• 대한토목학회논문집
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• 제29권2D호
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• pp.217-225
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• 2009

차량의 좌회전반경 및 궤적에 관한 연구는 미비한 실정이다. 이러한 이유로 교차로의 설계시 좌회전반경은 중요하게 반영 되지 않아 부적절하게 적용된 경우를 자주 찾아볼 수가 있으며 그에 따른 좌회전 유도선 또한 부적절하게 그려지고 있는 실정이며 이러한 교차로에서 상충에 의한 안전사고나 교차로용량의 감소가 자주 일어나고 있다. 본 연구는 유럽에서 교차로 설계 시 자주 사용되며 최근 국내에 소개된 바 있는 "물방울 교통섬(Drop Island)"을 교차로의 설계에 적용하여 위와 같은 문제점들을 해결하고자 한다. 기존의 물방울 교통섬 설계방법을 응용하여 실제 설계에 활용할 수 있도록 차종별, 교차각별로 설계방법을 제시하였으며 실제 설계를 통해 각각의 경우 교차점으로부터 정지선의 위치 및 회전 궤적의 시종점거리를 제시하여 설계자가 실무에서 참고하여 보다 쉽게 정확한 좌회전 궤적을 설계에 반영할 수 있도록 하였다.

• 대한기계학회논문집B
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• 제29권6호
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• pp.737-746
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• 2005

The present study investigates heat/mass transfer and flow characteristics in a ribbed rotating passage with turning region. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter ($D_h$) of 26.67 mm. Rib turbulators are attached in the cross arrangement on the leading and trailing surfaces of the passage. The ribs have a rectangular cross section of $2\;mm\;(e){\times}\;mm\;(w)$ and an attack angle of $70^{\circ}$. The pitch-to-rib height ratio (p/e) is 7.5, and the rib height-to-hydraulic diameter ratio ($e/D_h$) is 0.075. The rotation number ranges from 0.0 to 0.20 while the Reynolds number is constant at 10,000. To verify the heat/mass transfer augmentation, internal flow structures are calculated for the same conditions using a commercial code FLUENT 6.1. The heat transfer data of the smooth duct for various Ro numbers agree well with not only the McAdams correlation but also the previous studies. The cross-rib turbulators significantly enhance heat/mass transfer in the passage by disturbing the main flow near the surfaces and generating one asymmetric cell of secondary flow skewing along the ribs. Because the secondary flow is induced in the first-pass and turning region, heat/mass transfer discrepancy is observed in the second-pass even for the stationary case. When the passage rotates, heat/mass transfer and flow phenomena change. Especially, the effect of rotation is more dominant than the effect of the ribs at the higher rotation number in the upstream of the second-pass.

• Structural Engineering and Mechanics
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• 제66권3호
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• pp.285-294
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• 2018

An experimental study has been carried out to analyze the effect of cutting parameters (cutting speed, feed and depth of cut) and tool nose radius on the surface roughness and the cutting force components during hard turning of the AISI 52100 (50 HRC) steel with a ceramic cutting tool. The tests have been conducted according to the methodology of planning experiments, based on an orthogonal plan of Taguchi (L27). By using the response surface methodology (RSM), the components of the cutting force and the roughness of the machined surface were modeled and the effects of the input parameters were analyzed statistically by ANOVA and RSM. The results show that the feed (f), the tool nose radius (r), the cutting speed (Vc), the interaction between feed and tool nose radius ($f{\times}r$) as well as that of the quadratic effect ($f^2$) all have significant effects on the surface roughness (Ra). The feed is the most influencing factor with a contribution of 47.31%. The components of the cutting force were strongly influenced by the depth of cut, followed by the advance with a lower degree. By comparing the experimental values with those predicted by the models of the cutting force components and the surface roughness, it appears that they are in very good correlation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.448-451
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• 2005

An aspheric mirror, which requires less than $\lambda/2\;(\lambda=632.8nm)$ of form error for the $\phi$ 200mm reference curved surface, has been manufactured with an ultra-precision turning machine. We have known through several tests that the deformation patterns of the reflecting surface is related with bolting positions. In this paper the effect of main factors on deformation of a reflector is studied with a FE code. The considered factors are angular velocity, natural frequencies for a mirror, temperature increment during machining. The obtained test results are similar to the deformation shape due to the assumed temperature increment.

