• 소성∙가공
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• 제23권2호
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• pp.88-94
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• 2014

The under-drive brake piston is an essential part in the automatic transmissions of automobiles. This component is manufactured by forging after blanking from S55C plate with a thickness of 6mm. It is difficult to design the plate forging process using a thick plate approach since there will be limited material flow as well as large press loads. Furthermore, the under-drive brake piston has a complex shape with a right angle step, which often results in die unfill and abrupt increase in press load. To overcome these obstacles, a separate die for filling material sufficiently to the corner of the right angle step is proposed. However, this approach induces an uncontrolled workpiece surface between the dies, resulting in flash. This excess flash degrades the tool life in the final machining after cold forging as well as increases the cycle time to obtain the net-shape of the part. In the current study, we propose an optimum process design using a conventional die shaped with the benefit of finite element analysis. This approach enhanced the process efficiency without sacrificing the dimensional accuracy in the forged part. As the result, the optimum plate forging process was done with a two stage die, which reduces weight of by 6% compared with previous process for the under-drive brake piston.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3086-3103
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• 2017

Video images captured by vehicle cameras often contain blurry or dithering frames due to inadvertent motion from bumps in the road or by insufficient illumination during the morning or evening, which greatly reduces the perception of objects expression and recognition from the records. Therefore, a real-time electronic stabilization method to correct fuzzy video from driving recorders has been proposed. In the first stage of feature detection, a coarse-to-fine inspection policy and a scale nonlinear diffusion filter are proposed to provide more accurate keypoints. Second, a new antiblurry binary descriptor and a feature point selection strategy for unintentional estimation are proposed, which brought more discriminative power. In addition, a new evaluation criterion for affine region detectors is presented based on the percentage interval of repeatability. The experiments show that the proposed method exhibits improvement in detecting blurry corner points. Moreover, it improves the performance of the algorithm and guarantees high processing speed at the same time.

• 소성∙가공
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• 제24권4호
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• pp.280-286
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• 2015

Hemming is used to connect two sheet metal components by folding the edge of an outer panel around an inner panel to create a smooth edge. The minimization of hemming defects is critical to the final quality of automobile products because hemming is one of the last operations during fabrication. Designing the hemmed part is not easy and is influenced by the geometry of the bent part. Therefore, the main problem for automotive parts is dimensional accuracy since formed products often deviate geometrically due to large springback. Few numerical approaches using 3-dimensional finite element model have been applied to hemming due to the small element size which is needed to properly capture the bending behavior of the sheet around small die corner and the comparatively big size of automotive opening parts, such as doors, hoods and deck lids. The current study concentrates on the 3-dimensional numerical simulation of hemming for an automotive door. The relationship between the design parameters of the hemming operation and the height difference defect is shown. Quality improvement of the automotive door can be increased through the study of model parameters.

• 소성∙가공
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• 제21권3호
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• pp.202-206
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• 2012

Marking is a process that engraves letters or a pattern onto the surface of sheet metal. During marking, it is important to set the proper working conditions for clarity of the letters. In this study a simple case for forming circular protrusions by half-piercing and embossing was initially attempted to determine the working conditions which gave good results with respect to shape accuracy. Corner-radius and flatness of circular protrusions made under several experimental conditions were measured and compared. It is shown that the precision of protrusions by half-piercing is superior to that of embossing, and the clearance between punch and die exerts a strong influence on the shape accuracy rather than the penetration percentage into the thickness of the sheet metal. The marking dies for "SNUT" letters, as an example, by applying the above results were manufactured with four different clearances. The working variables for the experiment were clearance and marking depth. For the very shallow depth of 0.1mm the letters were not clearly read. Letters marked under other conditions were easily distinguished with increasing marking depth. It was confirmed that the half-piercing technique with proper values of the working variables gives good quality for the marking of sheet metal.

• 대한인간공학회지
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• 제23권3호
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• pp.39-52
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• 2004

Icons are the main element of the graphic user interface (GUI). They can help users perform effectively on the computer, especially when the icons reflect user`s mental model. However, few studies in Korea represented Korean users` mental models in icon design. The purpose of this study, therefore, was to ascertain whether existing icons agreement with Korean twentieth mental model, and to deduce properties of Korean twentieth mental model. To do that, 10 icons from two commercially available toolbar-icons of word processing programs were compared with the newly developed icons, which were developed to represent Korean user`s mental modelthrough interviews, surveys, and mental model sketches. The results show that five new metaphors were found: a dog-eared part on the bottom right corner new for new document, a magnifying glass for search, a red pencil for spell-check, `＋` and `` signs in the magnifying glass for zoom, and a yellow post-it for paste. These new icons were preferred to the existing. Korean twentieth users preferred rather complex and dynamic icons than simple and static ones even though icon development guideline said simple icons are better.

