• 한국기계가공학회지
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• 제21권2호
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• pp.130-136
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• 2022

Reducing production costs through net-shaped cold forging is an important aspect in the automobile industry. In this study, we intend to produce a net-shaped electronic parking brake (EPB) serration gear for automobiles, using multi-stage cold forging. These serrations are then assembled to the reduction gear of an EPB actuator. The forging process of the serrations and the cold forging design were verified through finite element analysis (FEA) in order to evaluate metal flow. The forging machine was selected by checking the load using FEA. Based on the FEA results, molds were designed, and parts were made using multi-stage cold forging to produce a net-shaped serration gear.

• 소성∙가공
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• 제21권8호
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• pp.473-478
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• 2012

The yoke, a component of conventional motor-driven power steering system, often contains welding defects from its manufacturing process. To eliminate these defects, the precision cold forging process has been tried. In this study, the double-action complex forging has been used to manufacture a torsion joint yoke. The backward extrusion proved faster than the forward extrusion in forging of the product. The double-action complex forging process utilized an upper die composed of a punch, a punch guide, a disc spring and a coil spring. The forged material pushes up the punch guide, and then the disc spring and the coil spring balances the backward extrusion force. Consequently, the flow of material was essentially in the forward direction, resulting in a successful forging operation. The forging load of Al 6061-T6 was higher than that of the automotive structural hot rolled plate.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1996년도 제6회 학술강연회논문집
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• pp.197-205
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• 1996

A combined extrusion process studied here consists of forward and backward extrusion, and it is formed in single operation. The metal flow involved in the operation has appeared to be difficult to analyze accurately because of mixed directions of the flow. In this study, conventional two operations of a forward and a backward extrusions is transformed into one operation of mixed extrusion. A process designed by an industry expert is simulated by the rigid-plastic finite element method to investigate the metal flow and defects. In addition to the FEM simulation, experimental analysis has been carried out to confirm the design in industry, which includes material characterization, preliminary expriment, and whole experimental forming operation. The experimental results show that warm forming of extrusion is more desirable than cold working and hot forming in view of grain growth. Also two conditions of lubrication between workpiece and die has been investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.499-502
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• 2005

A process map has been developed, which can identify the process conditions for weak mechanical bonding at the contact surface during the direct extrusion of a Cu-Ti bimetal bar. Bonding mechanism between Cu and Ti was assumed as a cold pressure welding. Then, the plastic deformation at the contact zone causes mechanical bonding and a new bonding criterion for pressure welding was developed as a function of the principal stretch ratio and normal pressure at the contact surface by analyzing micro local extrusion at the contact zone. Finite element analyses for extrusion of Cu-Ti bimetal bars were performed for various process conditions. The deformation history at the contact surface was traced and the proposed new bonding criterion was applied to predict whether the mechanical bonding at the Cu-Ti contact surface happens. Finally, a process map for the extrusion of Cu-Ti bimetal bar is suggested.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 압출 및 인발 심포지엄
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• pp.20-23
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• 1999

The current three-stage cold extrusion process including upsetting to produce a flange is investigated for the purpose of improvement of manufacturing process. The main goal of this study is to obtain an appropriate process sequence which can produce the required part most economically without overloading of tools and select an appropriate process for reducing manufacturing cost. The current process sequence is simulated and design criteria are examined. Based on the results of simulation of the current three-stage process, a design strategy for improving the process sequence is developed using the thick-wall pipes. Based on the results of simulation of the one-stage processes, the forming processes of a flange for improving the conventional process are proposed.

• 소성∙가공
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• 제16권1호
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• pp.67-74
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• 2007

This study is aimed to find out the optimal forming conditions by comparing and analyzing material flow, deformation pattern, and a forming load through rigid-plastic FEM for a flange using pipe. Flanges are widely used for various purposes as connectors of industrial steel pipes which are manufactured by drawing process. The forming feature of flange was reviewed through both heading process and radial extrusion process in a cold working condition. As a result of simulation, the shape of flange can not be made by heading process, but made by radial extrusion process. The effects of design factors, such as gap-height, die-comer radius, and frictional factors on maximum forming load and deformation pattern are investigated for radial extrusion process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.51-54
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• 2003

Internal defects such as chevron crack occasionally occur in the process of cold extrusion or cold drawing. It is known that the existence and property of inclusion greatly influences the generation of the internal crack. However, in the plastic working field, research about the effect of the inclusion on the fracture is not theoretically analyzed. This paper describes effects of the physical property of inclusion on the internal fracture generation in the process. Prediction of fracture was evaluated by critical damage value calculated by the equation of Cockcroft & Latham and its change by the inclusion physical property such as size and stiffness was investigated.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.79-88
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• 2001

This paper suggests to predict the failure of helical gear extrusion die. The basic assumption that constitutes the frame-work for any combined stress failure theory is that failure is predicted to occur when the maximum value of stress becomes equal to or exceeds the value of the same modulus that produces failure in a simple uniaxial stress test using the same material. The stresses which were calculated to each critical points are applied maximum normal stress theory and distor-tion energy theory. The theroretical analysis and experimental results for Samanta process and New process dies were com-pared.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.463-466
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• 2005

Restoring ductility or removing residual stresses is a necessary operation when a large amount of cold working is to be performed, such as in a cold-forging or warm forging process. The advantage of annealing temperatures was investigated. After Hydrostatic Extrusion process, extruded materials were annealed at $200^{\circ}C,\;350^{\circ}C,\;450^{\circ}C$ for 1 hour. Microstructure of the annealed material was observed to make an understand about the difference in mechanical properties.

• 소성∙가공
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• 제24권5호
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• pp.332-339
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• 2015

In the current paper, a cold forging sequence was developed to manufacture a precisely cold forged H/Lower, which is used as the air back unit in commercial automobiles. The preform shape of the H/Lower influences the dimensional accuracy and stiffness of the final product. The shape factor (SF) ratio and shape of the tools are considered as the design parameters to achieve adequate backward extrusion height and maintain appropriate thickness variations. The optimal conditions of the design parameters were determined by using an artificial neural network (ANN). To experimentally verify the optimal preform and tool shapes, the experiments of the backward extrusion of the H/Lower were executed. The process design methodology proposed in the current paper, can provide a more systematic and economically feasible means for designing the preform and tool shapes for cold forging.