• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.34-41
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• 2017

As an alternative of the existing honeycomb shock absorbing device, the new approach on shock absorbing design using the extrusion of hyper-viscoelastic material such as silicon rubber is studied in this paper. The strain energy and stress-strain characteristic of viscoelastic material at extrusion process through the metered orifice has a similarity with the honeycomb core for maximizing shock absorbing capability. And in order to evaluate the design feasibility of this device and to understand the shock absorbing mechanism of energy transformation, finite element analysis and quasi-static compression test of the multi-stage extrusion shock absorber are examined in this paper.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.221-230
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• 2014

This study deals with a series of experimental investigations on multi-stage cold forging of an outer race used for a constant velocity (CV) joint with six inner ball grooves. The multi-stage cold forging, which consists of forward extrusion, upsetting, backward extrusion, and combined sizing-necking including ironing, was used to produce a prototype of the outer race. The cold forging tools such as forging punches and dies required in this multi-stage cold forging were also designed and fabricated. For the combined sizing-necking, especially, the longitudinally six-segmentallized punches were developed to easily eject from the necked inner groove of the outer race with consideration of the operating mechanism. Spheroidized SCr420H billet was used in the experimental study. To verify the suitability of the proposed process, the obtained parts were obtained from each forging operation, and the geometries were compared with the target dimensions. It was confirmed that the outer race with six inner ball grooves was well forged by adopting the proposed multi-stage cold forging, and the dimensional accuracy of the forged outer race matched well with the requirements.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.211-220
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• 2014

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.130-137
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• 1996

Several cold extrusion processes to produce an axisymmetric steel piston-pin are investigated for comparing each other. Two methods among four conventinal ones are selected to be simulated using the rigid-plastic finite element method. One of the both methods using a mechanical press has one stage process and the other utilizing a cold header applies a multi-stage process to produce a final product. Because the main process is a backward extrusion, the design criteria such as the backward extrusion ration and punch diameter to depth rationare ocnsidered. FEM analysis is performed mainly for strain distributin and load-stroke relationshis. Based on the results of preliminary simulatin, both process sequences are proved to have proper charicteristics suitable for each production method in terms of maximum load. Those simulation results will be a good design criteria in the future work to advance the manufacturing process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.236-239
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• 1995

In this paper,Upper bound analysis to predict the formation of corner cavity during the final stage of backward extrusion is used. The critical condition for corner cavity formation is obtained by upper bound analysis. The quantitive relationships between corner cavity formation and process parameters are studied. To broaden forming limit area, driven container and multi-step forming process is proposed. As a result of FEM, forming limit is enlarged. And this results is compared with the analytric results

• Journal of Korea Foundry Society
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• v.34 no.4
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• pp.123-129
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• 2014

This work presents the results of a thixo-extrusion process applied to aluminum alloy and and reheating characteristics of semi-solid A356 Alloy using have been discussed. The reheating experiment was performed using an electric resistance furnace and multi-stage heating for uniform reheating. The thixo-extrusion was performed at the optimal reheating conditions of the semi-solid A356 alloy, the the extrusion conditions were an extrusion ratio of 33 and ram speed of 6 mm/sec. The results showed that the thixo-extrusion of semi-solid A356 alloy fabricated by the cooling slope reduced the extrusion pressure by 180% in comparison with hot extrusion, and that a sound extrusion could be obtained in spite of the same extrusion ratio and strain rate.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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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.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.121-129
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• 1996

This study aimsdetecting defects for the forming precesses of X2 spline, which is designed by an industry expert. The exist process consists of 3 runs and 7 operations with 3 heat treatments. The rigid-plastic FEM analysis was carried out to design a new process and some defects were found. Thus the design was modified to get better results. it is ocnfirmed that the industry expert agree the possibility of defects derived from the FEM results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.628-631
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• 2002

This paper has executed FE-analysis to review the feasibility for developing the process, which produces the narrow-cubic type cans, using the Backward Impact Extrusion process instead of using current process, multi-stage deep drawing. Proposes an analysis method by applying ALE(Arbitrary Lagrangian-Eulerian) description to non-axisymmetric extrusion. which is appreciated as one of good solution to mesh distortion in case of the large deformation plasticity process that has mass flux, and considers the factors which affects forming-loads related to punch velocity and fulid status of material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.641-645
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• 2002

In case of aluminum-cased battery, The ratio of height and base of square is generally above the ten times, square-shaped and problem of non-axis symmetry. It is typical model to set up the analysis method of finite element. The reliable analysis of finite element method is suggested, which is used to investigate the possibility that multi-stage deep drawing and ironing used currently is replaced by backward impact extrusion favorable in the respect of cost production and productivity. The influence of parameter was analyzed and compared, which was considered to analyze the process of large deformation plasticity such as extrusion. Die and billet was made as the same shape of finite element model. The results of experiment show good forming without the rupture and wrinkles with the optimum velocity 100mm/sec obtained by analysis.