• Structural Engineering and Mechanics
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• v.7 no.5
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• pp.457-471
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• 1999

In this paper, different curvature-rates are controlled to highlight the characteristic of viscoplastic response in cyclic bending tests. The curvature-ovalization apparatus, which was designed by Pan et al. (1998), is used for conducting the curvature-controlled experiments on thin-walled tubular specimens for AISI 304 stainless steel under cyclic bending. The results reveals that the faster the curvature-rate implies, the fast degree of hardening of the metal tube. However, the ovalization of the tube cross-section increases when the curvature-rate increases.

• International Journal of Automotive Technology
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• v.7 no.2
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• pp.209-216
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• 2006

A study has been conducted for an optimal processing and an apparatus for manufacturing a laser welded tube for one-body formed bumper beam. The tube dimensions used in calculation were the thickness of 1.4 mm, the diameter of 105.4 mm and the length of 2000 mm. The tube was formed of a cold rolled high strength steel plate(tensile strength of 600 MPa). The two-roll bending method was the optimal tube forming process in comparison with the UO-bending method, the bending method on the press brake, the multi-step continuous roll-forming method and the 3-roll bending method. Monitoring of the welding quality was conducted and the seam tracking along the butt-joint lengthwise to the tube axis was also examined. The longitudinal butt-joint was welded by using a $CO_2$ laser welding machine equipped with a seam tracker and a plasma sensor. The $CO_2$ laser tube welding machine could be used for precise seam tracking and real-time monitoring of the welding quality. As a result, the developed laser welded tube could be used for a one-body formed automobile bumper beam.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.7
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• pp.136-144
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• 2004

Optimal process and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from a cold rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.67-72
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• 2009

This paper covers finite element simulations to evaluate tube bending process of auto chassis component i.e. trailing-arm product. The rear of the auto chassis structure is primarily composed of CTBA and trailing-arm. When a car rolls into a corner, the trailing arm reacts to roll in the same degree as the car body. During the bending process of trailing arm the tube undergoes significant deformation. Thus forming defects such as excessive thinning and flattening of the tube will be formed in the outside of the tube. In this paper, we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters using orthogonal arrays method to minimize the forming defects. In this process we analyzed several parameters which are displacement of pressure die, boosting force, initial position of mandrel bar, dimensions of mandrel in regarding to the thinning and flattening of the tube.

• Journal of Industrial Technology
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• v.24 no.B
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• pp.199-206
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• 2004

Recently social demands of fuel economy and environmental regulations require the development of lightweight components and new manufacturing technologies. The aluminum tube hydroforming is a manufacturing process which can provide lightweight components as automotive parts. In this paper, the hydroformability of aluminium tube in different condition of bending process is presented. An investigation has been conducted on how to control the deformed shape and its effect on thinning distribution after hydroforming by using finite element simulation. Finite element simulation of tube hydroforming for automotive trailing arm is carried out to explore the effect of 2-dimensional and 3-dimensional bending.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.142-147
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• 2004

The aluminum tube hydroforming is a manufacturing process which can provide lightweight components as automotive parts. In this paper, the hydroformability of aluminium tube in different condition of bending process is presented. An investigation has been conducted on how to control the deformed shape and its effect on thinning distribution after hydroforming by using finite element simulation. Finite element simulation of tube hydroforming for automotive trailing arm is carried out to explore the effect of 2-dimensional and 3-dimensional bending.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.18-20
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• 2003

Optimal processing and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1337-1338
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• 2010

• Transactions of Materials Processing
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• v.25 no.3
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• pp.176-181
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• 2016

The exhaust tail pipe is the only visible part of the exhaust system on a vehicle. The conventional way to make the tail pipe is welding after stamping. There are various problems that occur during the stamping of stainless steel sheets such as scratching and local fracture. Problems during welding can also occur due to poor weldability. Tube hydroforming can be a solution, which eliminates these problems. The current study deals with the development of tube hydroforming for a vehicle tail pipe using finite element analysis for a free-feeding method. The current study focuses on the development of a proper load path for the tail pipe hydroforming and how bending influences the subsequent processing steps. The FE analysis results were compared with experimental results. This study shows the importance of bending and the necessity of considering bending when performing a tube hydroforming analysis.

• Structural Engineering and Mechanics
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• v.11 no.3
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• pp.315-324
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• 2001

This paper presents the experimetal result on the viscoplastic response and collapse of the titanium alloy tubes subjected to cyclic bending. Based on the capacity of the bending machine, three different curvature-rates were used to highlight the viscoplastic behavior of the titanium alloy tubes. The Curvature-controlled experiments were conducted by the curvature-ovalization measurement apparatus which was designed by Pan et al. (1998). It can be observed from experimental data that the higher the applied curvature-rate, the greater is the degree of hardening of titanium alloy tube. However, the higher the applied curvature-rate, the greater is the degree of ovalization of tube cross-section. Furthermore, due to the greater degree of the ovalization of tube cross-section for higher curvature-rates under cyclic bending, the number of cycles to produce buckling is correspondingly reduced. Finally, the theoretical formulation, proposed by Pan and Her (1998), was modified so that it can be used for simulating the relationship between the controlled curvature and the number of cycles to produce buckling for titanium alloy tubes under cyclic bending with different curvature-rates. The theoretical simulation was compared with the experimental test data. Good agreement between the experimental and theoretical results has been achieved.