• 소성∙가공
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• 제9권6호
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• pp.604-614
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• 2000

In this paper, the mechanical characteristics and fundamental mechanism of a roll-formed tube during the hydroforming process are investigated in order to obtain the ewly localization of the tube hydroforming skills which are the core production techniques for the super light weight and high safety of the car body. Also, the theoretical influences of the material variables and the processes on the formability in the tube hydroforming are studied. In addition, the techniques to evaluate the forming limit of the bulging process of a tube are developed.

• 소성∙가공
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• 제16권8호
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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.

• 소성∙가공
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• 제10권1호
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• pp.3-14
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• 2001

Hydroforming is the technology using hydraulic pressure and forming sheet or tube metals to desired shape in a die cavity. lt can be characterized as tube hydroforming and sheet hydroforming depending on the shape of used blank. Due to its prcess-related benefits, this production technology has been remarkably noticed for great potential for feasible applications and recently gained great attraction from many industrials including automotive and non-automotive. This Paper analyzed the tube and the welded blank hydroforming process and compared formability of the processes for automotive engine mount bracket. The mathematical analysis was performed by using the dynamic explicit finite element code, PAM-STAMP. In tube hydroforming, bending, springback, and forming analysis were carried out and the effect of mandrel and axial feeding were examined. In welded blank hydroforming, pressure curve history is determined and the results of forming analysis were evaluated by the comparison of experimental results in the aspects of deformed shape and thickness distribution.

• 소성∙가공
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• 제9권3호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.7-13
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• 1999

Hydroforming is the technology that utilizes hydraulic pressure to form sheet and tube metals in to desired shapes inside die cavities. It can be subdivided into tube hydroforming and sheet hydroforming according to the blanks used. In this paper the simulation of tube and welded blank hydroforming is carried out respectiyely. And simulation results are compared to evaluate formability in tube and welded blank hydroforming of engine mount bracket

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.244-248
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• 2003

Recently social demands of fuel economy and environmental regulations require the development of light materials and new manufacturing technologies. In this point, the aluminum tube hydroforming process which is satisfied with good strength-to-weight ratio and recyclability is innovative concept. However the level of the aluminum tube hydroforming technology is low in comparison with that of steel tube hydroforming. In this paper, the hydroformability of aluminum tubes in different heat treatments is presented. Theoretical results for forming limits of the wrinkling and bursting are compared with experimental results of aluminum tubes.

• 소성∙가공
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• 제9권6호
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• pp.631-637
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• 2000

The tube hydroforming technology is new key production technologies, which contribute to a light-weight cu. Because the tubes are used for hydroforming instead of the sheet materials formability test for tube is required to measure the formability of materials for hydroforming. In this Paper, a kind of formability test for tube, which can well represent the characteristics of tube hydroforming processes, is developed. Developed formability test method can consider not oかy the influence of material Properties but also contact with die and material. Some investigation was carried out to verify the effectiveness of developed formability test.

• 소성∙가공
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• 제9권6호
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• pp.644-652
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• 2000

Tube hydroforming is recently drawing attention of automotive industries due to its several 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. h successful tube hydroforming depends on the reasonable combination of the internal pressure and axial load at the tube ends. This paper deals with the optimal process design of hydroforming process using the genetic algorithm and neural network. An optimization technique is used in order to minimize the tube thickness variation by determining the optimal loading path in the tube expansion forming and the tube T-shape forming process.

• 소성∙가공
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• 제11권1호
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• pp.75-83
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• 2002

Recently, the hydroforming process is widely applied to the automotive industry and rapidly spreaded to other industries. In this paper, An implicit finite element formulation for simulating axisymmetric tube hydroforming processes is performed. 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 the frictionless contact between tube and fluid are considered using the mesh-normal vectors computed from the finite element mesh of the tube. The complete set of the governing relations comprising equilibrium and interfacial equations is linearized for Newton-Raphson procedure. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and the simulation results are compared with experimental measurements. In a simulation of stepped circular tube hydroforming processes, an optimal hydraulic pressure curve is pursued by considering simultaneously internal pressures and axial forces.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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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.