• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5789-5794
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• 2015

Recently, thin and light-weight production technologies are needed in IT industry in accordance with increase of the smart phones and mobile PC products. In order to make light and high rigidity products, engineering plastic and aluminum materials are frequently used in products appearance and frame hat support structure. Especially aluminum extrusion and CNC Brick processes are widely used for high strength and high rigidity technology. But extrusion method has constraints to apply exterior design and CNC Brick process has relatively high production cost and low speed of manufacturing. In this research, a new process method is introduced in order to reduce material cost and to improve manufacturing speed dramatically. Plate forging process means basically that thickening of local wall area thickness after deform exterior shape by deep drawing and bending process. Therefore, it is possible to minimize the waste of material and the manufacturing time. In this study the process of plate forging is designed using finite element program AFDEX-2D and the thickness and the width of initial deformed blank. And it is verified as a sample which is a part of laptop developed through the proposed plate forging method.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.320-324
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• 2016

A new eccentric forging process for camber bolts has been suggested in this study. The camber bolt is manufactured by a two-step process: the typical forging process for normal bolts and the trimming process for the eccentric flange. The processes are performed under high forging load and generate a large amount of chip during trimming. A new forging process has been required in order to overcome these problems. The eccentric forging is the new process in which the load axis is offset from the central axis, as against central load applied in a typical forging process. The eccentric forging process could reduce forging load and save the amount of chip. In order to manufacture camber bolts by an optimum process, it is required to adjust the geometry of eccentric die and the offset from the central axis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.107-114
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• 2003

Although cross rolling process has many advantages in forging a joint shaft, an automotive component of front axle unit, subsequent process is necessary to straighten its bending during forging process. In this paper the bending minimization of the joint shaft was studied to eliminate such an additional process. First of all, a characteristic diagram was used to find out factors affecting the bending of the shaft. Also design of experiments was utilized for estimating the influence of those factors. It was found that the phase angle, which is the difference in starting positions between upper and lower dies, was important to minimize the bending of joint shaft and die cooling is necessary to diminish the distribution of bending.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.03a
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• pp.124-130
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• 1995

An upper-bound elemental stream function technique(UBST) is proposed for solivng forging and backward extrusion problems that are geometrically complex or need a forming simulation . And in the forging problems, this study investigates that layer of elements effects dissipation of total energy and load. The element system of UBSTuses the curve fitting property of FEM and the fluid incompressiblity of the stream function . The foumulated optimal design problems with constraints ae solved by the flixible toerance method. In the closed-die forging and backward extrusion, the result of layer of element by this study produces a lower upper-bound solution than that fo UBET and conventional layer of element . And the main advantage of UBST program is that a computer code, once written , can be used for a large variety problems by simply changing the input data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.433-436
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• 2009

This study is concerned with an effect of frictional condition in a forward/backward combined extrusion process. Generally, the material flow of the billet is influenced by the corners of the die cavity, the ratio in reduction in area, and thickness ratio of backward can thickness to forward can thickness. In addition, the frictional condition in contact area between the billet and the punch/die also affect the material flow. This paper investigated the effect of frictional condition for variable friction factors. The FEM simulation has been carried out in order to examine the effect of frictional condition. Deformation patterns and flow characteristics were examined in terms of design parameters such as extruded length ratio etc. Die pressure exerted on the die-workpiece interface is calculated by the simulation results and analyzed for safe tooling. Therefore the numerical simulation works provide a combined extrusion process of stable cold forging process planning to avoid the severe damage on the tool.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.223-234
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• 2001

The characteristics of thixoforming process can decrease liquid segregation because of the improvement in fluidity in a globular microstructure state and utilizes flow without an air entrapment. Therefore, in order to obtain the sound parts of metal matrix composites by using thixoforming process which has co-existing solidus-liquidus phase, it is very important to design a die shape property and to obtain the fabrication conditions which affect the unifomity of the solid fraction on unfilling state and various defects throughout the fabricated parts. The die designs and fabrication conditions to obtain the good piston part are proposed for thixoforging process of metal matrix composites. When reheated metal matrix composites billets were transferred to the closed die gate, thixoforging were carried out under the various pressure(60, 80, 100MPa) with controled forging speed. The mechanical properties such as hardness and tensile strength for thixoforged parts have been investigated after T6 heat treatment.

