• Journal of Magnetics
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• v.16 no.3
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• pp.294-299
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• 2011

Nd-Fe-B high performance magnets were prepared by die-upset forging. The effects of the deformation parameters on magnetic properties and flow stress were studied. Deformation temperatures in the range of $600{\sim}900^{\circ}C$ enable to achieve an effective anisotropy and temperature $800^{\circ}C$ proves to be suitable for deformation of Nd-Fe-B magnets. The amount of c-axis alignment along the press direction seems to depend on the amount of deformation and a saturation behavior is shown at deformation ratio of 75%. Magnetic properties are also related to strain rate, and maximum energy product is attained at an optimum strain rate of ${\varphi}=1{\times}10^{-2}s^{-1}$. By analyzing the relationship of stress and strain at different deformation temperature during die-upset forging process, deformation behavior of Nd-Fe-B magnets was studied and parameters for describing plastic deformation were obtained. Nd-rich boundary liquid phase, which is additionally decreasing the flow stress during deformation, is supposed to play the role of diffusion path and enhance the diffusion rate.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.206-210
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• 2014

The metal lead frame, a semiconductor component, has product tolerances in micro units as compared to products made with a larger size mold. Therefore, small deflections of the mold and of the press as well as the press molding process itself have a strong influence on accuracy of the product. Hence, it is necessary for the process design to consider the structural response of the mold and the press during deformation. In the current study, the mold deflection and pressure on the punch is examined using the finite element modeling (FEM) program ABAQUS. The results from the simulation were verified with the dynamic deformation measurement equipment using digital image correlation (DIC).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2610-2618
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• 2000

In this paper, the elastic deformation of cold forging die has been investigated to improve the accuracy of forged parts with FEM analysis and experiments using the strain gages. In the finite element analysis, two types of analysis are used to predict elastic deformation of die. The one is that dies are considered to be elastic body from initial stage to final one, and the other is that the dies are considered to be rigid body during forging simulation and then considered to be elastic body at elastic analysis. Considering the results of analysis and experiments, it is likely that the analytical results are in good agreement with experimental inspections. The method using the elastic assumption of die relatively takes a lot of time to simulate the forming operation. However, It is better that using an elastic die to predict not only the shape of product but also filling of die cavity.

• Design & Manufacturing
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• v.11 no.1
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• pp.34-38
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• 2017

Deformation frequently occurring in injection molded products is a phenomenon displayed due to uneven shrinkage distribution and orientation of the whole molded product. Shrinkage deformation is a very serious problem because it causes deformation of the molded article and shortens the performance of the product. In this paper, we are focusing on the warpage of keypad in mobile phone. In other words, we focused on minimizing keypad deformation. In the study, the Taguchi method was applied to find the injection molding conditions that minimize the deformation of the keypad. In the case of this keypad, the main factors influencing the shrinkage deformation were predicted as the melting temperature, coolant temperature and cooling time. In addition, the optimum molding conditions were obtained and the shrinkage strain was minimized. Experiments for the Taguchi method and verification of optimal molding conditions were performed using an injection molding analysis program.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.110-113
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• 2008

This study was performed to predict the shape of polymer extrusion product and to find the cause of defective products Experiments was performed to extrude the complex profile shape using PC/ABS composite resin with new profile die and cooling die. A finite element analysis for the Polymer Extrusion process considering the heat transfer and thermal deformation was also performed, and the result was compared with the experimental data. It is found that the predicted profile shape in F. E. M was similar to the experimental result and the thickness of extruded product was thin when the velocity of profile die outlet was slow than the velocity of production (2m/min).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.86-89
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• 2002

Due to extremely large reduction of area or extrusion ratio in ordinary production of extruded profiles, anisotropy is naturally induced by large severe deformation during the extrusion process. Therefore, the anisotropic properties play a great role in the post processing of extruded profiles, such as in bending. Moreover, undesirable deformation will be involved when the deformation-induced anisotropy is ignored. In order to observe the deformation-induced anisotropy of the thin-walled product, the proposed algorithm is applied to some chosen industrial extrusion processes. In the resent work, the method for prediction of deformation-induced anisotropy employing the Barlats six-component yield potential to the rigid-plastic finite element method is proposed. The proposed algorithm is verified with the comparison to the crystallographic texture analysis, and then applied to the C-section exclusion process using a square die. The predicted anisotropy is then compared with the experimental and computational observations for validating the proposed algorithm.

• Transactions of Materials Processing
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• v.11 no.8
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• pp.724-730
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• 2002

Due to extremely large reduction of area or extrusion ratio in ordinary production of extruded profiles, anisotropy is naturally induced by large severe deformation during the extrusion process. Therefore, the anisotropic properties play a great role in the post processing of extruded profiles, such as in bending. Moreover, undesirable deformation will be involved when the deformation-induced anisotropy is ignored. In order to observe the deformation-induced anisotropy of the thin-walled product, the proposed algorithm is applied to some chosen industrial extrusion processes. In the present work, the method for prediction of deformation-induced anisotropy employing the Barlats six-component yield potential to the rigid-plastic finite element method is proposed. The proposed algorithm is verified with the comparison to the crystallographic texture analysis, and then applied to the C-section extrusion process using a square die. The predicted anisotropy is then compared with the experimental and computational observations for validating the proposed algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.723-730
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• 2012

During the cold wire-drawing process, the diameter of a wire is reduced and the length of the wire is increased as the wire passes through the die. The pressure and sliding motion at the interface between the wire and die cause elastic recovery of the workpiece and friction and wear on the die. In addition, wire deformation and frictional heating raise the temperature of the wire and die, resulting in difficulty in manufacturing the drawn products according to a designated inner diameter of the die, deviating from the designated dimension or the inner diameter of the die. In this study, considering the die temperature distribution, the effects of dimensional changes of the drawn products were analyzed quantitatively; these changes are caused by the elastic deformation of the die, the elastic recovery of the workpiece, and the thermal deformation of both the die and the workpiece. It was confirmed that the elastic recovery of the workpiece influenced these changes the most. The initial dies considering these factors could avoid deviation from the designated dimension, and the desired drawn products were obtained by using the designed initial drawing dies.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.237-240
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• 1999

The elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products. the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed and the final dimension of the computational product has been in good agreement with that of the experimental product.

• Design & Manufacturing
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• v.2 no.1
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• pp.7-10
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• 2008

Restriking method is to add to process in order to get the correct size and high precision accuracy of product which is formed in pre-process. This method is widely used at bending work and drawing work. Restriking die is particularly design and used as restriking process is performed. Therefore, production cost is increasing as one process or a two process are added. In this paper, punches and die block of square shell drawing die which could be performed drawing work and restriking process by using only one die are designed in order to solve these factors. The structure of sectional die which can integrate drawing die and restriking die was developed.