• 한국해양환경ㆍ에너지학회지
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• 제9권2호
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• pp.79-84
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• 2006

본 연구는 자연지형에 존재하는 다양한 형태의 크고 작은 거칠기 요소들로 인해 기본 유동장이 변화하는 양상을 밝히기 위한 기초연구로서, 본 제1보와 이어지는 제2보로 나뉘어 소개될 것이다. 실험은 동일한 2차원 사각단면을 갖는 많은 양의 거칠기 요소를 평판위에 규칙적으로 배열한 후 거칠기 주위 유동장을 계측하였다. 회류수조에서 PIV 기법을 사용하여 2종류의 거칠기요소 높이와 3종류의 거칠기 사이 간격을 택하여 총 6경우에 대하여 거칠기 유동의 특성을 비교하였다. 실험결과 거칠기 간격이 거칠기 높이의 7배와 14배인 경우가 3.5배에 비하여 거칠기로 인한 유통장의 교란이 더 활발하고, 그에 따라 유동장에 미치는 영향도 큼을 확인할 수 있었다.

• 한국기계가공학회지
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• 제14권6호
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• pp.63-68
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• 2015

Recently, 3D printer technologies have been used in many research efforts for high precision manufacturing. In particular, the rapid prototyping technology has been developing rapidly, because it can be manufactured in a short time with a 3D designed shape. This paper relates to the production characteristics of the straight bevel gear designed using a 3D print using the PolyJet method. The characteristics of a 3D printed straight bevel gear were compared with a machined straight bevel gear. The accuracy of the produced straight bevel gear was evaluated by backlash, meshing pattern, face angle, root angle, and surface roughness.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.349-354
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• 2001

In this study, we investigated the effect of the impacting ang1e of particles, the scanning times and the stand-off distance on the surface roughness and the weight-loss rate of samples with no mask, and the wall profile and overetching of samples with different mask pattern in powder blasting of soda-lime glass. The varying parameters were the different impact angles between 50$^{\circ}$ and 90$^{\circ}$, scanning times of nozz1e up to 40 and the stand-off distances 70mm and 100mm. The widths of mask pattern were 0.2mm, 0.5mm and 1mm. The powder was alumina sharp particles, WA#600. The mass flow rate of powder during the erosion test was fixed constant at 175g/min and the blasting pressure of powder at 0.2MPa

• 한국기계가공학회지
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• 제11권5호
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• pp.29-34
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• 2012

This study describes the selection of optimum machining conditions for a high-hardness resin by using a large 5-axis machine. The experiments were conducted to examine the main factors that affect the surface roughness, such as the spindle speed, axial and radial depths of the cut, and pattern of the cutter path. To analyze the experiment results, the factor with the biggest impact on machining was determined using the smaller-the-better characteristic of the Taguchi method; the effectiveness of the experiment was then confirmed by verifying the selected optimum machining condition.

• 한국공작기계학회논문집
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• 제16권1호
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• pp.53-59
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• 2007

The cutting tests of wood patterns are carried out using CNC milling machine. The cutting forces are monitored to analyse the cutting process. The surface characteristics of machined surface are investigated at various cutting conditions such as cutting speed, feed speed, cutting direction of wood pattern and wood material. In the CNC end-milling, the surface roughness increases as feed speed increases and decreases as cutting speed increases. However, the cutting force and surface roughness are different along the cutting direction and material of wood pattern.

• 동력기계공학회지
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• 제18권1호
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• pp.128-134
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• 2014

For the characteristic assessment of biomimetic shark skin structure pattern for engineering applications, we conducted the elastic hydrodynamic lubrication analysis for the shark skin surface pattern. The shark skin surfaces with roughness are generated numerically in the similar size with real shark skin scales. For the spherical contact on the generated shark skin surface with two different flow directions which are transversal and longitudinal, 3-dimensional elasto-hydrodynamic lubraction analysis are carried out. The result of the longitudinal flow which are similar with the flow of shark skin shows more beneficial effects with lower pressure and less sensitive effect with surface roughness.