• 소성∙가공
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• 제19권8호
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• pp.508-516
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• 2010

Thickening process in sheet metal forming is being increased to improve the strength as well as to reduce manufacturing process such as welding. This process can make it possible to obtain part locally thicker than that of initial sheet thickness. In this study, design method for manufacturing the component which has double sinks with local thickened wall is proposed. Deep drawing and upsetting processes are applied in order to form double sinks and thicken its walls. Used material is SPHC440 with the thickness of 2.0mm and initial blank size is determined on the basis of the final product. Distance between the center of double sinks and first drawing ratio to avoid fracture are the most significant factors during deep drawing. FE-analysis is implemented in order to determine the appropriate values. Progressive die is designed based on the proposed method and FE-analysis. As a result of experiment, locally thickened component can be manufactured, which has double sinks with the thickness about 3mm at the corner and wall.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제4권1호
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• pp.1-8
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• 2015

고안전성이 요구되는 소프트웨어의 경우 극히 낮은 확률로 발생하는 오류로 인하여 전체시스템의 안전에 치명적인 상황을 야기할 수 있으므로, 철저한 안전성 검증이 요구된다. 하지만 모든 가능한 실행경로를 고려해야 하는 안전성 검증은 고비용이 발생한다는 단점이 있다. 본 논문에서는 안전성 검증의 고비용 문제를 개선하기 위해 안전성 특질을 기준으로 코드 슬라이싱 기법[1]을 구현한 도구를 개발하였다. 개발한 도구를 OSEK/VDX[2] 기반의 개방형 차량 전장용 운영체제인 Trampoline[3] 소스코드에 적용한 결과 분석 대상의 코드의 크기를 평균 71% 줄일 수 있었고, 실제 검증을 수행했을 시에도 도구 적용 이전보다 검증 비용을 절감할 수 있었음을 보였다.

• 한국산학기술학회논문지
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• 제15권12호
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• pp.7302-7308
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• 2014

특정한 제한을 두지 않는 복잡한 자연환경에서 사용자가 원하는 목표 물체만을 정확하게 검출하는 작업은 컴퓨터 비전 및 영상처리 분야에서 중요하지만 매우 어려운 문제 중의 하나이다. 본 논문에서는 반사가 존재하는 여러 환경에서 목표하는 물체를 강인하게 검출하는 새로운 방법을 제안한다. 제안된 방법에서는 먼저 스테레오 카메라를 이용하여 목표 물체를 촬영한 다음, 물체를 가장 잘 표현하는 라인과 코너 특징들을 추출한다. 그런 다음, 촬영된 좌우 영상으로부터 호모그래픽 변환을 이용하여 실제로 존재하지 않는 반사된 특징들을 효과적으로 제거한다. 마지막으로, 반사된 특징들을 제거한 실제 특징들만을 군집화하여 대상 물체만을 강건하게 검출한다. 본 논문의 실험결과에서는 제안된 알고리즘이 기존의 알고리즘에 비해서 반사가 존재하는 자연 환경에서 목표 물체를 보다 강인하게 검출한다는 것을 보여준다.

• 소성∙가공
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• 제29권2호
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• pp.89-96
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• 2020

The finite element method has been widely applied in the sheet metal forming process. However, the finite element method is computationally expensive and time consuming. In order to tackle this problem, surrogate modeling methods have been proposed. An artificial neural network (ANN) is one such surrogate model and has been well studied over the past decades. However, when it comes to ANN with two or more layers, so called deep neural networks (DNN), there is distinct a lack of research. We chose to use DNNs our surrogate model to predict the behavior of sheet metal in the deep drawing process. Thickness variation is selected as an output of the DNN in order to evaluate workpiece feasibility. Input variables of the DNN are radius of die, die corner and blank holder force. Finite element analysis was conducted to obtain data for surrogate model construction and testing. Sampling points were determined by full factorial, latin hyper cube and monte carlo methods. We investigated the performance of the DNN according to its structure, number of nodes and number of layers, then it was compared with a radial basis function surrogate model using various sampling methods and numbers. The results show that our DNN could be used as an efficient surrogate model for the deep drawing process.

• 소성∙가공
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• 제14권9호통권81호
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• pp.772-778
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• 2005

This paper is concerned with the analysis of material flow characteristics of combined tube extrusion using pipe. The analysis in this paper concentrated on the evaluation of the design parameters for deformation patterns of tube forming, load characteristics, extruded length, and die pressure. The design factors such as punch nose radius, die corner radius, friction factor, and punch face angle are involved in the simulation. The combined tube extrusion is analyzed by using a commercial finite element code. This simulation makes use of pipe material and punch geometry on the basis of punch geometry recommended by International Cold Forging Group. Deformation patterns and its characteristics in combined forward and backward tube extrusion process were analyzed for forming loads with primary parameters, which are various punch nose radius relative to backward tube thickness. The results from the simulation show the flow modes of pipe workpiece and the die pressure at the contact surface between pipe workpiece and punch. The specific backward tube thickness and punch nose radius have an effect on extruded length in combined extrusion. The combined one step forward and backward extrusion is compared with the two step extrusion fer forming load and die pressure.