• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.53-59
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• 1999

Recently, Tailor Welded Blank (TWB) is widely used in automotive industry since the transformation characteristic of its material can be changed. However, clearance between welding surfaces becomes the important factor which affect the quality of the laser weld, causing difficulties in preparing the sheet. The objective of this paper is to systematically evaluate the effects of previously presented fracture criterion and shearing condition on precise mechanical shearing simulation result. For this purpose, a parametric study was peformed to investigate the effect of finite element size and fracture criterion on simulation result. Also, in order to predict the optimum shearing condition, effect of shearing conditions such as clearance and punch radius on the shear plane shape was evaluated.

• Transactions of Materials Processing
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• v.12 no.3
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• pp.251-258
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• 2003

The paper deals with an analysis of an extrusion process with a divided material flow in a combined radial - backward extrusion. The paper discusses the influences of tool geometry such as punch nose angle, relative gap height, die comer radius on material flow and surface expansion into can and flange region. To analyze the process, numerical simulations by the FEM and experiment, an Al alloy as a model material have been performed. Based on the results, the influence of design parameters on the distribution of divided material flow and surface expansion are obtained.

• Transactions of Materials Processing
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• v.14 no.9 s.81
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• pp.751-755
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• 2005

This paper is concerned with spring back after sheet forming of bulk amorphous alloys in the super cooled liquid state. The temperature-dependence and strain-rate dependence of Newtonian/non-Newtonian viscosities as well as the stress overshoot/undershoot behavior of amorphous alloys are reflected in the thermo-mechanical Finite Element simulations. Hemispherical deep drawing operations are simulated for various forming conditions such as punch velocity, die comer radius, friction, blank holder force, clearance and initial funning temperature. Here, spring back by an instantaneous elastic unloading was followed by thermal deformation during cooling, and two modes of spring back are examined in detail. It could be concluded that the superior sheet formability of an amorphous alloy can be obtained by taking the proper forming conditions for loading/unloading.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.389-395
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• 2001

To restrain contact failure, present study investigates the influence of edge machining of an indenter (punch). As for the edge machining, rounding, chamfering, and chamfering and rounding are considered. Contact mechanics is consulted to examine the traction profile and the size of the contact region which are directly influenced by the end profile of the indenter. The effect of rounding size (i.e., radius) in the case of the chamfering and rounding edge-indenter is studied. Shear traction is also evaluated within the regime of partial slip. Size of slip region and its expansion rate due to the increase of shear force are considered to investigate the shape effect of the indenter on contact failure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.992-998
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• 2004

During the tube hydropiercing, the region adjacent to the pierced hole will be deformed and will be drawn away from the die block as the punch advances through the wall of the tube. The deformation in the region may range from a substantially flat form to a countersunk form, so called rollover. In this study, the effects of material properties, shape of piercing punches, roundness of tube surface and internal pressure within the tube during piercing on the rollover have been investigated experimentally. The results provide the quantitative variation of rollover at given hydropiercing parameters, and a relationship between the deformed radius and the rollover caused by the deformation has been established.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.37-47
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• 1995

Forging of trapezoidal spline, serration and square spline with solid cylindrical billets and hollow one has been investigated by means of upper bound method. Kinematically admissible velocity fields for forging of splines have been proposed in this study. The half pitch of splines has been divided into deformation regons. The neutral surface is introduced into forging of splines with flat punch and, for each step, it is assumed as a circle with its radius rn upper bound solutions obtained obtained by proposed kinematically admissible velocity fields are useful to predict the loads for forging of splines.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.108-115
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• 1996

Forging of trapezoidal spline, serration and square spline with solid cylindrical billets and hollow one has been investigated by means of upper bound method. Kinematically admissible velocity fields for forging of splines have been proposed in this study. The half pitch of spline has been divided into several deformation regions. The neutral surface is introduced into forging of splines with flat punch and, for each step, it is assumed as a circle with its radius $r_n$. Upper bound solutions obtained by proposed kinematically admissible velocity fields are useful to predict the loads for forging of splines.

• Transactions of Materials Processing
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• v.20 no.6
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• pp.456-460
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• 2011

A major source of difficulty in die design for high strength steel is the high level of elastic recovery during unloading. The degree of elastic recovery is affected by factors such as material strength, bending angle, punch's corner radius and sheet thickness. Finite Element Method was used in the present work to quantitatively analyze the elastic recovery for various combinations of these parameters. In some cases elastic recovery happened in reverse direction. This phenomenon, which we call spring-go, was explained via changes in stress distribution in the panel occurring in the forming process.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.383-388
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• 2005

In this paper Research development about a micro metal forming manufacturing system has been developed. A micro forming system has been achieved in Japan and it's developed micro press is limited to single forming process. To coincide with the purpose to be more practical, research and development is necessary about the press which the multi forming process is possible. We set the development of the equipment including micro deep drawing, micro punching and micro restriking process to the goal. To achieve this goal, Research about micro forming process to be related to multi process forming must be preceded first. Material selection and analysis about micro forming process are accomplished in this paper. And the basis research to make actual system is accomplished.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.316-319
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• 2008

The L-bending of inner-structure bonded sandwich sheet metal is examined by using a bending die attached to the material testing machine. The specimen is composed of top and bottom layers and a middle layer of pyramid-core structure and each layer is bonded by brazing. The variables chosen for experiments were clearance between punch and die, location of bend line on the specimen surface and clamping type of specimen during L-bending. Effects of these variables on deformation of specimen around die-corner radius were investigated. It was shown that the irregular shapes of recess are formed in the inner layer of bended parts and they greatly depend on working conditions.