• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.799-809
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• 2020

In this study, the supercavitating flow of a high-velocity moving body near air-water surface is calculated and analyzed based on a commercial CFD software ANSYS Fluent. The effect of regular wave parameters including both wave height and wavelength on the cavitating flow and force characteristics of a body at different velocities is investigated. It is found that the cavity shape, lift coefficient and drag coefficient of the body vary periodically with wave fluctuation, and the variation period is basically consistent with wave period. When the wavelength is much greater than the cavity length, the effect of wave on supercavitation is the alternating effect of axial compression and radial compression. However, when the wavelength varies around the cavity length, the cavity often crosses two adjacent troughs and is compressed periodically by the two wave troughs. With the variation of wavelength, the average area of cavity shows a different trend with the change of wave height.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.393-398
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• 2001

The technique of high speed machining is widely studied in machining fields, because the high efficiency and accuracy in machining can be obtained in high speed machining. Unfortunately the development of tool for high speed machining in not close behind that of machine tool. In this study, several types flat endmill is prepared for obtaining data according to tool shape. Especially, we concentrated in helix angle, number of cutting edge, rake angle and relief angle. Machinability is measured by cutting force, tool life, tool wear, chip shape and surface roughness according to cutting length. 3-axis cutting forces are acquired from the invented tool dynamometer for high speed machining. Particularly, we found out that the axial cutting force waveform has a good relation with tool wear features. By above results, it is suggested the endmill tool with $45^{\circ}$ helix angle, 6 cutting edge, $-15^{\circ}$ rake angle and $12^{\circ}$ relief angle be suitable for high speed machining

• Structural Engineering and Mechanics
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• 제21권1호
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• pp.35-52
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• 2005

This paper proposes a realistic approach to pushover analyses of reinforced concrete (RC) structures with single column type and frame type. The characteristic of plastic hinge of a single RC column subjected to fixed axial load was determined first according to column's three distinct failure modes which were often observed in the experiments or earthquakes. By using the determined characteristic of plastic hinge, the pushover analyses of single RC columns were performed and the analytical results were investigated to be significantly consistent with those of cyclic loading tests. Furthermore, a simplified methodology considering the effect of the variation of axial force for each RC column of the frame structure during pushover process is proposed for the first time. It would be helpful in performing pushover analysis for the structures examined in this study with efficiency as well as accuracy.

• 산업기술연구
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• 제19권
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• pp.235-243
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• 1999

Vibration analysis for some of simple supported antisymmetric composite laminated plate loaded uniformly distributed axial force and attached mass was carried out. Because it is complicated to analysis this type of plate by theory of antisymmetric laminate, possibility for application of theory of special orthotropic laminate was studied, and natural frequency of laminated plate attached mass was calculated. Stiffness $B_{16}$, $B_{26}$, $D_{16}$, $D_{26}$ for this type of antisymmetric laminated plate converge on zero as the number of ply increases and it is possible to use classical theory by reason that considered plate has quasi-homogeneity without relevance to variation of angle. Difference between results by theory of antisymmetric and special orthotropic laminate is 0.36~1.96%, therefore it is convenient to analyze this by use of theory of special orthotropic laminate. When composite laminated plate with attached mass is analyzed range that was able to neglect self-weight of plate was proposed.

• Steel and Composite Structures
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• 제34권1호
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• pp.75-89
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• 2020

The current paper illustrates the effect of in-plane varying compressive force on critical buckling loads and buckling modes of sandwich composite laminated beam rested on elastic foundation. To generalize a proposed model, unified higher order shear deformation beam theories are exploited through analysis; those satisfy the parabolic variation of shear across the thickness. Therefore, there is no need for shear correction factor. Winkler and Pasternak elastic foundations are presented to consider the effect of any elastic medium surrounding beam structure. The Hamilton's principle is proposed to derive the equilibrium equations of unified sandwich composite laminated beams. Differential quadrature numerical method (DQNM) is used to discretize the differential equilibrium equations in spatial direction. After that, eigenvalue problem is solved to obtain the buckling loads and associated mode shapes. The proposed model is validated with previous published works and good matching is observed. The numerical results are carried out to show effects of axial load functions, lamination thicknesses, orthotropy and elastic foundation constants on the buckling loads and mode shapes of sandwich composite beam. This model is important in designing of aircrafts and ships when non-uniform compressive load and shear loading is dominated.

