• 한국정밀공학회지
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• 제15권8호
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• pp.17-25
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• 1998

Aluminum alloys have low density, relatively high strength and yield strength, good plasticity, good machinability, and high corrosion and acid resistance. Therefore, they are suitable for large containers for the food, chemical and other industries. Large containers are often bodies of revolution consisting of shell courses, stiffening rings, heads and other elements joined by annular welds. Larger containers have longer welds and require greater leak-tightness and higher weld mechanical properties. The LNG tank consists of aluminum plates with various sizes, so its construction should by divided by several sections. Moreover, each section has its own sub-section consisted of several aluminum plates. To guarantee the quality of huge LNG tank, therefore, the precise control of plate dimension should by urgently needed in conjunction with the appropriate selection of process parameters such as cutting speed, depth of cut, rotational speed and so on. In this paper, a manufacturing system was developed to implement automatic circular tracking in height direction and automatic circular interpolation in depth of cut direction. Also, the neural network based on the backpropagation algorithm was used to predict the cutting quality and motor load related with the life time of the developed system. It was revealed that the manufacturing system and the neural network could be effectively applied to the bevelling process and to predict the quality of machined area and the motor load.

• Structural Engineering and Mechanics
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• 제64권5호
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• pp.591-610
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• 2017

This paper is concerned with the static analysis of variable thickness of two directional functionally graded porous materials (FGPM) circular plate resting on a gradient hybrid foundation (Horvath-Colasanti type) with friction force and subjected to compound mechanical loads (e.g., transverse, in-plane shear traction and concentrated force at the center of the plate).The governing state equations are derived in terms of displacements based on the 3D theory of elasticity, assuming the elastic coefficients of the plate material except the Poisson's ratio varying continuously throughout the thickness and radial directions according to an exponential function. These equations are solved semi-analytically by employing the state space method (SSM) and one-dimensional differential quadrature (DQ) rule to obtain the displacements and stress components of the FGPM plate. The effect of concentrated force at the center of the plate is approximated with the shear force, uniformly distributed over the inner boundary of a FGPM annular plate. In addition to verification study and convergence analysis, numerical results are displayed to show the effect of material heterogeneity indices, foundation stiffness coefficients, foundation gradient indices, loads ratio, thickness to radius ratio, compressibility, porosity and friction coefficient of the foundation on the static behavior of the plate. Finally, the responses of FG and FG porous material circular plates to compound mechanical loads are compared.

• 대한기계학회논문집A
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• 제27권4호
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• pp.601-607
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• 2003

The column type is used as the sensing element of the load cell to measure the large force in the range of 10$^4$~ 10$^{7}$ N. However. it is not easy to handle the load with large capacity due to its size. It is, therefore, necessary to design a compact load cell with a low aspect ratio. Thus this paper showed the characteristic evaluation of compact load cell with respect to the shape of supporting plate. The supporting plate of the load cell was an annular type with inner(D$_{i}$) and outer(D$_{o}$) diameters. Using the strain distribution obtained from FEM. the supporting plate was designed to get the stable output voltage of the load cell. The three designed supporting plates were manufactured, and the result of characteristic experiment of the load cell, using the 10 MN hydraulic force standard machine, was compared with FEM.M.M.

• 대한기계학회논문집B
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• 제24권7호
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• pp.1002-1009
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• 2000

Among the various types of diesel after-treatment device, the corona discharge reactor may be considered as a powerful process for trapping submicron particles. But after precipitation on the electrodes occurs, the reentrainment of particles is severe and often causes low or negative precipitation efficiency. Experiments were performed to investigate the effect of an applied voltage on the reentrainment of soot particles from the electrodes. A co-annular laminar diffusion flame burner was used as the soot generator. When a highly negative voltage was applied, exfoliation of the deposited soot particles and an increase in concentration of particles smaller than approximately 150 nm were observed. Turbulence induced from the negative tuft corona and sputtering caused particle reentrainment from the corona wire and from plates as well. Under soot laden combustion gas, a streamer corona often occurred in the wire-cylinder reactor. Because of its transient nature, streamer corona violently increased the concentration of reentrained particles and CO gas.

