• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.23-26
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• 2008

In order to examine the deformation characteristics of Al circular pipe underthe biaxial compression, the horizontal biaxial compression die for the experiment was manufactured. From this, in the various compressive strain rate (1 mm/min. ${\sim}$ 400 mm/min.)conditions, the circular pipes, which were made by Al materials, were investigated based on the properties change of cross section area, punch load and deformation behavior. The tensile and compressive strains were evaluated from micro Vickers hardness tester. From these results, the punch load and deformation characteristic of Al circular pipes were highly changed in the compressive strain rate about 200 mm/min. The Al circular pipes had the tendency that the punch load decreased with increasing the compressive strain rate. In addition, following as the change of the shape and position of neutral axis due to the deformation proceeding of the circular pipe, the special point of the internal circular pipe at maximum load showed the maximum deformation strain and the maximum measured hardness value. The CAE (computer aided engineering) simulation using Deform-2D program was performed on the circular pipe in order to know and verify the exact compressive deformation behavior. From these results, the experimentally measured results were reasonably in good agreement with the simulation results.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.804-807
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• 1997

Recently equal-channel angular pressing (ECAP) has been employed to produce ultra-fine grain size materials. In this paper pure-Zirconium is considered due to its applicability to nuclear reactors. Among many process parameters of ECAP frictional effect on the plastic deformation of die has been investigated. The back pressure effect due to friction increases the stress level of die especially at the crossing area of channels, which may result in plastic deformation of die. The finite element method has been employed to investigate this issue.

• Transactions of Materials Processing
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• v.15 no.7 s.88
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• pp.524-528
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• 2006

Although equal channel angular pressing (ECAP), imposing large plastic shear strain deformation by moving a workpiece through two intersecting channels, is a promising severe plastic deformation method for grain refinement of metallic materials, its batch type characteristic makes ECAP inefficient for multiple-passing. Rotary-die ECAP (RDECAP) proposed by Nishida et al. can achieve high productivity by using continuous processing without taking out the samples from the channel. However, plastic deformation behavior during RD-ECAP has not been investigated. In this study, material plastic flow and strain hardening behavior of the workpiece during RD-ECAP was investigated using the finite element method. It was found that plastic deformation becomes inhomogeneous with the number of passes due to an end effect, which was not found seriously in ECAP. Especially, decreasing corner gap with increasing the number of passes was observed and explained by the strain hardening effect.

• Transactions of Materials Processing
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• v.9 no.3
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• pp.219-225
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• 2000

Equal channel angular pressing (ECAP) is a convenient forming process to extrude material without substantial changes in the sample geometry and this deformation process gives rise to produce ultrafine grained materials. The properties of the materials are strongly dependent on the plastic deformation behaviour during ECAP. The major process variables during ECAP are 1) die geometries, such as a channel angle and coner angles, and 2) the processes variables, such as lubrication and deformation speed. In this study, the plastic deformation behaviour of materials during the ECAP has been theoretically analysed by the finite element method (FEM). The effect of the die friction on the plastic deformation behaviour during the pressing is discussed by means of FEM calculations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1751-1758
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• 2001

Among severe plastic deformation processes, ECAP has drawn much attention due to its advantages including ultra-fine grain size material production. In this paper, ECAP process with pure -Zirconium is investigated due to its applicability to nuclear reactors. The finite element method is employed to investigate the deformation behavior of materials during ECAP process. In particular, effects of process parameters such as die deformation and channel angles on the material behaviors have been investigated. Experimental studies have also been performed to verify the numerical results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.23-26
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• 2003

This paper explains the die cooling method for improving tool life in the hot forging process. In continuous forming operation such as hot forging process, performed at high speeds, temperature increases of several hundred degrees may be involved. Die hardness was reduced due to thermal softening. Factor of die fracture are wear and plastic deformation of die due to hardness reduction by high temperature. Because die service life was reduced due to this phenomenon during hot forging, quantified data for optimal die cooling method is required. The new developed techniques for predicting tool life applied to estimate the production quantity for a spindle component and these techniques can be applied to improve the tool life in hot forging process

• 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 of Precision Engineering Conference
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• 1997.10a
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• pp.1051-1055
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• 1997

Hot forging is widely used in the manufacturing of automotive component. The mechanical, thermal load and thermal softening which is happened by the high temperature die in hot forging. Tool life of hot forging decreases considerably due to the softening of the surface layer of a tool caused by a high thermal load and long contact time between the tool and workpieces. The service life of tools in hot forging process is to a large extent limited by wear, heat crack, plastic deformation. These are one of the main factors affecting die accuracy and tool life. It is desired to predict tool life by developing life prediction method by FE-simulation. Lots of researches have been done into the life prediction of cold forming die, and the results of those researches were trustworthy, but there have been little applications of hot forming die. That is because hot forming process has many factors influencing tool life, and there was not accurate in-process data. In this research, life prediction of hot forming die by wear analysis and plastic deformation has been carried out. To predict tool life, by experiment of tempering of die, tempering curve was obtained and hardness express a function of main tempering curve.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.59-66
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• 2008

This paper has proposed a new parameter to interpret the effects of plastic deformation in bending of strips in cylindrical die and punch. With reference to the parameter, we have provided an insight on the separation between strips and punches, the occurrence of the multi-point bending during the process of deformation, the final shapes of strips, and the springback ratios. Also using the parameter, we have considered the different effects between the bending deformation in the cylindrical die and the bending deformation due to pure bending.