• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.78-84
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• 2017

Consistent efforts have been made to reduce the weight of automotive parts by using lightweight materials. This has resulted in the replacement of conventional steels in car body structures with high-strength steels, and the current usage rate has reached 50%. This study examines the structural stiffness and energy absorption capability of bumper beams made of high-strength steels. New types of bumper beam cross sections are proposed.The structural stiffness and maximum bending force were computed via finite element analysis as about 25tons and 7.5tons/mm, and there were no significant differences among the proposedcross sections. Dynamic analysis was also carried out to investigate the energy absorption capabilities of the bumper beams, and the effects of materials and thickness reduction were analyzed. High-strength steel can be used to achieve weight reduction with comparable structural performance to conventional bumper beams.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2002.05a
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• pp.45-48
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• 2002

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.33-38
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• 2012

Sandwich composite panel with high strength steel face can reduce the weight of the automotive structural parts. Unlike the parts in aerospace application, the automotive parts are made by the forming process for mass production. The CAE simulation can predict the failures caused by forces and deformation during the forming process. Since the material properties are very important factor for the simulation, we performed the tensile test to get the material properties. The inspections by the optical microscope at each strain level show the states of the polymer resin. The material properties measured by the tensile tests are used for the input data of simulation. The simulation predicts the forming process of the bumper back beam very exactly compared with the try out results.

• 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.

• Composites Research
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• v.12 no.5
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• pp.23-30
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• 1999

Fiber reinforced composite materials are widely used in automotive industry to produce parts that are large, thin, lightweight, strong and stiff. It is very important to know a charge shape in order to have good products in the compression molding. In particular, the product such as a bumper beam is composed of the random and unidirectional fiber mats. The characteristics of flow fronts such as a bulging phenomenon for random mat and unidirectional fiber mat and slip parameters are studied numerically. And the effects of viscosity ratio and stack type on mold filling parameters are also discussed.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.226-232
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• 2000

This paper develops a finite element model for studying the crashworthiness analysis of a mid-size truck. A simulation for a truck frontal crash to a rigid barrier using the model is performed with PAM-CRASH installed in super computer SP2. Full vehicle model is composed of 86467 shell elements, 165 beam elements and 98 bar elements, and 86769 nodes. The model uses four material model such as elastic, elastic-plastic(steel), rigid and elastic-plastic(rubber) material model which are in PAM-CRASH. Frame and suspension system are modeled with 28774 shell elements and 31412 nodes. Cab is modeled with 34680 shell elements and 57 beam elements, and 36254 nodes. Bumper is modeled with 2262 shell elements, and 2508 nodes. Axle, steering shaft, etc are modeled using beam or bar elements. Mounting parts are modeled using rigid bodies. Bodies are interconnected using nodal constrains or joint options. To verify the developed model, frontal crash test with 30mph velocity to a rigid barrier is carried out. In the crash test, vehicle pulse at lower part of b-pillar is measured, and deformed shapes of frame and driver seat area are photographed. Those measured vehicle pulse and photographed pictures are compared those from the simulation to verify the developed finite element model.

• Journal of Welding and Joining
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• v.26 no.5
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• pp.74-78
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• 2008

The laser welding of the car body and components has been spread in the automotive industry. The Nd:YAG laser welding system could be used in 3D welding with robot. However, this system cannot efficiently reduce the welding cycle time according to various welding sequences because the robot's moving time is same that of the resistant spot welding system. But the remote welding system with high power $CO_2$ laser and scanner makes it possible welding cycle time much faster than the robot laser welding system. In the $CO_2$ laser remote welding system, laser beam can be rapidly transferred to a workpiece by moving mirrors of scanner system. So, it makes reducing the cycle time of welding process and shaping various welding patterns easily. Therefore, in this paper, the characteristic of weld strength according to patterns of weld bead on $CO_2$ laser welding was investigated. Also, the relationship between shape of weld bead and value of tensile load was studied. Finally, the optimum remote welding condition for car bumper was investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.297-300
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• 2009

The roll forming process is often used to manufacture long, thin-walled products such as a pipe. The final cross-section is a comparatively simple open-channel, a closed tube section or a complex profile with several bends. In recent years, that process is often applied to the bumper beam in the automotive industries. In this study, a optimal Center Floor Cross Member manufacturing technology, model deign and proper roll-pass sequences can be suggested by forming number of roll-pass and bending angle, and also effects of the process parameters on the final shape formed by roll forming defects were evaluated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.377-384
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• 2004

지구환경 문제가 대두되면서 자동차 경량화를 위한 재료의 고강도화는 필수적인데, 재료의 고강도화는 성형성의 감소를 야기한다. 이러한 문제점은 가공방법으로 해결할 수 있는데, 그 대표적인 것이 프레스 경화(Press Hardening)공정이다. 프레스 경화 공법이란 성형성이 좋은 고온$(900^{\circ}C)$에서 성형하면서 성형 중 프레스에서 고강도를 부설하는 공법이다. 프레스 경화 공정은 스웨덴의 SSAB자회사인 프라냐에서 1973년에 개발된 공법으로 초기에는 높은 경도가 필요한 산업용 설비 (톱 등)에 적용되다가 1990년대부터 Bumper와 Door Impact Beam등의 자동차 부품으로 개발을 하여 적용되기 시작하였으며, 현재 그 적용 영역을 보다 넓혀나가고 있는 상태이다. 본 발표에서는 프레스 경화 공정의 대표 부품인 범퍼 임펙트을 개발하기 위해 관련한 성능해석을 수행하였다. 수행한 결과에 의하면 기존 소재 대비하여 $30\%$이상 경량화가 가능함을 알수 있었다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.101-106
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• 1999

Fiber reinforced plastic composites is widely used to make be lightening of aircraft and automotive owing to having high specific strength and specific modulus. And it is very important to know a charge shape in order to have good products in the compression molding. In particular, the product such as a bumper beam is composed of the random and unidirectional composite mats. Its deformation and charge shape are very different by stack type of random and unidirectional mats. In this paper, the characteristics of flow fronts such as a bulging phenomenon for step-type random/unidirectional composite mats and slip parameters are studied numerically. And the effects of viscosity ratio and stack type on the mold filling parameters are also discussed.