• Design & Manufacturing
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• 제17권1호
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• pp.33-39
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• 2023

The ball end mill is a type of cutting tool that is widely used to process complex mold shapes including aspheric surfaces. Unlike the flat end mill in which the cutting edge is formed on the cylindrical handle, the cutting edge is formed from the cylindrical handle to the hemispherical shape, which is advantageous for processing curved shapes. However, since the cutting speed continuously changes during machining due to the helix angle of the cutting edge or the machining inclination angle, it is difficult to obtain a precise machined surface. Therefore, in this paper, machining was performed while changing the helix angle of the ball end mill and the angle of the machining slope under the same cutting conditions for STD 11 material, which is widely used as a mold material. Through this, the effect of the two variables on the roughness of the machined surface was analyzed. As a result, if the helix angle was 0 degrees, it showed the best surface roughness of Ra. 0.16 ㎛. When the helix angle was 20 degrees, the best surface roughness of Ra. 0.18 ㎛ was occurred.

• 콘크리트학회논문집
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• 제24권2호
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• pp.147-156
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• 2012

최근 몇 년간 보-기둥 접합부에 영향을 줄 수 있는 경사기둥을 포함한 비정형 구조 시스템을 가진 초고층 빌딩이 증가하고 있다. 경사기둥-보 접합부에 외력이 작용 시 전단과 휨 모멘트의 분포가 정형화된 보-기둥 접합부와 상이하여 접합부의 파괴모드, 전단강도, 연성능력 및 에너지소산능력이 변화할 가능성이 크다. 이 연구에서는 6개의 철근콘크리트 경사기둥-보 접합부($90^{\circ}$, $67.5^{\circ}$, $45^{\circ}$) 실험을 수행하고 결과를 분석하였다. 실험 결과에 의하면 경사기둥-보 접합부에서 비대칭 파괴가 발생하였으며 수직기둥-보 접합부에 비해서 최대하중과 에너지소산능력이 감소하는 것으로 나타났다. 이것은 경사기둥으로 인해 발생되는 접합부의 상이한 모멘트 분포와 압축력만 받는 수직기둥과 다르게 경사기둥이 압축력뿐 아니라 인장력도 작용하기 때문이다.

• 대한기계학회논문집B
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• 제33권6호
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• pp.435-442
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• 2009

Three-dimensional heat transfer characteristics for natural convection flows are numerically investigated in the doubly-inclined cubical-cavity according to the variation of a newly defined orientation angle �� of the hot wall surface from horizontal plane at moderate Rayleigh numbers. Numerical simulations of laminar flows are conducted in the range of Rayleigh numbers($10^4{\leq}Ra{\leq}10^5$) and $0^{\circ}{\leq}{\alpha}90^{circ}$ with a solution code(PowerCFD) employing unstructured cell-centered method. Comparisons of the average Nusselt number at the cold face are made with benchmark solutions and experimental results found in the literature. It is found that the average Nusselt number at the cold wall has a maximum value around the specified orientation ${\alpha}$ at each Rayleigh number. Special attention is also paid to three-dimensional thermal characteristics in natural convection according to new orientation angles at Ra��= $1{\times}10^5$, in order to investigate a new additional heat transfer characteristic found in the range of above Ra = $6{\times}10^4$.

• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1003-1012
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• 2008

A three dimensional numerical study has been applied to predict the turbulent fluid flow and heat transfer characteristics for the rectangular channel with different types of baffles. Four different types of the baffles are used. The inclined baffles have the width of 19.8 cm, the square diamond type hole having one side length of 2.55 cm, and the inclination angle of $5^{\circ}$. Reynolds number is varied between 23,000 and 57,000. The SST k-${\omega}$ turbulence model is used in the present numerical study. The validity of the numerical results is examined with the experimental data. The numerical results of the flow field depict that the flow patterns around the different baffle type are entirely different and it significantly affects the local heat transfer characteristics. The heat transfer and friction factor depend significantly on the number of baffle holes. It is found that the heat transfer enhancement of baffle type II (3 hole baffle) has the best values.

• Ocean Systems Engineering
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• 제3권2호
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• pp.79-95
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• 2013

Suction anchors are widely adopted in mooring systems. However there are still challenges in predicting the failure mode and ultimate pullout capacity of the anchor. Previously published methods for predicting the inclined pullout capacity of suction anchors are mainly based on experimental data or the FEM analysis. In the present work, an analytical method that is capable of predicting the failure mode and ultimate pullout capacity of the suction anchor in clay under inclined loading is developed. This method is based on a rational mechanical model for suction anchors and the knowledge of the mechanism that the anchor fails in seabed soils. In order to examine the analytical model, the failure angle and pullout capacity of suction anchors from FEM simulation, numerical solution and laboratory tests in uniform and linear cohesive soils are employed to compare with the theoretical predictions and the agreement is satisfactory. An analytical method that can evaluate the optimal position of the attachment point is also proposed in the present study. The present work proves that the failure mode and pullout capacity of suction anchors can be reasonably determined by the developed analytical method.

