• Structural Engineering and Mechanics
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• 제52권2호
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• pp.323-349
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• 2014

In this paper, linear buckling analysis of a curved sandwich beam with a flexible core is investigated. Derivation of equations for face sheets is accomplished via the classical theory of curved beam, whereas for the flexible core, the elasticity equations in polar coordinates are implemented. Employing the von-Karman type geometrical non-linearity in strain-displacement relations, nonlinear governing equations are resulted. Linear pre-buckling analysis is performed neglecting the rotation effects in pre-buckling state. Stability equations are concluded based on the adjacent equilibrium criterion. Considering the movable simply supported type of boundary conditions, suitable trigonometric solutions are adopted which satisfy the assumed edge conditions. The critical uniform load of the beam is obtained as a closed-form expression. Numerical results cover the effects of various parameters on the critical buckling load of the curved beam. It is shown that, face thickness, core thickness, core module, fiber angle of faces, stacking sequence of faces and openin angle of the beam all affect greatly on the buckling pressure of the beam and its buckled shape.

• Journal of Advanced Marine Engineering and Technology
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• 제10권4호
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• pp.50-56
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• 1986

This report deals with a study on the boundary layer characteristics of TP620 hydrofoil in the steady state by using two dimensional boundary layer theory. On the basis of complex velocity and laminar and turbulent boundary layer theory, the author attempts to know some tendency by evaluating the performance characteristic values of TP620 hydrofoil working in a uniform flow. In deriving characteristic values, he calculates numerically velocity, momentum thickness, skin friction coefficient, shape factor, and displacement thickness on the TP620 hydrofoil working at each attack angle in a uniform flow. Applying this present numerical calculation using Thwaites' and Head's method, the results of boundary layer on the hydrofoil are shown to be influenced by surface velocity and attack angle.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.124.1-124.1
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• 2016

In this work, uniform thickness and good adhesion of electrodeposited copper layer were achieved on AZ91 Mg alloy in alkaline noncyanide copper solution containing pyrophosphate ion by employing appropriate zincate pretreatment. Without zincate pretreatment, the electrodeposited copper layer on AZ91 Mg alloy was porous and showed poor adhesion which was explained by small number of nucleation sites of copper due to rapid dissolution of the magnesium substrate in the pyrophosphate solution. The zincate pretreatment was found as one of the most important steps that can form a conducting layer to cover AZ91 surface which decreased the dissolution rate of AZ91 Mg alloy about 40 times in the copper pyrophosphate solution. Electrodeposited copper layer on AZ91 Mg alloy after an appropriate zincate pretreatment showed good adhesion and uniform thickness with bright surface appearance, independent of the deposition time but the surface roughness of the electrodeposited copper layer increased with increasing Cu deposition time.

• Structural Engineering and Mechanics
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• 제60권4호
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• pp.707-727
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• 2016

In this paper, thermal vibration of a nonlocal functionally graded (FG) plates with arbitrary boundary conditions under linear and non-linear temperature fields is explored by developing a refined shear deformation plate theory with an inverse cotangential function in which shear deformation effect was involved without the need for shear correction factors. The material properties of FG nanoplate are considered to be temperature-dependent and graded in the thickness direction according to the Mori-Tanaka model. On the basis of non-classical higher order plate model and Eringen's nonlocal elasticity theory, the small size influence was captured. Numerical examples show the importance of non-uniform thermal loadings, boundary conditions, gradient index, nonlocal parameter and aspect and side-to-thickness ratio on vibrational responses of size-dependent FG nanoplates.

• 대한기계학회논문집
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• 제6권3호
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• pp.247-255
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• 1982

The heat diffusion equation for an annular fin is analyzed by Laplace transformation. The fin has a uniform thickness, with its end insulated, and three different temperature profiles at the base such as step change, harmonic and exponential functions. The exact solutions for the temperature and heat flux of the fins are obtained with the infinite series. The series solutions converge rapidly for large values of dimensionless time, but slowly for small values. Therefore some approximate solutions are presented here to fine the temperature distribution and heat flux for small values of dimensionless time. Furthermore a simple approximate heat flux, .OMEGA.=1.13c.tau.$^{1}$2/ is found in the range of .tau. .leg. o.1/c for the exponential function at the base.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.96-99
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• 2007

The microstructure with fine and uniform AGS(austenite grain size) along thickness direction over no recrystallization temperature is strongly required for production of the high strength steels. The previous AGS prediction only based on the average strain improves to find the rolling conditions for accomplishment of the fine grain, but cannot find those for uniform grain. In this paper, an integrated mathematical model for prediction of the strain distribution along thickness direction is developed by carrying out finite element simulation for a series of rolling conditions. Also, the AGS distribution after rough rolling is predicted by applying the proposed model with AGS prediction model.

• 대한설비공학회지:설비저널
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• 제14권2호
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• pp.138-149
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• 1985

The heat diffusion equation for an annular fin is analyzed using Laplace transformations. The fin has a uniform thickness with its edge heat loss and two temperature profiles at the base such as a step change in temperature or heat flux. To obtain the exact solutions for temperature distribution, this paper can detect the eigenvalues which satisfy the roots of transcendental equations in above two cases during inverse Laplace transformations. The exact solutions for temperature and heat flux are obtained with the infinite Series by dimensionless factors. The solutions are developed for small and large values of times. These series solutions converge rapidly for large values of time, but slowly for small.

• 한국전자파학회논문지
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• 제15권8호
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• pp.794-800
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• 2004

본 논문에서 TM 파가 입사할 때 얇은 유전체 strip의 산란특성에 대한 새로운 근사식을 구했다. 구한 식은 uniform하다. 즉 이 식은 어떠한 입사각 또는 관측점, 유전률, strip의 두께 등 모든 경우에 사용할 수 있고 다른 수치해석 방법, MoM을 이용하여 구한 식의 정확도를 여러 경우에 관해 검사해 보았다.

• Structural Engineering and Mechanics
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• 제24권5호
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• pp.515-528
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• 2006

This article presents a unified analytical solution for the analysis of thermal deformations and stresses in elastic annular disks with arbitrary cross-sections of continuously variable thickness. The annular disk is assumed to be under steady heat flow conditions, in which the inner surface of the annular disk is at an initial temperature and the outer surface at zero temperature. The governing second-order differential equation is derived from the basic equations of the thermal annular disks and solved with the aid of some hypergeometric functions. Numerical results for thermal stresses and displacement are given for various annular disks. These disks include annular disks of thickness profiles in the form of general parabolic and exponential functions. Additional annular disks with nonlinearly variable thickness and uniform thickness are also included.

• Steel and Composite Structures
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• 제19권3호
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• pp.679-695
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• 2015

A numerical solution using finite difference method to evaluate the thermal buckling of simply supported FGM plate with variable thickness is presented in this research. First, the governing differential equation of thermal stability under uniform temperature through the plate thickness is derived. Then, the governing equation has been solved using finite difference method. After validating the presented numerical method with the analytical solution, the finite difference formulation has been extended in order to include variable thickness. The accuracy of the finite difference method for variable thickness plate has been also compared with the literature where a good agreement has been found. Furthermore, a parametric study has been conducted to analyze the effect of material and geometric parameters on the thermal buckling resistance of the FGM plates. It was found that the thickness variation affects isotropic plates a bit more than FGM plates.