• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.992-998
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• 2004

During the tube hydropiercing, the region adjacent to the pierced hole will be deformed and will be drawn away from the die block as the punch advances through the wall of the tube. The deformation in the region may range from a substantially flat form to a countersunk form, so called rollover. In this study, the effects of material properties, shape of piercing punches, roundness of tube surface and internal pressure within the tube during piercing on the rollover have been investigated experimentally. The results provide the quantitative variation of rollover at given hydropiercing parameters, and a relationship between the deformed radius and the rollover caused by the deformation has been established.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.237-240
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• 2003

Deformation surrounding the hole in the tube during the hydro-piercing process has been investigated in this study. The tube is expanded and internally pressurized between upper and lower dies, and a piercing punch is driven forcefully through a cross passage in the die and through the wall of the tube. The pressurized fluid within the tube provides support to the wall of the tube during a piercing step to form a hole in the tube having less deformation surrounding the hole in the tube. The deformation area may be fully retracted to a substantially flat form or partially retracted to a countersunk form. In this study, a mathematical model that can predict deformation surrounding the hole has been proposed and experimentally verified by actual hydro-piercing test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1503-1508
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• 2006

To increase the applicability and productivity of hydroforming process, hydro-embedding process was developed by combining the hydro-forming process with embedding process simultaneously. It is necessary in the automotive parts to form hollow bodies with connection elements which combine one part with another. The hydro-embedding process is embedding the connection element hydraulically during the operating steps of the hydroforming. In this study, technique of rotational piercing is added on the existing hydro-embedding to increase the connection force of hydro-embedded element. To estimate the feasibility of new trial process, integrated researches on the hydro-embedding process technology have been performed by analyzing the deformed mode of the tubes and the optimal process parameters for various shapes of the connection elements.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.154-159
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• 2004

Deformation surrounding the hole in the tube during the hydropiercing process has been investigated in this study. The tube is expanded and internally pressurized between upper and lower dies, and a piercing punch is driven forcefully through a cross passage in the die and through the wall of the tube. The pressurized fluid within the tube provides support to the wall of the tube during a piercing step to form a hole in the tube having less deformation surrounding the hole in the tube. The deformation area may be fully retracted to a substantially flat form or partially retracted to a countersunk form. In this study, a mathematical model that can predict deformation surrounding the hole has been proposed and experimentally verified by actual hydropiercing test.

• Transactions of Materials Processing
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• v.16 no.3 s.93
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• pp.157-162
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• 2007

The hydropiercing process gives a lot of advantages to the tube hydroforming such as cost reduction and high productivity. However it has a drawback, the amount of deflection around the hole is bigger than that of conventional die piercing process. The deflection can cause the problem at the assembly process of stamped parts and hydroformed part. Therefore the reduction of deflection is one of the most important issues for hydropiercing process. In this study, the deflection around hydropierced hole was investigated by experiment. As a result of investigation, the amount of deflection is influenced by the internal pressure, the material thickness' and the size of hole. Especially the hole size is most influencing factor on the deflection around the hydropierced hole.