• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.469-479
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• 2001

In the present study, free vibration analysis of multi-delaminated beams is performed. In order to investigate the effects of mu1ti-delaminations on the dynamic characteristics of multi-delaminated beams, the general kinematic continuity conditions are derived from the assumption of constant curvature at the multi-delamination tip. Frequency equations of multi-delaminated beams are obtained by dividing the global multi-delaminated beam into beam segments and by imposing recurrence relation from the continuity conditions un each sub-beam. The comparisons between the results of numerical analysis obtained by finite element analysis and those of present analysis give good agreement with each other. It is shown that the effects of multi-delaminations on free vibration characteristics of laminated beams could be used to detect their sizes, types and locations from the results.

• 전기의세계
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• v.32 no.3
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• pp.142-149
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• 1983

지금까지 알려진 내부마찰측정방법으로는 자유감쇄법(free decay method), 강제진동법(forced vibration method), 비공진강제진동법(non-resonance forced vibration method) 및 초음파법(ultrasoni method) 등이 있다. 이상의 모든 내부마찰실험방법에 관한 실험장치는 그 기계의 동작특성에 따라 실험주파수가 극히 한정되어 있어 연속적인 변화를 시킬 수 없으므로 완화효과를 연속적으로 추적하기 위하여 온도를 변화시키는 방법이 널리 사용되고 있다. 이상에서 소개한 방법들중 본인들이 국산제작실험에 성공한 바 있는 장치는 자유감쇄법에 속하는 염회진자장치(torsion pendulum device) 이므로 이 장치를 중심으로 내부마찰측정원리와 그의 장치에 관하여 소개하고저 한다.

• Journal of KSNVE
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• v.7 no.1
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• pp.135-142
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• 1997

This paper presents a digital modeling technique of the distributed system. The basic idea of the proposed technique is to discretize a continuous system with respect to the spatial coordinates using bilinear method. The response of the discretized system is analyzed by Laplace transform and z-transform. The computational results in torsional shaft and Timoshenko beam using the proposed technique are compared with the exact solutions and the results of finite element method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2413-2419
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• 2000

Harmonic resonances in a continuous rotating shaft with distributed mass are discussed. The restoring force of the shaft has geometric stiffening nonlinearity due to the extension of the shaft centerline. The effect of a distributed lateral force, such as the gravity, is assumed. The possibility of the occurrences of harmonic resonances, the shapes of resonance curves, and internal resonance phenomena are investigated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.43-50
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• 2001

Subharmonic resonances of order 1/2 of a continuous rotating shaft with distributed mass are discussed. The restoring force of the shaft exhibits geometric stiffening nonlinearity due to the extension of the shaft center line. It is assumed that a distributed lateral force, such as the gravity, acts on the rotor. The possibility of the occurrence of subharmonic resonances, the shapes of resonance curves, and internal resonance phenomena are investigate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.484-490
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• 2008

For CSLDV, the Chebyshev demodulation (or polynomial) technique and Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. In this paper, the Hilbert-Huang transform approach was applied as an alternative to impact excitation cases in terms of a numerical approach. The vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a simply supported beam was chosen as the test rig. With additional innovative steps which are the ideal-band pass filter and the nodal point determination, Hilbert-Huang transformation can be used for a good mode shape reconstruction even in the impact excitation case.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.274-280
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• 2002

This paper addresses the vibration mode shape measurement technique utilizing a Continuous Scanning Laser Doppler Vibrometer (CSLDV). The continuous scanning capability is added to the conventional discrete Laser Doppler Vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning method is eliminated by feedback control. The velocity output signal from the CSLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fast Fourier Transformation of the time dependent velocity signal. Using the Chebyshev series form, the analysis of the vibration mode shape techniques for straight Bine scanning and 2 dimensional scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.414-419
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• 2003

There are some methods fur extracting mode shapes from a continuously scanned data such as a modulation, Chebyshev polynomial, and Hilbert approach. In this paper, Chebyshev and Hilbert approaches were investigated through the numerical experiment first. As some experimental parameters were altered with small quantities, data were checked and plotted. From those results, the effects of unexpected parameters will be configured. And then, it will be actually helpful to select the proper method for specific testing environments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.252-253
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.334-335
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• 2014