• Geomechanics and Engineering
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• 제10권2호
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• pp.155-174
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• 2016

A total of 104 laboratory model tests on a square footing subjected to eccentrically inclined loads supported by sand reinforced with randomly distributed polypropylene fibers were conducted in order to compare the results with those obtained from unreinforced sand and with each other. For conducting the model tests, uniform sand was compacted in a test box at one particular relative density of compaction. The effect of percentage of reinforcement used, thickness of the reinforced layer, angle of inclination of load to vertical and eccentricity of load applied on various prominent factors such as ultimate load, vertical settlement, horizontal deformation and tilt were investigated. An improvement in ultimate load, vertical settlement, horizontal deformation and tilt of foundation was observed with an increase in the percentage of fibers used and thickness of reinforced sand layer under different inclinations and eccentricities of load. A statistical model using non-linear regression analysis based on present experimental data for predicting the vertical settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) of square footing on reinforced sand at any load applied was done where the dependent variable was predicted settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) respectively.

• Structural Engineering and Mechanics
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• 제44권6호
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• pp.801-814
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• 2012

The strain rate effects on the interaction between a Mode I matrix crack and an inclined elliptic matrix-inclusion interface under dynamic tensile loadings were investigated numerically, and the results are in agreement with previous experimental data. It is found, for a given material system, that there are the first and the second critical strain rates, by which three kinds of the subsequent crack growth patterns can be classified in turn with the increasing strain rate, namely, the crack deflection, the double crack mode and the perpendicular crack penetration. Moreover, such a crack deflection/penetration behavior is found to be dependent on the relative interfacial strength, the inclined angle and the inclusion size. In addition, it is shown that the so-called strain rate effect on the dynamic strength of granule composites can be induced directly from the structural dynamic response of materials, not be entirely an intrinsic material property.

• 한국지능시스템학회논문지
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• 제21권3호
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• pp.283-289
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• 2011

본 논문에서는 차륜형 역진자에 적용되는 속도 추정기 기반 제어기 설계와 다양한 수치 시뮬레이션이 수행되었다. 차륜형 역진자는 불안정한 평형점과 안정한 평형점을 동시에 갖는다. 불안정한 평형점에 대하여 평형을 유지하기 위하여 차륜형 역진자는 지속적으로 제어되어야 한다. 제어기의 입력으로 차륜형 역진자 몸체의 각도, 각속도, 변위 속도 등이 필요하다. 필요한 속도는 모터에 부착된 에코더 신호를 차분하여 얻어지며, 엔코더의 해상도에 민감하게 의존한다. 저해상도 엔코더와 속도 추정기에 기반하여 개선된 속도 검출법이 제안되고 경사면에서 유효함을 보이기 위해서 다양한 수치 시뮬레이션이 수행되었다.

• Imaging Science in Dentistry
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• 제32권1호
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• pp.35-39
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• 2002

Purpose: The altered gantry angle during scanning for some multiplanar reconstruction CT program (CT/MPR) may cause distortion of the image. The aim of this study was to ascertain whether there is a image distortion in a reformatted image when the gantry and the object are equally inclined using ToothPix and DentaScan program. Materials and Methods: A resin block model with four cylindrical holes and a human dry mandible were used. Two MPR software packages, ToothPix and DentaScan program, were used for reformatted panoramic images. The block and the gantry were equally inclined at 0°, 15°, and 30°. Results: With ToothPix program, a resin block model with empty holes and a dry mandible showed inclined images in the reformatted panoramic image. Increasing the gantry angle, the depth and inclination of the holes were increased in the reformatted central panoramic images. However, a resin block model with gutta perch a in its holes and a dry mandible with a wire in its mandibular canal didn't show image distortion. With DentaScan program, image distortion was not seen in any situation. Conclusion: ToothPix program may distort the reformatted image when the gantry angle is not at zero degrees. However, with DentaScan program, the patient may be positioned comfortably and the gantry can be adjusted to the patient positioning.

• 대한방사선기술학회지:방사선기술과학
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• 제43권6호
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• pp.489-494
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• 2020

The Law method is observing the temporal bone. There are two types of methods: the double angle method, which manipulates the center ray angle of the tube twice, and the single angle method, which manipulates once. The purpose is to increase the reproducibility of the image by making vertical incidence by making an assistive device using a 3D printer. Two assistive devices with a wedge-shaped 8.5 × 10 × 2.3 cm, an inclined surface of 7.5 cm, and an inclination angle of 15° were fabricated. Assistive devices can be combined with each other in the form of grooves, and PLA (Poly Lactic Acid) is used as a material. In the first experiment, 10 examiners operated the tube 15° in the caudad direction and 15° in the anterior direction, and measured it with a protractor to conduct a reproducibility experiment. Second, two examiners acquired vertically incidence images using the existing law method and assistive devices, and measured the distance between each measurement point to evaluate the reproducibility. The tube center ray angle reproducibility experiment was not statistically significant, but the angle difference was up to 9° between examiners. The reproducibility experiment of radiographic images was not statistically significant with the conventional method, and the method using an assistive device was statistically significant. Therefore, regardless of skill level, an image capable of securing reproducibility, which is the advantage of vertical incidence, could be obtained.