• 소성∙가공
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• 제25권1호
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• pp.43-48
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• 2016

H-beams are generally produced by hot rolling composed of a Break Down Mill (BDM) and a Finishing Mill (FM). The goal of the current study was to develop BDM rolling of H300ｘ300 beams from blooms slit from slabs. In order to manufacture H300ｘ300 beams, the caliber design and the pass schedule of BDM rolling were proposed for a bloom instead of a beam blank. The proposed BDM caliber design and pass schedule were tested using FE-simulation and pilot tests. For the major shape dimensions, such as flange width, web height, web thickness, as well as BDM rolling loads, a comparative analysis between the FE-simulation and the pilot rolling tests was conducted. The results of FEM analysis and pilot rolling tests showed good consistency. Moreover, BDM rolling loads were predicted to be in the range of allowable rolling loads. It was concluded that the designed BDM rolling is suitable for implementation within current manufacturing capacity.

• Journal of Welding and Joining
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• 제20권4호
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• pp.510-516
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• 2002

Recently the laser welding technology has been applied increasingly for the automotive bodies. But the lap joint laser welding for 3 dimensional automotive body is new while the butt joint laser welding is well known as the tailored blank technology. In this study, the process window was found for the full penetration welding of the lap joint of the 1mm-thick high strength steel sheets. The limit curves and characteristic curves were suggested to define the boundaries and the contour lines in a space of the welding speed and the gap size. The characteristics of the weld sectional geometry were used to determine the limit curves. They are bead width, penetration depth and sectional area. After the observed data was analysed carefully, it was noticed that there was a transition point at which the sectional shape was changed and the bead area jumped as the welding speed was increased. Also a new concept of 'input energy Per volume' was suggested to distinguish the difference at the transition Point. The difference of sectional areas at the transition point can be related to the dynamic keyhole phenomena.

• 대한기계학회논문집A
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• 제33권3호
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• pp.276-282
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• 2009

Wrinkling in the flange and wall of a deep-drawn part is one of the major defects in sheet metal processes. Wrinkling is influenced by many factors, such as material properties, shape of the body, forming conditions, stress state and thickness, etc. It is difficult to analyze the wrinkling initiation and growth according to the factors because the effects of the factors are very complex and the wrinkling behavior may show wide variation even though small deviation of factors. In this study, the influence of wrinkling parameters, such as material properties (Al1050, Al5052), the blank holding force and the drawing depth on the wrinkling initiation and growth is investigated by using the experimental method and the dynamic explicit finite element analysis. From the results, it is shown that the dynamic explicit finite element method can be used effectively to prevent the wrinkling problems advancely in the deep drawing process. Also, there is a good agreement between the experimental result and the dynamic explicit finite element analysis.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.56-60
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• 2010

Since the forming process involves the strain rate effect, a yield function considering the strain rate is indispensible to predict the accurate final blank shape in the forming simulation. One of the most widely used in the forming analysis is the Hill48 quadratic yield function due to its simplicity and low computing cost. In this paper, static and dynamic uni-axial tensile tests according to the loading direction have been carried out in order to measure the yield stress and the r-value. Based on the measured results, the Hill48 yield loci have been constructed, and their performance to describe the plastic anisotropy has been quantitatively evaluated. The Hill48 quadratic yield function has been modified using convex combination in order to achieve accurate approximation of anisotropy at the rolling and transverse direction.

• Asian Journal of Atmospheric Environment
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• 제11권1호
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• pp.54-60
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• 2017

Quantifying the trace elements in infinitesimal ambient liquid samples (e.g., single raindrop, cloud/fog water, and the soluble fraction extracted from the particles collected for a short time) is an important task for understanding formation processes, heating/cooling rates, and their health hazards. The purpose of this study is to employ an in-air micro PIXE system for quantitative analysis of the trace elements in a thimbleful of reference liquid sample. The bag type liquid sample holder originally designed with $10{\mu}m$ thick $Mylar^{(R)}$ film retained the original shape without any film perforation and apparent peaks of film blank by the end of the analysis. As one of tasks to be solved, the homogeneity of the elemental distribution in liquid reference species was verified by the X-ray line profiles for several references. It was possible to resolve the significant peaks for whole target elements corresponding to the channel number of micro-PIXE spectrum. The calibration curves for the six target elements (Si, S, Cl, Fe, Ni, and Zn) in standard solutions were successfully plotted by concentration (ppm) and ROI of interest net counts/dose (nC).

