• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.153-156
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• 1999

In this paper, a plate type ozonizer has been designed and manufactured to minimize the size of ozonizer. This ozonizer have following benefits : \circled1 convenience of shift and installation \circled2 maximize space utility. Therefore, ozone generation characteristics have been investigated by varying flow rate, supplied voltage and gap spacing of plate electrodes.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.271-278
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• 1999

An alternative panel flutter approach utilizing minimum angle is presented. The minimum angle is the lowest value among the angles between modes i and j at a certain pressure condition. This method utilizes eigenvectors rather than eigenvalues. Cross-ply composite plates are considered in this study. A remarkable result of this investigation is that the angle always dropped gradually to zero for all presented examples

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.42-50
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• 2016

Overlay welding affects the chemical components and weld hardness by dilution of the lamination layer thickness, which determines the surface properties. This study experimentally investigates different numbers of layers for overlay welding monel materials, which are anti-corrosion materials. The Fe content, weldability of the base metal and monel materials, hardness, and surface flatness were examined. Each evaluation was carried out after overlay welding with three layers on the base material and pipe base material of the plate. The Fe content was evaluated by analyzing the constituents of each layer. The Fe content was satisfactory in the three layers. The weldability of the laminate specimens was evaluated by a bending test. The hardness and bead flatness of the laminate specimens were evaluated by micro Vickers and 3D measurements. The hardness was highest in the heat-affected zone with one layer, and it decreased with increasing lamination. In the case of bead flatness, there is a sharp difference in the deviation with increasing numbers of laminations, which should be considered carefully.

• Composites Research
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• v.18 no.6
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• pp.9-18
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• 2005

With the wide applications of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joints have become a very important research area because the joints are often the weakest areas in composite structures. This paper presents an analytical study of the stress distributions in mechanically single-fastened and multi-fastened composite laminates. The finite element models which treat the pin and hole contact problem using a contact stress analysis are described. A dimensionless stress concentration factor is used to compare the stress distributions in composite laminates quantitatively In the case of single-pin loaded composite laminate, the effects of stacking sequence, the ratio of a hole diameter and the width of a laminate (W/D ratio), the ratio of hole diameter and distance from edge to hole (E/D ratio), friction coefficient and clamping force are considered. In the case of multi-pin loaded composite laminate, the influence of the number of pins, pitch distance, number of rows, row spacing and hole pattern are considered. The results show that P/D ratio and E/D ratio affect more on stress distributions near the hole boundary than the other factors. In the case of multi-pin loaded composite laminate, the stress concentration in the double column case is better than the other cases of multi-pin loaded composite laminate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.153-158
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• 1995

보 및 평판의 진동에 대해서 에너지의 손실은 재료감쇠를 이용한 표면감쇠처리나 지지부에서의 감쇠처리에 의하여 증가될 수 있다. 감쇠재료를 이용한 표면감쇠처리의 예로서 보/평판 표면에 접착되는 감쇠 테이프나 코팅등은 아주 효과적임이 입증되었다. 마찬가지로 지지부 감쇠처리는 점탄성재료의 삽입에 의해서 설명될수 있다[1]. 보/평판의 감쇠에 대한 최근의 많은 연구들은 진동하고 있는 보/평판의 표면에 적용하는 감쇠 테이프 혹은 적층형태의 감쇠 처리방법에 대해서 주로 수행되었다. 일반적으로 표면감쇠처리방법은 진동감소에 아주 효과적이지만 실제 적용상에서 항상 가능한 것은 아니며, 이와 같은 경웨는 지지부 감쇠 처리방법에 의존하게 된다[2]. 감쇠특성을 갖는 점탄성재료를 실제로 적용할 때 보/평판의 유한한 길이가 점탄성재료로 지지되며 점탄성재료의 물성치와 치수에 따라서 계의 모우드 매개변수(고유진동수, 계의 손실계수 그리고 모우드형상)가 크게 달라진다. 그리고 이와 같은 계에 대해서는 지지부의 거동보다는 전체 시스템의 고유진동수와 손실계수 그리고 보 영역에서의 모우드 형상에 더 관심이 있으므로 지지부 영역을 집중매개변수(lumped parameter)로 나타내어 계를 해석할 수 있다. 일반적으로 보와 평판의 경계에서는 병진 및 회전방향의 강성 뿐만 아니라 두 강성사이에 연성효과도 동시에 발생하게 되므로 이 항을 고려하여 계를 모델링해야 한다. 본 연구에서는 우선 점탄성 재료에 의한 지지부영역의 등가 강성계수들을 구하고 경계에 강성행렬을 갖는 보의 등가시스템을 얻는다. 그리고 등가시스템의 주파수방정식으로부터 모우드 매개변수에 대한 지지부의 영향을 살펴본다. 또한 시스템이 비교적 복잡한 사각 평판의 진동에 대해서도 동강성행렬법(dynamic stiffness matrix method)을 이용하여 해석하고자 한다. 수준임이 입증되었다. 본 연구의 결과를 토대로우리나라 젊고 건강한 남성에게 적합한 무게상수는 작업자군에 대하여 25.05kg, 학생군에 대하여 20.24kg 으로 나타나 이는 미국 NIOSH 안전기준과 대체로 일치함을 발견하였다.ive structures utilized in Client/server architecture for distribution and cooperative processing of application between server and client this study presents two different data management methods under the Client/server environment; one is "Remote Data Management Method" which uses file server or database server and. the other is "Distributed Data Management Method" using distributed database management system. The result of this study leads to the conclusion that in the client/server environment although distributed application is assumed, the data could become centralized (in the case of file server or database server) or decentralized (in the case of distributed database system) and the data management method through a distributed database system where complete responsi

• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.295-303
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• 2004

In this paper, an improved four-node Reissner-Mindlin plate-bending element with enhanced assumed strain field is presented for the analysis of isotropic and laminated composite plates. To avoid the shear locking and spurious zero energy modes, the transverse shear behavior is improved by the addition of a new enhanced shear strain based on the incompatible displacement mode approach and bubble function. The "standard" enhanced strain fields (Andelfinger and Ramm, 1993) are also employed to improve the in-plane behaviors of the plate elements. The four-node quadrilateral element derived using the first-order shear deformation theory is designated as "14EASP". Several applications are investigated to assess the features and the performances of the proposed element. The results are compared with other finite element solutions and analytical solutions. Numerical examples show that the element is stable, invariant, passes the patch test, and yields good results especially in highly distorted regimes.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.134-144
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• 1993

Sandwich plate is consisted of equal two isotropic, thin, stiff and strong sheets of dense material separated symmetrically by an isotropic thick layer which may be much less stiff and strong. This study analyzed the dependency of the natural frequencies and mode shapes of sandwich plates on material properties, thicknesses of faces and cores, and various boundary conditions using Rayleigh-Ritz method. E-glass Woven Roving and another two kinds of materials were selected as a face, P.V.C. and another kinds of materials were selected as a core. Natural frequencies and mode shapes obtained by Rayleigh-Ritz method were compared with F.E.M. solutions using ADINA program.

• Composites Research
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• v.20 no.1
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• pp.8-14
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• 2007

Nonlinear aeroelastic analyses of composite wing with flap are performed considering free-play and dynamic stiffness of actuator. Doublet-Hybrid method is used for the calculation of subsonic unsteady aerodynamic forces. Free-play is modeled as a bilinear spring and is linearized by using the describing function method. Dynamic stiffness is obtained from governing equation of gear system and the aeroelastic analyses were performed according to ply-angle of laminate and material. The linear and nonlinear flutter analysis results show that the flutter characteristics are significantly dependent on the free-play and dynamic stiffness. from the nonlinear flutter analysis, various types of limit cycle oscillations are observed in a range of air speeds below or above the linear divergent flutter boundary.

• Composites Research
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• v.13 no.1
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• pp.40-49
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• 2000

The objective of this research is to develop the impact monitoring techniques providing impact identification and damage diagnostics of smart composite laminates susceptible to impacts. This can be implemented simultaneously by using the acoustic waves by the impact loads and the acoustic emission waves from damage. In the previous research, we have discussed the impact location detection process in which impact generated acoustic waves are detected by PZT using the improved neural network paradigm. This paper describes the implementation of time-frequency analysis such as the Short-Time Fourier Transform (STFT) and the Wavelet Transform (WT) on the determination of the occurrence and the estimation of damage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.369-380
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• 2001

Although extensive efforts have been devoted to the optimal design of composite laminated plates in recent years, some practical issues still need further research. Two of them are: the handling of the ply angle as either continuous or discrete; and that of the uncertainties in material properties, which were treated as continuous and ignored respectively in most researches in the past. In this paper, an algorithm for stacking sequence optimization which deals with discrete ply angles and that for thickness optimization which considers uncertainties in material properties are used for a two step optimization of composite laminated plates. In the stacking sequence optimization, the branch and bound method is modified to handle discrete variables; and in the thickness optimization, the convex modeling is used in calculating the failure criterion, given as constraint, to consider the uncertain material properties. Numerical results show that the optimal stacking sequence is found with fewer evaluations of objective function than expected with the size of feasible region taken into consideration; and the optimal thickness increases when the uncertainties of elastic moduli considered, which shows such uncertainties should not be ignored for safe and reliable designs.