• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.89-90
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• 2009

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.89-92
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• 2007

The metallic bipolar plate in PEMFC is widely used for automotive driving because of its advantages, i) high strength, ii) high chemical stability, iii) low gas permeability and iv) applicability to mass production. Especially, the metallic bipolar plate which is manufactured with the sheet metal stamping process can be applied in automotive PEMFC with less volume and weight because of its thin thickness but the formability and springback problems arise in real manufacturing process. The assessment for formability and springback of metallic bipolar plate should be performed before making stamping die sets. In this work, the methodology for determining the allowable draft angle of flow passage is introduced by using finite element analysis. In analysis results, as the draft angle of flow passage increase, the major strain and thinning is increase with exponential function. The allowable draft angle without fracture is presented by fitting the results. Additionally, the staking results with manufactured metallic bipolar plates by stamping process is presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2055-2067
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• 1997

Values of process parameters in sheet metal forming can be estimated by various one-step inverse methods. One-step inverse methods based on deformation theory, however, cause some amount of error. The amount of error is generally increased as the deformation path becomes more complex. As a remedy, a new three dimensional multi-step inverse method is introduced for optimum design of blank shapes and strain distributions from desired final shapes. The approach extends a one-step inverse method to a multi-step inverse method in order to reduce the amount of error. The algorithm developed is applied to square cup drawing to confirm its validity by demonstrating reasonably accurate numerical results. Rapid calculation with this algorithm enables easy determination of an initial blank of sheet metal forming.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2245-2252
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• 2002

Design sensitivity analysis scheme is proposed in an elasto -plastic finite element method with explicit time integration using a direct differentiation method. The direct differentiation is concerned with large deformation, the elasto-plastic constitutive relation, shell elements with reduced integration and the contact scheme. The design sensitivities with respect to the process parameter are calculated with the direct analytical differentiation of the governing equation. The sensitivity results obtained from the present theory are compared with that obtained by the finite difference method in a class of sheet metal forming problems such as hemi-spherical stretching and cylindrical cup deep-drawing. The result shows good agreement with the finite difference method and demonstrates that the preposed sensitivity calculation scheme is a pplicable in the complicated sheet metal forming analysis and design.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.47.1-47.1
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• 2009

최근 환경과 에너지에 대한 관심이 증대됨에 따라 차체의 경량화를 위한 고합금계 알루미늄 합금의 연구가 활발히 진행되고 있다. 특히 5000계 알루미늄 합금은 비중이 낮을 뿐만 아니라 Mg의 첨가에 의해 높은 강도 및 성형성을 얻을 수 있기 때문에 자동차용 판재로 많은 주목을 받고 있다. 현재 사용되는 대부분의 알루미늄 합금판재는 DC주조법과 추가적인 압연공정으로 제조되기 때문에 경제성 문제와 낮은 냉각속도로 인한 금속학적인 문제를 갖는다. 그러나 DC주조법과는 달리 쌍롤 박판주조법은 용탕으로부터 직접 판재를 제조하기 때문에 경제적이며 효율적인 주조공정이다. 또한 냉각속도가 빠르기 때문에 비교적 주조편석이 적고 전반적인 미세조직이 균일하여 고합금계 알루미늄 합금 판재제조에 매우 유용하게 응용될 수 있다. 본 연구에서는 쌍롤 박판주조법으로 고합금계 알루미늄 합금 판재를제조하고, 제조된 합금의 열간압연 및 열처리 조건에 따른 기계적 특성을 비교 및 평가하였다. 또한 미세조직 및 집합조직을 분석함으로써 고합금계 알루미늄 합금 판재의 실용화 가능성을 평가하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.350-355
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• 2005

소형 PEMFC(Proton Exchange Membrane Fuel Cell)는 전기를 만들기 위해서 고순도의 수소를 필요로 한다. 각각의 마이크로 성형된 금속박판(스테인레스 스틸, 알루미늄)을 진공 브레이징법으로 접합하여 수소공급용 소형 개질기를 제작하였다. 마이크로 채널의 내부는 졸-겔법(스테인레스 스틸)과 양극산화법(알루미늄)으로 촉매를 지지하기 위한 다공성 $Al_2O_3$ 층을 형성시켰다. 스테인레스 스틸 박판은 에칭과 브레이징에 유리하였으나, 표면산화층 코팅을 균일하게 하여 안정적인 촉매반응을 유도하기 위한 균일한 표면 산화층 형성이 힘들었다. 반면 알루미늄 박판은 표면 산화층 형성이 상대적으로 용이했으며, 촉매를 상하지 않는 낮은 온도에서의 적층이 가능했다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.529-535
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• 2013

A new thin sandwich panel composed of an aluminum expanded metal core adhesively jointed with stainless steel face sheets is introduced, and its mechanical behavior under three-point bending is investigated. The strength and stiffness are analyzed theoretically, and the press-formability and strength enhancement are evaluated experimentally. The specimens with the specific configurations exhibit face yielding well before face-core separation, which means that the sandwich panel can be formed by a press without failure. The measured load levels corresponding to the face yielding and the face-core separation agree fairly well with the theoretical estimations. For a given weight, the sandwich panel is superior to a solid panel in terms of strength, stiffness, and press-formability.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.66-66
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• 2007

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.217-221
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• 1997

In this study, 3D sheet metal forming analysis program is developed by explicit finite element method. In this program, analysis flow just follows the real engineering process to provide the user intuitive understanding and smooth contact alorithm improves the accuracy of stress prediction. The capability of this program are demonstrated by various examples.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.171-177
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• 2008

The characteristics of sheet metal process are little loss of material during process, the short processing time and the excellent price and strength. It has been widely used in autobody, electronic components, aircraftbody, etc. Lancing is a press operation in which a single-line cut or slit is made on part way across the strip stock, without removing any metal. In this paper, we examined the validity of finite element method analysis on the automobile CTR-PLR -L/R stamping process by using the lancing engineering method. As a result, it has shown that the proper lancing engineering method could prevent fracturing by improving sheet metal flow.