• Structural Engineering and Mechanics
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• v.47 no.3
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• pp.421-442
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• 2013

This paper is concerned with the theoretical treatment of transient thermoelastic problems involving a functionally graded hollow cylinder with piecewise power law due to asymmetrical heating from its surfaces. The thermal and thermoelastic constants of each layer are expressed as power functions of the radial coordinate, and their values continue on the interfaces. The exact solution for the two-dimensional temperature change in a transient state, and thermoelastic response of a hollow cylinder under the state of plane strain is obtained herein. Some numerical results for the temperature change and the stress distributions are shown in figures. Furthermore, the influence of the functional grading on the thermal stresses is investigated.

• Interaction and multiscale mechanics
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• v.4 no.3
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• pp.219-237
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• 2011

Recent advances in scientific computing enable the full atomistic simulation of DNA molecules. However, there exists length and time scale limitations in molecular dynamics (MD) simulation for large DNA molecules. In this work, a two-level homogenization of DNA molecules is proposed. A wavelet projection method is first introduced to form a coarse-grained DNA molecule represented with superatoms. The coarsened MD model offers a simplified molecular structure for the continuum description of DNA molecules. The coarsened DNA molecular structure is then homogenized into a three-dimensional beam with embedded molecular properties. The methods to determine the elasticity constants in the continuum model are also presented. The proposed continuum model is adopted for the study of mechanical behavior of DNA loop.

• Structural Engineering and Mechanics
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• v.20 no.5
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• pp.559-573
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• 2005

This paper is concerned with the theoretical treatment of transient thermal stresses involving an orthotropic functionally graded thick strip due to nonuniform heat supply in the width direction. The thermal and thermoelastic constants of the strip are assumed to possess orthotropy and vary exponentially in the thickness direction. The transient two-dimensional temperature is analyzed by the methods of Laplace and finite sine transformations. We obtain the exact solution for the simply supported strip under the state of plane strain. Some numerical results for the temperature change, the displacement and the stress distributions are shown in figures. Furthermore, the influence of the orthotropy and nonhomogeneity of the material is investigated.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.3
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• pp.256-266
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• 1997

The authors apply the transfer influence coefficient method to the 3. dimensional vibration analysis of beam with multi - joints and formulate a general algorithm to analyse the longitudinal, flexural and torsional coupled forced vibration. In this paper, a structure which is mainly found in the robot arms, cranes and so on, has some crooked parts, subsystems and joints, but has no closed loop in this system. It is modeled as the beam of a distributed mass system with massless translational, rotational and torsional springs in each node, and joint elements of release or roll at node which the displacement vector is discontinuous. The superiority of the present method to the transfer matrix method in the computation accuracy was confirmed from the numerical computation results. Moreover, we confirmed that boundary and intermediate conditions could be controlled by varying the values of the spring constants.

• Journal of applied mathematics & informatics
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• v.30 no.1_2
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• pp.253-264
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• 2012

In the present article, we construct the exact traveling wave solutions of nonlinear PDEs in the mathematical physics via the (1+1)-dimensional Boussinesq equation by using the following two methods: (i) A further improved ($\frac{G}{G}$) - expansion method, where $G=G({\xi})$ satisfies the auxiliary ordinary differential equation $[G^{\prime}({\xi})]^2=aG^2({\xi})+bG^4({\xi})+cG^6({\xi})$, where ${\xi}=x-Vt$ while $a$, $b$, $c$ and $V$ are constants. (ii) The well known extended tanh-function method. We show that some of the exact solutions obtained by these two methods are equivalent. Note that the first method (i) has not been used by anyone before which gives more exact solutions than the second method (ii).

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.4
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• pp.257-265
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• 1981

A modified subsonic wind tunnel was employed to investigate the turbulent flow of a valve jet. To effectuate this experimental study, an actual valve and valve seat of a diesel engine were equipped at its outlet (ref. Fig. 3) Theoretically, using the equation of motion of Navier-Stokes in the chlindrical coordinates, the turbulent equation of motion for the incompressible fluid was derived with three assumptions; steady flow (.delta./.delta.t=0), axisymmetry and revolutionary homogeneity(.delta./.delta..phi.=0), no ensemble revolution (V.iden.0). Experimentally, mean and fluctuation velocities have been measured in the redial direction. With a assumption of a non-dimensional velocity distribution equation, a sami-emperical similarity profile equation of the jet flow have been derived, whose empirical constants were deterimed graphically with the data obtained.

• Structural Engineering and Mechanics
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• v.57 no.6
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• pp.1143-1156
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• 2016

This paper presents a comparative study of finite element method (FEM) and analytical method for the plane problem of a layered composite containing an internal perpendicular crack in literature. The layered composite consists of two elastic layers having different elastic constants and heights. External load is applied to the upper elastic layer by means o a rigid punch and the lower elastic layer rests on two simple supports. Numerical simulations are realized by the world wide code ANYS software. Two dimensional analysis of the problem is carried out and the results are verified by comparison with solutions reported in literature. Main goal of the numerical simulation is to investigate the normal stress ${\sigma}_x$(0, y), stress intensity factors at the crack factor and the crack opening displacements.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.54-58
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• 2003

In this study, the solution of Gel'fand-Levitan-Marchenko integral equation in the inverse scattering problem is efficiently solved for arbitrarily specified spectra pattern which are reflected from the restricted potential. The procedure is based on the successive approach without iterations. This method lessens the truncation errors which plague conventional design schemes using specific windows for reflection coefficients. It is shown that the method is adequate for the synthesis of the continuously varying one-dimensional potential of the nonuniformly distributed dielectric constants.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1841-1850
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• 1993

A simplified one-dimensional analysis has been performed to predict the local pressure distributions in Y-Jet twin-fluid atomizers. Fluid compressibility was considered both in the gas(air) and two-phase(mixing) ports. The annular-mist flow model was adopted to analyze the flow in the mixing port. A series of experiments also has been performed; the results show that the air flow rate increases and the liquid flow rate decreases with the increase of the air injection pressure and/or with the decrease of the liquid injection pressure. From the measured injection pressures and flow rates, the appropriate constants for the correlations of the pressure loss coefficients and the rate of drop entrainment were decided. The local pressures inside the nozzle by prediction reasonably agree with those by the experiments.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.252-261
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• 1999

The 3-dimensional finite element program is developed to analyze the non-isothermal forming processes of aluminum-alloy sheet metals. Bishop's method is introduced to solve the heat balance and force equilibrium equations. Also, Barlat's non-quadratic anisotropic yield function depicts the planar anisotropy of the aluminum-alloy sheet. To find an appropriate constitutive equation, four different forms are reviewed. For the verification of the reliability of the developed program, the computational try-outs of the non-isothermal cylindrical cupping processes of AL5052-H32 and Al1050-H16 are carried out. As results, the constitutive equation relating to strain and strain-rate, in which the constants are represented by the 5th-degree polynomials of temperature, is in good agreement with measurement. The computational try-outs can predict optimal forming conditions in non-isothermal forming processes.