• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2039-2052
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• 1994

In this study, an expert system for multi-stage cold forging process design of axisymmetric parts is developed. The available geometries are axisymmetric shape and cylinder with a hold in one end. The overall system is composed of knowledge-based system for process sequence design, output module interfaced with CAD system and material data-base. In the developed system, designed process can be modified in order to reduce the number of processes and make the distribution of forming load be almost equal at various deforming stages within the machine capacity. After process sequence design is completed, results can be stored as a text file or a commercial CAD system file. The capabilities of the developed system are illustrated through various examples of process design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.86-89
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• 2000

In cold forging by multi stage former, crowing process is important process for the high production rate and automation of forging process. But various cropping defects occur in cropping process such as orthogonality, ovality and unevenness, etc. These defects have harmful effects on the dimensional tolerance of products and tool life. So in this study, the cropping experiment is performed to examine influence of cropping process variables(clearance, cutting velocity, H/D) on occurrence of crowing defects and optimum process variables are selected, and then FE analysis is performed to verify influence of these defects on dimensional tolerance and tool life.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.82-85
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• 2000

In cold forging, the final product is usually given by multi-stage process and the preform with stepped shape can be manufactured through the various forging method. The forward extrusion and upsetting processes for preform with stepped shape have been analyzed by using the rigid-plastic finite element analysis code, InteFORM and compared for load and stroke according to ae reduction of weを An engineer should select the proper processes considering the capacity and the stroke of the corresponding press in the forging of the preform with stepped shape.

• 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 the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.614-622
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• 2003

In this paper, the stress-strain curves of bearing steels at hot working conditions are obtained by hot compression test with a computer controlled servo-hydraulic Gleeble 3800 testing machine and elongations and reductions of area of the bearing steels are also obtained by hot tensile test with a Gleeble 1500 testing machine. Experiments are conducted under the various strain-rates and temperatures and their results are used to obtain the flow stress information. A rigid thermo-viscoplastic finite element method is applied to the multi-stage hot forging process in order to predict temperature distribution of workpiece. The experimental results and the analysis results are used to obtain an optimal hot forging condition.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.93-100
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• 1996

In this paper, a computer simulationtechnique for the forging process having a spring-attached die was presented . The penalty rigid-thermoviscoplastic finite element method was empolyed together with an interatively force-balancing method, in which the convergence was achieved when the forming load and the spring reaction force are in equilibrium within the user-specified allowable accuracy. The force balance was controled by adjusting the velocity of the spring-attched die. th minimize the number of internations, a velocity estimating schemewas proposed. Two application examples found in the related company were given. In the first application example, the predicted metal folw lines were compared with the acturally forged ones. in the second example, a hot forging process with a spring-attached die was simulated and the analyzed results were discussed in order to investigated the effects of spring-attached dies on the metal flow lines and the forming loads.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.197-200
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• 2001

In the multi-stage former, manufacture of hexagonal fitting nut was generated in a defective products about $70{\~}80\%$. Defective products reduced in a product stiffness and increased a product cost. Defects for manufacturing hexagonal fitting nut caused in a increase of ductile fracture value. So in the study, a preform designed to reduce ductile fracture value and designed preform verified through the finite element simulation. In conclusion, Ductile fracture value reduced if A round dimension of preform reduced and a part of opposition angle contributed in Plenty a volume.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.983-987
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• 2001

This paper deals with an automated computer-aided process planning system by which designer can determine operation sequences even if they have little experience in process planning of wheel bolt products by a multi-stage former. The approach to the system is based on knowledge-based rules and a process knowledge base consisting of design rules is built. Knowledge for the system is formulated from plasticity theories, empirical results and the empirical knowledge of field experts. Programs for the system have been written in AutoLISP for the AutoCAD using a personal computer and are composed of two main modules. An attempt is made to link programs incorporationg a number of expert design rules to form a useful package. Results obtained using the modules enable the designer and manufacturer of wheel bolt product to be more efficient in this field.

• Transactions of Materials Processing
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• v.14 no.8 s.80
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• pp.675-680
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• 2005

This study was aimed at the design of the dies for the automobile part for the engine oil leakage prevention using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation,'eesy-2-form' of 2D FEM simulation package and 'eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the simulation of 'eesy-2-form', we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of 'eesy-DieOpt', we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for cold forging has been developed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1515-1516
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• 2011