• 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.

• Transactions of Materials Processing
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• v.9 no.6
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• pp.561-566
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• 2000

Recently, the hydroforming technology has been recognized as a general technique in manufacturing industry, especially in automotive industry. Hydroforming is applied to increase strength, and to decrease weight, cost and parts. Hydroforming is based on the inflation of, for Instance, a tube, coupled with axial or radial compression and by subsequent expansion and sizing against the die wall. Expansion, axial feeding, calibration are important parameters in this process. In this paper, the effects of various parameters such as internal pressure, axial feeding and friction on hydroforming of automotive bumper rail have been considered.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.22-28
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• 2000

By using the finite element method, the Oyane's ductile fracture integral I was calculated from the histories of stress and strain according to every element and then the forming limit of hydroforming process could be evaluated. The fracture initiation site and the forming limit for two typical hydroforming processes, tee extrusion and bumper rail under different forming conditions are predicted in this study. For tee extrusion hydroforming process, the pressure level has significant influence on the forming limit. When the expansion area is backed by a supporter and bulged, the process would be more stable and the possibility of bursting failure is reduced. For bumper rail, the ductile fracture integral i is not only affected by the process parameters, but also by the shape of preforming blank. Due to no axial feeding on the end side of the blank, the possibility of cracking in hydroforming of the bumper rail is influenced by the friction condition more strongly than that of the tee extrusion. All the simulation results show reasonable plastic deformation, and the applications of the method could be extended to a wide range of hydroforming processes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.563-566
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• 2000

Recently vehicle development trend puts emphasis on cost reduction and performance improvement through weight reduction, and safety security to protect passenger and chassis against external impact. Primary factors effected on vehicle safety are chassis structure, chassis system, and safety equipment like bumper. Research in part of weight reduction is proceeding actively about prohibition of over-design and material through optimal design method. Bumper in these factors is demanded two of all factors, safety security and weight reduction. It is the part that prohibits or reduces a physical impact in low speed crash. Bumper is composed of a few parts but this study exhibits the shape of bumper rail has a role on energy absorption of safety security and weight reduction from structure analysis of bumper rail's variable shape surface.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.381-393
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• 2001

The current traffic situation in Korea can be described as rapid change in traffic volume and diversity in vehicle size from compact cars to large trucks. W-beam barrier most widely used in Korea was found not to satisfy the stiffness requirement for the Koran impact condition of 14 ton-60Km/h-15deg. and it was too stiff for small vehicles impacting with more realistic speed to satisfy the safety of vehicle occupants. To develop a guardrail system satisfying the two contradicting goals, a thrie-beam guardrail system, which had the beam thickness of 3.2mm and rubber cushions, was conceived. Even though the height of the thrie-beam(450mm) is increased by 100mm as compared to that of W-beam (350mm), there was only 2% increase in the weight of the thrie-beam. The new thrie-beam barrier system could contain more wide range of vehicle bumper heights, and showed better performance in the viewpoint of stiffness and energy absorbing capability than the W-beam system. The impact performance was evaluated from a crash test. The developed thrie-beam guardrail system satisfied all applicable criteria for NCHRP 350 test designation 3-10.

• Journal of Korean Society of Steel Construction
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• v.13 no.3
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• pp.313-325
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• 2001

Tubular bridge rail was developed to restrain and redirect a 14ton van-type truck. The developed bridge rail permits better visibility than concrete safety-shape bridge rail, and it has better structural adequacy than the existing steel and aluminum bridge rails in Korea. The new bridge rail consists of a tubular thrie beam(TTB) rail and a steel guard rail, which are connected to composite posts. The TTB shape provides both better containment of diverse bumper heights and more tight fit between the ends of bridge rail and roadside guardrails than the existing bridge rail sections currently used in Korea. Making composite post by filling concrete inside the steel pipe of the same size as are used for the roadside guardrail post was found to be more efficient in increasing the stiffness and ultimate strength than simply increasing the size of the steel pipe. The system was crash-tested for the impact condition of 14ton-80km/h-$15^{\circ}$, and it satisfied all evaluation criteria set forth in NCHRP Report 350 for a Test Level 4 safety appurtenance. Acceptable performances were obtained in computer simulations for the impact condition of S2.