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임성준(S. J. Lim),김석봉(S. B. Kim),허훈(H. Huh) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
In this paper, forming limit diagrams of DP780, DP980, TRIP590 and TRIP780 steel sheets were investigated for high-speed sheet metal forming. The static and high speed forming limit tests were conducted with the aid of punch stretch tests with arc-shaped and square-shaped specimens. The width of arc-shaped specimen was changed to compose the uniaxial tension region of FLD and the friction condition was also varied to obtain the biaxial tension region of FLD. A high speed crash testing machine with a specially designed high speed forming jig was used in order to realize the high speed forming condition. The forming speed of each test condition was determined by comparing the results of the finite element simulation and the experimental results.
고속 성형의 성형성 향상 입증을 위한 실험 및 이론적 성형한계선도 획득 및 비교
김민석,장윤호,김정 한국소성∙가공학회 2024 소성가공 : 한국소성가공학회지 Vol.33 No.2
The current study aims to prove that high-speed forming has better formability than conventional low-speed forming. Experimentally, the quasi-static forming limit diagram was obtained by Nakajima test, and the dynamic forming limit diagram was measured by electrohydraulic forming. For the experiments, the LS-DYNA was used to create the optimal specimen for electrohydraulic forming. The strain measurement was performed using the ARGUS, and comparison of the forming limit diagrams confirmed that EHF showed better formability than quasi-static forming. Theoretically, the Marciniak-Kuczynski model was used to calculate the theoretical forming limit. Swift hardening function and Cowper Symonds model were applied to predict the forming limits in quasi-static and dynamic status numerically.
Incremental sheet forming technique and its applications
V. C. Do(도반추옹),D.T. Nguyen(규엔득투완),K. C. Park(박기철),Y. S. Kim(김영석) 한국소성가공학회 2015 금형가공 심포지엄 Vol.2015 No.8
Computer aided manufacturing technology is widely used in the sheet forming industry. Conventional press forming technique, in which the whole plate is deformed at the same time, has been the effective in mass production. To achieve the flexible manufacturing requirement, a new forming technology called incremental sheet forming (ISF) that gradually and locally deforms the sheet metal has been developed. Unlike conventional large-capacity press forming, this technology does not use the upper and lower dies. This technology has been beneficial in rapid production of prototypes and small batch production (rapid prototyping technology). The product is incrementally made by using a CNC machine or a robot that has the ability to control the path of the tool moving along the trajectory of the outer shape of the product. Nowadays, this flexible manufacturing technology has expanded its application into a variety of asymmetry or symmetry stockpile products, such as the front end of the high-speed train, aircraft shell components, dental parts etc. This study briefly summarizes the basic mechanism of the ISF technology, recent developments in ISF technology, and some applications in forming complex shaped products.
Matula G.,Dobrzanski L.A.,Kloc A.,Herranz G.,Varez A.,Levenfeld B.,Torralba J.M. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Based on the comparison of structures and properties of the HS6-5-2 high speed steels made with the powder injection moulding method, pressureless forming, compacting and sintering, and commercial steels made with the ASEA-STORA method, fine carbides spread evenly in the steel matrix were found in the structure of all tested high-speed steels in the sintered state. The steels made with the pressureless forming method are characteristic of the lowest sintering temperature and the highest density, resulting from the high carbon concentration coming from the binding agent degradation.
Poly(ethylene 2,6-naphthalene dicarboxylate) 섬유의 고속방사에 따른 미세구조 형성과 물성
조현혹,이화경,김주애,Takeshi Kikutani 한국섬유공학회 2001 한국섬유공학회지 Vol.38 No.11
PEN fibers of two different molecular weights. low and high, were prepared by high-speed melt spinning. The fine structure and physical properties of PEN fibers were investigated with various techniques such as wide-angle X-ray diffraction, birefringence, density. DSC, dynamic viscoelasticity, and tensile testing. From the WAXD test, PEN fibers of high molecular weight was found to have a reflection peak associated with orientation-induced crystallization that started to appear at take up velocities above 3km/min. In this region, the crystalline structure was dominated by $\beta$ form crystal. This tendency was also confirmed by DSC thermogram, density, and birefringence data. In the DSC thermograms, the melting peak shifted to higher temperature with increasing take-up velocity, while the area of cold crystallization peak decreased. Especially, the temperature of melting peak increased remarkably with increasing take-up velocity in the range of 2$65^{\circ}C$ to 298$^{\circ}C$ for PEN fibers of high molecular weight. Mechnaical properties of the two PEN fibers were relatively improved by the high-speed melt spinning at higher spinning speeds. However, the initial modulus and tenacity of PEN fibers of high molecular weight decreased slightly at the take-up velocity of 7km/min.
