• Journal of applied mathematics & informatics
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• v.32 no.5_6
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• pp.761-781
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• 2014

An exponentially accurate nonconforming spectral element method for elasticity systems with discontinuities in the coefficients and the flux across the interface is proposed in this paper. The method is least-squares spectral element method. The jump in the flux across the interface is incorporated (in appropriate Sobolev norm) in the functional to be minimized. The interface is resolved exactly using blending elements. The solution is obtained by the preconditioned conjugate gradient method. The numerical solution for different examples with discontinuous coefficients and non-homogeneous jump in the flux across the interface are presented to show the efficiency of the proposed method.

• Multiscale and Multiphysics Mechanics
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• v.1 no.1
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• pp.15-33
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• 2016

In this paper, an asymptotic method is employed to formulate nano- or micro-beams based on strain gradient elasticity. Although a basic theory for the strain gradient elasticity has been well established in literature, a systematic approach is relatively rare because of its complexity and ambiguity of higher-order elasticity coefficients. In order to systematically identify the strain gradient effect, an asymptotic approach is adopted by introducing the small parameter which represents the beam geometric slenderness and/or the internal atomistic characteristic. The approach allows us to systematically split the two-dimensional strain gradient elasticity into the microscopic one-dimensional through-the-thickness analysis and the macroscopic one-dimensional beam analysis. The first-order beam problem turns out to be different from the classical elasticity in terms of the bending stiffness, which comes from the through-the-thickness strain gradient effect. This subsequently affects the second-order transverse shear stress in which the surface shear stress exists. It is demonstrated that a careful derivation of a first strain gradient elasticity embraces "Gurtin-Murdoch traction" as the surface effect of a one-dimensional Euler-Bernoulli-like beam model.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.32-36
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• 1995

A study was conducted to evaluate the dynamic mechanical properties (modulus of elasticity, resonant frequency and interanal friction) of compression wood in Pinus densiflora. Vibration method was used for estimation of dynamic modulus of elasticity and the values were compared to those of static bending modulus of elasticity. The results obtained are as follows: 1. The dynamic modulus of elasticity of compression wood decreased, whereas that of normal wood increased, with increasing specific gravity. 2. The resonant frequency of compression wood decreased, whereas that of normal wood increased, with increasing specific gravity. 3. The internal friction of compression wood increased with increasing specific gravity. 4. The correlation coefficients between dynamic and static moduli of elasticity in compression and normal woods were high.

• Structural Engineering and Mechanics
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• v.7 no.2
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• pp.181-202
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• 1999

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

• Interaction and multiscale mechanics
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• v.1 no.2
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• pp.231-250
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• 2008

The statistical two-order and two-scale method is developed for predicting the mechanics parameters, such as stiffness and strength of core-shell particle-filled polymer composites. The representation and simulation on meso-configuration of random particle-filled polymers are stated. And the major statistical two-order and two-scale analysis formulation is briefly given. The two-order and two-scale expressions for the strains and stresses of conventionally strength experimental components, including the tensional or compressive column, the twist bar and the bending beam, are developed by means of their classical solutions with orthogonal-anisotropic coefficients. Then a new effective mesh generation algorithm is presented. The mechanics parameters of core-shell particle-filled polymer composites, including the expected stiffness parameters, minimum stiffness parameters, and the expected elasticity limit strength and the minimum elasticity limit strength, are defined by means of the stiffness coefficients and elasticity strength criterions for core, shell and matrix. Finally, the numerical results for predicting both stiffness and elasticity limit strength parameters are compared with the experimental data.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.183-186
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• 2005

