• 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.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.4
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• pp.84-93
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• 1989

This paper describes some development of Computer-Aided Process Planning System for cold-forging of rotationally symmetric parts(soild shape and solid-can combined shape) produced by the presses or formers. Using the developed system, forming sequences for producing final product are generated as graphic forms and process names, preform dimensions and process parameters(load, punch pressure, die pressure) are generated as routing sheets. Konwledges for forming sequence and process parameters are extracted from process limitations, plasticity theories, handbooks, relevent refferences and empirical know-how of experts in cold forging companies. Among extracted knowldeges, general and consistent knowledges are represented as design rules and are constructed as knowledge base. The developed system provides more powerful tool for through checking the producibilities of design, conformation of appropriate forming sequences and discoveries of new possibility. The results of the developed system are in good agreement with the practical data.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.597-602
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• 2006

Bulk plastic forming characteristics were studied for the magnesium alloy, AZ31 in warm backward extrusion. Effects of process conditions such as extrusion ratio, forming temperature, and punching speed were investigated respectively. Variation of microstructure induced by the warm backward extrusion process was observed. Microstructure of the work piece showed evidences of recrystallization under the experiment conditions. It is estimated that in specific punch speed region fast stroke accelerates recrystllization and reduces the forming load.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.76-83
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• 2001

This paper is concerned with the analysis of the forming characteristics of radial-backward extrusion. The single action pressing is analyzed by using the rigid-plastic FEM. The design factors such as die corner radius, gap height, and friction factor are involved in the simulation. The analysis is focused on the influences of the design factors on the maximum punch farce and metal flow into can and flange region. As a result of analysis, the gap height among the design factors is known to have a major effect on the metal flow of radial-backward extrusion for single action pressing compared with other design factors. As is expected, forming load and volume of flange increase as gap height and die corner radius increase, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.183-186
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• 1995

A simulation method basee on upper bound method is developed in order to characterize forging characters in forging of spur gears. In this paer, utlizing a kinematically admissible velocity field and applying it to study the effect of inner diameter of holow billet. To predict the variation of inner diameter of hollow billet, neutal surface has been introduced into forging of hollow gears from hollow billes with flat punch. The neutral surface of each step is assumed as a circle and determined in order to have minimum forging energy by golden section method. According to the analysis, the magnitude of inner diameter of initial billet is vary important to reduce the relative pressure and forging load. And the variation of inner diameter of billet during spur gear forging is successfully predicted.

• Transactions of Materials Processing
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• v.15 no.2 s.83
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• pp.143-147
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• 2006

Effect of processing condition on the hot extrusion of Al-Zn-Mg-Sc alloy was investigated. For this purpose, hot compression test and FE-simulation were conducted via Thermecmaster-Z and DEFORM-3D, respectively. The microstructure evolution during hot extrusion and post heat-treatment was investigated and deformation mechanisms were analyzed by constructing processing map. FE-simulation results show that the temperature difference between container and billet has considerable influence on the final shape of extruded T-shape bar. The relation between applied load and processing time was predicted by the FE-analysis as well as punch speed vs. stroke chart.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.202-205
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• 2005

Effect of processing condition on the hot extrusion of Al-Zn-Mg-Sc alloy was investigated. For this purpose, hot compression test and FE-simulation were conducted via Thermecmasteer-Z and DEFORM-3D, respectively. The microstructure evolution during hot extrusion and post heat-treatment was investigated and deformation mechanisms were analyzed by constructing processing map. FE-simulation results show that the temperature difference between container and billet has considerable influence on the final shape of extruded T-shape bar. The relation between applied load and processing time was predicted by the FE-analysis as well as punch speed vs. stroke chart.

• Transactions of Materials Processing
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• v.19 no.5
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• pp.273-276
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• 2010

In this paper, back pressure forging processes of which back pressures are exerted by mechanical forces including spring reaction are simulated by three-dimensional finite element method. The basic three-dimensional approach extended from two-dimensional approach is accounted for. An axisymmetric backward and forward extrusion process having a back pressing die, which is exposed to oscillation of forming load due to variation of reduction ratios with stroke and its related frequent variation of major deforming region, is simulated by both two and three dimensional approaches to justify the presented approach by their comparison. A three-dimensional forging process having a back pressing die attached to the punch by a mechanical spring is simulated and the results are investigated to reveal accuracy of the presented approach.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.989-994
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• 2000

Nine tests to failure are performed on full-scale eight composite beams with unreinforced web opening having ribbed slabs with formed deck which are perpendicular to the steel section and one steel beam. The effects of slab width, reinforcing of stud, moving of rib, moment-shear ratio are studied. At the low M/V ratio, Vierendeel action around the high moment end of the opening is occurred and the large deflection across the opening and transverse cracking are occurred with increasing of applied load. As the M/V ratio increases, the relative deflection across the opening decreases. And at failure, full tensile strain are occurred at bottom T section of steel beam, and concrete crushes at the High Moment End of the opening. With narrow slabs, diagonal tension failure at the high moment end of the opening is occurred. And with wide slabs, rib punch-through failure is occurred near the high moment end of the opening. The implications for design are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.330-336
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• 1989

In analyzing the axisymmetric backward extrusion process a new method of analysis using upper-bound theorem is proposed in which the plastic zone and dead metal zone cam be predicted. Experiments are carried out with commercial aluminum. The metal flow on the meridional plane has been visualized experimentally by using the gridded specimens. It is shown that the theoretical results both in extrusion load and deformation pattern are in good agreement with the experimental results and they can be used for effective punch and die design to consider various process parameters in axisymmetric backward extrusion.