• 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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.92-96
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• 2005

Among the failure modes which can be occurred in tube hydroforming such as wrinkling, bursting or buckling, the bursting by local instability under excessive tensile stresses is irrecoverable phenomenon. Thus, the accurate prediction of bursting condition plays an important role in producing the successfully hydroformed part without any defects. As the classical forming limit criteria, strain-based forming limit diagram has widely used to predict the failure in sheet metal forming. However, it is known that the FLD is extremely dependant on strain path throughout the forming process. Furthermore, the path-dependent limitation of FLD makes the application to hydroforming process, where strain path is no longer linear throughout forming process, more careful. In this work, stress-based forming limit diagram (FLSD), which is strain path-independent and more general, was applied to prediction of forming limit in tube hydroforming. Combined with the analytical FLSD determined from plastic instability theory, finite element analyses were carried out to find out Ihe state of stresses during hydroforming operation, and then FLSD is utilized as forming limit criterion. In addition, the approach is verified with a series of bulge tests in view of bursting pressure and shows a good agreement. Consequently, it is shown that the approach proposed in this paper will provide a feasible method to satisfy the increasing practical demands for judging the farming severity in hydroforming processes.

• 동력기계공학회지
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• 제6권3호
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• pp.31-35
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• 2002

Brake tube is considered one of the most important parts in automobile. The shape of brake tube end has a great influence on the function of brake, and the quality and productivity of brake tube have relation to die design. The forming process of brake tube end is performed by hydraulic press forming machine. In this paper, the forming processes of tube end for automobile is analyzed and designed to make the optimal form of brake tube end. Also, finite element analysis has been carried out using $DEFORM^{TM}% 3D to predict the optimal shape of brake tube end and the results obtained showed the optimal length between punch and chuck is $1.0{\sim}1.2mm$. The shape of tube end is in good agreement with the finite element simulations and the experimental results.

• Journal of Advanced Marine Engineering and Technology
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• 제29권3호
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• pp.275-280
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• 2005

Recently there has been a growing interest in the design and manufacturing of the muffler tube due to the strict environment regulations, A muffler is an important part used to reduce noise and to purify exhaust gas in cars and heavy equipment. The shape of the muffler tube and the number of the tube hole has been made variously according to the weight and function of the car. The perforating technique of the muffler tube has a great influence on the manufacturing cost. In this study, metal forming analysis has been carried out to investigate the perforating process for the muffler tube and predict an optimal forming conditions of the muffler tube, Also its simulation results by the finite element method were reflected to the die design and the manufacturing system for the muffler tube. The perforating process is performed in the longitudinal direction of the tube. According to the simulation results, when the shear angle of punch was similar to the tube curvature, the optimal shape was obtained. Also when the clearance of die was 0.2mm, the burr was minimized and optimal shear section was obtained.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.26-29
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• 2008

Recently, the hydroforming of high strength aluminum tubes has many studies and applications in manufacturing industry, especially in automotive industry. But high strength aluminum tube has limited expansion capability at most 15% at normal temperature. New manufacturing process, called hot air forming, is introduced to apply aluminum tube to the automotive sub frame components which have complex shape and require high expansion ratio about 40%. The process is carried out at the elevated temperature above $500^{\circ}C$, so numerous material properties and process parameters related to high temperature should be investigated and determined to get a sound product. In this paper, the hot air forming process of automotive sub frame was investigated. The effect of the forming parameters such as the temperature of tool, axial feeding and gas pressure are analyzes by using explicit finite element method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.310-313
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• 2007

This paper covers finite element simulations to evaluate the bending limit of double pipe for tube-hydroforming. The tube-hydroforming process starts with a straight precut tube. The tube is often prebent in a rotary draw bending machine to fit the hydroforming tool. During the bending the tube undergoes significant deformation. So forming defects such as wrinkling, thinning and flattening are generated in the tube. Consequently we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters to minimize the forming defects using orthogonal arrays. The characteristic to evaluate the effects of the process parameters is the bending angle which wrinkling is generated, we define the bending angle at that time as bending limit. Of many process parameters, the process parameters of the bending process such as gab between inner and outer tube, boosting force, dimensions of mandrel were analyzed. And we observed the deformation modes of bent double pipe at specific bending angle in each parameter combination.

• 소성∙가공
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• 제12권6호
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• pp.558-565
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• 2003

Rotary swaging is one of the incremental forming process which is a chipless metal forming process for the reduction of cross-sections of bars, tubes and wires. In the present work, the rotary swaging machine and dies were designed to investigate the formability of TDS(Tube Drive Shaft) used in automotive industry. The process variables such as the speed of forming, the shape of the formed materials and the reduction of area were also estimated to study experimental analyses of rotary swaging process using the materials of 34Mn5 and S45C. From experimental results, it was found that the process variables affected the quality of TDS in terms of hardness, the precision of products and the surface roughness. The hardness after swaging approved to be Increased with the increase in the reduction of diameter. And it was found that the grain size became smaller and the elongated grains were formed in the axis direction.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.50-53
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• 2001

Hydroforming process has become an effective manufacturing process because it can be adaptable to forming of complex structural components. Tube hydroforming has been successfully developed in the real industrial field by many researchers. However, there still remains the constraint about shape which can be manufactured by tube hydroforming. In order to improve this constraint of shape and formability of conventional sheet metal forming, hydroforming process of sheet metal pairs becomes an important technology. In the present work, the finite element analysis of hydroforming process of sheet metal pairs is presented. After basic study about experimental parameters based on numerical analysis, hydroforming process of sheet metal pairs is developed which uses hydraulic pressure as a main forming source.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.25-28
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• 2001

Bi-2212 HTS tube was fabricated by centrifugal forming process(CFP). As a variation of melt casting process(MCP) or centrifugal casting technique, the centrifugal forming process is a flexible method for manufacturing Bi-2212 bulk tubes and has been optimized to achieve smooth surface and uniform thickness. At this process, the slurry was prepared in the mixing ratio of 10:1 between Bi-2212 powder and binder and initially charged into the rotating mold under the speed of 300~450 rpm Heat-treatment was performed at the temperature ranges of 860 ~ $890^{\circ}C$ in air for partial melting. The HTS tube fabricated by centrifugal forming process at $890^{\circ}C$ under the rotating speed of 450 rpm was highly densified and the plate-like grains with more than 20$\mu$m were well oriented along the rotating axis. The measured Tc and Jc at 10K were around 85K and 3,000A/cm2 respectively.

• 소성∙가공
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• 제23권8호
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• pp.507-512
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• 2014

The objective of the current investigation is to establish techniques in micro pattern forming operations of polymeric circular tubes by using hydrostatic pressing. This method was developed and successfully applied to the micro pattern forming on polymeric plates. The key idea of the new technique is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature of the polymeric substrates. The new process is thought to be a promising micro-pattern fabrication technique for two reasons; first, (hydro-) isostatic pressing ensures a uniform micro-pattern replicating condition regardless of the substrate area and thickness. Second, multiple curved substrates can be patterned at the same time. With the prototype forming machine for the new process, micro prismatic array patterns, 25um in height and 90 degrees in apex angle, were successfully made on the PMMA circular tubes with diameters of 5~40mm. These results show that this process can be also used in the micro pattern forming process on curved plates such as circular tube.