• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1092-1103
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• 1989

본 논문에서는 기존의 금속성형의 유한요소해석에서 사용한 바 있는 기하적경 계조건을 직접 유한요소방정식에 대입하는 방법들을 비교검토하고 3차원박판성형에 적용하기 위하여 개선된 방법을 개발하였다.

• Clinical and Experimental Pediatrics
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• v.48 no.2
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• pp.212-215
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• 2005

Renal artery stenosis is a major cause of renovascular hypertension and the most common cause of treatable secondary hypertension. There are several methods to treat renal artery stenosis, including surgery, percutaneous transluminal renal angioplasty(PTRA), and renal artery stenting(RAS). But, renal artery embolization can be tried in atherosclerotic stenosis, multiple stenosis, microaneurysm, and stenosis difficult to try PTRA or RAS. We report a case of renovascular hypertension in a 14-year-old female who had multiple segmental renal artery stenosis. Hypertension was controlled by renal ablation therapy with renal artery embolization.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.129-137
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• 1994

A rigid-viscoplastic finite element method has been used for modeling superplastic stretch/blow process design to improve thickness distribution. Punch velocity-time relationship of the stretch forming and pressure-time cycle of the blow forming for a given strain rate are calculated. A superplastic material is assumed to be isotropic and a plane-strain line element based on membrane approximation is employed for the formulation. The effects of the width, corner radius and height of the punch during stretch forming are examined for the final thickness distribution, and the process design to improve thickness distribution can be established.

• Transactions of Materials Processing
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• v.7 no.4
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• pp.354-363
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• 1998

In order to analyze the stretch forming characteristics of tailored blanks, laser welded blanks of different thickness and strength combinations were prepared and stretching tests were done. The stretching formability of laser welded blanks was reduced as increasing the deformation restraining force ($strength{\times}thickness$) ratio between two welded sheets. Weld line movement was attributed to strain concentration at weaker sheets and resulted in fracture at weaker sid, so that fracture could be predicted by the forming limit of the weak sheet. In the case of a welded blank with the similar deformation restraining force rations between two welded sheets, crack occurred at weld and its forming limit was about 15% less than the base sheet. The effects of lubrication and weld line position on stretch-ing formability were also investigated by experiments. Lower friction did not always give better formability for tailored blanks. Stretching formability was observed to be improved as increasing the area of weak sheet.

• Transactions of Materials Processing
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• v.7 no.3
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• pp.207-214
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• 1998

Influence of final thickness distribution in superplastic forming processes on mechanical properties of the product becomes very crucial. We should improve the thickness distribution of products by combining process parameters adequately In this paper we adopt a non-linear optimization technique for optimal process design of superplastic forming. And optimum design variable which makes the most adequate thickness distribution in combined stretc/blow forming and blow forming is predicted by this optimization scheme and rigid-viscoplastic finite element method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.25-32
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• 1994

In order to analyse stretching of perforated sheets for shadow masks by the finite element method for use with the associated flow rule, yield functions which can explain the yield stresses and the apparent plastic contraction ratios of the sheets have been obtained. Coefficients in the yield functions could be determined from the measured apparent plastic contraction ratios under uniaxial tension. Using this yield function and estimated coefficients, the stretching of hole-type and slot-type sheets has been analysed and compared with the experimental results. The calculated results were in good agreement with the experimental results.

• Transactions of Materials Processing
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• v.7 no.1
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• pp.36-48
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• 1998

In order to analyze the stretch flange forming characteristics of tailored blanks. laser welded blanks of different thickness and strength combinations were prepared and hole expansion tests were done. The stretch flange formability of laser welded blanks was reduced as increasing the deformation restraining force($strength{\times}thickness$) ratio between two welded sheets. Simulation of stretch forming mode deformation and comparson with experimental results showed that the stretch flange formabili-ty was influenced not only by the difference of the deformation restraining forces between two base sheets but also by the difference of the deformation restraining forces between base sheet and weld. Therefore the stretch flange formability was reduced more rapidly than tensile elongation as increas-ing the deformation restraining force ration. It was also found that simulation of stretch flange forming was more accurate when material properties of weld was given.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.89-92
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• 2002

편성물은 신축성이 좋으므로 의류용 소재로써 다양하게 사용되어지고 있다. 편성물의 장점으로는 직물과는 달리 루프 형태로 얽힌 편환으로 구성되어 있기 때문에 제편 과정에서 필요한 형태로의 성형이 용이해서 제품의 다양화를 기대할 수 있다. 뿐만 아니라 신축성과 유연성, 다공성, 구김안정성 등이 우수하여 인체의 여러 가지 활동에 따른 구속감이 적으며 인체의 굴곡을 아름답게 나타내어 주는 등의 장점이 있어 의복 소재로써 차지하는 비중이 높다. (중략)

• 기계와재료
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• v.23 no.4
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• pp.16-25
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• 2011

본고는 자연모사공학에서 출발하여, 자연계에 존재하는 건식 접착 성질을 이용하기 위한 방법으로서 게코도마뱀의 발바닥 섬모 구조를 모사하기 위한 방안들을 설명하고 그 응용분야를 전망한다. 도마뱀의 섬모 구조가 가지는 네 가지 특징들은 고분자 폴리머 재료와 나노 신장 기술, 2단계 UV 자외선 성형 기술, 전자빔 조사 등과 같은 기술을 통해 구조 및 기능의 모사가 가능하고 실제로 제작된 구조는 좋은 접착 특성을 나타냄을 알 수 있었다. 이를 토대로 다양한 섬모 구조에서의 접착 성능을 분석하고 실제 생활에서 바이오 패치로의 응용 가능성을 제시하였다.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.413-416
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• 2011

Flip top cap은 경량성, 가공성, 내식성 우수하여 최근에 생활 용기 뚜껑으로 많이 활용되고 있다. Flip top cap은 사출성형에 의해 제작 되며 사출성형 과정에서 힌지부분에 웰드라인(Weldline)이 형성되어 기계적 강도가 떨어지게 된다. Flip top cap은 생활용기에 사용되며 실제생활에서 많은 작동을 요구하기 때문에 힌지부분의 웰드라인은 제품불량에 큰 원인이 된다. 또한 Flip top cap은 생산성을 높이기 위해 멀티캐비티(Multi-cavity) 사출방식을 선호한다. 멀티캐비티 방식은 높은 사출압력을 요구하기 때문에 사출품의 불량과 사출기에 많은 부하가 예상된다. 본 연구에서는 게이트 위치를 조정함으로써 사출품 힌지부분에서 발생할 수 있는 웰드라인을 품질에 영향이 없는 곳으로 이동시키고 최적의 사출 압력을 찾기 위한 유동해석을 통해 최적의 사출조건을 도출함으로써 Flip top cap의 기계적 품질과 제품생산성 향상을 위한 연구가 수행되었다.