• Current Optics and Photonics
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• 제2권2호
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• pp.147-152
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• 2018

We propose a novel bi-focal metallic Fresnel zone plate (MFZP) with shallow depth-of-field (DOF) characteristics. We design the specific annular slit patterns, exploiting the phase-selection-rule method along with the particle swarm optimization algorithm, which we have recently proposed. We numerically investigate the novel characteristics of the bi-focal MFZP in comparison with those of another bi-focal MFZP having equivalent functionality but designed by the conventional multi-zone method. We verify that whilst both bi-focal MFZPs can produce dual focal spots at $15{\mu}m$ and $25{\mu}m$ away from the MFZP plane, the former exhibits characteristics superior to those of the latter from the viewpoint of axial resolution, including the axial side lobe suppression and axial DOF shallowness. We expect the proposed bi-focal MFZP can readily be fabricated with electron-beam evaporation and focused-ion-beam processes and further be exploited for various applications, such as laser micro-machining, optical trapping, biochemical sensing, confocal sensing, etc.

• 한국전산구조공학회논문집
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• 제22권5호
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• pp.463-474
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• 2009

기존에 설치되어 있는 구조물의 양면대칭 패치보강은 항상 면내거동만을 유발하나 시공상 어려움이 있다. 반면에 일면 패치보강의 경우 인장력의 증가에 따라 중립축의 위치가 대칭이 아니므로 휨에 대한 강성도가 증가하게 되며, 결과적으로 적층판의 휨을 심화시키게 된다. 이 연구에서는 일면 패치보강된 적층판의 두께방향은 물론이고 원공주위의 응력집중계수를 산정하기 위해 p-수렴 완전층별모델을 제안하였다. 가정된 변위장의 정의를 위해, 임의의 층에서 변위-변형률 관계와 3차원 구성방정식은 2차원 및 3차원 계층적 형상함수의 조합이 사용된다. 원형경계의 기하형상을 나타내기 위해 초유한사상기법이 사용되며, 다른 외삽법을 사용하지 않고 각 층마다 절점에서의 응력값을 직접적으로 얻기위해 가우스-로바토 수치 적분이 수행되었다. 제안된 모델의 정확도와 단순성은 기존의 3차원 유한요소해석과 실험에 의해 구해진 결과들과의 비교를 통해 검증되었다. 또한 정사각형, 원형, 고리형 형상의 다양한 패치보강에 따른 휨효과를 조사하였다.

• 대한기계학회논문집A
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• 제35권4호
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• pp.417-424
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• 2011

핵연료집합체는 상단고정체, 하단고정체, 지지격자체, 제어관/계측관과 핵연료봉의 5 가지 주요 구성품으로 이루어져 있다. 여기서 상/하단고정체는 다른 구성품과 달리 ASME, Section III, Division 1 - Subsection NB 의 운전조건 A, B 에서의 stress intensity limits 를 만족하여야 한다. 이중냉각 핵연료집합체는 집합체당 출력을 증가시키기 위해서 기존의 가압경수로용 핵연료집합체에서 핵연료봉의 배열과 위치를 변화시켰는데 이로 인하여 핵연료봉 내/외부유로로 냉각수가 잘 흐를 수 있도록 상/하단고정체의 유로판의 형상을 수정하여야 한다. 본 논문에서는 설계하중조건에 대하여 수정된 상단고정체 유로판의 건전성평가를 위해 수행한 응력선형화과정을 자세히 설명하고 평가결과에 대하여 기술하였다.

• 대한기계학회논문집B
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• 제25권9호
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• pp.1209-1218
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• 2001

The present paper proposes a new correlation for the flow boiling heat transfer coefficients in the low flow rate condition (Re(sub)LF$\leq$200) within horizontal rectangular channels with small gaps (heights). The gap between the upper and the lower plates of each channel ranges from 0.4 to 2mm while the channel width being fixed to 20mm. Refrigerant 113 was used as the test fluid. The mass flux ranges from 50 to 200kg/㎡s and the channel walls were uniformly heated with the heat flux range of 3-15kW/㎡. The quality range covers from 0.19 to 0.76 and the flow pattern is considered to be annular. The measured heat transfer coefficients increase with the mass flux and the local quality; however the effect of the heat flux appears to be minor. At the low mass flux condition, which is more likely with the smaller gap size, the heat transfer is primarily controlled by the liquid film thickness. The proposed F factor for the heat transfer coefficient in the range of Re(sub)LF$\leq$200 well represents the experimental data within the deviation of $\pm$20%. The Kandlikars flow boiling correlation covers the higher flow-rate range(Re(sub)LF>200) within the deviation of $\pm$20%.