• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.685-693
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• 2002

Analytical model of beat response is derived on a slightly asymmetric ring and the model is veryfied by experiment. The asymmetric ring is a simplified model used to explain the beat property of a Korean bell. The asymmetric ring has mode pairs having slight frequency difference in each radial mode. Each mode pair produces beat phenomenon by the interaction of the two close frequency components. Based on the analytical model, beat maps are first proposed and characteristics of beat on the circumference are detaily explained.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1170-1176
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• 2008

In this study, we propose a new method to control both the beat clarity and beat period in a ring structure. An equivalent ring which satisfies the measured mode condition is determined by using the equivalent ring theory. Theoretical analysis and finite element analysis on the equivalent ring are performed to investigate the effect of the local structural modification on the beat clarity and beat period. Beat clarity and period are improved by attaching asymmetric mass or decreasing local thickness. Through the analysis on the equivalent ring, the proper position and the amount of the local variation are determined to satisfy the required clarity and period condition. All the analysis results are compared and verified by the experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.854-855
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• 2013

As an unique acoustic characteristic of a Korean bell. beat phenomenon is a periodic repetition of strong and weak sounds. Beat sounds good when it is clear and it has a proper period, however, it is not easy to satisfy these two conditions simultaneously. In this study, we propose a beat tuning method to satisfy these two conditions, by using an equivalent bell model. First, we construct an equivalent bell which has the same beat property with the 1st beat of a real bell and we investigate the change of mode pair by finite element analysis, when thickness of the bell is locally decreased at $22.5^{\circ}$ from the striking point. From the analysis result, minimum thickness reduction amount is determined to make a clear and strong beat.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.228-229
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• 2008

In this study, we propose an effective method to improve the clarity and period of the beat in a ring structure. Ring is an simplified model of a Korean bell, in which beating vibration and sound are very important features. An equivalent ring theory is applied and finite element analysis on the equivalent ring is performed to determine the condition of the asymmetric element for the clear and proper period beat. The clarity and the period of the beat are improved by attacking asymmetric mass and decreasing local thickness. Using the equivalent ring, the amount and position of the local variation for the required beat condition are determined and the results are verified by experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.776-779
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• 2005

Liquefied Natural Gas takes up six hundredths of the volume of natural gas, which makes storage and transportation much easier. To send out natural gas via a pipeline network across the nation, high pressure LNG pumps supply highly compressed LNG to high-pressure vaporization facilities. The Number of high Pressure LNG pumps determined the send out amount in LNG receiving terminal. So it is main equipment at LNG production process and should be maintained on best conditions. In this paper, to find out the cause of high beat vibration at cryogenic pumps, vibration and motor current analysis have been performed. And high beat vibration of cryogenic pumps could be reduced due to the modification of motor rotor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1218-1223
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• 2007

In this study, we experimentally investigate the equivalent ring theory for a slightly asymmetric ring. The slightly asymmetric ring has mode pair and frequency pair due to the small asymmetry and this mode pair generates beat in vibration and sound. In this paper, a slightly asymmetric ring is modeled as the equivalent ring, i.e., the assemblage of a symmetric ring and imperfect point masses. The equivalent ring has the same mode pair condition as that of the original asymmetric ring. Effect of the additional mass attachment is investigated by the equivalent ring theory and the result is compared with those of the measurement and the finite element analysis. It is confirmed that the original ring and the equivalent ring show the same change in frequency and mode under the various additional imperfection mass conditions. The equivalent ring theory explains how the asymmetric elements influence the mode characteristics and provides useful information to tune the beat property.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.472-475
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• 2013

This study proposes an equivalent bell model for the Sacred Bell of the Great King Seongdeok An equivalent bell model bas the modal property of the real bell and it consists of an axi-symmetric bell body and a point mass, The 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 can be controlled by decreasing the thickness of local area. This study aims at showing a beat period control method for a large bell having the similar size to the Sacred Bell of the Great King Seongdeok.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.93-100
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• 1994

Friction-induced vibration characteristics of automotive brake lining pad are investigated on the basis of experimental observations from a pin-on-disk type friction-induced vibration experimental apparatus. The measured responses of the experimental apparatus show limit cycles of quasi-harmonics type and beat phenomena due to the velocity dependence of friction force. To deduce the friction coefficient vs. relative velocity Lienard method is adopted with least square fit. It shows Scurve which characterizes a quasi-harmonic vibration. The calculation of amplitudes and friquencies of the limit cycles is done using slowly changing phase and amplitude method. The theoretical and numerical results show fairly good agreements with those of experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.845-851
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• 2003

The nonlinear vibration of moving viscoelastic belts excited by the eccentricity of pulleys is investigated through experimental and analytical methods. Laboratory measurements demonstrate the nonlinearities in the responses of the belt particularly in the resonance region and with the variation of tension, The measurements of the belt motion are made using noncontact laser sensors. Jump and hysteresis phenomenon are observed experimentally and were studied with a model. which considers the nonlinear relation of belt stretch. An ordinary differential equation is derived as a working form of the belt equation of motion, Numerical results show good agreements with the experimental observations, which demonstrates the nonlinearity of viscoelastic moving belts.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.81-88
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• 2006

The Chun-cheon Citizen's Bell was cast in memory of hosting the 2010 world leasure conference and a striking ceremony was held at the city hall on December 31, 2005. In this study, vibration and sound of the bell are measured and the property of the magnificent sound of the bell is scientifically investigated. Frequency components making the sound are identified and how the frequency components decrease with time is observed using waterfall plot(3-dimensional frequency spectrum). Beat characteristics of the hum(1st frequency) and the fundamental(2nd frequency)are examined by experiment. Directivity of the sound radiation of the bell is examined by measuring the vibration and sound in several directions. Duration of the vibration and the sound is estimated using damping ratio.