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Effects of shear deformation and rotary inertia on the natural frequencies of axially loaded beams
구교남 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.3
The purpose of this study is to investigate how the axial load in beams influences the relationships between the natural frequencies andthe effects of shear deformation and rotary inertia. Four beam theories are considered in this study. Finite element equations of motion forthe beams under a tensile load are formulated to allow the application of various axial loads as well as to impose any type of boundaryconditions. The results demonstrate that the stiffening effect by a tensile load may not reduce the frequency error of the Euler beam theory,unlike the results reported in other studies.
Elastic stresses and failure of rotating cross-ply laminate disks
구교남 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.5
Centrifugal force acting on a rotating disk induces in-plane loads in the radial and circumferential directions. An application of fiber-reinforced composite materials to a rotating disk can satisfy the demand for increasing its rotating speed. However, previous researches have been confined to single lamina disks. In this paper, a stress analysis of rotating disks made of multidirectional laminates is performed. The Tsai-Wu failure criterion is applied to the strength analysis of the rotating laminate disks, from which the maximum allowable speeds are obtained. The cross-ply ratios providing the maximum allowable speeds are obtained for the glass/epoxy and carbon/epoxy cross-ply laminate disks with CD geometry.
구교남 울산대학교 2002 공학연구논문집 Vol.33 No.1
항공기 날개의 테이퍼 비가 공력탄성 안정성에 미치는 영향을 조사하였다. 일반적인 형상의 공탄성 해석에 적합한 유한요소법과 DPM을 이용하여 해석을 수행하였다. 알루미늄 날개와 복합재료 날개의 자유진동해석을 수행한 뒤 이 해석결과를 이용하여 플러터 속도 및 진동수를 계산하였다. 알루미늄 날개와 복합재료 날개 모두 플러터 모우드의 변화가 없다면 테이퍼 비가 감소함에 따라 플러터 속도는 증가하는 것으로 나타났다. An effect of taper ratio on aeroelastic stability has been studied for aluminum and composite wings. Aeroelastic analyses utilize the finite element method and the doublet point method which are suitable for arbitrary wings. The flutter velocity and frequency are computed using the results from the free vibrational analysis for the aluminum and composite wings. The flutter velocity of the aluminum and composite wings increases as the taper ratio decreases as long as there is no change in flutter mode.
면내 변위의 변화를 고려한 Cross-ply 적층판의 진동 및 감쇠해석
구교남,이인 한국소음진동공학회 1992 소음 진동 Vol.2 No.4
In order to investigate the effects of layer-wise in-plane displacements on vibration and damping characteristics of composite laminated plates, the finite element method based on the generalized laminated plate theory(GLPT) has been formulated. Specific damping capacity of each mode was obtained by modal strain energy method. To see the effect of transverse shear on deformation, the strain energy of stress components was computed. The accuracy of this study was examined for the cylindrical bending vibration of cross-ply plate strip. The results were very accurate compared with 3-D solutions. The numerical results show that through-thickness variation of in-plane displacements has not so much influence on the natural frequency, but has a great influence on the damping of composite plates, especially on the damping of thick composite plates since the damping is affected by local behavior while the natural frequency is affected by global behavior.