• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.241-244
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• 2008

Automotive companies have conducted a study for light weigh body and crash safety. But It is difficult to adapt a mass production because of formability with high strength steel in the conventional stamping process. Recently, Automotive maker in the Europe, USA, Japan has applied a hot stamping with boron steel in the body structure. Hot stamping technology spread fast in various body parts of automobile. Bumper beam has been applied in the foreign automotive company so much nowadays. In this study, We will optimize crash performance of bumper beam using hot stamping through comparison with conventional bumper beam.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.1-9
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• 2010

The purpose of this study is to analyze the bumper mounting structure of passenger vehicles at low speed collision. In order to improve the repairability and damageability of the vehicle, the low speed crash tests of RCAR(Research Council for Automobile Repairs) standard(front & rear 15km/h 40% offset crash test) were carried out for analysis of 3 different types of bumper mounting structures. The results of experiments show that the impact energy absorbing ability of bumper stay with rectangular crash box type vehicle which is inserted into the bumper rail was superior to another two different bumper mounting structures that are applied to many passenger vehicles. In this thesis, well designed bumper mounting structure such as rectangular crash box type can enhance the safety of occupants as well as contribute to reduce repair cost at low collision accident by improving repairability and damageability of vehicle.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1376-1380
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• 2005

In recent automotive industry, vehicle weight can be reduced by one-step forming of tailored blanks welded with two or more sheets of metal blanks. Tailored blank(TB) welding is a production method for blanks involving welding together materials of different quality, thickness, and coating, and has proved popular in fabrication automotive parts. This paper deals with the forming characteristics of mash seam welded tailored blanks. Using these forming characteristics, the bumper beam was developed using the mash seam welded tailored blank with the different thickness. We performed the forming simulation with respect to strain distribution on blank during the stamping of the bumper rail part. Based on these results, we made some stamping tryouts with selected types of blank designs to investigate the formability of tailored blank with different thickness. During the tryouts, we knew that it was important the BHF(Blank Holding Force). We obtained to reducing 10.5% weight and cost with adapting the bumper beam of automotive component using the tailored blank of mash seam welding.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.125-132
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• 2002

Bumpers are structural components to reduce physical damage to the front and rear ends of a passenger motor vehicle from low speed collisions. Damage assessment and the protectiveness are the commonly used designing criteria but in this study, relative displacements of the bumper are examined. To absorb the crash energy without significant damage to the bumper itself, foam material is installed between fascia and beam. However, it is not easy to predict the exact displacements generated in bumper structures through FEM because the compressive stress-strain curve of a foam material depends on strain rates that deviates significantly on each trial. Under this uncertain condition, a range of displacements is calculated and the optimum design is performed using the design of experiments. The result will be used to find the design that minimizes the weight within displacement constraints. The orthogonal array of L9 is introduced to find the optimum of the design variables that considers the thickness of inner beam, outer beam and stay, This study will suggest the design procedure of a front bumper using the uncertain stress-strain curve of a foam material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.357-358
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• 2006

Importance of using an injection molding analysis has been increased. However the application of it has not been increased because the results of analysis do not sometime match to practical molding. Therefore, the difference of flow analysis and practical molding should be decreased. This study presents reasons of the difference for the location of weld-line in the flow analysis and practical molding on automobile bumper molding.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.206-215
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• 2002

It is to be classified into friendly environment and safety problems, as a main technology development of the recent automotive industry. As these tendency, lots of automobile companies focus on a reduction of fuel expenses and strengthen of crash safety using high strength steel. In this study advanced technologies such as tailored blanks, aluminum extrusion and high strength steel forming applied to bumper beam will be described. As a result of impact analysis and an actual impact test, in terms of beam performance and a possibility fur the mass production will be discussed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.109-114
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• 2005

The large injection molded parts technology such as instrument panel, front and rear bumper are presented for a precision molding. Some lead time and cost are required to product these part from design to mass product. Recently, CAE is widely used in product design, mold design and analysis of molding conditions to reduce time and cost. The optimal molding conditions can be obtained by DOE(Design of Experiment). The optimal design applications with CAE and DOE have been used in small molded parts. However, application to the large molded body is not reported. In this paper, optimization of injection molding process is studied for quality control in mass production of automobile bumper. Mold temperature difference is chosen through robust design of injection molding process, the molding process being optimized in term of shrinkage and deflection. The optimal conditions through DOE are validated by using injection molding analysis.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1156-1161
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• 2008

Nonlinear dynamic analysis is generally used in automobile crash analysis and structural optimization considering crashworthiness uses the results of nonlinear dynamic analysis. Automobile crash optimization has high nonlinearity and difficulty in calculating sensitivity. Recently the equivalent static load (ESL) method has been proposed in order to overcome these difficulties. The ESL is the static load set generating the same displacement field as the nonlinear dynamic displacement field at each time step in dynamic analysis. From various researches regarding the ESL method, it has been proved that the ESL method is fairly useful. The ESL method can mathematically optimize a crash optimization problem through nonlinear analysis and well developed static optimization. The ESL is applied to nonlinear dynamic structural optimization of the automobile frontal impact problem. An automobile bumper is optimized. The mass of the structure is minimized while some constraints are satisfied.