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허훈(Woo-Jong Kang),강우종(Hoon Huh) 한국자동차공학회 1998 한국자동차공학회 학술강연초록집 Vol.1998 No.4
Identification of dynamic response of the auto-body is important to evaluate the crash worthiness of a car. A split Hopkinson bar could be used for obtaining high strain rate material properties of sheet metals. In this paper, experiments have been carried out with a new split Hopkinson bar apparatus specially designed for the dynamic tensile test of sheet metals. The experimental results are used to construct a dynamic constitutive relation of sheet metals as the Johnson-Cook model. The conventional Johnson-Cook model has a linear term for strain hardening of the semi-logarithmic scale, which must be modified to a higher-order term to satisfy the experimental results. The constructed constitutive relations are applied to simulating the crashworthiness of a simplified car body.
유한요소법에 의한 VCB 접속부의 대전류에 대한 전열해석
강우종,허훈,강경록,Kang, Woo-Jong,Huh, Hoon,Kang, Kyeong-Rok 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.4
A large electric system of a vacuum circuit breaker(VCB) has been studied for the electro-thermal analysis by finite element methods. Since the heat generation in VCB causes not only energy loss but deterioration of the VCB system with oxidization of parts, the overheating of the system must be prevented. For the analysis, a finite element formulation is derived for both electric analysis and thermal analysis that are coupled together. Two sets of formulations are uncoupled after finite dimensional approximation. First, the electric potential is obtained for the entire field and scaled to the given electric current. The electric field obtained is then used to calculate the heat generation in the VCB system including contacts and connections for the calculation of the temperature distribution in the entire domain. The finite element analysis is carried out to study the effect of shapes and locations of contacts and connections. From the results, the existing VCB has been modified to enhance its capacity with reduction of heat generation and temperature elevation.
[구조강도부문] 인장형 홉킨슨 바의 오차 분석 및 자동차용 냉연강판의 고속인장 특성 연구
강우종(Woo-Jong Kang),허훈(Hoon Huh),한수식(Soo-Sik Han) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The dynamic behavior of vehicle body materials is dependent on material strain rates. In high speed tensile test of sheet metals, a new tension split Hopkinson bar specially designed for sheet metals is used. The tension split Hopkinson bar has some sources of errors such as grips and the plate type specimen. In this paper, these errors estimated and minimized. The results from both quasi-static and dynamic tests show that the strain rate hardening effect for sheet metals can not be described by the original Johnson-Cook constitutive relation. This relation has been modified to include a higher-order term for the hardening effect.
Tension Split Hopkinson bar를 이용한 자동차 성형용 금속 박판의 고속인장 시험
강우종(Woo-Jong Kang),조상순(Sang-Soon Cho),허훈(Hoon Huh),정동택(Dong-Taek Jung) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
A split Hopkinson bar could be used for obtaining high strain rate material properties of sheet metals for an autobody. In high speed tensile test of sheet metals, a new tension split Hopkinson bar is needed. From the experiments with the new apparatus, the material properties of SPCEN, SPCC, SPRC in the high strain rate state have been acquired and compared with quasi-static experimental results. The experimental results are used to obtain the constants of Johnson-Cook constitutive relation.<br/>
새로운 Tension Split Hopkinson Bar를 이용한 박판의 고속 인장시험
강우종,조상순,허훈,정동택,Kang, Woo-Jong,Cho, Sang-Soon,Huh, Hoon,Jung, Dong-Taek 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.12
A split hopkinson bar could be used for obtaining the high strain rate material properties of sheet metals for an autobody. In high speed tensile tests of sheet matals, a new design of a tension split Hopkinson bar apparatus is needed. The design of grips and an anvil length are numerically analyzed with ABAQUS/Explicit for the new apparatus of split Hopkinson bars. From the experiments with the new apparatus, the material properties of SPCEN in the high strain rate state have been acquired and compared with quasi-static experimental results. The material properties of SPCEN as well as other sheet metals in an autobody are indispensible for the analysis of crashworthness. Nevertheless the experiment of sheet metal in the high strain rate state has not been done or reported.