC, ABS), crystalline resins(PP, PA66), and 30% glass fiber reinforced-resins(PC, ABS, PP, PA66).Specimens with rib and Crystalline resins show more warpage than specimens without rib and non-crystalline resins, respectively. Glass fiber reinforced-resins and specimens with rib parallel to flow direction show smaller warpage than conventional resins and specimens with rib perpendicular to flow, respectively. Specimens with rib and specimens without rib show reduced warpage as packing time increases. In addition, warpage increase as resin temperature increases. It is found that CAE shows similar tendency with experiment as packing time, resin temperature. when the rib is caused, warpage will reduce and prevent the transformation. product of a irregular form occurs warpage. In the study It'll be basic data that product occurs warpage, preferablity.

• 대한기계학회논문집
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• 제14권5호
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• pp.1166-1180
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• 1990

본 연구에서는 열간 반경단조를 해석하는데 있어서 재료의 변형 해석은 강-점 소성해석법으로 해석하고 온도분포도 유한 요소법으로 해석한다.

• Design & Manufacturing
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• 제9권2호
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• pp.20-24
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• 2015

Recently, the light guide plate (LGP), a component of the BLU, becomes thinner and larger than ever. In industrial field, specialized injection molding technique is applied to mold the ultra-thin LGP such as a ultra-high speed injection molding. Usually very high melt temperature is used for low viscosity. High injection speed and melt temperature lead to yellowing of LGP. In the present paper a series of injection molding experiment was performed under various injection molding conditions. Yellow index, CIE xy, spectral transmittance of sample were measured using the UV-Visible spectrophotometer. Systematic decrease of spectral transmittance in UV-B range was found as the melt temperature was higher. Yellow index and CIE xy were became higher near the gate location in LGP. From the result of analysis of variance, the main factor to affect for yellow index was mold temperature and that for spectral transmittance(at 315 nm) was melt temperature.

• 한국재료학회지
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• 제27권10호
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• pp.544-551
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• 2017

In order to develop a new commercial Al-12%Si casting alloy with improved physical properties, we investigated the effect of adding Sr and TiB to the alloy. Al-12%Si alloys were prepared by die casting at $660^{\circ}C$. The eutectic temperature of the Sr-modified Al-12%Si alloy decreased to $9^{\circ}C$ and the mushy zone region increased. The shape of the Si phase changed from coarse acicula to fine fiber with the addition of Sr. The addition of TiB in the Al-12%Si alloy reduced the size of the primary ${\alpha}$-Al and eutectic Si phases. When Sr and TiB were added together, it worked more effectively in refinement and modification. The density of twins in the Si phase-doped Sr increased and the width of the twins was refined to 5 nm. These results are related to the impurity induced twinning(IIT) growth.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.136-143
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• 2002

Warm draw die technique which is one of the new forming technologies to improve formability of sheet metal is applied to the cylindrical and square cup drawing of stainless-aluminum clad sheets. In experiments the temperature of die and blank holder is varied from room temperature to $180^{\circ}C$, while the punch is cooled by circulation of coolant to increase the fracture strength of workpiece on the punch comer area. Test materials chosen for experiments are STS304-A1050-STS304 clad sheets. Teflon film as a lubricant is used on both sides of a workpiece. The limit drawing ratio and relative drawing depth as well as quality of drawn cups(distribution of thickness)are investigated and validity of warm drawing process is also discussed. No separation between each laminated material after drawing occurred through inspection by microscope as well as application of penetrant remover and bond strength test. Therefore, warm forming technique was confirmed to give better results in deep drawing of stainless clad sheet metal.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.373-376
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• 2005

In recent years, there has been a growing need fur productivity improvement of ACS wire (Aluminum clad Steel wire) In optical communication market. So, it is necessary to improve the production speed and following quality of ACS wire to reduce the unit cost of the products. In this study, the pre-heating temperature and cladding speed is chosen as the factors can influence the mechanical and metallurgical properties during cladding, and the changing behavior of mechanical property and microstructure by controlling above two factors are investigated. And the bearing length and approach angle in cladding die are selected as the important elements for designing optimum die enabling high speed cladding. So we carried out FE(Finite Element) analysis using the above two elements as variables. This paper aims to understand the change of mechanical properties and microstructure according to the change of each factor during cladding and suggest the optimized cladding condition to get the best quality of OPGW. And also we would like to introduce the optimum die structure that enables high-speed cladding.

• 소성∙가공
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• 제19권6호
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• pp.352-356
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• 2010

This paper was designed to fabricate the micro-spur gear by the LIGA and hybrid powder extrusion process. It is important to manufacture a micro-die with a high aspect ratio and determine appropriate extrusion conditions for a microforming. Ni has been used to fabricate micro-dies. LIGA process was capable to produce micro-extrusion dies with close tolerance, longer bearing length and adequate surface quality. Superplastic Al-78Zn powders have the great advantage in achieving deformation under low stresses and exhibiting good micro-formability with average strain rate raging from $10^{-3}$ to $10^{-2} s^{-1}$ and constant temperature ranging from 503 to 563K. Al-78Zn powders were compacted into a cylindrical shape ($\Phi3\times$h10mm) under compressive force of 10kN and, subsequently, the compacted powders were extruded by the hybrid powder extrusion process controlling of the temperature holing time for a improvement on formability of Al-22Zn powder. Micro-extrusion has succeeded in forming micro-gear shafts.

• Preventive Nutrition and Food Science
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• 제5권1호
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• pp.25-31
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• 2000

Extrusion conditions for production of rice extrudate were studied. The optimal production conditions of rice extrudate were determined by the relationship between dependent variables such as expansion ratio, shear strength and color change and independent variables such as moisture content of raw material, screw speed, and die tem-perature of extruder. The textural quality of rice exturdate was significantly affected by the moisture content of raw material (x1), screw speed (x2), and die temperature (x3) of extruder. The expansion ratio of rice extrudate showed the highest value at the moisture content of 18% of raw material, and the lowest at 24%, and whose regression equation was Y=34.8967 - 3.219X1 - (0.623$\times$10-2)X2 + 0.136X3 + (0.648$\times$10-1)X12 + (0.138$\times$10-3)X1X2 + (0.456$\times$10-4)X22 + (0.719$\times$10-3)X1X3 -(0.515$\times$10-3)X2X3- (0.552$\times$10-3)X32. The most desirable texture of rice extrudate determined by shear test and sensory evaluation was obtained at the following conditions : mois-ture content of 18% of raw material, screw speed of 210 rpm and die temperature of 11$0^{\circ}C$. The rice extrudate prepared under the above conditions showed the lowest shear force of 954g at which the highest sensory score was obtained.