• 소성∙가공
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• 제16권8호
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• pp.590-595
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• 2007

This paper introduces a new approach to take account of bending history in finite element inverse analysis during sheet metal forming process. A modified membrane element was adopted for finite element inverse analysis so that bending-unbending energy was additionally imposed in the total plastic energy, predicting bending-unbending regions using the geometry of the final shape and tools. An algorithm was applied to a cylindrical cup deep drawing process. The blank shape and the distribution of the thickness strain were compared with those obtained from the incremental finite element analysis in order to evaluate the effect of the bending history. The algorithm reduced the difference between the results of the inverse analysis from those of the incremental analysis due to bending history. The analysis was also carried out with the variation of the thickness of the initial blank to investigate the effect of bending deformation. The results showed that the difference was remarkably reduced as the thickness of the initial blank increased. This indicates that the finite element inverse analysis cooperated with the suggested scheme is useful to obtain more accurate results, especially when bending effects are significant.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3728-3740
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• 1996

High-quality cups of deep drawing ratio of more than four cannot be simply drawn by conventional drawing and redrawing processes. In the present study, after the first deep drawing process, subsequent hydromechanical reverse redrawing with controlled radial pressure is employed. In order to increase the deep drawing ratio up to muchmore than four, the radial pressure should be controlled independently of the chamber pressure and thus an optimum forming condition can be found easily by varying the radial pressure. The process has been subjected to finite element analysis by using the rigid-platic material modeling considering all the frictional conditions induced by the hydrostatic pressure. In order to consider the pressure effect on the sheet, the pressure distributions on the flange part and the side wall part are calculated mumerically from simplified Navier-stokes equation. The comparison of the computation with the experiment has shown that the finite element modeling can be conveniently emplyed for the design of the process with reliability from the viewpoint of formability.

• 한국재료학회지
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• 제3권1호
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• pp.43-49
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• 1993

AI킬드한 극저탄소강에 Ti, Nb등의탄화물 또는 질화물 형성원소를 첨가하면 우수한 디프드로잉특성과 내시효성을 나타내는 강판을 얻을 수 있다고 알려져 있으므로 본 연구에서는 Ti및 Nb를 단독 또는 동시에 첨가하거나 B를 추가로 첨가한 고강도 극저탄소 강판을 제조하여 각각의재결정 집합조직과 기계적 성질을 측정비교하여 보았다. 역극점도에 나타난 집합조직강도의 변화를 조사한 결과 어닐링처리에 의하여 (100)면 강도와 (111)면 강도의 변화가 가장 많이 나타난 것은 Nb첨가강이며, Nb와 Ti를 단독으로 첨가한 강과 Ti를 단독으로 첨가한 강은 변화정도가 비슷하였다.극점도를 비교하면,Nb와 Ti를 동시에 첨가한강, Nb를 단독으로 첨가한 강 그리고 Ti를 단독으로 첨가한강 모두 냉간 압연한 상태에서는{112}<110>집합조직이 발달하였으며 어닐링처리한 후에는 {111}<112>집합조직이 잘 발달하였다. 그러나 세 종류의 강간에 집합조직의 차이는 별로 없었다. 결정립도와 관계가 깊은 경도에서는 결정립도가 가장 작은 Nb 및 Ti동시첨가강에서 경도가 가장 높고, Nb단독첨가강, Ti단독첨가강의 순서로 감소하는 경향을 보였다.