• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.364-367
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• 2007

Typical seamless tube production methods are an extrusion and a rotary tube piercing. The rotary piercing process is more competitive than the extrusion process form view point of productivity, quality, and flexibility. It consists of twin rolling mills, a pair of disc or flat guides, and a plug. Twin rolling mills are skewed with proper angles in two directions. A round billet is progressively fed forward and rotated due to the rotation of twin rolling mills. Internal crack initiation and growth at central area of the billet are gradually progress because of the repeating actions of tension and rotation. Design variables in the rotary piercing rolling process are the feed angle, the cross angle, the reduction ratio, and the position of plug. In this work, a rotary tube piercing machine was developed and parametric studies on design variables were carried out using finite element analysis. The Brozzo ductile fracture criterion was utilized to determine an internal crack initiation.

• 소성∙가공
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• 제26권1호
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• pp.11-17
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• 2017

In this study, process analysis of elbow-shaped tubes using a mandrel has been performed. To reach the final shape within the dimensional tolerance, the process analysis has been performed at various processing parameters such as tube dimensions, the curved cutting surface and the radius of curvature. The area outside the boundary of the target shape was expressed as a quantitative index to analyze the formability. The validation experiments have also been performed in order to increase the reliability of the process analysis. For the processing of elbow-shaped tubes, it is preferable to make the angle of the portion where the punch touches the tube smaller than the opposite angle. And the convex cutting surface is advantageous due to the increased contacts between the punch and the tube ends during the bending process. Elbow tube having larger radius of curvature shows higher dimensional accuracy due to the relatively uniform strain distribution.

• 설비공학논문집
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• 제16권11호
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• pp.1028-1034
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• 2004

Recently, the ice storage system using ice slurry has been used increasingly since it has been introduced where the rapid cooling load change is required. Because it overcomes a decrease of the melting performance and an increase of the thermal resistance on the ice layer in static ice thermal storage system. This study is performed to understand the effects of transporting ice slurry through horizontal, vertical and inclined tubes ($30^{\circ},\;45^{\circ}$). It used propylene glycol-water solution and ice particles (diameter of about 2 mm) in this experiment. The experiments were carried out under various conditions, with concentration of water solution ranging from 0 to $20wt\%$, and velocity of water solution at the entry ranging from 1.5 to 2.5 m/s. The results were as follows: Regarding the angle of inclined tube, the highest pressure loss was measured for vertical tube and the pressure loss for $45^{\circ},\;30^{\circ}$, horizontal straight tubes were lower successively. The lowest pressure loss in these tubes was measured at velocity of $2.0{\sim}2.5m/s$ and concentration of $10wt\%$. The outlet IPF was likewise stable in these ranges.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.76-79
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• 2005

Bending deformation and energy absorption characteristics of aluminum-composite hybrid tube beams have been analyzed for improvement in the bending performance of aluminum space frame by using experimental tests combined with theoretical and finite element analyses. Hybrid tube beams composed of glass fabric/epoxy layer wrapped around on aluminum tube were made in autoclave with the recommended curing cycle. Basic properties of aluminum material used for initial input data of the finite element simulation and theoretical analysis were obtained from the true stress-true strain curve of specimen which had bean extracted from the Al tube beam. A modified theoretical model was developed to predict the resistance to the collapse of hybrid tube beams subjected to a bending load. Theoretical moment-rotation angle curves of hybrid tube beams were in good agreement with experimental ones, which was comparable to the results obtained from finite element simulation. Hybrid tube beams strengthened by composite layer on the whole web and flange showed an excellent bending strength and energy absorption capability.

• 한국방사선학회논문지
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• 제7권4호
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• pp.271-275
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• 2013

어깨뼈 검사는 일상생활, 스포츠 활동 시에 어깨관절의 후측부나, 후외측부에 강한 외력이 가해서 발생하는 직접외상에 의한 경우와 상완부에 주로 외전, 신전, 외회전력이 가해져 어깨관절 탈구 등 병변의 유무를 관찰하는데 유용하게 사용되고 있다. 본 연구의 목적은 어깨관절 후전사방향촬영(shoulder PA oblique projection, scapula Y-view)의 촬영각도에 따른 영상의 왜곡을 방지하고 방사선학적 진단에 가장 유용한 촬영 각도를 알아보고자 하였다. 어깨뼈체부와 봉우리(acromion) 및 부리돌기(coracoid process)는 Y자를 이루게 되는데 $10^{\circ}$에서는 어깨뼈와 봉우리사이의 각도가 협착되어 나타나고, $20^{\circ}{\sim}25^{\circ}$에서는 Y자에 위팔뼈머리가 겹쳐 보이며, 어깨관절과의 위치도 적절해 보였다. $35^{\circ}$에서는 위팔뼈머리가 Y자에 겹쳐 보이지만, 위팔뼈머리와 어깨관절이 왜곡되어 보였다. 환자체위는 $45^{\circ}$ 거상시킬 때 가장 적합한 측면상을 관찰되며, 봉우리(acromion) 및 부리돌기(coracoid process)도 Y 자를 이루었다.