• 한국공작기계학회논문집
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• 제10권3호
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• pp.38-42
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• 2001

In the machining of glass fiber reinforced plastics(GFRP), turning has been often used. But the most of past studies have been interested in the effect of fiber orientation on tool wear. In this study, the effects of fiber contents and cutting speeds on tool wear, cutting force and surface roughness are investigated experimentally. By proper selection of cutting tool, the variables are cutting speed, fiber contents and cutting length with fixed feed rate and depth of cut. The fiber contents have major effects on coated tool wear which observed as abrasive wear type.

• 한국정밀공학회지
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• 제16권7호
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• pp.94-100
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• 1999

This study adopted the ultra precision machining system which was composed of an air bearing spindle, a granite bed, air pad and a linear feeding mechanism. It also applied the cutting experiment on the aluminum alloy. To evaluate the safety of high speed machining, we examined the surface roughness according to the changes of cutting speed and obtained the speed limit. This paper also studied the effect of cutting condition such as feed rates and depths of cut on the surface roughness within the speed limit. This provided practical information regarding ultra precision machining.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.939-942
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• 2000

Single point diamond turning technique for optical crystals is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle material.

• 한국정밀공학회지
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• 제20권10호
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• pp.56-64
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• 2003

The effect of tool geometry on the tool wear in turning the austenitic stainless steel, STS 304 was investigated. The wear of TiN-TiCN-TiC-TiAlN coated tungsten carbide tool was the smallest, showing larger wear in the order of Si-Al-O-N ceramic, TiN coated tungsten carbide, TiN- TiCN- TiN coated tungsten carbide, TiC-TiN cermet and M20 tungsten carbide tools at the same cutting conditions. The S-type tool of M20 with the larger side cutting edge angle showed the smallest tool wear in all tests due to preventing the groove wear of the side cutting edge. The wear of the S-type tool with the rake angle of $15^{\circ}$ became smaller than with that of $-5^{\circ}$, but the tool with the nose radius of 0.8mm did not perform much better with increasing the rake angle.

• 천문학회보
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• 제42권1호
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• pp.57.3-58
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• 2017

Single Point Diamond Turning (SPDT) is a cost-effective technique to fabricate metallic mirrors. In particular, the servo-assisted diamond turning option is highly useful for the fabrication of freeform surfaces. However, the SPDT process leaves periodic tool marks on machined mirror surfaces, leading to undesirable diffraction effect, as well as the deviation of input beam. In order to solve this problem, we propose new SPDT machining conditions to minimize tool marks. We will also show the results from optical measurement and Power Spectral Density (PSD) analysis to evaluate the expectable performance for applications in wide field infrared telescopes.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.173-177
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• 2005

The heat/mass transfer characteristics on the plane tip surface of a high-turning first-stage turbine rotor blade has been investigated by employing the naphthalene sublimation technique. The heat/mass transfer coefficient is measured for four tip clearance height-to-chord ratios of h/c = 1.0%, 2.0%, 3.0%, and 4% at the Reynolds number of $2.09{\times}105$. The result shows that at lower h/c, there exists a strong flow separation/re-attachment process, which results in severe thermal load along the pressure-side comer. As h/c increases, the re-attachment is occurred further downstream of the pressure-side comer with lower thermal load. At higher h/c, a pair of vortices on the tip surface near the leading edge are found along the pressure-side and suction-side comers, and the pressure-side tip vortex have significant influence even on the mid-chord local heat transfer.