• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.309-315
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• 2001

The Stress intensity factors for edge cracks located at the bonding interface between the elastic semiconductor chip and the viscoelastic adhesive layer have been investigated. Such cracks might be generated due to stress singularity in the vicinity of the free surface. The domain boundary element method(BEM) has been employed to investigate the behavior of interface stresses. The overall stress intensity factor for the case of a small interfacial edge crack has been computed. The magnitude of stress intensity factors decrease with time due to viscoelastic relaxation.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.631-638
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• 2003

The wind turbine blade is the equipment converted wind into electric energy. The effect of the blade has influence of the output power and efficiency of wind turbine. The design of blade is considered of lift-to-drag ratio, structure, a condition of process of manufacture and stable maximum lift coefficient, etc. This study is used the simplified method for design of the aerodynamic blade and aerodynamic analysis used blade element method. This process is programed by delphi-language. The program has any input values such as tip speed ratio, blade length, hub length, a section of shape and max lift-to-drag ratio. The program displays chord length and twist angle by input value and analyzes performance of the blade.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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• pp.468-473
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• 1992

A boundary element analysis using parallel algorithm on transputers is described for three-dimensional magnetostatic field computations. The parallel algorithm are applied to assembling the system matrix and solving the matrix equation. Through the numerical results, it is shown that the computation time is ideally inverse proportional to the number of transputers, and the computational efficiency increases as the size of the system matrix becomes large. The easiness and simplicity in configuring the system hardware and making programs and computation times are compared in three kinds of topologies.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.104-106
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• 2005

In this paper, 3-dimensional magnetic field of coil is analyzed by using biot-sarvart law considering singularity. The RMSP(reduced magnetic scalar potential) arc employed in order to reduce the number of unknown variables in FEM(Finte Element Analysis) or BEM(Boundary Element Method). It Is necessary to calculate magnetic field of souce current when RMSP is used. Biot-savart law is generally used. it is difficult to calculate the field when the source point is in inside the coil. To integrate using gaussian quadrature, the cross section of coil is divided considering the position of field point when field point is inside coil. The proposed method shows good agreement of magnetic field compared with FEMLAB, OPERA3D.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.149-154
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• 2004

The design sensitivity analysis of Zwicker's loudness with respect to structural sizing design variables is developed. The loudness sensitivity in the critical band is composed of two equations, the derivative of main specific loudness with respect to 1/3-oct band level and global acoustic design sensitivities. The main specific loudness is calculated by using FEM, BEM tools. i.e. MSC/NASTRAN and SYSNOISE. And global acoustic sensitivity is calculated by combining acoustic and structural sensitivity using the chain rule. Structural sensitivity is obtained by using semi-analytical method and acoustic sensitivity is implemented numerically using the boundary element method. For sensitivity calculation, sensitivity analyzer of loudness (SOLO), in-house program is developed. A 1/4 scale car cavity model is optimized to show the effectiveness of the proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.6 s.123
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• pp.531-538
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• 2007

A new method for free nitration analysis using series functions is proposed to obtain the eigenvalues of arbitrarily shaped, polygonal plates with clamped edges. Since a general solution used in the method satisfies the equation of motion for the transverse vibration of a plate, the method offers very accurate eigenvalues, compared to FEM or BEM results. In addition, the method can minimize the amount of numerical calculation because it has the advantage of not needing to divide the plate of interest. Two case studies show that the proposed method is valid and accurate when the eigenvalues by the proposed method are compared to those by FEM (NASTRAN) or another analytical method.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.1-16
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• 2006

This paper presents a virtual boundary element-equivalent collocation method (VBEM) for the plane magnetoelectroelastic solids, which is based on the fundamental solutions of the plane magnetoelectroelastic solids and the basic idea of the virtual boundary element method for elasticity. Besides all the advantages of the conventional boundary element method (BEM) over domain discretization methods, this method avoids the computation of singular integral on the boundary by introducing the virtual boundary. In the end, several numerical examples are performed to demonstrate the performance of this method, and the results show that they agree well with the exact solutions. So the method is one of the efficient numerical methods used to analyze megnatoelectroelastic solids.

• Smart Structures and Systems
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• v.26 no.6
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• pp.703-720
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• 2020

This paper investigates the safety of the wind turbine blade against excessive deformation. For this purpose, the performance of the blade in the along-wind direction is improved by longitudinal stiffener made of shape memory alloy. The rationale behind the selection of this smart material is due to its ability to offer excellent thermo-mechanical behaviour at low strain. Here, Liang-Roger model is adopted for vibration control, and the super-elastic effects are utilised for blade stiffening. Turbulent wind fields are generated at the hub height using TurbSim and the corresponding loads are evaluated using blade element momentum theory. An efficient switching algorithm is developed along with performance curves that enable the designer to select an optimal mode of heating depending upon the operational scenario. Numerical results presented in this paper clearly demonstrate the performance envelope of the proposed stiffener and its influence on the reliability of the blade.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.391-397
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• 2005

Power Flow Analysis(PFA) is used as the promising tools for the vibration and noise predictions of complex structures in medium-to-high frequency ranges. When the noise and vibration of a complex structure are analyzed, Power Flow finite Element Method combining PFA with FEM is efficient in vibration analysis, and Power Flow Boundary element Method combining PFA with BEM is usful in noise analysis. PFFEM software, PFADS has been developed for the vibration analysis of coupled system structures. Also, NASPFA, the noise analysis software based on PFBEM, has been developed. Through the several upgrades, the current version PFADS R3 and NASPFA R2 are used for the vibration and noise analysis of system structures in medium-to-high frequency ranges. In this paper, the structure and function of each software are explained, and the vibration and noise levels of vehicle structures predicted by each software are shown.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.5-12
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• 2016

This paper describes the development process for vibration and acoustic characteristics of a balanced armature speaker. The design parameters were chosen in consideration of the influence of the bending stiffness of balanced armature which is the form of a cantilever structure in the speaker. For study of the performance of the speaker according to the design parameters, in the first step, we analyzed the characteristics of the velocity of the diaphragm to the electrical input. Next step, acoustic characteristics were analyzed by structural-acoustic coupled analysis. And the reliability of the analysis was verified by comparing the result of analysis with test results. Finally, we proposed a design method for implementing an enhanced balanced armature speakers through analysis method.