• Transactions of Materials Processing
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• v.8 no.6
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• pp.604-611
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• 1999

This paper is concerned with the family of parts that generally feature a central hub with radial protrusions. As opposed to conventional forward and backward extrusion, in which the material flows in a direction parallel to that of the punch or die motion, the material flows perpendicular to the punch motion in radial extrusion. Three variants of radial extrusion of a collar or flange are investigated. Case I involves forcing a cylindrical billet against a flat die, Case II involves deformation against a stationary punch recessed in the lower die, and Case III involves both the upper and lower punches moving together toward the center of the billet. Extensive simulational work is performed with each case to see the process conditions in terms of forging load, balanced and symmetrical flow in the flange. Also, the effect of the gap size and die corner radii to the material flow are investigated. In this study, the forming characteristics of radial extrusion will be considered by comparing the forces, shapes etc. The design factors during radial extrusion are investigated by the rigid-plastic FEM simulation.

• Transactions of Materials Processing
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• v.14 no.9 s.81
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• pp.772-778
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• 2005

This paper is concerned with the analysis of material flow characteristics of combined tube extrusion using pipe. The analysis in this paper concentrated on the evaluation of the design parameters for deformation patterns of tube forming, load characteristics, extruded length, and die pressure. The design factors such as punch nose radius, die corner radius, friction factor, and punch face angle are involved in the simulation. The combined tube extrusion is analyzed by using a commercial finite element code. This simulation makes use of pipe material and punch geometry on the basis of punch geometry recommended by International Cold Forging Group. Deformation patterns and its characteristics in combined forward and backward tube extrusion process were analyzed for forming loads with primary parameters, which are various punch nose radius relative to backward tube thickness. The results from the simulation show the flow modes of pipe workpiece and the die pressure at the contact surface between pipe workpiece and punch. The specific backward tube thickness and punch nose radius have an effect on extruded length in combined extrusion. The combined one step forward and backward extrusion is compared with the two step extrusion fer forming load and die pressure.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.146-154
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• 1996

In this work, rapid prototyping and three-dimensional finite element analysis are simultaneously applied to the die design of metal forming processes. Rapid prototyping is a new prototyping technology which produces three-dimensional part models directly from CAD data and has been extensively applied to various manufacturing processes. There are many types of rapid prototyping systems due to their building principles and materials. In this work, Stereolithography Apparatus(SLA), which is the most widely used rapidprototyping system, is introduced to manufacture the die set. For general preparation of STL file, which is the standard input file of rapid prototyping system, mesh data which are used in describing the die surface in finite element analysis are translated so that rapid prototyping and finite element analysis are dffectively connected. A die set for spider forging and a clover punch for deep drawing section are manufactured effciently using SLA prototypes, and metal forming experiments are carried out using them. Comparing the result of experiments with that of analyses, the processes can be predicted and designed successfully.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.44-51
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• 2006

This paper deals with the aspects of die design for the multistage fine tooth hub gear in the cold forging process. In order to manufacture the cold forged product for the precision hub gear used as the ARD 370 system of bicycle, it examines the influences of different designs on the metal flow through experiments and FE-simulation. To find the combination of design parameters which minimize the damage value, the low gear length, upper gear length and inner diameter as design parameters are considered. An orthogonal fraction factorial experiment is employed to study the influence of each parameter on the objective function or characteristics. The optimal punch shape of fine tooth hub gear is designed using the results of FE-simulation and the artificial neural network. To verify the optimal punch shape, the experiments of the cold forging of the hub gear are executed.