• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.318-321
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• 2007

This paper is concerned with improvement of surface quality of a sheet metal member in the stamping process. The CAE procedure of the stamping process is utilized in order to investigate cause of surface troubles and to improve surface quality. A complicated shape of the sheet metal member can induce surface troubles such as wrinkles because of insufficient tensions force and non-uniform contact of a blank sheet with tools. This paper proposes two guidelines such as a change of tool shape and added draw-beads on the tool surface in order to increase tension forces and to induce uniform contact. The proposed guidelines are verified with the CAE of the stamping process. The CAE results show that the changed shape of tools and added draw-beads can reduce the amount of wrinkles and improve surface quality.

• 한국정밀공학회지
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• 제16권12호
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• pp.143-151
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• 1999

The shape of surface micro-crack is very irregular due to nonhomogeneous microstructure but is very important in respect to qualitative estimation of fatigue life. Fractal geomety can quantify the shape of surface mciro-crack. Fractal dimension is measured for surface micro-cracks with coast line and box counting method and estimates cycle ration in Al 2024-T3. The average fractal dimension $D_{favg}$ of surface micro-cracks has 3-parameter weibull distribution and location parameter is nearly constant but shape parameter decreases as cycle ration increases. The fractal dimension by coast line method is measured for individual surface micro-crack but the fractal dimension by box countin method is measured for all the surface micro-cracks under sampling area. Therefore, This paper shows fractal dimension $D_{fb}$ can predict cycle ratio $N/N_f$ more convenient than fractal dimension $D_{favg}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3116-3121
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• 2007

In this paper, the inverse shape design is introduced using the permeable wall boundary condition. Inverse shape design defines the blade shape for the prescribed Mach numbers or pressure distribution on its surface. It calculates the normal mass flux from the difference between the calculated and prescribed pressure at the surface. A new geometry can be achieved after applying the quasi one-dimensional continuity equation from the leading edge to the trailing edge. For validation of this method, two test cases are studied. The first test case of inverse shape design illustrates the cosine bump with a strong shock. After seven geometry modifications, the shock-free bump geometry can be obtained. The second example concerns the redesign of a transonic turbine cascade. The initial isentropic Mach distribution has a peak on the upper surface. The target isentropic Mach number distribution was imposed smoothly. The peak of Mach distribution has disappeared at the final geometry. This proposed inverse design method has proven to be an efficient and robust tool in turbomachinery design fields.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.112-118
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• 2008

In order to meet the optical performance in the process of the micro lens manufacturing with plastics, it is important to embody accuracy in shape and surface roughness to the intended design. Since it is difficult to machine exactly the mold core of lens fit to the designed shape, in this paper, a simple program using MATLAB is developed for shape correction of the mold core after first machining it. This program evaluates correction parameters(aspheric coefficients and curvature) and generates aspheric NC data for compensating the core surface in prior machining process. The program provides the way to manufacture plastic injection molding lens with aspheric shape of high precision, and is expected to be effective for correction and to shorten the processing time.

• 한국표면공학회지
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• 제49권5호
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• pp.416-422
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• 2016

We have investigated the effects of applied potential, deposition time and electrolyte types on shapes and physical properties of Cu dendrites by potentiostatic electrodeposition. Finer shape of dendrites was observed at less cathodic potential by 100mV than at the limiting current, due to 'effective overpotential'. The shape of copper dendrite is related to the deposition time, too. The dendrite depositing for 10 min showed the finest shape. The finer dendrite has the less apparent density and the larger specific surface area. Dendrite from chloride solution has the lowest density and the largest surface area among three plating solutions, sulfate, chloride and pyrophosphate.

• 대한기계학회논문집
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• 제14권3호
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• pp.617-623
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• 1990

본 연구에서는 표면방향과 깊이 방향으로 표면균열의 피로성장률이 다르게 나 타나고 있는 경우의 표면균열 형상변화를 표면균열의 균열 열림을 고려하여 해석할 수 있는 식이 수정 제안되었으며, 압력용기 소재에서 측정된 표면균열의 형상변화와 본 연구에서 제안된 형상 변화식에 의한 예측과 비교 분석하였다. 또한 균열 성장과 형 상변화를 평균 응력강도계수에 대해 분석하였고 다른 표면균열 형상 변화식들에 의한 표면균열 형상변화해석이 같이 비교 검토되었다.

• 기술사
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• 제27권3호
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• pp.121-131
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• 1994

3차원 자유 형상 곡면으로 이루어진 선형을 부분적으로 표현하기란 매우 힘들다. 선박 설계에 컴퓨터를 이용한 기술이 적용되기 시작하면서, 기하학적 모델링 기법이 개발되어 왔다. 선형 모델링에서,곡률 변화가 심한 선체 곡면의 국부적인 곡면 형상을 Blending 기법을 써서 표현하는 연구는 이루어지지 않았다. Blend곡면을 써서, 설계시에 도면상에 표시되는 작은 곡면을 부드럽게 표현하는 방법을, 선체표면과 돌출된 접합 부분을 Blending 하고져 하였다. 본 연구에서는, 두개의 Base곡면에 Blend반지름을 입력 했을 때, Blend곡면에 Blending방법을 이용하여 공간 좌표인 Offsets 데이터를 얻을 수 있도록 선박 설계에 적용하여 보았다.

• 소성∙가공
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• 제10권7호
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• pp.579-583
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• 2001

Shape changes of a workpiece in an Eulerian Finite Element analysis for the steady state, three-roll-stand shape rolling are modelled. Although an Eulerian analysis has many advantages for the steady state rolling problems, it necessitates an assumption about the unknown shape of the control volume. In almost all cases, the assumed control volume does not match the final shape and the control volume should be updated. This update can be accomplished by performing a free surface correction. The final shape of a material point, which has a spherical shape at the inlet, can be also predicted by integrating a deformation gradient along a stream line. Analyses of three-roll-stand shape rolling are performed and the results are discussed in detail.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.328-331
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• 2001

Shape changes of a workpiece in an Eulerian Finite Element analysis for the steady state. three-roll-stand shape rolling are modelled. Although an Eulerian analysis has many advantages for the steady state rolling problems, it necessitates an assumption about the unknown shape of the control volume. In almost all cases. the assumed control volume does not match the final shape and the control volume should be updated. This update can be accomplished by performing a free surface correction. The final shape of a material point, which has a spherical shape at the inlet, can be also predicted by integrating a deformation gradient along a stream line. Analyses of three-roll-stand shape rolling is in detail examined.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.341-345
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• 2005

Structural Dynamics Modification (SDM) is a very effective technique to improve structure's dynamic characteristics by adding or removing auxiliary structures, changing material properties and shape of structure. Among those of SDM technique, the method to change shape of structure has been mostly relied on engineer's experience and trial-and-error process which are very time consuming. In order to develop a systematic method to change structure shape, surface grooving technique is studied. In this work, the shape of base structure was modified to improve its dynamic characteristics such as natural frequencies via surface grooving technique. Grooving shape was formed by mergingthe neighboring small embossing elements after analyzing frequency increment sensitivities of all the neighboring emboss elements. For this process, Criterion Factor was introduced and the initial grooving was started from the element having highest strain energy and the grooving is expanded into neighboring element. The range of targeting grooving area to check its frequency variations restricted to their neighboring area to reduce the computation effort. This surface grooving technique was successfully applied to a hard disk drives (HDD) cover model to raise its natural frequency by giving some groove on its surface.