• The Journal of the Acoustical Society of Korea
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• v.31 no.8
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• pp.561-568
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• 2012

This study proposes a method of an equivalent bell model in order to tune the beat period of a Korean bell. In a Korean bell having a slight asymmetry, each circumferential mode splits into a mode pair which has a slight difference in frequency, and the interaction of the mode pair makes a beat in vibration and sound. An equivalent bell model which consists of an axi-symmetric bell and an equivalent point mass, has the same mode property as in a real bell. The equivalent bell model is constructed by the finite element analysis based upon the theory of a revolutionary shell. Using the equivalent bell model, the beat period is predicted when the bell thickness is locally decreased to improve the beat property. The predicted result is verified by experiment on a test bell. The proposed method is useful to save the time required for tuning the beat period of a large bell.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.81-91
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• 2003

Recently, many high-rise reinforced concrete(RC) bearing-wall structures of multiple uses have been constructed, which have the irregularities of weak(or soft) story and torsion at the lower stories simultaneously. The study stated herein was performed to investigate seismic performance of such a high-rise RC structure through a series of shaking table tests of a 1: 12 model. Based on the observations of the test results, the conclusions are drawn as follows: 1) Accidental torsion due to the uncertainty on the properties of structure can be reasonably predicted by using the dynamic analysis than by using lateral force procedure. 2) The mode coupled by translation and torsion induced the overturning moments not only in the direction of excitations but also in the perpendicular direction: The axial forces in columns due to this transverse overturning moment cannot be adequately predicted using the existing mode analysis technique, and 3) the hysteretic curve and the strength diagram between base shear and torque(BST) clearly reveal the predominant mode of vibrations and the failure mode.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.507-515
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• 2008

In this study, a method predicting the displacement response of structures from the measured dynamic strain signal is proposed by using mode decomposition technique. Evaluation of bridge stability is normally focused on the bridge completed. However, dynamic loadings including wind and seismic loadings could be exerted to the bridge under construction. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. As previous studies on the prediction of displacement response by using the FBG sensors, the static displacement has been mainly predicted. For predicting the dynamic displacement, it has been known that the measured strain signal includes higher modes and then the predicted dynamic displacement can be inherently contaminated by broad-band noises. To overcome such problem, a mode decomposition technique was used. Mode decomposition technique estimates the displacement response of each mode with mode shape estimated to use POD from strain signal and with the measured strain signal decomposed into mode by EMD. This is a method estimating the total displacement response combined with the each displacement response about the major mode of the structure. In order to examine the mode decomposition technique suggested in this study model experiment was performed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.936-938
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• 2017

In this paper, the progressive failure analysis of a bolted composite joint which is used in combustion tubes of projectiles and weapon systems is performed. Hashin's failure criterion is considered as fiber tensile failure mode, fiber compressive failure mode, matrix tensile failure mode, and matrix compressive failure mode for this analysis. And this criterion is used to make user subroutine, UMAT. Through the progressive failure analysis we predicted failure strength and compared failure strength with specimen test result.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.649-665
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• 2015

The present paper attempts to investigate the propagation of plane waves in generalized piezo-thermoelastic medium under the effect of rotation. The normal mode analysis is used to obtain the expressions for the displacement components, the temperature, the stress and the strain components. Comparisons are made with the results predicted by different theories (Coupled theory, Lord-Schulman, Green-Lindsay) in the absence and presence of rotation.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.36-37
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• 2003

Three-dimensional numerical analysis of the flow around rectangular cylinders with various side ratios, D/H, from 0.2 to 2.0 is carried out for Reynolds number of 1000 by using multi-directional finite difference method in multi-grid. The predicted results are well compared with the experimental data. It is found that fluid dynamics characteristics alternate between high pressure mode. and low pressure mode of the base pressure for rectangular cylinder of D/H=0.2-0.6.

• Journal of Theoretical and Applied Mechanics
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• v.1 no.1
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• pp.89-96
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• 1995

An analytical method is presented for predicting the effect of a local deviation in the form of a concentrated mass along a radial line on the free bending vibration characteristics of a nearly axisymmetric circular plate. The approach is based on the Rayleigh-Ritz method and the expression of local deviation of the concentrated radial mass as the variation of heaviside unit step function. The effects of the concentrated mass on the natural frequencies and mode shapes of the plate are predicted with a proposed nondimensional mass parameter.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.187-194
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• 2002

It has been reported that cracks in mechanical joints is generally under mixed-mode and there is critical inclined angle at which mode I stress intensity factor becomes maximum. The crack propagates in arbitrary direction and thus the prediction of crack growth path is needed to provide against crack propagation or examine safety. In order to evaluate the fatigue life of cracks in mechanical joints, horizontal crack normal to the applied load and located on minimum cross section is major concern but critical inclined crack must also be considered. In this paper mixed-mode fatigue crack growth test is performed far horizontal crack and critical inclined crack in mechanical joints. Fatigue crack growth path is predicted by maximum tangential stress criterion using stress intensity factor obtained from weight function method, and fatigue crack growth rates of horizontal and inclined crack are compared.

• Journal of Power System Engineering
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• v.17 no.1
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• pp.36-41
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• 2013

A study of the possible axisymmetric modes that propagate at low frequencies in buried, water-filled pipes is presented. It is well known that for a vacuum-pipe-vacuum system the sole non-torsional axisymmetric mode that exists at low frequencies is the fundamental L(0,1) mode. When a pipe is filled with water and still surrounded by a vacuum it is also known that another mode then appears which at low frequencies is characterized by predominantly axial water-borne displacements. In addition to these modes. this paper explores two other, less well known axisymmetric modes whose exitence depends on the acoustic properties of the outer medium that surrounds a pipe. The predicted characteristics of these modes are presented and the likelihood of them propagating over any significant distance in a buried water pipe is discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.4
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• pp.351-361
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• 2001

In this paper, a generalized framework called as robust internal-loop compensator(RIC) is presented, and by using this, a structural design method of sliding of sliding mode controller is proposed. First, a general sliding mode controller is derived and a stabilizing control input is designed based on Lyapunov redesign for the system in the presence of uncertainty and disturbance. And adopting the internal model following control, RIC is proposed. Next, using the structural characteristics of the proposed RIC, disturbance attenuation characteristics are analyzed and the performance of the closed-loop system is predicted. Through this analysis, it is shown that if the control gain of RIC is increased by N times, the magnitude of error is reduced to its 1/N. the proposed method is verified through experiments using a high-precision positioning system and the performance is evaluated.