• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.5
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• pp.583-595
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• 2018

Stiffened panels are widely used in naval architecture and ocean engineering, and knowledge about their dynamic behaviour represents important issue in the design procedure. Ordinary vibration analysis consists of natural frequencies and mode shapes determination and can be extended to forced response assessment, while the Structural Intensity (SI) analysis, assessing magnitude and direction of vibrational energy flow provides information on dominant transmission paths and energy distribution including sink positions. In this paper, vibrational energy flow in stiffened panels under harmonic loading is analyzed by the SI technique employing the finite element method. Structural intensity formulation for plate and beam element is outlined, and developed system combining in-house code and general finite element tool is described. As confirmed within numerical examples, the developed tool enables separation of SI components, enabling generation of novel SI patterns and providing deeper insight in the vibrational energy flow in stiffened panels, comparing to existing works.

• Journal of Ocean Engineering and Technology
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• v.31 no.5
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• pp.364-370
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• 2017

A numerical model based on the mode superposition method is used to study the vortex-induced vibration response characteristics of a deep-sea riser such as steel catenary riser (SCR). A steel catenary riser can be modeled using a flexible cable with simple supports at both ends. The natural frequency, mode shape and mode curvature of the riser are calculated and the vortex-induced vibration response of the riser is obtained using the equilibrium of the input and output power. The mode superposition method is applied to the vibrational stresses for each mode to calculate the overall riser fatigue life.

• Journal of KSNVE
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• v.6 no.4
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• pp.447-456
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• 1996

Dynamic characteristics of the bell-type structure including acoustic effects and transient dynamic problems were analyzed numerically. Natural frequencies, mode shapes and transient dynamic analysis used the finite element method with 3-D general shell element. Mode shapes and stress distributions of transient dynamic analysis were expressed by computer graphics. The method using this study was evaluated by comparision of theoretical results at reference papers(14), (15) and the experimental test using Fast Fourier Transform analyzer. Vibrational modes governing acoustic characteristics of the typical bell-type structure depended on the first flexural mode(4-0 mode) and the second flexural mode(6-0 mode). Asymmetric effects by Dangiwas, acoustic holes gave rise to beat frequencies, and the Dangjwa was found to be most effective. When impact load acted on the bell, stress concentration occured at the rim part of bell. It was found that the bell type structure should be designed thickly at the rim part in order to prevent impact load from stress concentration.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.82-87
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• 1997

High pressure FTIR and Raman spectra of soild $C_{70}$ were measured at pressure up to 11 GPa and room temperature. The slope (dv/dp) of the frequency-pressure plots for several IR and Raman mode changed around 1.5 GPa, where a solid-solid transition might occur. In IR study, we can observe new mode appeared around 777$cm^{-1}$1 above 5.5 GPa which might indicate another solid-solid transition. Our study showed that this transition might be irreversible.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.612-617
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• 2000

The vibrational characteristics of Langevin-type piezoelectric torsional transducers have been studied theoretically and experimentally in this paper. The differential equations of piezoelectric torsional motion have been derived in terms of the circumferential displacement and the electric potential. Solutions of the boundary-value problem have yielded the natural frequencies and mode shapes of the transducers. The theoretical solutions have been verified by comparing the numerical results with experimental ones.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.227-236
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• 2002

We have performed two kinds of experimental modal analyses fur a radial tire for passenger car under free-suspension. One is the modal analysis to obtain three-dimensional modes of tire using accelerometers and the other is the one to identify cavity resonance frequency using a pressure sensor. From the first analysis, we have obtained the three-dimensional natural modes, which makes it possible to grasp the features of the modes and to classify the vibrational modes into symmetric, non-symmetric, and antisymmetric modes in a simple way by using the experimental results. From the first and the second experimental analyses we have identified the cavity resonance frequency and its three-dimensional mode shape.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.248-253
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• 1992

In the development of a high speed and light weight manipulator, it is necessary to consider the structural elasticity of a robotic arm. The analysis of the infinite mode dynamic of robotic arm must be performed to obtain the finite mode modelling to achieve the feasible controller design of the robotic arm. The modelling procedure of the robotic arm is also illustrated. The controlled mode of the modelled dynamic can be derived by truncating the higher vibrational mode to result in the low order system for the sampling in the control signal is confined to the higher mode. And it is controlled by the pole assignment which can compensate the unmodelled dynamic effects. The unmodelled dynamic can result in the instability of the controlled system, which is known as spillover. The controller design of the low order system is simulated by the pole assignment and optimal control theory.

• Tribology and Lubricants
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• v.36 no.5
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• pp.290-296
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• 2020

When two layers of carbon nanotube (CNT) arrays are loaded to mate, the free ends of individual CNTs come into contact at the interface of the two layers. This leads to a higher contact resistance due to a smaller contact region. However, when the free CNT ends of one array penetrate into the mating array, the contact region increases, effectively lowering the contact resistance. To explore the penetration of mating CNTs, we perform molecular dynamic simulations of a simple unit cell model, incorporating four CNTs in the lower array layer coupled with a single moving CNT on the upper layer. The interaction with neighboring CNTs is modelled by long-range carbon bond order potential (LCBOP I). The model structure is optimized by energy minimization through the conjugate gradient method. A NVT ensemble is used for maintain a room temperature during simulation. The time integration is performed through the velocity-Verlet algorithm. A significant vibrational motion of CNTs is captured when penetration is not available, resulting in a specific vibration mode with a high frequency. Due to this vibrational behavior, the random behaviors of CNT motion for predicting the penetration are confirmed under the specific gap distances between CNTs. Thus, the probability of penetration is examined according to the gap distance between CNTs in the lower array and the aspect ratio of CNTs. The penetration is significantly affected by the vibration mode due to the van der Waals forces between CNTs.

• Advances in nano research
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• v.3 no.4
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• pp.193-206
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• 2015

The present paper investigate the elastic buckling of chiral double-walled carbon nanotubes (DWCNTs) under axial compression. Using the non-local elasticity theory, Timoshenko beam model has been implemented. According to the governing equations of non-local theory, the analytical solution is derived and the solution for non-local critical buckling loads is obtained. The numerical results show the influence of non-local small-scale coefficient, the vibrational mode number, the chirality of carbon nanotube and aspect ratio of the (DWCNTs) on non-local critical buckling loads of the (DWCNTs). The results indicate the dependence of non-local critical buckling loads on the chirality of single-walled carbon nanotube with increase the non-local small-scale coefficient, the vibrational mode number and aspect ratio of length to diameter.

• Journal of the Korean Wood Science and Technology
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• v.26 no.3
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• pp.16-25
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• 1998

This study was carried out to compare vibrational properties and adsorption among shellac, cashew finished plate and untreated plate of Sitka spruce(Picea sitchensis Carr). By the method of statistical regression modeling, the fundamental resonance frequency of finished plate was higher than that of untreated plate. The fundamental resonance frequency of cashew finished plate was higher than that of shellac finished plate. By the method of modal analysis, mode frequency ratio of cashew finished plate was higher than that of shellac finished plate. Amounts of adsorption of finished plate was lower than that of untreated plate, and amount of adsorption of cashew finished plate was lower than that of shellac finished plate. It was clarified that the vibrational properties and adsorption of finished plate were superior to those of untreated plate. The vibrational properties and adsorption of cashew finished plate was superior to those of shellac finished plate.