• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.11-11
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• 2006

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.317-317
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• 2009

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.329-337
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• 2000

This study describes a pressure tracking control of hydroforming process which is used for precision forming of sheet metals. The hydroforming operation is performed in the high-pressure chamber strictly controlled by pressure control valve and by the upward motion of a punch moving at a constant speed, The pressure tracking control is very difficult to design and often does not guarantee satisfactory performances be-cause of the punch motion and the nonlinearities and uncertainties of the hydraulic components. To account for these nonlinearities and uncertainties of the process and iterative learning controller is proposed using Cerebellar Model Arithmetic Computer (CMAC). The experimental results show that the proposed learning control is superior to any fixed gain controller in the sense that it enables the system to do the same work more effectively as the number of operation increases. In addition reardless of the uncertainties and nonlinearities of the form-ing process dynamics it can be effectively applied with little a priori knowledge abuot the process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.58-61
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• 2001

An implicit finite element formulation for axisymmetric tube hydroforming is investigated. In order to describe normal anisotropy of the tube, Hill's non-quadratic yield function is employed. The frictional contact between die and tube and frictionless contact between tube and fluid are considered using the mesh-normal vector computed from finite element mesh of the tube. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and simulation results are compared with experimental measurements. In the axisymmetric tube hydroforming process, an optimal hydraulic curve is pursued by performing the simulation with various internal pressures and axial forces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.354-357
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• 2001

In the present study, front lower arm and engine cradle which are automotive chassis parts were developed using the hydroforming technology. For systematic establishment of parts development process, material properties of tube were reflected at the start of design and problems of initial design drawing were solved by forming analysis. Design and manufacturing technology of hydroforming die were established and the relationship between internal pressure and feeding stroke was studied during try-out. Durability and buckling strength of hydrofromed parts were estimated.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.481-485
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• 2008

The subframe type rear suspension consisting of a side member and a front/rear cross member is widely used in a medium car and full car. In the small car case, the beam of tubular type without independent suspension system is used to reduce manufacturing cost. In this study, a subframe type rear suspension by hydroforming has been developed. In designing suspension, a driving stability and durability should be considered as an important factor for the performance improvement, respectively. Thus, we focus on increasing the stiffness of suspension and decreasing the maximum stress affecting a durability cycle life. Several optimization design techniques such as shape, size, and topology optimization are implemented to meet these requirements. The shapes of rear suspension obtained from optimization are formed by using hydroforming process. Through commercial software based on the finite element, the superiority of this design method is demonstrated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.153-157
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• 2000

This paper presents possible defects when welded blank hydroforming and focus on wrinkling, and the die design to prevent this defect An explicit finite element code, PAM-STAMP, is used to simulate welded blank hydroforming process. The numerical results are compared to the experimental results in the aspect of deformed shape. An automobile subframe is taken as an example to carry out finite element analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.198-201
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• 2004

Aluminum alloys have high potential for weight reduction in automotive and other applications. But aluminum alloys have relatively low tubular hydroformability which can be enhanced by conducting the hydroforming at elevated temperatures. Hot working processes are commonly used in bulk forming such as forging and rolling, but still is rare in sheet metal forming like hydroforming. In this study hydroforming test at elevated temperatures is performed by special designed induction heating system to investigate the hydroformability of aluminum alloys. The high temperature formability characteristrics are obtained by 1?fitting forming test and circular bulging test and the effects of the process parameters such as feeding amount, internal pressure and temperatures on the tubular forming limits are mainly investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.27-31
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• 2004

A bumper comprises a bumper face, a bumper beam for distributing the load from the impacts applied to the bumper face and reinforcing the bumper, an absorber member interposed between the bumper face and the bumper beam, and a pair of bumper stays which secure the bumper beam to the vehicle body. A conventional bumper stay structure is assembled into several stamped parts, so several processes are needed and the structure is complicated. In this study the bumper stay is applied to the tubular hydroforming which is known to have several advantages such as the reduction of the number of the process and the part weight. The thickness distribution of the tube is mainly considered to evaluate the hydro-formability and the shape of the tube is determined.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.38-42
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• 2005

A bumper comprises a bumper cover, a bumper beam for distributing the load from the impacts applied to the bumper cover and reinforcing the bumper, an absorber member interposed between the bumper cover and tile bumper beam, and a pair of bumper stays which secure the bumper beam to the vehicle body. A conventional bumper stay structure is assembled into several stamped parts, so several processes are needed and the structure is complicated. In this study the bumper stay is applied to the tubular hydroforming which is known to have several advantages such as the reduction of the number of the process and the part weight. The thickness distribution of the tube is mainly considered to evaluate the hydro-formability and the shape of the tube is determined.