Development of a Ro- Ro Passenger Ferry with a Large High-Speed Monohull
Jang, Hag-Soo,Joo, Young-Ryeol,Chun, Ho-Hwan The Korean Association of Ocean Science and Techno 2004 Journal of Ocean Science and Technology Vol.1 No.1
Samsung Heavy Industries built and delivered three large high-speed Ro-Ro passenger ferries for Minoan Lines from 2001 to 2002. This paper presents the application method of computational fluid dynamics for hull form optimization and the results of model test and sea trial. In addition to this, the core technology for passenger vessel, i.e., the design concept of general arrangement, interior design, equipment and system design will be described.
전극봉의 와이어 체결 유무에 따른 자유 벌징 금형의 액중방전성형 실험을 통한 SUS430 소재의 성형성 비교
장윤호,김민석,김정 한국소성∙가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.6
Electrohydraulic forming(EHF), one of the high-speed forming method, can supplement the weak point of previous forming process such as deep-drawing and electromagnetic forming. Indeed, EHF is time-consuming process during installing wire before experiment that hard to apply to industry. In this research, applying wireless electrode, the formability of SUS430 sheet was compared through EHF experiments using wire-installed electrode and the other, wireless. Although the power was a little lacking, the advantages of the experiment using wireless electrode could be confirmed with checking the optimal location of electrodes where the plasma is generated and comparing free-bulging height depending on former and later condition of electrodes with performing several single and multistage experiments for same voltage, 6 kV.
45노트급 고속정의 초기선형 개발과 저항성능에 관한 연구
김주남(JU-NAM KIM),정우철(UH-CHEUL JEONG),박제웅(JE-WOONG PARK),김도정(DO-JUNG KIM) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.1
The initial hull form of a 100 ton, 45 knot class high-speed craft is newly developed. The resistance performances are investigated using a model test at high speed in a circulating water channel. The effect of the initial trim is studied together. Wave patterns are observed to clarify the relationship between the resistance performance and the wave characteristics. It can be found that the initial trim plays a role in increasing the resistance performance above a certain velocity.
중형급 알루미늄 고속 Rigid Inflatable Boat 선형개발과 저항성능에 관한 연구
정우철 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.1
In this study, a high speed Rigid Inflatable Boat(RIB) with about 10 meters length is developed. Design speed of the boat is 30 knots (15.43 m/s) using 250 hp twin engines and main material is aluminum. Resistance performance related to the free running attitude as trim and sinkage are discussed and wave patterns are observed to make clear the relationship between the performance and wave characteristics using model test and CFD analysis. The results show that not only wave patterns but also free running attitude of the boat have a strong influence on resistance performance. CFD results including free surface give good relative tendency for effective power and the attitude comparing model test results. CFD analysis used in this study can be used at initial ship design stage of high speed boat.
전자기성형 공정해석을 위한 순차적 전자기-구조 연성 기법
김정(J. Kim),고세진(S. J. Ko),김태정(T. J. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
Electromagnetic forming(EMF) is an impulse or high-speed forming technology using pulsed magnetic field to apply Lorentz forces to workpieces. In this study, a sequential electromagnetic-structural coupling simulation was performed by using the FEM. In each time step, firstly the transient electromagnetic field analysis are executed with the electromagnetic model to obtain the Lorentz forces which are then used as input load to analyze transient dynamic plastic deformation of sheet with the mechanical model. In the simulation, the effect of sheet deformation on electromagnetic field analysis is taken into account. In order to confirm the sequential electromagnetic-structural coupling simulation results, a free bulge test of spec sheet using an EMF apparatus was carried out. As a consequence, it shows that the final bulge height of the sheet predicted from the proposed method in this study is in good agreement with experimental one.