• Wind and Structures
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• 제27권6호
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• pp.357-368
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• 2018

For a long cable-stayed bridge, stay cables are its most important load-carrying components. In this paper, long-term monitoring of super-long stay cables of Sutong Bridge is introduced. A comprehensive data analysis procedure is presented, in which time domain and frequency domain based analyses are carried out. In time domain, the vibration data of several long stay cables are firstly analyzed and the standard deviation of the acceleration of stay cables, and its variation with time are obtained, as well as the relationship between in-plane vibration and out-plane vibration. Meanwhile, some vibrations such as wind and rain induced vibration are detected. Through frequency domain analysis, the basic frequencies of the stay cables are identified. Furthermore, the axial forces and their statistical parameters are acquired. To investigate the vibration deflection, an FFT-based decomposition method is used to get the modal deflection. In the end, the relationship between the vibration amplitude of stay cables and the wind speed is investigated based on correlation analysis. Through the adopted procedure, some structural parameters of the stay cables have been derived, which can be used for evaluating the component performance and corresponding management of stay cables.

• 전산구조공학
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• 제7권3호
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• pp.133-141
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• 1994

강도활용을 극대화한 볼트의 소성역체결시 볼트의 항복은 볼트에 발생한 인장응력과 너트 나사산과의 접촉면에서 오는 마찰토오크에 의한 전단응력과의 조합에 의한 영향을 받는다. 볼트는 최소단면적인 나사부중 너트와 물리지 않은 여우나사부에서 먼저 항복을 일으킨다. 볼트재료는 대체로 항복과 더불어 소성경화를 보이며 그 정도는 고강도재료에서 인장강도의 10%정도이다. 본 연구에서는 소성역체결시의 거동해석을 변형도증분이론에 의거 해석하였다. 항복은 최소단명이 원통의 표면에서 시작되며 이를 두께가 얇은 원통으로 취급하였다. 항복의 전파는 이들 얇은 원통이 체결이 진행됨에 따라 순차적으로 항복에 이르는 것으로 보고 이 얇은 원통들을 항복시키는데 필요한 축력과 토오크를 합하여 체결종료시의 볼트축력과 (나사면마찰) 토오크로 하였다. M10미터 가는 나사를 계산과 실험에 사용하였다. 축력과 마찰토오크의 마찰계수에 대한 변화관계를 보여주는 그래프와 더불어 실험에서 사용한 볼트의 설계보조 선도를 제시하였다. 이 설계보조용 선도는 실험실에서 얻어진 토오크계수와 마찰계수와의 관계를 그린 것으로 윤활, 포면처리등 현장조건에 따라 달라진 마찰계수를 적절히 취급하는데 효과적으로 활용이 가능하다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권4호
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• pp.229-236
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• 2004

In this paper, the effect of permanent magnet overhang structure on the characteristics in Brushless DC motor has analyzed quantitatively. We classified the overhang structure as symmetric and asymmetric. 3D equivalent magnetic circuit network (EMCN) method which uses the permeance as the distributive variable is used for the efficient analysis of magnetic field. The overhang effect which increases the linkage flux at the stator is verified by comparison between overhang and no overhang structure. In addition, it is known that no load back electro motive force (EMF) is also increased due to the overhang effect. In case of asymmetric overhang structure, the ratio effect of the upper to lower overhang length on the magnetic forces is analyzed. Form the analysis results, the variation of the asymmetric overhang ratio has a significant effect on the axial magnetic force except the radial and tangential magnetic forces. The validity of the analysis results is also clarified by comparison between calculated results and measured ones such as back EMF and cogging torque.

• Advances in Computational Design
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• 제6권1호
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• pp.1-13
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• 2021

Failure of a Multi-storeyed reinforced concrete framed structure occurs when a primary vertical structural component is isolated or made fragile, due to artificial or natural hazards. Load carried by vertical component (column) is transferred to neighbouring columns in the structure, if the neighbouring column is incompetent of holding the extra load, this leads to the progressive failure of neighbouring members and finally to the failure of partial or whole structure. The collapsing system frequently seeks alternative load path in order to stay alive. One of the imperative features of collapse is that the final damage is not relative to the initial damage. In this paper, the effect on the column and beam adjacent to statically removed vertical element in terms of axial force, shear force and bending moment is investigated. Using Alternate load path method, numerical modelling of two dimensional one bay, two bay with variation in storey heights are analysed with FE model in order to obtain better understanding of failure mechanism of multi-storeyed reinforced concrete framed structure. The results indicate that the corner column is more susceptible to progressive collapse when compared to middle column, using this simplified methodology one can easily predict how the structure can be made to stay alive in case of sudden failure of any horizontal or vertical structural element before designing.

• Structural Engineering and Mechanics
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• 제21권5호
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• pp.519-537
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• 2005

A new generalized Bernoulli/Timoshenko beam-column element on a two-parameter elastic foundation is presented herein. This element is based on the exact solution of the differential equation which describes the deflection of the axially loaded beam resting on a two-parameter elastic foundation, and can take into account shear deformations, semi - rigid connections, and rigid offsets. The equations of equilibrium are formulated for the deformed configuration, so as to account for axial force effects. Apart from the stiffness matrix, load vectors for uniform load and non-uniform temperature variation are also formulated. The efficiency and usefulness of the new element in reinforced concrete or steel structures analysis is demonstrated by two examples.