• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.3
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• pp.45-50
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• 2005

A roll forming process for an automotive part of high strength steel is developed. The preliminary flower is generated semi-automatically by an AutoLISP program. The roll forming process is approximated as a multi-step bending process and the preliminary flower is analyzed by the plane strain finite element method. Then, the first flower is selected and modified through the finite element analysis. With the final flower, forming rolls are designed and constructed. Experiments are carried out on a prototype roll forming machine.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.480-483
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• 2005

A roll forming process is developed for an automotive part of high strength steel. Forming rolls are designed through the plane strain elastic-plastic finite element analysis to estimate the springback. It is assumed that the process can be approximated as a series of multi-step bending processes. Then the 3D elastic-plastic finite element analysis with the solid element is carried out for the designed roll forming process. The prototype roll forming machine and the forming rolls are made and the experiments are carried out. The results of the analysis and the experiments are compared.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.103-111
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• 2024

With the increasing global interest in carbon neutrality, the automotive industry is also transitioning to the production of eco-friendly cars, specifically electric vehicles. In order to achieve comparable driving distances to internal combustion engine vehicles, the application of high-capacity battery packs has led to an increase in vehicle weight. To achieve light-weighting and durability requirements of automotive components simultaneously, there is a demand for research on the application of Ultra-High Strength Steel (UHSS). However, when manufacturing chassis components using UHSS, there are challenges related to fracture defects due to lower elongation compared to regular steel sheets, as well as spring-back issues caused by high tensile strength. In this study, a simulated specimen that is not affected by the property changes of four materials was designed to improve formability of the rear cross member, which is the most challenging automotive chassis component. The influence and correlation of material-specific variables were analyzed through finite element analysis (FEA) for each material with tensile strength of 440, 590, 780, and 980 MPa grades, resulting in the development of a predictive equation. To validate the equation, the simulated specimens of 980 MPa grade were produced from the test molds. Then the reliability of the FEA and predictive equation was verified with measured specimen data using a 3D scanner. The results of this study can be proposed to improve the formability of UHSS chassis components in future researches.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.39-44
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• 2009

This paper is concerned with forming technology of an automotive front side member part with ultra high strength steel sheet of DP980. The forming technology considered in this paper is the draw & form type, which installs the upper pad and lower pad to produce the complicated shape of ultra high strength steel sheet. In order to produce sound product, comparison between form type and draw & form type and between draw type and draw & form type are investigated by FE-analysis. FE-analysis is carried out with commercial sheet metal forming analysis S/W, DYNAFORM. It was shown from FE-analysis that the draw & form type satisfied the required specifications such as the dimensional accuracy and soundness of automotive front side member part. The effectiveness of the analytical result was verified by the experiment. From this investigation, the draw & form type is proved to be able to supply useful forming technology in forming ultra high strength steel.

• Journal of Power System Engineering
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• v.14 no.1
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• pp.59-64
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• 2010

Ferritic stainless steel is currently increasingly used for automotive exhaust material. The material for exhaust manifold is used in the temperature range of 500∼$850^{\circ}C$. Therefore, high temperature characteristic is an important one that affects it's life span. It has been investigated the effect of alloying elements of Cr, Mo, Nb, Ti in the ferritic stainless steel for exhaust manifold on the high temperature tensile strength. There was a few difference in the tensile strength at $600^{\circ}C$ with the exception of low Cr steel, but the steels containing higher Cr, Mo or Nb elements showed significantly higher tensile strength at the temperature of $800^{\circ}C$. The precipitates of the specimens after heat treating at the test temperature were electrolytic extracted, and quantitatively analysed using by SEM-EDS and TEM. The alloying elements of Cr and Mo increased the tensile strength as a solid solution strengthener, and on the other hand Nb element enhanced the strength by forming the fine intermetallic compounds such as NbC or $Fe_2Nb$.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.68-73
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• 2010

Welding conditions in process of spot welding must become optimum and need to guarantee stability and reliability of vehicle body considering dynamic load history. Because welding parameters in process of spot welding are various, it is difficult that the quality of spot weldment was included in the optimum levels. In this paper, we found the optimum welding conditions satisfying KS spot welding qualities using genetic algorithm and spot welding experiments of high tensile strength steel and galvanized steel. Those experiments were dissimilar weld and 2-lap spot welding. Genetic algorithm created random welding condition after that, selected optimum individuals by probability concept.

• Transactions of Materials Processing
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• v.30 no.5
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• pp.236-241
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• 2021

This study describes the cold stamping process design procedure to secure the formability and dimensional accuracy of the automotive structural component fabricated by 1.5GPa grade ultra-high strength steel sheet. The target product is selected as the front side rear lower member which is the most important energy absorption part in the frontal impact condition. To secure the product quality, an intermediate product shape is added while considering the low elongation and high strength characteristics of 1470Mart. The sequential optimization procedure of the intermediate product shape, the fine dimensional quality is then achieved without any crack or wrinkling. The cold stamping method with ultra-high strength steel sheets is validated by conducting the die tryout of the front side rear lower member.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.22-27
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• 2006

As the regulation and assessment program for safety of passengers become stringent, automakers are required to develop lighter and safer vehicles. In order to fulfill both requirements which conflict with each other, automobile and steel companies have proposed the application of AHSS(Advance High Strength Steel) such as DP, TRIP and martensite steel. ULSAB-AVC model is one of the most remarkable reactions to offer solutions with the use of steel for the challenge to improve simultaneously the fuel efficiency, passenger safety, vehicle performance and affordability. This paper is concerned with the crash analysis of ULSAB-AVC model according to the US-SINCAP in order to compare the effectiveness between the model with AHSS and that with conventional steels. The crashworthiness is investigated by comparing the deformed shape of the cabin room, the energy absorption characteristics and the intrusion velocity of a car.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.8-12
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• 2012

This study aims to analyze the formability property of surface texturing processed automotive steel sheet for improving the sheet forming property. In the paper, the effect of cavities fabricated using the laser surface texturing technique on automotive high strength steel sheets was studied. The frictional behavior of the sheet drawing is a function of interface parameters such as sheet surface roughness, holding force, contact pressure, etc. For these reasons, automotive steel researchers want to optimize the surface topography of automotive steel sheets in order to enhance the formability. Therefore, this study presents the behavior of deformation of a laser surface texturing steel sheet by considering the frictional operation during the deep drawing process.