This study investigates material properties of epoxy resins and reinforced materials for adhesion repairing-reinforced of RC construction. According to the test. elasticity modulus of mortar indicated 16-26(GPa) and that of concrete was 18-27(GPa). It became decreased as mixture proportion, W/C and fluidity of both mortar and concrete increased In addition the elasticity modulus of epoxy resins exhibited around 45.3-220(GPa), while that of steel plate and Carbon Bar indicated 338(GPa) and 34.1 (GPa), respectively. It is obvious that individual materials had big different value of elasticity modulus. Meanwhile, thermal expansion coefficients of mortar was 10-13 ${\mu}\varepsilon$ /$^{\circ}C$ and that of concrete was 9-11 $\mu \varepsilon$ /$^{\circ}C$ The increase of mixture Voportion and W/C resulted in lower value of thermal expansion coefficients and the increase of flow and slump exhibited slightly higher value. The epoxy resin indicated 41-54 ${\mu}\varepsilon$ /$^{\circ}C$ which is 4-5 times larger value than concrete and steel plate and Carbon Bar was 11.93 ${\mu}\varepsilon$ /$^{\circ}C$ and -1.68 ${\mu}\varepsilon$ /$^{\circ}C$ respectively. Hence, the adhesion strength of the epoxy resins should be considered before it is used in field condition, due to different thermal expansion coefficient of each material.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.696-709
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• 2020

A board was manufactured for each resin and sawdust addition using the chaff made by carbonizing the chaff charcoal, an agricultural by-product that emerge during the rice pounding process, and sawdust. And effects of the additions of resin and sawdust on coefficients of dynamic and static modulus of elasticity, modulus of rupture, as well as the relationship between the dynamic modulus of elasticity, statis modulus of elasticity, and modulus of rupture were investigated. As phenol resin addition of chaff charcoal-sawdust compound board increases to 10~25%, the bending performance has increased. This suggests that resin addition largely effects the bending performance. Although the bending performance was gradually increased with the increase in sawdust addition, since the coefficients of determination (R²) between the sawdust addition with the coefficients of dynamic, static modulus of elasticity, and modulus of rupture were 0.4012, 0.0809, and 0.1971, respectively. Thus, it showed a relatively lower correlation, and the effect of sawdust on bending performance was small. Since a high correlation was confirmed between dynamic and static modulus of elasticity, and modulus of rupture of chaff charcoal-sawdust compound board, it was confirmed that prediction of static modulus of elasticity and modulus of rupture can be made in a nondestructive way from the dynamic modulus of elasticity.

• Advances in materials Research
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• v.11 no.1
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• pp.41-57
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• 2022

This paper is focused on delamination analysis of a multilayered inhomogeneous viscoelastic beam subjected to linear creep under constant applied stress. The viscoelastic model that is used to treat the creep consists of consecutively connected units. Each unit consists of one spring and two dashpots. The number of units in the model is arbitrary. The modulus of elasticity of the spring in each unit changes with time. Besides, the modulii of elasticity and the coefficients of viscosity change continuously along the thickness, width and length in each layer since the material is continuously inhomogeneous in each layer of the beam. A time-dependent solution to the strain energy release rate for the delamination is derived. A time-dependent solution to the J-integral is derived too. A parametric analysis of the strain energy release rate is carried-out by applying the solution derived. The influence of various factors such as creep, material inhomogeneity, the change of the modulii of elasticity with time and the number of units in the viscoelastic model on the strain energy release rate are clarified.

• Tribology and Lubricants
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• v.5 no.1
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• pp.64-68
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• 1989

The dynamic characteristics of the annular pressure seal employed in pump have been theoretically deduced with consideration of the effects of elastic deformation due to the centrifugal stress. The deformation of the shaft is governed by the linear theory of elasticity. The results derived herein considering the elastic deformation are compared with the previously published author's results in the stiffness and damping coefficients.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.998-1004
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• 2005

U.J.S.(Ultra Jetting System) is a new ground improvement method registered as a Utility Model No.0205798, which has fundamentally improved the existing jetting method of J.S.P.(Jumbo Special Pattern System). In this study, the uniaxial compressive strengths of improved soil-grout structures by U.J.S. and J.S.P. which have been conducted on the construction site are compared. Also, the differences between the U.J.S. and J.S.P. are analyzed by considering the role of the auger bit, the injection distance measured from the axis of boring tubes, and angle of injection measured from the horizontal. The specimens of soil-grout structures are taken from the improved soils by using the U.J.S. and J.S.P. The uniaxial tests for the samples are conducted after the curing period of 28 days. The uniaxial compressive strengths and the coefficients of elasticity of surface and distance from the axis of boring. This study shows that the mean strength of the improved structure by J.S.P. is 1.9 times greater than by J.S.P.