• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.87-92
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• 2015

The injection molding process is widely used in the production of most plastic products. In order to make metal-colored plastic products like those found in modern luxury home alliances, metallic pigments are mixed with a basic resin material for injection molding. However, process control for metal-colored plastic products is extremely difficult due to the non-uniform melt flow of the metallic resin pigments. In this study, the effect of process parameters on the quality of a metal-colored plastic product is evaluated. A rapid mold cooling method using a compressed cryogenic fluid is also proposed to decrease the content of undesired compounds within the plastic product.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.6
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• pp.1810-1818
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• 1996

A new finite elemetn approach is introduced for direct prediction of bland shapes and strain distributions from desired final shapes in sheet metal forming. The approach deals with the geometric compatibility of finite elements, plastic deformation theory, minimization of plastic work with constraints, and a proper initial guess. The algorithm developed is applied to cylindrical cup drawing, square cup drawing, and fron fender forming to confirm its validity by demonstratin reasonable accurate numerical results of each problems. Rapid calculation with this algorithm enables easy determination of various process variables for design of sheet metal forming process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2262-2269
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• 2002

Process optimization is carried out to determine process parameters which satisfy the given design requirement and constraint conditions in sheet metal forming processes. Sensitivity -based-approach is utilized for the optimum searching of process parameters in sheet metal forming precesses. The scheme incorporates an elasto-plastic finite element method with shell elements . Sensitivities of state variables are calculated from the direct differentiation of the governing equation for the finite element analysis. The algorithm developed is applied to design of the variablc blank holding force in deep drawing processes. Results show that determination of process parameters is well performed to control the major strain for preventing fracture by tearing or to decrease the amount of springback for improving the shape accuracy. Results demonstrate that design of process parameters with the present approach is applicable to real sheet metal forming processes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1751-1760
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• 1993

The squeeze casting process is considered as an attractive way to form the primary product of near net shape metal matrix composites for wide use in automobile industry. To understand for infiltration limit in squeeze casting processes, the SAFFIL short fiber preform of volume fraction $10%{\sim}23%$ were fabricated by vaccum pumping and speed control press, and the optimal condition for fiber preform fabrication had been experimentally obtained. The composite materials were fabricated by forced infiltration of molten metals such as Al6061, Al7075, pure Al, AC8A, and Al2024. The infiltration distance and deformation of fiber preform are observed, and tensile strength were measured from at the room temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.301-304
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• 2005

Metallic sandwich plates are ultra-light materials with not only high strength and stiffness but also multifunctional. Inner dimpled shell structure can be fabricated by piecewise sectional forming process, and then bonded with same material face sheets by resistance welding. Tests have shown that sandwich plates with dimpled shell structure subject to bending have more collapse load, energy absorption and deflection before collapse than other types of sandwich plates. Consequently, inner dimpled shell structure can improve formability of sandwich plates for bending.

• Proceedings of the KAIS Fall Conference
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• 2000.10a
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• pp.42-42
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• 2000

반응소결 탄화규소는 소결체 내에 잔존 실리콘이 남아 있어 고온강도의 감소를 초래하는 단점이 있어 고온 구조재료로서의 사용이 제한되어 왔다. 따라서 이러한 문제점을 해결하기 위한 방법으로 Si 단독으로 용응침투시키는 대신 Si-MoSi₂를 침투시키는 방법이 시도되고 있으며, 이외에도 TiC 성형체에 Co, Ni 등의 금속, ZrB₂ 성형체에 Zr 금속 등을 용융, 침투시켜 성능향상을 유도하는 연구가 진행되고 있다. 본 연구에서는 반응소결에 대한 기본이론과 응용분야, 반응소결 비산화물계 세라믹스의 제조공정 및 이들 소결체의 미세구조와 기계적 특성 등을 소개하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.111-118
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• 1984

On the basis of plasticity theory for porous metal, an analysis of ring compression is carried out, employing the upper bound approach. The plastic flowability and the neutral radius of porous metal ring are calculated and deformation characteristics of power forging are obtained from this result. The experiments on ring compression are carried out for sintered iron porous metal with various relative densities under various friction conditions. A good agreement is observed between the shapes of the calculated curves and the experimental results from the ring compression test. The friction factor for powder metal forming can be determined not only from the relationship between reduction in height and reduction in internal diameter but independently from the relationship between reduction in height and relative density, if the initial relative density is known.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.53-63
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• 1995

In the analysis of metal forming problems, the explicit time integration finite element method, which does not have convergence problems, is frequently used. The present work is to assess the applicability of the explicit time integration finite element method to quasi-static metal forming problems. Compressing analyses of thin-walled tubes and solid cylinders are performed with different loading velocities. The computed buckled profiles of thin walled tubes are compared with the theoretical and experimental ones and it is found that at sufficiently low loading velocity, the explicit time integration finite element method accurately predict quasi-static buckled profiles. When loading volocity is increased, the computed buckled profiles of thin-walled tubes are very sensitive to loading velocity however the computed profiles of solid cylinders are less sensitive to loading velocity. In orther words, the geometrically self-constrained specimens like solid cylinders are less sensitive to loading velocity than the geometrically unconstrained specimens like thin-walled tubes. As a result, it is found that the geometrically self-constrained problems which include the greater part of metal forming problems can be efficiently analyzed with loading velocity control technique.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1543-1548
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• 2010

Powder metallurgy processes are used to form Net-Shape products and have been widely used in the production of automobile parts to improve its manufacture productivity. Powder-forging technology is being developed rapidly because of its economic merits and because of the possibility of reducing the weight of automobile parts by replacing steel parts with aluminum ones, in particular while manufacturing automotive parts. In the powder-forging process, the products manufactured by powder metallurgy are forged in order to remove any pores inside them. Powderforging technology can help expand the applications of powder metallurgy; this is possible because powder-forging technology enables the minimization of flashes, reduction of the number of stages, and possible grain refinement. At present, powder forging is widely used for manufacturing primary mechanical parts as in combination with the technology of powder forging of aluminum alloy pistons.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.69-76
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• 2012

Theoretical backgrounds on the experimental methods of explosive welding, explosive forming and shock consolidation of powders are introduced. Explosive welding experiments of titanium (Ti) and stainless steel (SUS 304) plate were carried out. It was revealed that a series of waves of metal jet are generated in the contact surface between both materials; and that the optimal collision velocity and collision angle is about 2,100~2,800 m/s and $15{\sim}20^{\circ}$, respectively. Also, explosive forming experiments of Al plate were performed and compared to a conventional press forming method. The results confirmed that the shock-loaded Al plate has a larger curvature deformation than those made using conventional press forming. For shock consolidation of powders, the propagation behaviors of a detonation wave and underwater shock wave generated by explosion of an explosive are investigated by means of numerical calculation. The results revealed that the generation and convergence of reflected waves occur at the wall and center position of water column, and also the peak pressure of the converged reflected waves was 20 GPa which exceeds the detonation pressure. As results from the consolidation experiments of metal/ceramic powders ($Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$), shock-consolidated $Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$ bulk without cracks was successfully obtained by adapting the suggested water container and strong bonding between powder particles was confirmed through microscopic observations.