• Transactions of Materials Processing
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• v.18 no.6
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• pp.488-493
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• 2009

The very big springback of advanced high strength steel(AHSS) sheets invokes undesired shape defects, which can be generally eliminated by die correction or process parameter control. The springback reduction by controlling the forming process parameters is easy for the application, but limited for the bulky achievement. In this study, the effective die correction method, which obtains the modification of tool shape from the relationship between die design variable and springback, is introduced and is applied to the TWB tool of automotive side rail to show the validity and usefulness. Among the die correction trials repeatedly performed, the first trial is carried out by correcting the tool shape to the opposite direction to the springbacks of several tool sections. Next trials are done by extrapolating the springbacks of among the original tool uncorrected and the tools corrected negative amounts of the springback and by finding tool shapes without springbacks. After the angle of side wall and radius of curvature of horizontal bottom floor are chosen as design variables in the tool design of side rail, the tool shape is corrected 3 times. The accuracy of final shape within the assembly limit of 1mm and the springback reduction of 75.8% compared to the uncorrected tool are achieved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.769-773
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• 2002

The die easting process was used to manufacture a motor housing for automobile. Specially automobile parts were required light and high strength. Therefore simulations have been carried out die casting process of motor housing. In this paper, we investigated about characteristics of the die casted motor housing with HPDC(High Pressure Die Casting) process. Also the MAGMAsoft was used as computer simulation code and used material was ADC12(Aluminum Die Casting Alloy). We present the results of filling behavior and solidification process of a motor housing cast. The analysis results obtained about filling behavior and solidification of cast showed good agreement with test results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.461-470
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• 2002

The present paper investigates the effect of hot isostatic pressing (HIPing) on mechanical properties, e.g., tensile strength, ductility and impact absorption energy of sand and die casted aluminum alloys. After HIPing at various temperatures and pressure conditions, uniaxial tensile test and Izod impact test of the samples were carried out. The experimental results showed improvements in uniaxial tensile strength, elongation and Izod impact toughness of sand casted aluminum alloy, while deterioration of a tensile strength fur die casted aluminum alloy. The effect of HIPing for microstructure of the cast aluminum alloy was also investigated.

• Journal of Korea Foundry Society
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• v.30 no.4
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• pp.137-141
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• 2010

The effects of Zn amounts on the castability and tensile properties of Al-Zn-Mg-Cu alloys were investigated for development of high strength die casting aluminium alloys. Al-Zn-Mg-Cu alloys with 3.5% Zn showed high cast cracking tendency and poor mold filling behaviour. Al-Zn-Mg-Cu alloys with 5wt% Zn and 7wt% Zn had the tensile strengths of 300~400MPa and the elongations of 2~18%. The effect of Zn on the tensile strength of Al-Zn-Mg-Cu alloys was insignificant, but Al-Zn-Mg-Cu alloy with high Zn amount had lower elongation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.198-203
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• 2016

Computer-Aided Engineering (CAE) durability analysis and experiments of an aluminum alloy brake pedal were carried out for the car lighter by die casting method. In the CAE analysis, KS standards and criteria of the Volvo Car Corporation were applied, and in the experiment, KS standards were applied. The CAE analysis results show that aluminum alloy brake pedals are stronger than the conventional steel brakes pedals because the yield strength of the aluminum alloy increased by almost 97% over that of steel. Further, the structures of the cylinder and the frame were reinforced with increasing thickness of flame and were changed to suit the die-casting process. Through a durability test based on the KS standard, the strength of a prototype of the aluminum alloy brake pedal was confirmed to be sufficient.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.53-57
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• 1998

In order to investigate the effects of the variables during the stamping process upon the side wall curl behavior, experiments and finite element analyses were done using a 90 degree draw-bending test. The variables considered were the die radius, the forming speed, the restraint force, the lubrication and the sheet grade. The experiments and simulation conditions were selected according to the design of experiment (DOE) approach. The effects of the restraint force, the lubrication and the forming speed were the same for both high strength and mild steels, but the effects of the die radius on the side wall curl were dependent on the magnitude of the die radius and the sheet grade. A straight side wall was observed for both high strength and mild steels when the die radius was about 2∼3 times of the sheet thickness. It was recommended that the restraint force, the forming speed and the friction be increased in order to reduce the side wall curl.