• 한국정밀공학회지
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• 제25권12호
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• pp.55-64
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• 2008

This paper describes a research work of developing an automated progressive design system for manufacturing the product with multi processes such as piercing, bending, and deep drawing. An approach to the system for progressive working is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system consists of three main modules, which are shape treatment, strip layout, and die layout modules. Based on knowledge-based rules, the system is designed considering several factors, such as material and thickness of a product, piercing, bending and deep drawing sequence, and the complexities of the blank geometry and punch profiles. It generates the strip layout drawing for an automobile product. Die design for each process is carried out through the die layout module from the results of the strip layout module. Results obtained using the modules enable the designers for manufacturing products with multi processes to be more efficient in this field.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.125-128
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• 2002

The automotive industry have made an effort to reduce the weight of vehicle structures with increased safety, while initial model of the final product does not contain any prehistoric effects in a design stave. It takes lots of time to calculate forming effects that have great influences on the energy absorption of structures. In this paper, finite element inverse analysis is adopted to calculate forming effects, such as thickness variation and effective plastic strain as well as an initial blank shape with small amount of computation time. Crash analysis can be directly performed after inverse analysis of the forming process without remeshing scheme. The direct mesh mapping method is used to calculate an initial guess from the sliding constraint surface that is extracted from the die and punch set. Analysis results show that energy absorption of structures is increased with consideration of forming effects and finite element inverse analysis is usefully applicable to calculate forming erects of vehicle structures for the crash analysis.

• 한국추진공학회지
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• 제18권6호
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• pp.88-95
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• 2014

액체로켓 엔진 재생냉각챔버의 무게 감량을 위하여 내피에 스피닝 공정을 적용하였다. 스피닝 도중 실린더부와 노즐목부의 블랭크에 파손이 발생하였다. 이 문제를 극복하기 위해 맨드럴 및 블랭크 형상을 수정하였으며 이러한 수정을 통해 스피닝을 사용하여 내피를 제작할 수 있었다. 제작된 노즐목부 스피닝 시제품은 균열이나 네킹없이 성공적으로 벌징이 되어 연소기 제작에 적용할 수 있는 충분한 성형성을 확보한 것을 확인하였다.

• 소성∙가공
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• 제7권6호
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• pp.554-561
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• 1998

This paper describes a research work of developing a computer-aided design of lead frame semicon-ductor with piercing operation which is very precise for progressive working. An approach to the sys-tem is based on to knowledge-based rules. Knowledge for the system is formulated from plasticity theories experimental results and the empirical knowledge of field experts. This system has been writ-ten using AutoLISP to AutoCAD on a personal computer and is composed of three main modules which are input and shape treatment production feasibility check and strip-layout module. Based on the knowledge-based rules the system is designed by considering several factors such as material and thickness of product complexities of blank geometry and punch profile, and availability of press. Also strip-layout drawing generated by piercing operation according to punch profiles considered V-notch dimple. pad chamfer spank cavity punch camber and cross bow of lead frame is displayed in graphic forms. This system can be used by a novice who may not have any knowledge of tool design and will invrease efficiencies to the designer in this field.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.374-377
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• 2008

Magnesium alloy sheets are usually formed at temperatures between $150^{\circ}C$and $300^{\circ}C$ because of their poor formability at room temperature. In the present study, the formability of AZ31B magnesium alloy sheets was investigated by the analytical and experimental approaches. First, tensile tests and the limit dome height test were carried out at elevated temperatures to get the mechanical properties and forming limit diagram, respectively. And then deep drawing of cross shaped die was tried to get the minimum corner radius and forming limit at specific temperature. Blank shape, punch velocity, minimum corner radius, fillet size, etc, were determined by finite element analysis physical try-outs. Especially, optimum punch and die temperature were suggested through the temperature-deformation analysis using Pam-stamp.