• 대한치과보철학회지
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• 제40권2호
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• pp.184-192
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• 2002

The purpose of this study was to investigate the abrasion resistance and surface roughness of conventional dental stones and improved dental stones and newly developed dental stones. Materials included in this study were several dental stones and newly developed dental stone; 2 type III. 6 type IV (including newly developed dental stone). 1 type V Ten specimens for each material, total ninety specimens were made. Each specimen was subjected to 50 complete cycle abrasion under constant load 0.42N at speed or 6mm per sec. The depth after abrasion test was measured for each specimen. Surface roughness before and after abrasion test was compared. The results were as follows ; 1. The resin containing die materials such as Tuff Rock and Resin Rock had superior abrasion resistance. 2. Type IV, V dental stone exhibited greater abrasion resistance than Type III dental stone. 3. The results or the surface roughness showed similar pattern with the abrasion resistance.

• 한국해양환경ㆍ에너지학회지
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• 제9권2호
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• pp.85-91
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• 2006

본 연구는 자연지형에 존재하는 다양한 형태의 크고 작은 거칠기 요소들로 인하여 기본 유동장이 변화하는 양상을 밝히기 위한 연구로서 회류수조에서 PIV 기법을 사용하여 수행되었다. 먼저 제1보에서는 동일한 2차원 사각단면을 가지는 많은 양의 거칠기 요소를 평판위에 규칙적으로 배열한 후 거칠기요소의 높이와 거칠기 사이의 간격이 다른 세 경우에 대하여 유속, 유선 및 와도분포를 계측하여 거칠기 유동의 특성을 살펴보았다. 본 2보에서는 난류유동특 성을 비롯하여 벽법칙을 이용한 해석과 경계층 적분변수 도출을 통하여 거칠기 간격이 유동장 변화에 미치는 영향을 정량적으로 비교하고자 하였다. 실험결과 거칠기 간격이 거칠기 높이의 7배와 14배인 경우 3.5배에 비하여 거칠기로 인한 유동장의 변화가 큼을 재차 확인할 수 있었다.

• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.43-55
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• 2015

This paper presents the thermal hydraulic performance of a three dimensional rib-roughened solar air heater (SAH) duct with the one principal wall subjected to uniform heat flux. The SAH duct has aspect ratio of 12.0 and the Reynolds number ranges from 2000 to 12000. The roughness has relative rib height of 0.045, ratio of dimple depth to print diameter of 0.5 and rib pitch ratio of 8.0. The flow attack angle is varied from $35^{\circ}$ to $70^{\circ}$. Various turbulent flow models are used for the heat transfer and fluid flow analysis and their results are compared with the experimental results for smooth surfaces. The computational fluid dynamics (CFD) results based on the renormalization k-epsilon model are in better outcomes compared with the experimental data. This model is used to calculate heat transfer and fluid flow in SAH duct with the compound roughness of V-shaped ribs and dimples. The overall thermal performance based on equal pumping power is found to be the highest (2.18) for flow attack angle of $55^{\circ}$. The thermo-hydraulic performance for V-pattern shaped ribs combined with dimple ribs is higher than that for dimple rib shape and V-pattern rib shape air duct.

• 한국생산제조학회지
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• 제19권5호
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• pp.616-621
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• 2010

New type of the base material of the light-emitting diode requires copper wafer in view of heat and electrical conductance. Therefore, polishing process of the substrate level is needed to get a nanometer level of surface roughness as compared with pattern structure of nano-size in the semiconductor industry. In this paper, a series of lapping and polishing technique is shown for the rough and deflected copper substrate of thickness 3mm. Lapping by sand papers tried air cooling method. And two steps of polishing used the diamond abrasives and the $Al_2O_3$ slurry of size 100mm considering the residual scratch. White-light interferometer proved successfully a mirror-like surface roughness of Ra 6nm on the area of $0.56mm{\times}0.42mm$.