• Journal of the Korean Society for Nondestructive Testing
• /
• v.26 no.3
• /
• pp.198-205
• /
• 2006

The necessity of nondestructively inspecting austenitic steels, fiber-reinforced composites, and other inherently anisotropic materials has stimulated considerable interest in developing beam models for anisotropic media. The properties of slowness surface playa key role in the beam models based on the paraxial approximation. In this paper, we apply a modular multi-Gaussian beam (MMGB) model to study the effects of material anisotropy on ultrasonic beam profile. It is shown that the anisotropic effects of beam skew and excess beam divergence enter into the MMGB model through parameters defining the slope and curvature of the slowness surface. The overall beam profile is found when the quasilongitudinal(qL) beam propagates in the symmetry plane of transversely isotropic austenitic steels. Simulation results are presented to illustrate the effects of these parameters on ultrasonic beam diffraction and beam skew. The MMGB calculations are also checked by comparing the anisotropy factor and beam skew angle with other analytical solutions.

• Steel and Composite Structures
• /
• v.25 no.4
• /
• pp.389-401
• /
• 2017

In this work, a new higher shear deformation theory (HSDT) is developed for the free vibration and buckling of functionally graded (FG) sandwich plates. The proposed theory presents a new displacement field by using undetermined integral terms. Only four unknowns are employed in this theory, which is less than the classical first shear deformation theory (FSDT) and others HSDTs. Equations of motion are obtained via Hamilton's principle. The analytical solutions of FG sandwich plates are determined by employing the Navier method. A good agreement between the computed results and the available solutions of existing HSDTs is found to prove the accuracy of the developed theory.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.11a
• /
• pp.265-269
• /
• 1996

In this paper, electric field interference was analyzed in the Printed Circuit Board to restrain the elcctromagnetic wave using Boundary Element Method and Finite Element Method. First, charge density distribution was simulated using Boundary Element Method and the characteristic impedance was caculated to restrain the reflex wave, and mutual capacitance was caculated in the multi-strip line PCB. Finally, electric field was simulated in the variable patterns using Finite Element Method. As a result, the optimal structure and characteristics of strip line was obtained and the imformations about the optimal design pattern could be obtained with the analysing the feild distribution.

• Structural Engineering and Mechanics
• /
• v.60 no.2
• /
• pp.313-335
• /
• 2016

In this article, a four-variable refined plate theory is presented for buckling analysis of functionally graded plates subjected to uniform, linear and non-linear temperature rises across the thickness direction. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. Young's modulus and Poisson ratio of the FGM plates are assumed to remain constant throughout the entire plate. However, the coefficient of thermal expansion of the FGM plate varies according to a power law form through the thickness coordinate. Equilibrium and stability equations are derived based on the present theory. The influences of many plate parameters on buckling temperature difference such ratio of thermal expansion, aspect ratio, side-to-thickness ratio and gradient index will be investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.530-531
• /
• 2008

본 논문에서는 우수한 광학 특성으로 활발히 연구되고 있는 광자결정(PCs)과 이를 변형시킨 광자준결정(PQCs) 구조를 설계하고 특성을 평가, 비교하였다. 특성 평가는 cubic 및 hexagonal 기본격자의 PCs와 8-fold PQC 구조를 비교하였으며 각각 동일한 충진률 동일한 굴절률 차이의 조건을 갖도록 설계하여 구조에 따른 PBGs 변화를 살펴보았다. 계산 방법은 Maxwell 방정식을 이용한 finite difference time domain (FDTD) 전산모사법을 사용하였다. 본 연구의 결과로부터 잘 설계된 2차원 PQCs는 낮은 굴절률차이(${\Delta}n$)의 물질 구조에서도 완전한 광자밴드갭(photonic bandgaps: PBGs)를 가질 수 있다는 것을 확인하였다. 본 연구진은 다중회전 홀로그래피 방법 (multi-rotational holographic method)을 이용하여 설계된 PQCs를 완벽하게 재현하려는 공정을 진행 중에 있다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.5
• /
• pp.407-412
• /
• 1998

In this paper, we design PHASAR(Phased Array) WDM(Wavelength Dvision Division Multi- and Demultiplexing) filters and evaluate their performance. The PHASAR WDM filter is designed to have flat-passband characteristics by inserting the multimode waveguides between input waveguides and a first star coupler. BPM simulation results show that the excess loss is smaller than 6.5 dB, the crosstalk is less than -22 dB and the 1 dB passband is about 50 GHz. The effect of the path difference error is also investigated.

• Structural Engineering and Mechanics
• /
• v.68 no.6
• /
• pp.661-675
• /
• 2018

In this paper, buckling analysis of hybrid functionally graded plates using a novel four variable refined plate theory is presented. In this theory the distribution of transverse shear deformation is parabolic across the thickness of the plate by satisfying the surface conditions. Therefore, it is unnecessary to use a shear correction factor. The variations of properties of the plate through the thickness are according to a symmetric sigmoid law (symmetric S-FGM). The principle virtual works is used herein to extract equilibrium equations. The analytical solution is determined using the Navier method for a simply supported rectangular plate subjected to axial forces. The precision of this theory is verified by comparing it with the various solutions available in the literature.

• Steel and Composite Structures
• /
• v.44 no.1
• /
• pp.91-104
• /
• 2022

The purpose of the present work is to study the parametric nonlinear vibration behavior of three layered symmetric laminated plate. In the analytical formulation; both normal and shear deformations are considered in the core layer by means of the refined higher-order zig-zag theory. Harmonic balance method in conjunction with Galerkin procedure is adopted for simply supported laminate plate, to obtain its natural and damping properties. For these aims, a set of complex amplitude equations governed by complex parameters are written accounting for the geometric nonlinearity and viscoelastic damping factor. The frequency response curves are presented and discussed by varying the material and geometric properties of the core layer.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.7 no.3
• /
• pp.75-80
• /
• 2008

The progressive die performs a work of sheet metal processes with a piercing, notching, embossing, bending, drawing, cut-off etc. in many kinds of pressing. Now a days, these processes have been evaluated as a advanced tooling method to increase the productivity and high quality assurance. The first step analyzing of die design is production part review, then the arrangement drawing of product design and strip process layout design should be done as a next steps with a FEM simulation for its problem solution. After upper procedure were peformed, it was started to make the die, then tryout and its revision of the die and product quality, safety, productivity etc. were done continually. For the all of these process, we mobilized the theory and practice of sheet metal forming, die structure, the function and activity of die components, and the others of die machining, die material, heat treatment and know‐how so on. In this study the features of representative are production part analyzing through the FEM simulation of bending area with a considering spring back problem by DEFORM.

• Korean Chemical Engineering Research
• /
• v.46 no.3
• /
• pp.604-609
• /
• 2008

This study is about the modeling and simulation of heat transfer in the box for packaging and shipping of vaccines. Comparison of the simulation results with experimental data revealed that a one-dimensional model (a spherical model of using a radius equivalent to the rectangular geometry of box) showed good agreement with experimental data during cooling process but did not successfully simulate heating process. It is considered that a rigorous boundary condition is not properly applied for outer surface of the box. However, we could successfully develop a basic algorithm for simulating heat transfer through multi-slabs combined with different materials including phase change material.