http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Heo, Seong Chan,Kim, Jeong,Kang, Beom Soo Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.340-341 No.1
<P>Loading path is one of the most influential parameter in tube hydroforming(THF) process. Load history has a major effect on failures such as buckling, necking, bursting, and so on. Because loading conditions that consist of axial feeding and internal pressure are imposed simultaneously. Therefore suitable loading path should be determined to prevent onset of failures i.e. bursting on final products. This paper deals with the procedure on determination of the loading path in order to ensure the robustness of the final products after the THF. In order to verify the availability and feasibility of the proposed methodology a subframe model of engine cradle module in automotive is implemented. In this study, thinning ratio and forming limit stress diagram is used to demonstrate the improvement of the finished product. The result shows that the developed algorithm has successfully promoted the effectiveness and feasibility in the THF. Consequently, it is shown that the automatic approach on the determination of loading condition which is proposed in this paper will provide a valuable method to satisfy the increasing practical demands for designing process condition in THF.</P>
Application of flexible forming process to hull structure forming
Heo, Seong-Chan,Seo, Young-Ho,Park, Jung-Won,Ku, Tae-Wan,Kim, Jeong,Kang, Beom-Soo 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
The conventional line heating method has been applied for the manufacture of various curved blocks used for hull structures in the ship-building industry. However, it has low economical efficiency and productivity because most of its processes are based entirely on the skillful experience of experts. In this study, a flexible forming process is proposed and utilized to substitute for the conventional manual process. In the proposed process, numbers of punches which have round shapes on the contact tip are adopted to configure an equivalent forming surface according to the arbitrarily curved objective surface. A simple punch height determination algorithm that considers the discrete surface and its spatial planar equations is applied to determine the discrete forming surface composed of the adjusted punches. Punch height data are transferred to a numerical simulation model using ANSYS parametric design language, and finite element analysis is conducted to check the formability of the process. Further, experimental investigations are carried out to verify the feasibility of the process using a flexible forming apparatus. Consequently, it is confirmed that a double-curved thick plate could be obtained by the flexible forming process.
Formability evaluation of dimple forming process based on numerical and experimental approach
Heo, Seong-Chan,Seo, Yung-Ho,Ku, Tae-Wan,Kang, Beom-Soo 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.2
Exhaust gas recirculation (EGR) cooler consists of a number of heat transfer tubes that have relatively larger net area than that of flat type tubes. The surface of the tubes is made up with lots of grooves and protrusions for enlarging the net heat transfer area. Most tubes are manufactured through forming processes, such as bending, spinning, roll forming, stamping and so on. Therefore, a series of fracture or detect can occur during the various forming processes. In this study, the manufacturing process of a dimple-type rectangular heat transfer tube used for an EGR cooler system is investigated based on the numerical simulation and the experimental approach. A prototype of the tube is designed and modified to a newly designed tube considering the conservation of the net heat transfer area based on the numerical and analytical approach. Formability evaluation of the tube sheet is carried out by using forming limit curves based on the plastic instability conditions. Strain- and stress-based forming limit curves are utilized to ensure the strain path independence. The newly designed tube having a number of dimples on the both sides are manufactured by the press forming process. Thickness distributions for the principal cross-sections are observed from both the simulation and the experiment and compared each other. From the results, it is confirmed that the forming process is robust to manufacture the dimple type rectangular tubes with the comparison of thickness, and application of the forming limit curves.
응력기반성형한계선도를 이용한 관재액압성형 부품의 성형한계 예측
허성찬(Seong-Chan Heo),김정(Jeong Kim),강범수(Beom-Soo Kang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
In tube hydroforming process, bursting is the most frequently occured failure mode among the major failures such as wrinkling, folding, buckling, bursting and so on. Forming limit diagram(FLD) is well known as a criteria for estimation of bursting failure in almost of sheet metal forming but it is dependent on strain path while stress based diagram is independent on it. Generally, tube hydroforming consists of three processes such as pre-bending, pre-forming, and hydroforming. It means that the strain paths of hydroformed materials are nonlinear. Therefore, forming limit stress diagram(FLSD) is more suitable to predict forming limit for hydroformed parts. In this study, FLSD is applied to estimate bursting failure for an engine cradle of an automobile part. Consequently, it is proved that application of FLSD to predict forming limit is available for tube hydroforming parts.
허성찬(Seong Chan Heo),구태완(Tae Wan Ku),송우진(Woo Jin Song),김정(Jeong Kim),강범수(Beom Soo Kang) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.3
가변성형 공정에서 동일한 크기의 성형펀치 배열로 구성된 가변금형을 이용하는 경우 펀치의 크기가 일정하여 성형 가능한 곡률 반경이 제한되기 때문에 비교적 유연성이 낮다. 이에 본 연구에서는 가변금형의 유연성을 높이기 위하여 분할가변금형에 대한 개념을 제안하였다. 임의의 성형면을 형성하기 위하여 두 가지 크기의 펀치로 구성된 펀치 블록을 착안하였다. 상대적으로 큰 곡률 반경을 갖는 성형영역에 대해서는 크기가 큰 펀치 블록을 적용하였으며, 작은 곡률 반경을 갖는 성형영역에 대해서는 작은 크기의 펀치로 구성된 펀치 블록을 적용하였다. 해석적 연구를 토대로 성형된 제품의 단면 형상을 비교하였으며 이로부터 서로 다른 크기의 펀치 블록을 조합하여 구성한 분할가변금형을 이용한 판재의 성형공정이 비교적 복잡한 곡률 반경 분포를 갖는 곡면 가공에 적합함을 확인하였다. In general, the flexible forming die that has been used in the flexible forming process has the identical punch size; hence, its flexibility is relatively low because the range of allowable curvature radii is limited due to the uniform punch tip radius. Hence, a conceptual design of a sectional flexible die is presented for enhancing the flexibility of the forming process. Two punches of different sizes are used to configure the arbitrary forming surface. For a forming region with a relatively large curvature radius, a large punch array block is used; on the other hand, for the forming regions with small curvature radii, a small punch block is used. The cross-sectional profiles are compared with the target shape for evaluating the effectiveness of the process. Consequently, it is confirmed that the sectional flexible die can be used along with a combination of punch blocks of different sizes for manufacturing objective surfaces of complex shapes.
7톤급 연소기 챔버용 구리 개스킷의 체결하중 예측 및 구조 안정성 평가
허성찬(Seong-Chan Heo),유철성(Chul-Sung Ryu),최환석(Hwan-Seok Choi) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11
헤드부와 연소실부가 분리된 형태로 제작되는 7톤급 액체로켓 연소기 개발 시제의 기밀 조건에 대한 구조 안정성을 평가하였다. 기밀 소재로 이용된 구리 링의 소성변형을 고려하여 볼트 체결 하중을 예측하였다. 구리 소재를 강소성 재료로 가정한 성형해석을 수행하였으며 기밀을 위해 요구되는 볼트의 규격을 제안하였다. 산출된 볼트 체결 하중에 대한 연소기 체결부의 구조해석을 수행하여 구조 안정성을 확인하였다. Structural stability of a 7-tonf class thrust chamber which consists of separable mixing head and combustion chamber had been investigated for the metal-sealed condition using bolt clamp. A copper gasket was used as the sealing material and its plastic deformation behavior was considered. Bolt clamp load was estimated from the metal forming simulation of the clamp situation and the required bolt mechanical specification was proposed. Finally, numerical simulation of the assembled thrust chamber subjected to the bolt clamp load was conducted to verify the structural integrity of the combustion chamber.