• 한국염색가공학회지
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• 제28권4호
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• pp.246-252
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• 2016

In comparison to metal alloys, braided composite features a high impact resistance and crash energy absorption potential, and also it still remained competitive stiffness and strength properties. Braiding angle is one of the most important parameters which affect the mechanical behaviors of braided composite. This paper presents transverse low velocity impact failure behavior analysis on the carbon 3D triaxial braided composite tube with the braiding angle of $20^{\circ}$, $50^{\circ}$ and $80^{\circ}$. The flexural behaviour of 3D triaxial braided composite tube under bending loads was studied by conducting quasistatic three point bending test. Also, the low velocity impact responses of the braided composite tubes were also tested to obtain load-displacement curves and energy absorption. Consequently, the increase of the braided angle, the peak load also increases owing to the bigger bending stiffness.

• 한국방사선학회논문지
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• 제12권3호
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• pp.397-402
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• 2018

본 연구는 엉치엉덩관절의 골절, 탈구, 엉치엉덩 퇴행성관절염 진단을 위한 가장 좋은 영상을 얻기 위해 골반 팬톰과 엑스선관을 각도 변화를 주어 엉치엉덩관절의 Joint space 가장 잘 나타내는 영상을 얻어 방사선사에게 주관적 평가를 받아 보았다. 평가 결과 결론으로 엉치엉덩관절염과 퇴행성 관절염 발견을 위한 단순촬영에서는 엎드린상태에서 촬영은 검사반대쪽 엉덩이를 $25^{\circ}{\sim}30^{\circ}$ 들어올리고 엑스선관을 앞엉덩뼈가 시에서 2.5 cm 안쪽을 지나는 시상면에 대해 수직촬영 하고 누운자세에서는 검사쪽 엉덩이를 $25^{\circ}{\sim}30^{\circ}$ 들어 올리고 위앞엉덩뼈가시가 중앙에서 위앞엉덩뼈가시가 중앙에 대해 엑스선관 각도를 발쪽으로 $5^{\circ}$ 촬영 하며 반드시 양쪽 엉치엉덩관절후전사방향(RAO,LAO) 및 전후사방향(RPO, LPO) 모두 촬영을 하게 되면 관절염 진단을 내리는데 있어 많은 도움이 되리라 본다.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3014-3021
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• 2015

셀-튜브 열교환기는 다양한 크기와 유동형태로 쉽게 제작이 용이함으로 산업분야에 널리 이용된다. 본 연구에서는 열교환기의 열전달성능을 도모하고자 배플의 컷 방향, 배플의 경사각 및 배플의 회전각 등을 변경하여 ANSYS FLUENT v.14를 사용한 SST $k-{\omega}$ 난류모델을 적용하여 쉘 내부의 열전달률 및 압력강하 특성을 해석하였다. 그 해석결과로 배플의 컷 방향은 수평형 모델 A보다 수직형 모델 B 및 각도 $45^{\circ}$형 모델 C가 이 열전달성능이 향상되는 것으로 나타났다. 또한 배플의 경사각을 $10^{\circ}$로 적용한 경우와 배플의 회전각을 $0^{\circ}-90^{\circ}-180^{\circ}-270^{\circ}$로 배치한 모델 D의 경우가 열전달률 및 압력강하 특성이 우수한 결과를 나타냈다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.634-639
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• 2001

The current study addresses experimental and computational work of impulse wave discharged from the exit of two kinds of right-angle pipe bends, which are attached to the open end of a simple shock tube. The weak normal shock wave with its magnitude of Mach number from 1.02 to 1.20 is employed to obtain the impulse wave propagating outside the exit of the pipe bends. A Schlieren optical system visualizes the impulse wave discharged from the exit of the pipe bends at an instant. The experimental data of the magnitude of the impulse wave and its propagating directivity are analyzed to characterize the impulse waves discharged from the exit of the pipe bends and compared with those discharged from a straight pipe. Computational results well predict the experimented dynamic behaviors of the impulse wave. The results obtained show that a right-angle miter bend considerably reduces the magnitude of the impulse wave and its directivity toward to the pipe axis, compared with the straight pipe and right-angle smooth bend. It is believed that the right-angle miter bend pipe can playa role of a passive control against the impulse wave.

• 한국초전도ㆍ저온공학회논문지
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• 제1권1호
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• pp.42-47
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• 1999

Enthalpy transport in a pulse tube was investigated by two-dimensional analysis of mass. momentum an energy equations of the gas as well as energy conservation of the tube wall. The mean temperature of the gas and the tube wall was obtained directly by assuming that the outer surface of a pules tibe wall is adiabatic. Axial profile of mean temperature is small. but it deviates significantly from linear profile when the dimensionless frequency is large. Effect of operating frequency. tube wall thickness, velocity ratio and velocity phase angle between both ends of a pulse tube on net enthalpy flow were shown.