• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.604-609
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• 2001

In the sheet metal forming process, the drawbead is used to control the flow of material during the forming process. The drawbead provides proper restraining force to the material and prevents defects such as wrinkling or breakage. For these reasons, many studies for designing the effective drawbead have been conducted. For the analysis, the numerical method called the static-explicit finite element method was used. The finite element analysis code for this method has been developed and applied to the drawbead process problems. In result, convergence problem and computation time due to large non-linearity in the existing numerical analysis methods were no longer a critical problem. Futhermore, this approach could treat the contact friction problem easily by applying very small time intervals. It is expected that various results from the numerical analysis will give very useful information for the design of tools in sheet metal forming process.

• 소성∙가공
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• 제15권8호
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• pp.533-538
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• 2006

A simplified numerical procedure to predict drawbead restraining forces(DBRF) has been developed based on the hybrid membrane/bending method which superposes bending effects onto membrane solutions. As a semi-analytical method, the new approach is especially useful to analyze the effects of various constitutive parameters. The present model can accommodate general anisotropic yield functions along with non-linear isotropic-kinematic hardening under the plane strain condition. For the preliminary results, several sensitivity analyses for the process and material effects such as friction, drawbead depth, hardening behavior including the Bauschinger effect and yield surface shapes on the DBRF are carried out.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2010년도 춘계학술발표논문집 2부
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• pp.618-621
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• 2010

럼버 서포트는 허리에 가해지는 압력을 지지하여 장시간 운전시 피로감을 해소하는 자동차 시트의 부품이다. 본 연구에서는 자동차 시트의 럼버 서포트를 모델링 하였으며, 해석은 럼버 서포트의 베드부분에 여러가지의 비드를 보강하여 사람이 자동차 시트에 앉아 있을 때 작용하는 하중에 따른 변형에 대해 구조해석을 하여 안락성면에서 적합한 모델을 찾는 것이 주된 목적이다. 5줄 보강타입과 풀타입이 5mm안쪽의 변형과 500 N의 접촉력이 나타나 승객의 안락감에 있어 가장 적합하고 내구성도 양호한 것으로 사료된다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.493-497
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• 2002

In the part industry, pipe has required high accuracy in surface roughness and size. Especially, when producing the high frequency welding pipe, cutting process is very important as the finishing process that remove the hot welding bead. The objective of this paper is to investigate the hot machining high frequency welded pipe by simulation and experimental tests. To test the cutting process as hot machining, all cutting environment is reproduced in turning with heating system, and the test is accomplished by comparing with room temperature machining and hot machining in consideration of cutting force, tool wear and cutting temperature.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.275-281
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• 2001

In the sheet metal forming process, the drawbead is used to control the flow of material during the forming process. The drawbead provides proper restraining force to the material and prevents defects such as wrinkling or breakage. For these reasons, many studies for designing the effective drawbead have been conducted. In this paper, the effect of the drawbead shape will be introduced. For the analysis, the numerical method called the static-explicit finite element method was used. The finite element analysis code for this method has been developed and applied to the drawbead process problems. In result, convergence problem and computation time due to large non-linearity in the existing numerical analysis methods were no longer a critial Problem. Futhermore, this approach could treat the contact friction problem easily by applying very small time intervals. It is expected that various results from the numerical analysis will give very useful information for the design of tools in sheet metal forming process.

• 한국산업융합학회 논문집
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• 제10권1호
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• pp.5-14
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• 2007

It is necessary for development of drawing product with press to have suitable material selection & all process design and the problem during press process has been cleared from judgement of experience & trial and error. Recently we can estimate press process result from computer aided design & FEM. But we can get more reliable result when we can put more precise process variants during FEM. In case of using a drawbead that is used for the material inflow, it is considered for us to put material property, other analysis condition & friction figure when material is passing through the drawbead for better FEM. From our study, we have drawn an analogy bead connection depth, friction figure & drawing and restraining load according to kinds of lubrication from experiment & FEM for the drawbead. We applied above result to the drawing experiment & FEM and confirmed the validity. We could notice the relation between friction figure & drawing load and the friction figure variation according to kinds of lubrication. It is expected to draw more precise analogy that can be used for real process due to more precise process variants application to FEM.

