• 한국소음진동공학회논문집
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• 제12권2호
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• pp.161-169
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• 2002

Based on the analytic expression for the elasto-dynamic behavior of rotating shaft, the transfer matrix is formulated for the shaft element with uniform cross-section. Timoshenko beam theory is Introduced for modeling the behavior of shaft. Complex variables representing the displacement, slope, moment and shear force are used for deriving the transfer matrix between both ends of the shaft element. Simulation result obtained by applying the transfer matrix to a general rotor model is compared with the reference result and proved to be exact. Natural frequencies and the corresponding modes are analyzed with varying the bearing: stiffness. The generally used bearings are considered for discussions. and the bearing stiffness is shown to affect the vibration characteristics of rotor.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.5-14
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• 1999

Free vibration characteristics of a cantilevered laminated composite beam with multiple non-propagating transverse open cracks are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The multiple open cracks are modelled as equivalent rotational springs whose spring constants are calculated based on the fracture mechanics of composite material structures. Governing equations of a composite beam with open cracks are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect is adopted. The effects of various parameters such as the ply angle, fiber volume fraction, crack numbers, crack positions and crack depthes on the free vibration characteristics of the beam with multiple cracks are highlighted. The numerical results show that the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack.

• 소음진동
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• 제9권5호
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• pp.1019-1028
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• 1999

Free vibration characteristics of cantilevered laminated composite beams with a transverse non0propagating open carck are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The open crack is modelled as an equivalent rotational spring whose spring constant is calculated on the basis of fracture mechanics of composite material structures. Governing equations of a composite beam with a open crack are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect. the effects of various parameters such as the ply angle, fiber volume fraction, crack depth, crack position and transverse shear on the free vibration characteristics of the beam with a crack is highlighted. The numerical results show that the natural frequencies obtained from Timoshenko beam theory are always lower than those from Euler beam theory. The presence of intrinsic cracks in anisotropic composite beams modifies the flexibility and in turn free vibration characteristics of the structures. It is revealed that non-destructive crack detection is possible by analyzing the free vibration responses of a cracked beam.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.71-81
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• 2008

This paper proposes a spectral element which can represent dynamic responses in high frequency domain such as Lamb waves on a thin plate. A two layer beam model under 2-D plane strain condition is introduced to simulate high-frequency dynamic responses induced by piezoelectric layer (PZT layer) bonded on a base plate. In the two layer beam model, a PZT layer is assumed to be rigidly bonded on a base beam. Mindlin-Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with electro mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are formulated through equations of motions converted into frequency domain. A detailed spectrum element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through comparison results with the conventional 2-D FEM and the previously developed spectral elements.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1157-1169
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• 2008

This paper presents spectral element formulation which approximates Lamb wave propagation by PZT transducers bonded on a thin plate. A two layer beam model under 2-D plane strain condition is introduced to simulate high-frequency dynamic responses induced by a piezoelectric (PZT) layer rigidly bonded on a base plate. Mindlin-Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Euler-Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with the electro-mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are obtained through equations of motions converted into frequency domain. Detailed spectrum element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through numerical examples.

• 한국강구조학회 논문집
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• 제20권2호
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• pp.303-312
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• 2008

본 논문에서는 초고층 전단벽-골조 아웃리거 구조시스템의 지진하중에 대한 시간이력해석을 수행하였다. 전단벽과 골조를 전단변형과 휨변형이 모두 고려된 (티모센코) 보 이론을 기본으로 하여 개발되었으며, 개발된 해석모델은 일차원 유한요소로 정식화되어 다양한 수치해석 예제들의 거동 분석을 하였다. 해석모델은 아웃리거 트러스의 강성을 회전 스프링 강성으로 치환하여 적용한 것으로 아웃리거 트러스의 형태나 위치에 의한 구조물의 거동 효과를 쉽게 알 수 있다. 앞선 연구를 바탕으로 전단벽-골조 시스템과 전단벽-골조에 아웃리거 시스템을 결합한 건물의 지진해석모델을 개발하고자 하였다. 전단벽-골조 구조는 전단벽과 골조의 전단변형과 휨병형을 동시에 고려한 해석모델을 기반으로 하였으며, 아웃리거 트러스의 강성 해석 역시 전단변형과 휨변형을 모두 고려한 해석 모델을 기반으로 지진해석모델을 개발하였다. 개발되어진 해석 모델의 정확성을 입증하기 위해서 3차원 해석 프로그램인 MIDAS GEN을 이용하여 그 해석결과를 비교하였다. 그 결과 초고층건물의 초기설계단계에서 많은 시간이 소요되는 지진하중에 대한 시간이력해석을 효율적이며 또한 비교적 정확히 수행할 수 있을 것으로 기대된다.