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REF SILL OTR-R/L 차체판넬 스템핑공정에서의 금형개발에 관한 초기 연구
정동원,황재신,안현길 濟州大學校 海洋硏究所 2004 해양과환경연구소 연구논문집 Vol.28 No.1
Finite element method is very effective method to simulate the forming Processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate tool model is required. Due to the geometrical complexity of real-size Part stamping tools it is hard to make FE model for real-size auto-body stamping parts. In this paper, it was focussed on the drawability factors on auto-body panel stamping by AUTOFORM with using tool planing alloy to reduce law price as well as high precision from Design Optimization of die. According to this study. the results of simulation will give engineers good information to access the Design Optimization of die.
Development of Step-Wise Combined Implicit-Explicit Finite Element Method
정동원 濟州大學校 産業技術硏究所 2001 산업기술연구소논문집 Vol.12 No.1
A combined implicit-explicit scheme for the analysis of sheet forming problems has been proposed in this work. In the finite-element simulation of sheet metal forming processes. the robustness and stability of computation are important requirements. since the computaion time and convergency become major points of consideration in addition to the solution accuracy. due to the complexity of the geometry and boundary conditions. The implicit scheme employs a more reliable and rigorous scheme in considering the equilibrium at each step of deformation. whilst in the explicit scheme the problem of convergency is eliminated at the cost of solution accuracy. The explicit approach and the implicit approach have both merits and demerits. In order to combine the merits of these two methods. a step-wise combined implicit-explicit scheme has been developed. Computations are carried out for the deep drawing of an oil pan by implicit. explicit and combined implicit-explicit schemes. From the comparison between the methods the advantages and disadvantages of the methods are identified and discussed.
정동원 濟州大學校 産業技術硏究所 2001 산업기술연구소논문집 Vol.12 No.1
In the interest of improved automotive fuel economy, one solution is reducing vehicle weight. Achieving significant weight reductions will normally require reducing the panel thickness or using alternative materials such as aluminum alloy sheet. These changes will affect the dent resistance of the panel. In this study. the correlation between panel size. curvature. thickness, material properties and dent resistance is investigated. A parametric approach is adopted. utilizing a "design software" tool incorporating empirical equations to predict denting and panel stiffness for simplified panels. The developed design program can be used to minimize panel thickness or compare different materials. while maintaining adequate panel performance.
탄소나노튜브에 담지된 PtCo 촉매 제조 및 PEMFC Cathode 전극 특성
정동원,박순,강정탁,김준범,Jung, Dong-Won,Park, Soon,Kang, Jung-Tak,Kim, Jun-Bom 한국재료학회 2009 한국재료학회지 Vol.19 No.5
The electrocatalytic behavior of the PtCo catalyst supported on the multi-walled carbon nanotubes (MWNTs) has been evaluated and compared with commercial Pt/C catalyst in a polymer electrolyte membrane fuel cell(PEMFC). A PtCo/MWNTs electrocatalyst with a Pt:Co atomic ratio of 79:21 was synthesized and applied to a cathode of PEMFC. The structure and morphology of the synthesized PtCo/MWNTs electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. As a result of the X-ray studies, the crystal structure of a PtCo particle was determined to be a face-centered cubic(FCC) that was the same as the platinum structure. The particle size of PtCo in PtCo/MWNTs and Pt in Pt/C were 2.0 nm and 2.7 nm, respectively, which were calculated by Scherrer's formula from X-ray diffraction data. As a result we concluded that the specific surface activity of PtCo/MWNTs is superior to Pt/C's activity because of its smaller particle size. From the electrochemical impedance measurement, the membrane electrode assembly(MEA) fabricated with PtCo/MWNTs showed smaller anodic and cathodic activation losses than the MEA with Pt/C, although ohmic loss was the same as Pt/C. Finally, from the evaluation of cyclic voltammetry(CV), the unit cell using PtCo/MWNTs as the cathode electrocatalyst showed slightly higher fuel cell performance than the cell with a commercial Pt/C electrocatalyst.