• 한국해양공학회지
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• 제15권2호
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• pp.72-78
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• 2001

The bead is used to provide properly restraining force in the sheet metal forming process. This bead process includes bending and geometrical non-linearity, and affects the state of binderwrap. Therefore, the analysis of bead process is very important to obtain the desired formability. In this paper, the research about the influence of the punch stroke of bead on the draw-bead process was conducted. Results from the analysis will give useful information to the effective tool design of blank forming process. To analyze the bead process, and elasto-plastic finite element formulation is constructed from the equilibrium equation and the considered boundary conditions involved a proper contact condition. The static-explicit finite element method as a numerical method for the analysis was applied to the analysis program code. It was found that this method could solve too much computation time and convergence problem owing to high non-linearity of bead forming process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.46-46
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• 2008

스텔스 기능을 가진 군사용 항공기는 레이다 망의 추적을 피하기 위해 일반 냉각수 대신에 절연유를 냉각매체로 사용한다. 그러나 절연유는 물에 비하여 열전달특성이 매우 낮기 때문에 항공기 전기전자 기기/부품 발열부를 효과적으로 냉각시키지 못하는 한계성을 가지고 있다. 따라서 본 연구에서는 나노유체(Nanofluid) 개념을 이용하여 절연유에 알루미나 및 질화알루미늄 나노분말을 미랑 분산시킨 나노절연유를 제조하고 이것의 열전달특성을 순수 절연유의 그것과 비교 평가함으로써, 냉각특성이 크게 개선된 새로운 냉매로서의 적용 가능성을 확인하고자 하였다. 다만 나노절연유를 제조함에 있어서 가장 큰 장애물은 오일에 대한 분산성 확보에 있기 때문에, 비드밀 및 초음파를 이용한 나노분말 응집체의 습식분산 및 분산제를 이용한 친유성 표면개질을 동시에 수행함으로써 장시간 안정된 분산성을 확보하도록 노력하였다. 나노유체의 열전도도 및 대류열전달계수는 비정상열선법을 이용하여 측정하였으며, 유체 속의 분말 분산 상태는 원심력을 이용한 분산안정성 평가장치 및 cryo FE-SEM을 이용하여 확인하였다. 또한 분말 형상이 대류열전달에 미치는 영향을 조사하기 위하여 알루미나 나노분말은 구상과 침상의 분말을 모두 사용하였고, 질화알루미늄 외에 다이아몬드 나노절연유도 함께 제조, 평가함으로써 냉각 및 절연특성, 그리고 물리화학적 안정성이 우수하고 실적용 가능성이 가장 높은 재료를 도출하고자 하였다.

• Journal of Welding and Joining
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• 제29권6호
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• pp.77-81
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• 2011

In most industry, manual GTAW welding is preferred for formation of stable back bead in root weld of butt joint. However, manual GTAW welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this paper, the design of U-groove with 3mm root face was applied to extend the tolerance of misalignment in condition of standard root gap 1.5mm. Consequently, for the formation of stable back bead in root pass of butt welding, in case of the narrow root gap(0.5mm) the large arc force was applied by increasing the current and voltage. In case of the large root gap(2.5mm), the small arc force was applied by decreasing the current and voltage. Considering the various root gap, the required deposited metal was controlled by welding speed only.

• 미생물학회지
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• 제55권3호
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• pp.286-288
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• 2019

벼 종자에서 분리한 Pseudomonas parafulva PpaJBCS1880 (PpaJBCS1880) 균주는 lipopeptide를 분비하여 식물의 세균 병원균에 대해 강력한 항균력을 나타냈다. 또한, PpaJBCS1880는 콩불마름병의 발생을 억제하였을 뿐만 아니라, 벼의 생육을 촉진하였다. 이에 따라, 본 연구에서는 PpaJBCS1880 균주의 전체염기서열을 해독하고 분석하였는데, 총 염기서열은 5,208,480 bp였고, GC 함량은 63.4%였다. 염색체는 4,487개의 단백질을 암호화하였고, 19개의 rRNA와 74개의 tRNA로 구성되어 있었다. 유전체의 분석을 통해 2차 대사산물인 lipopeptide, pyoverdine, phenazine 및 hydrogen cyanide 등을 생산하는 것을 확인하였는데, 이들 대사산물에 의해 항균력, 생물방제 및 생육촉진 효과를 나타내는 것으로 판단된다.