• 대한기계학회논문집
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• 제18권8호
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• pp.2123-2138
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• 1994

A study on the dynamic mechanical properties of the high strength carbon fiber epoxy composite beam was carried out. The macromechanical model was used for the theoretical analysis of the symmetric laminated composite beam. The anisotropic plate theory and Bernoulli-Euler beam theory were used to predict the effective flexural elastic modulus and the specific damping capacity of laminated composite beam. The free flexural vibration and torsional vibration tests were carried out to determine the specific damping capacities of the unidirectional laminated composite beam. The vibration tests were performed in a vacuum chamber with laser vibrometer system and electromagnetic hammer to obtain accurate experimental data. From the computational and experimental results, it was found that the theoretical values with the macromechanical analysis and the experimental data of symmetric laminated composite beam were in good agreement.

• Journal of Welding and Joining
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• 제34권1호
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• pp.35-40
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• 2016

Recent developments of Laser metal 3D deposition with wire feeding are reviewed which provide an alternative to powder feeding method. The wire feeding direction, angle and position as well as laser power, wire feeding rate, and deposition speed are found to be key parameters to make quality deposition with high throughput. When compared with the powder feed, the wire feed shows higher material efficiency, higher deposition rate, and smoother surface. Large elongated columnar grains which have epitaxial growth across deposit layers are observed in deposit cross sections. The growth direction is parallel to the thermal gradient during the deposit process. Tensile properties are found to be dependent on the direction due to the anisotropic deposit property. A real-time feedback control is demonstrated to be effective to improve the deposition stability.

• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.291-297
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• 2000

Modern helicopter rotor blades with non-homogeneous cross sections, composed of anisotropic material, require highly sophisticated structural analysis because of various cross sectional geometry and material properties. They may be subjected by the combined axial, bending, and torsional loading, and the dynamic and static behaviors of rotor blades are seriously influenced by the structural coupling under rotating condition. To simplify the analysis procedure using one dimensional beam model, it is necessary to determine the principal coordinate of the rotor blade. In this study, a method for the determination of the principal coordinate including elastic and shear centers is presented, based upon continuum mechanics. The scheme is verified by comparing the results with confirmed experimental results.

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.385-390
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• 2008

For taking account of the two-dimensional magnetic properties of a grain-oriented electrical steel sheet, the effective anisotropic tensor reluctivity is examined, and a computationally efficient algorithm is suggested by using the response surface method to model the two-dimensional magnetic properties. It is shown that the reconstructed two-dimensional magnetic properties are fairly effective to stabilize the convergence characteristics of the Newton-Raphson iteration in the nonlinear magnetic field analysis.

• 한국세라믹학회지
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• 제47권2호
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• pp.132-135
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• 2010

Thermal properties of layered metal chalcogenides such as $WT_2$ (T=S,Se) with two-dimensionally disordered structure were evaluated. Thermal conductivity shows a marked decrease after exfoliation and subsequent restacking because of random stacking of two-dimensional crystalline sheet, which circumvents thermal conduction pathways along longitudinal direction in anisotropic materials.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.234-238
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• 1999

This study suggests the design of the functionally gradient composite, [0/90/0/core]$_s$ cross-ply laminate, to prevent stress concentration induced from the difference of rigidity between the bone and the artificial hip joint and to reinforce the wear property of the surface and the expectation of their mechanical properties. First, the four-point bending test is done about wet bones and dry bones to know the mechanical properties of the cortical bones. In result, the wet bone shows the viscoelastic behavior and the dry bone shows the elastic behavior. Moreover, we expect the properties of the proposed gradient composites as a function of carbon fiber volume fraction in each layer to apply Halpin-Tsai equation, CLPT(classical laminate plate theory), and Bernoulli beam theory etc. and decide the thickness ratio of each lamina in order to match Young's modulus of the anisotropic cortical bone with the proposed gradient composites.

• Structural Engineering and Mechanics
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• 제18권6호
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• pp.759-768
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• 2004

The torsion of a penny-shaped crack in a transversely isotropic strip is investigated in this paper. The shear moduli are functionally graded in such a way that the mathematics is tractable. Hankel transform is used to reduce the problem to solving a Fredholm integral equation. The crack tip stress field is obtained by taking the asymptotic behavior of Bessel function into account. The effects of material property parameters and geometry criterion on the stress intensity factor are investigated. Numerical results show that increasing the shear moduli's gradient and/or increasing the shear modulus in a direction perpendicular to the crack surface can suppress crack initiation and growth, and that the stress intensity factor varies little with the increasing of the strip's height.

• 대한기계학회논문집A
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• 제25권8호
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• pp.1261-1268
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• 2001

Effective material properties of active fiber composites with interdigitated electrodes are derived as a function of the fiber volume fraction. For the purpose of applying the rule of mixture, three unit cell models are introduced; each for the deformation and stress continuities in the out of plane and in-plane directions, and the continuity of the electrical displacement in the longitudinal direction. Derived effective material properties are compared with the results by the finite element method; good agreements are observed between them. As an application, the electromechanical behavior of the angle ply laminates with the active fiber layers bonded on the top and bottom surfaces are investigated; the angle of piezoelectric fiber to maximize the twisting curvature is obtained using the present model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.267-269
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• 1997

유한요소법에 의해 자계를 계산할 경우에 일정한 투자율을 두고 선형 해석을 하거나 비선형을 고려할 때에는 하나의 자화곡선을 이용한 뉴튼 랩슨법이 많이 사용된다. 그러나 최근 자계의 세기와 자속밀도간의 위상차를 고려할 수 있는 계산법에 대한 연구가 늘어나면서 여러 가지 방법들이 제시되고 있다. 본 논문에서는 간단한 실험데이타를 이용하여 정확히 자계의 세기와 자속밀도간의 비선형성을 고려하면서 특히, 이방성이 강한 재료를 사용하는 전기기기의 해석에 적합한 방법을 제안하며, 이 방법에 의해 삼상 변압기의 코어에서의 자계를 계산하며, 계산 결과에서 기존의 방법으로는 어려운 이방성 영향을 정확히 고려할 수 있음을 실험에 의하여 검증하였다.

• 한국군사과학기술학회지
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• 제13권1호
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• pp.126-132
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• 2010

A Lamb wave guided by a plate structure has dispersive characteristics because phase and group velocity change with the variation of frequency and thickness. The Lamb wave has two modes, symmetric and anti-symmetric mode, which propagates symmetrically and non-symmetrically with respect to centerline. In this paper, the derivation of Lamb wave equation with anisotropic material property is investigated. The phase velocity and group velocity dispersion curves are shown using the stiffness matrix of composite materials with the variation of angle.