• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.81-87
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• 2006

This study has been focused on the analysis of high speed shear forming process for lead-acid battery grids. The grid plays an important role of electrical charge. It is necessary to ensure the best battery's performance that the grid should have a best quality. The clearance between punch and die, the velocity of punch and the critical damage value are very important parameters for making a good grid form. The finite element analysis of the shear forming process is carried out by measuring and optimizing these three important parameters. The result of this study concludes that these parameters has a great influence on grid quality.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.27-30
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• 2007

In order to measure the friction coefficient used in sheet metal forming analysis, a friction tester was manufactured and friction tests were performed in various forming conditions. Based on the friction coefficients measured, a mathematical friction model was constructed in terms of lubricant viscosity, blank holding force, punch velocity and sheet roughness. In addition, the effect of the number of forming parameters in the calculation of friction coefficient on the accuracy of sheet metal forming analysis was investigated by comparing the punch loads obtained from the FEM simulation, in which the friction coefficients were determined by a few parameters with the experimental measurement.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.2
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• pp.129-135
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• 1997

Experimental studies have been carried out to obtain uniform cups by one operation of backward extrusion. A lot of factors on dimensional accuracy of backward extruded cups are billet material, billet shape, punch shape, punch velocity, geometry of tool, tool material, and lubrication etc. In manufacturing cup-shaped parts by backward extrusion, it is very important to design the initial billet shape or the preform. The objective of this paper is to find that the shape of the initial billet is related to dimensional accuracy and also to manufacture the more accurate product simultaneously reducing the loss of material as forming the shape of the initial billet by means of upsetting.

• Transactions of Materials Processing
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• v.11 no.3
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• pp.262-268
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• 2002

The bending process for the rectangular and circular curled tube can be developed by the hot metal extrusion machine with the multiple punches moving in the different velocity. The bending phenomenon has been known to be occurred by the different of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the cohesion of billet Inside the porthole die chamber. The bending phenomenon can be controlled by the two variables, the one of them is the difference of velocity at the die edit section by the different velocity of billets through the multi-hole container The other is the difference by the different hole diameter The results of the experiment show that the rectangular curved tube can be formed by the extrusion process, that the curvature of the curved product can be controlled by the velocity of punch and the diameter of container hole, that the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling of thin tube did not happen after the extra-bending processing by the extrusion bending machine.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.158-161
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• 2003

Extrusion of forward-gear and backward-rod by combined extrusion with controlling the extrusion velocity using a counter tool is studied. In the combined forward-backward extrusion with controlling extrusion velocity, only parts with short gear can be formed. To obtain longer gear parts, extrusion with reverse ram motion is carried out after the combined forward-backward extrusion process. In this method, combined forward-backward extrusion is carried out until excessive extrusion length is attained and then, the motion of the punch is stopped and the counter tool is moved in the inverse direction and returned to the position for obtaining the desired extrusion length. The experiment is carried out by using lead for billets as a model material. With reverse ram motion, longer gear teeth without under-filling defect can be formed than that by only combined extrusion with controlling extrusion velocity.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.94-104
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• 2000

A kinematically admissible velocity field for near-net shape forging of a crown gear form is proposed. This takes into account the profiled shape of the teeth chosen by approximating these kinematically as radially straight taper teeth, (rectangular and trapezoidal teeth). The upper bound to the forging load, the relative forging pressure and the deformed configurations, with both the initially solid circular cylindrical and hollow billets, are predicted using the velocity field at varying incremental punch movements considering differing frictional factors. These and other results are given and commented upon.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.06b
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• pp.185-194
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• 1999

This paper suggests the new techmology to control metal flow in order to reduce the number of preforming and machining for the cold forged product with complex geometry. This technology can be summarized the complex forming, which consists of bulk forming and sheet forming, and multi-action forging, which be preformed double action dies. To analyze the process, finite element simulation has been performed. The proposed technology is applied to hub which is part of air conditioner clutch. According to the result of this study, the relative velocity of mandrel and punch is primary process variable.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.176-180
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• 1996

Continuous wave CO$_{2}$laser beam welding and formability of zinc coated steel shets were investigated. First, optimal welding condition could be obtained in but welding by using the data for heat input and welding velocity. The highest value of Erichsen test is 79.3% compare to that of base matel. Secondly, Formability of laser welds was investigated by using ball punch tester. Finally, the forming results of butt-welded sheets showed that the joing design was important to apply the laser welded blank in the automotive production.

• Proceedings of the KWS Conference
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• 1996.05a
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• pp.46-50
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• 1996

Continuous wave $CO_2$ laser beam welding and formability of zinc coated steel sheets were investigated. First, optimal welding condition could be obtained in butt welding by using the data for heat input and welding velocity. The highest value of Erichsen test is 79.3% compare to that of base metal. Secondly, Formability of laser welds was investigated by using ball punch tester. Finally, the forming results of butt-welded sheets showed that the joining design was important to apply the laser welded blank in the automotive production.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.204-207
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• 2001

The bending process for the circular curved tube and rectangular curved tube with fins can be developed by the hot metal extrusion machine with the multiple punches moving in the different velocity. The bending phenomenon can be controlled by the two variables. The one of them is the difference of velocity at the die exit section by the different velocity of billets through the multi-hole container. The other is the one by the different hole diameter. The results of the experiment show that the circular curved tube with fins and rectangular curved tube with pins can be formed by the extrusion process and that the curveture of the product can be controlled by the velocity of punch and diameter of container hole and that the defects such as the distortion of section and the thickness change of the wall of tube the folding and wrinkling of thin tube and fins did not happen after the bending processing by the extrusion bending machine.