• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.255-261
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• 2000

Tube bending is one of the conventional manufacturing process. Recently, tube bending was highlighted in automotive industry by hydroforming. Tube hydroforming process is divided into pre-bending process and hydroforming process. It's initial state is very important in die cavity of first hydroforming process. So tube bending is important factor of the hydroforming process. In this paper, two pre-bending simulations, by a rotary draw bending machine and a bend die. This paper presents the simulation results in pre-bending process that is used to form an automotive part, tie-bar.

• Transactions of Materials Processing
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• v.9 no.6
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• pp.615-623
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• 2000

The industrial application of hydroforming has a great potential in saying cost and achieving dimensional accuracy in automotive industry presently. The aim of the following article is to investigate the effect of process parameters on hydroformed part. Firstly, we have to investigate the change of mechanical properties for sheet and pipe material according to various radius/thickness ratio(r/t). The change of mechanical properties affects the yield stress more than the total elongation. Increase of yield stress for pipe has a bad influence on formability of hydroforming. Among the roll-forming process, the sizing process didn't change mechanical properties. The process parameters such as the initial pressure, mandrel shape and friction have seriously influenced on formability of hydroforming. Therefore we need to check formability of given material through the FE analysis in the beginning stage of process design and the predicted hydroforming process parameters ate generally a good starting point for the prototype tryout stage. The results of pretending, hydroforming analysis using FE model are good agreement with experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.36-39
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• 2001

Tubular hydroforming has attracted increased attention in the automotive industry recently. In this study, a professional finite element program for analysis and design of tube hydroforming processes has been developed, called HydroFORM-3D, which is based on a rigid-plastic model. With the developed program several hydroforming processes such as a tee extrusion, an automotive rear axle housing and lower arm are analyzed and designed. And also, the Oyane's ductile fracture integral I was calculated from the histories of stress and strain according to every element and then the forming limit of the hydroforming process could be evaluated. The pediction of the bursting failure and the plastic deformation during typical hydroforming processes shows to be reasonable so that this approach can be extended to other various tube hydroforming processes.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.42-48
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• 2012

Hydroforming has attracted the attention of manufacturing industries for vehicles and transportation systems. A wide range of products such as subframes, camshafts, radiator frames, axles and crankshafts are made by the hydroforming process. Hydroformed parts often need to be structurally joined to other components during assembly. Therefore it is useful if the hydroformed automotive parts can be attached with a localized flange. In this study, a hydroforming process to produce a rectangular shape flange is proposed. FE analysis to form the flanged rectangular shape was performed by Dynaform 5.5. The hydroforming characteristics at various die aspect ratios and feeding conditions were analyzed and optimal process conditions which can avoid defects are suggested. For validation purposes, hydroforming experiments to form the flange were conducted with the optimized conditions. The results show that the flanged parts can be successfully formed with a hydroforming process without additional processing steps.

• Transactions of Materials Processing
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• v.19 no.1
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• pp.32-37
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• 2010

Hydroforming has attracted a great deal of attention in the manufacturing industries for vehicles and transportation systems. Hydroforming technology contributes to weight reduction, increased strength, improved quality and reduced tooling cost. Hydroformed automotive parts used as structure components in vehichle body frame often have to be structurally joined at some point. Therefore it is useful if the hydroformed automotive parts can be given a localized attachment flange. For a given flange shape, a parting plane for the dies is established relative to which the various surfaces of the flange shape, in cross section, have no significant reverse curvature. In this study, hydroforming process for flange forming was proposed. FE analysis to form flanged circular shape and flanged rectangular shape was preformed with Dynaform 5.5. To accomplish successful hydroforming process design, thorough investigation on proper combination of process parameters such as tool geometry and hydraulic pressure has been performed and optimized. The results show that flanged automotive parts can be successfully produced with tube hydroforming.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.592-597
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• 2001

An automobile lower arm has been fabricated in a prototype form by hydroforming with the aids of numerical analysis and experiments. For the numerical process design, a program called HydroFORM-3D developed here on the basis of a rigid-plastic model, has been applied to the lower arm hydroforming. The friction calculation between die and workpiece has been dealt carefully by introducing a new scheme in three-dimensional surface integration. To accomplish successful hydroforming process design, thorough investigation on proper combination of process parameters such as internal hydraulic pressure, axial feeding, and tool geometry has been performed. Results obtained from numerical simulation for a lower arm in hydroforming process are compared with a series of experiments. The comparison shows that the numerical analysis successfully provides the manufacturing information on the lower arm hydroforming, and it predicts the geometrical deformation and the thinning.

• Transactions of Materials Processing
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• v.9 no.3
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• pp.249-256
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• 2000

Tube hydroforming is recently drawing attention of automotive industries due to its seberal advantages over conventional methods. It can produce wide range of products such as subframes, engine cradles, and exhaust manifolds with cheaper production cost by reducing overall number of processes. Tube hydroforming process is divided into prebending process and hydroforming process. Tube bending ins an important factor of the hydroforming process to enable the tube to be placed in the die cavity. This paper presents the theoretical analysis and the simulation results of the tube bending process. With some assumptions, approximate equations are derived to predict the thickness distribution on the cross section and the spring back of the bent tube. Bending simulations are carried out and compared to the analytical and experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.269-272
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• 2006

The hydroforming processing is a relatively new technology in comparison with conventional stamping process. The hydroforming processing makes torsion beam in rear suspension of automobile. The durability of torsion beam is very important characteristic that operate in an automobile. In order to optimize the hydroforming process and satisfy the durability, the hydroforming simulation which could control an axial compression and high internal pressure with computer simulation has to be operated. This paper is about an optimum design to improve the kinematic and compliance characteristics of a torsion-beam of suspension system. The result from finite element analysis shows that the forming and the durability are optimized. If there is effect of First pressure in hydroforming processing that gap is in the die tool, the prototype of tube is not satisfied on the durability test.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.783-788
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• 2000

Hydroforming is a method for forming circular tubes. If this technology is to be applied economically, it is essential to have knowledge of the avoidance of failure cases as well as of the behavior of the tube in the tool under the compressive stress and forces that are exerted by the machine. A finite element simulation for manufacturing of lower arm from straight tubes, using the hydroforming method, was performed to investigate the effects of varying process parameters. Explicit method is used to simulate hydroforming in many cases, but that is not included flow rule. And then it needs simulation for implicit method. It was simulated by two methods, implicit and explicit, to compare the result of the hydroforming.

• Transactions of Materials Processing
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• v.16 no.8
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• pp.567-574
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• 2007

Double layered tube is assembled with an inner tube and an outer tube, similar in material or not, contacting closely and deforming simultaneously when subjected to external force. For the manufacturing of double layered tube, the hydroforming assembly technology has several advantages. Therefore in this study, hydroforming characteristics of double layered tube was investigated. The free bulge test was performed to produce formability diagrams of double layered tubes at various forming pressure and feeding amounts. The hexagonal shape hydroforming test was also performed to estimate the dimensional accuracies of double layered tube through the corner filling ratio and the gap between inner and outer tube. Besides experimental analyses, the analytical model that can predict internal pressure for the hydroforming of double-layered tube was proposed and experimentally validated.