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서오석(Oh Suk Seo),김헌영(Heon Young Kim),박종규(Jong kyu Park),서창희(Chang Hee Suh) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
A hot stamping process can be divided into two types, direct process and indirect process, according to the sequence of heating, forming and quenching. In this study, the indirect hot stamping of boron steel tube was adopted to be numerically analyzed. The whole process including forming at room temperature, heating and cooling process with phase transformation was analyzed and simulated by the implicit code DEFORM. From the analyses, it was found that different heat transfer coefficients should be used at different zones of the model in order to ensure the accuracy of the heating and cooling analysis. Therefore, the heat transfer coefficients applied in the analysis were measured at various positions in the tube, e.g., outside, inside, bending area by using heat cartridges. Finally, these coefficients were determined through a correlation of values in the real tests and those from the numerically backward traced analysis. Comparison between experiments and analysis of the final deformed shape and the distribution of the temperature shows good agreement. Hot stamping process consists of forming at the elevated temperature and rapid quenching, which induces phase transformation and results in the press hardening of steel parts. In this study, the hot stamping process of boron steel tube was analyzed by applying different heat transfer coefficients which had been experimentally measured and numerically backward traced.
서오석(Oh Suk Seo),김헌영(Heon Young Kim),이명규(Myoung-Gyu Lee),김지훈(Ji Hoon Kim),김대용(Dae Yong Kim) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Recently, lightweight material has been used widely in the field of automotive and electronic industries. However, some difficulties exists in characterizing the material, poor formability and abnormal stress-strain behavior such as Mg alloy sheet. In this paper, a new cyclic load tester, which can measure the stress-strain curves of thin sheet metals under non-monotonous condition such as tension /compression or compression /tension, was developed. Material tests including tension / compression/ tension or compression/tension/compression test are performed to aluminum and magnesium alloy sheets and construct a database of its material properties.
보론강 튜브 Hot Press Forming시 두께 변화에 따른 냉각 채널 설계
서오석(Oh Suk Seo),이은국(Eun Guk Lee),김헌영(Heon Young Kim),윤석진(Suk Jin Yoon) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Ultra high strength products can be manufactured by the hot press forming process of Boron steel. The hot press forming should be accompanied by quenching process in order to ensure high strength. In the quenching process, cooling rate is key factor to get the high strength, which is closely related to the design of cooling system such as the diameter, the position and the arrangement of the cooling channels. In this study the quenching process including phase transformation was analyzed to obtain the optimized cooling channel according to the thickness variation of the boron tube.
서오석(Oh Suk Seo),김기정(Ki Jung Kim),김헌영(Heon Young Kim),박종규(Jong Kuy Park),서창희(Chang Hee Suh) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
A hot press forming process consists of forming at the elevated temperature and rapid quenching, which induces phase transformation and results in the press hardening of steel parts. In this study, the hot press forming process of boron steel tube was analyzed by applying different heat transfer coefficients which had been experimentally measured and numerically backward traced.
윤석진(Suk Jin Yoon),박종규(Jong Kyu Park),이기동(Gi Dong Lee),서오석(Oh Suk Seo),김헌영(Heon Young Kim) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Press quenching process is an advanced metal forming method for manufacturing automotive parts with high strength and minimum spring back. In this process, the cooling time and conditions is the most important parameters. This study investigates the thermal deformation and mechanical properties of tubular beam with press quenching process. In order to compare with experimental result, a finite element analysis of the press quenching process coupled with phase transformation and heat transfer.