• 소성∙가공
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• 제10권2호
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• pp.115-122
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• 2001

It is well known, for many years, that deep drawability can be improved by applying variable blank holding force. To apply variable blank holding force during cup drawing, we set up cushion pressure control system on the hydraulic press, and the pressure control system is often called NC(Numerically Controlled) cushion system. A cushion pressure control experiment was carried out using the NC cushion and it was shown that the proposed system produced good performance. The comparison of drawability of square cups with and without NC cushion showed that the drawability could be greatly improved when S-shaped pressure curve was applied. This paper includes design details of the NC cushion system and experimental analysis of drawability with NC cushion system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.471-476
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• 2001

Milli-structure components ate classified as a component group whose size is between macro and micro scales, that is, about less than 20mm and larger than 1mm. The forming of these components has a typical phenomenon of bulk deformation with thin sheets because of the forming size. In this study, milli-structure rectangular cup drawing is analyzed and measured using the finite element method and experiment. Generally, milli-structure containers or cases like cellular phone vibrator consist of rectangular-shaped drawing to save installation space. A systematic approach is established for the design and the experiment of the forming processes for rectangular milli-structure cases. To verify the simulation results, the experimental investigations were also carried out on a real industrial product. The numerical analysis by FEM shows good agreement with the experimental results in view of the deformation shape of the product.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.175-179
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• 2004

Since the formability of AZ31 magnesium alloy is not good in room temperature, it is known that high temperature forming is advantageous. However, many studies are necessary to find the proper forming temperature for Mg alloy. In this study, experimental and FEM analysis are performed to investigate the forming temperature for AZ31 sheet. The deep drawing process of square cup is used in forming experiment and FEA. The investigations are performed in three forming temperature, room temperature, $250^{\circ}C\;and\;400^{\circ}C$. The square cup is well formed in $250^{\circ}C$ forming temperature, on the other hand, the crack and failure is presented in corner section in room and $250^{\circ}C$ forming temperature. The main cause is investigated as the effect of hardening range by the experimental and FEM results.

• 소성∙가공
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• 제21권5호
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• pp.291-297
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• 2012

In this paper, the effect of back tension in multi-pass drawing or wiredrawing on the central bursting defect is investigated using finite element predictions. A rigid-plastic finite element method was used together with the McClintock damage model. Central bursting defects under different back tension stress values ranging from 0% to 20% of the yield strength of the material were predicted and they were compared to understand the effect of the back tension stress values on the central bursting defect. It is found that the level of back tension has a strong influence on the cumulative damage. Thus, higher back tension raises the possibility of the central bursting defect occurring, even though it decreases the interfacial pressure between the die and the work piece.

• 한국정밀공학회지
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• 제13권1호
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• pp.116-122
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• 1996

In forming processes, die failure must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The die wear affects the tolerances of formed parts, metal flow and costs of processes etc. The only way to control these failures is to develop methods which allow prediction of the die wear and which are suited to be used in the design state in order to optimize the process. In this paper, wire drawing processes were simulated using the rigid-plastic finite element method and its results were used for predicting the die wear by Archard's wear model. The effects of the temperature rising on the wear profiles of die were also investigated. The simulation results were compared with the measured die profiles.

• 한국해양공학회지
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• 제14권4호
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• pp.86-91
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• 2000

Numerical simulation of sheet metal forming for panels as other components has wide acceptance in the automotive industry. Therefore this paper was focused in the drawability factors (which are friction coefficient , radius of die and punch ) on the square cup deep drawing by the explicit finite elements code $PAM-STAMP^{TM}$. The computed results are compared with the experimental results to show the validity of the analysis. In order to compare the simulation results with the experiment results and predict the effect of drawability factors, the relationships between punch load punch stroke, and the relationships between thickness strain and distance are used. According to this study, the results of simulation by using $PAM-STAMP^{TM}$ will give engineers good information to access the drawability of square drawing.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.341-346
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• 2002

The production part requiring multiple processes such as piecing, blanking and notching are performed with a high production rates in progressive die. In order to prevent the defects of process result, the optimum of strip process layout design, die design, die making, and tryout with inspection etc. are needed. According to these factors of die development process, they required theory and practice of metal working process and its background, die structure, machining conditions for die making, die materials, heat treatment of die components, know-how and so on. In this study, we designed and analyzed die components also simulated the strip process layout of multiple stage drawing by DEFORM. Especially the result of tryout and its analysis become to the feature of this study.

• 한국환경교육학회지:환경교육
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• 제21권2호
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• pp.68-79
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• 2008

This study investigated undergraduate students' perceptions and mental models of the environment. A total of 192 students were sampled from a university of Gyoungbuk area. The environmental task was administrated to students drew a picture of an environment and explained their drawing. The results are as follows: First, a majority of undergraduate students perceived an environment from a comfortable environment. Second, five mental models emerged from a content analysis of students' responses about environmental drawing. Third, the dominant model was mental model 4, the environment as a place where animals, plants, and humans live. This means that the majority of students perceived a 'relation' rather than 'objects' views of the environment. Therefore, undergraduate students' conceptualizations about environment depends on a view or mental models of the environment which places humans in a sustaining relationship with the environment and its natural resources. The implications of these findings for environmental education are discussed.

• 소성∙가공
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• 제23권3호
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• pp.159-163
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• 2014

In the current study, the effect of small surface defects in the starting material including roughness, indentations, or scratches, which are perpendicular to the direction of drawing, on the product quality is investigated using the finite element method. An axisymmetric defect is assumed. Such defects are defined by a cylindrical defect area and two tapered regions connecting the defect area to the non-defective area of the material. Various conditions for these initial surface defects are considered, including defect depth, defect slope and defect length. To describe the plastic deformation of the defect in detail during the simulation, local remeshing is applied. Based on the finite element results, defect disappearance maps were generated. It was found that defect disappearance is significantly dependent on the defect depth and the defect length coupled with the defect slope.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3687-3691
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• 2012

다양한 디지털 콘텐츠 생성 기술은 최근의 컴퓨터 및 태블릿 PC의 발전으로 더욱 널리 활용되고 있다. 본 연구에서는 실제 화가의 스케치 작품을 분석해, 그와 유사한 스케치 효과를 생성하는 기법을 제안한다. 이를 위해, 우리는 반 고흐의 실제 드로잉 작품을 분석하고, 각 객체별로 사용된 스케치 스트로크의 패턴을 분석하고 DB를 구성한다. 그리고 이를 기반으로, 각 오브젝트별로 해당 스트로크 패턴을 적용하여 스케치 효과를 재현하였다.