• Transactions of Materials Processing
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• v.6 no.4
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• pp.346-356
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• 1997

The fiber orientation distribution and interface bonding in hot extrusion process have an effect on the maechanical properties of metal matrix composites(MMC's). Aluminium alloy matrix composites reinforced with alumina short fibers are fabricated by compocasting method. MMC's billets are extruded at high temperature through conical and curved shaped dies with various extrusion ratios and temperature. This present study was directed to describe the systematic correlation between extrusion die shape and subsequent results such as fiber breakage, fiber orientation and tensile strength to hot extruded MMC's billet. Extrusion load, tensile strength and hardness for variation of extrusion ratios and temperature are investigated to examine mechanical properties of extruded MMC's SEM fractographs of tensile specimens are observed to analyze the fracture mechanism.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.191-194
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• 2009

Very big springback in advanced high strength steel(AHSS) sheets invokes undesired shape defects, which can be eliminated by the tool surface correction method or the forming process control method. Since the springback reduction by controlling the forming process is limited, in this study, the die correction method which finds die correction from the relationship between die design variable and springback is introduced to achieve springback reduction and is applied to the automotive side rail to reduce the springback of 75.8% within the assembly limit of 1 mm.

• Transactions of Materials Processing
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• v.13 no.5
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• pp.409-414
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• 2004

TRIP steel has got attention in automobile industry because of its high strength and high formability. However, the information on deformation behavior of TRIP steel, including bending and springback, is not enough until now. In this research, the V-die bending experiment and analysis have been done to obtain the information of springback of TRIP steel. And a new numerical method, where elastic modulus is varied with the change of the strain, was suggested. Tensile test for TRIP steel was done to get tensile properties as well as strain dependency of elastic modulus of the material. Strain-dependency of elastic modulus was used the numerical analysis of V-die bending and unbending process to predict springback amount. The results were compared with experiment, showing reasonable agreement. Through the analysis of V-die bending as well as draw bending of TRIP steel, the proposed scheme with variable elastic modulus was proven to well predict the deformation behavior of TRIP steel during bending and springback.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.6
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• pp.888-899
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• 1998

In-Ceram system is one of contemporary esthetic all ceramic restorations and has relatively high flexural strength. The purpose of this study was to evaluate the marginal fidelity according to type of resin cement and measuring position, and to evaluate fracture strength according to type of resin cement. In this study, twenty seven In-Ceram crowns were fabricated on the metal master die of prepared maxillary right central incisor and devided into three groups. All specimens were cemented with Panavia 21 (group PV), Super-bond (group SB) and Lute-it (group LI) on the metal master die. After cementation, specimens were measured marginal gap between the margin of the In-Ceram crown and the finishing line of metal master die by using a stereomicroscope (SZ-ST, Olympus, Japan). Marginal gaps were recorded at the labial, lingual, mesial and distal measuring points on the metal master die. For the mesurement of fracture strength, lingual surfaces of cemented specimens were loaded at a distance of 1mm from incisal edge by using the Autograph S-2000 (Shimadzu, Japan). The results of marginal fidelity and fracture strength were statistically analyzed with the SPSS version 8.0 programs. The results of this study were as follows: 1. In comparison of marginal fidelity according to the measuring points, there was no significant difference. 2. The marginal fidelity according to the type of resin cement was decreased in order of group $LI\;(63.75{\mu}m),\;SB\;(77.78{\mu}m),\;PV\;(86.53{\mu}m)$, and there was significant difference between group LI and PV (p<0.05). 3. The fracture strength according to the type of resin cement was showed descending order of group $LI\;(60.00kg/cm^2),\;SB\;(56.80kg/cm^2),\;PV\;(56.11kg/m^2)$, but there was no significant difference.