• 수산해양기술연구
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• 제50권1호
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• pp.75-82
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• 2014

In vibration analysis of ships, the principle aim is to determine the natural frequencies and excitation frequencies, and use this information to avoid resonances and vibration damage. The simplest method is to prevent resonance conditions, which is effective as long as the natural frequencies and excitation frequencies can be regarded as independent from environmental conditions. For ships that use electric propulsion systems, the sources of vibration are reduced compared with those caused by a diesel engine or other combustion-based propulsion systems. However, the frequency spectrum of these vibrations may be different; therefore, to understand the characteristics of the electric propulsion, we also should investigate how the ship responds to these vibrations. We focused on a 1,000-ton deadweight (DWT) ocean-research vessel using an electric propulsion system and analyzed the response to vibration.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.661-667
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• 2002

With the increase of storage density, high rotational speed and high access technologies in optical disk drive, mechanical issues, mainly noise and vibration, become critical. Up to now the researches of rubber mount for anti-vibration focused on how to calculate the static and the dynamic stiffness of rubber mount and loaned out consideration of the dimensional tolerance of rubber mount for anti-vibration. This paper presents the effects of dimensional tolerance of rubber mount for anti-nitration on the dynamic characteristics of optical disk drive by finite element analysis and dynamic test. The relation between dimensional tolerance and dynamic characteristics of optical disk drive is observed and discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.223-228
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• 1997

In this study, the vibration were measured to analyze the characteristics of propagating vibration on the railroad, the roadbed and the ground nearby railroad induced by traveling trains. About Fifty cases of passing trains were measured with different types and speed, changing the source of loading and the points of measurement. The measured signals were analyzed in time domain and frequency domain. As a result of analysis, sudden reduction of energy was shown in near part from vibration source and the contents of high frequency was reduced more rapidly as the distance was increased. The amplitude of vibration and the contents of frequency did not make big differences in spite of different types of train which is recently used in Korea.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.329-336
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• 1998

The characteristics of vibration and sound signals which occurs at the driving system of electric train are investigated in this study since the vibration of driving system is one of the main sources of vibration and sound in electric train. The vibration signals are changed its signal patterns during the transmission from the source to passengers due to noise or several unknown factors. To avoid the complexity of actual signals of electric train, signals from experimental apparatus of motor/gear driving system are analyzed to find the appropriate method of analysis and to characterize the signal patterns. The used methods are waterfall diagram, transfer function and modal analysis. The results shows that the vibration signals are usually originated from motor bearing and gear meshing and these signals are transmitted to bottom or bogie. Also, the sound signal is similar to the vibration of bottom or bogie, but it is not so clear to figure out the source of vibration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.330-335
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• 2003

Analysis and experiment on dynamic characteristics of automotive roof have been carried out experimentally and numerically to design a lightweight roof. Finite element analysis of a conventional steel automotive roof was verified by experiments on vibration characteristics. The dynamic analysis of carbon fiber reinforced composite automotive roof shows that the roof stiffness changes as the fiber orientation of the laminated panel changes. Optimization results yielded a composite roof, which was 52% lighter, than the steel conventional steel automotive roof. This paper addresses a design strategy of composite roof for weight reduction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.516-521
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• 2000

Most of studies, using ESPI method, have handled tension, thermal and vibration analysis, and is limited to isotropic materials. However, tension and vibration simultaneously are loaded in real structure. Also, almost study using ESPI method is locally limited to the analysis on the isotropic materials and a few studies on the anisotropic materials have reported. Existing methods, such as the accelerometer method and FEA method, to analyze vibration have some disadvantages. Using the accelerometer method that is generally used to analyze vibration phenomena, it is impossible to analyze vibration on the oscillating body and one can observe no vibration mode shape during experiment. In case of the FEA method, it is difficult to define boundary conditions correctly if the shape of a body tested is complex, and one can just obtain vibration mode shapes on the peak amplitude in each modes. In this study, plane plate of stainless steel(STS304), isotropic material, that is used as structural steel is analyzed about vibration characteristics under tension. Also, in the study of stainless steel, the characteristics of composite material(AS4/PEEK) used as high strength structural material in aircraft is evaluated about vibration under tension, and studies the effect of tension on vibration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.522-527
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• 2012

This paper presents a result of the mechanical noise and vibration analysis as well as the electrical characteristics analysis of the permanent magnet (PM) motor according to the driving method that is Brushless DC (BLDC) drive and Brushless AC (BLAC) drive. To do that, the characteristics of the PM motor, which have the same output power but different driving method, are investigated. At that time, the characteristics such as torque, torque ripple and flux density, and so on, are obtained by finite element analysis (FEA). Besides, noise and vibration are obtained by spectrum analysis. The magnetic noise is defined as noise generated from vibrations due to electromagnetic excitation force. In this paper, the electromagnetic excitation force is analyzed and design process of noise reduction is proposed. Finally, The validity of the analysis results is verified by test.

• Structural Engineering and Mechanics
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• 제74권1호
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• pp.121-128
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• 2020

This paper presents an experimental study on the dynamic characteristics of infilled reinforced concrete (RC) frames. A 1/3-scaled, one-bay, three-storey RC frame was produced and tested by using operational modal analysis (OMA). The experiments were performed on five specimens: one reference frame with no infill walls and four frames with infill walls. The RC frame systems included infill walls made of hollow clay brick, which were constructed in four different patterns. The dynamic characteristics of the patterns, including the frequency, mode shapes and damping ratios in the in-plane direction, were obtained by 6 accelerometers. Twenty-minute records under ambient vibration were collected for each model, and the dynamic characteristics were determined using the ambient vibration testing and modal identification software (ARTeMIS). The experimental studies showed that the infill walls significantly affected the frequency value, rigidity and damping ratio of the RC frame system.

• Computers and Concrete
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• 제12권1호
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• pp.79-90
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• 2013

In this study, dynamic characteristics such as natural frequencies, mode shapes and damping ratios of RC frame is determined for different construction stages using Operational Modal Analyses method under ambient vibration. Full scaled, one bay and one story RC frames are selected as an application for different construction stages such as plane, brick in-filled and brick in-filled with plaster. The RC frame is vibrated by natural excitations with small impact effects and the response signals are measured using sensitive accelerometers during ambient vibration tests. Measurement time-frequency span and effective mode number are determined by considering similar studies in literature. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, output-only system identification technique is employed namely; Enhanced Frequency Domain Decomposition technique in the frequency domain. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of RC frames.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.297-309
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• 2015

The purpose of this work is to analyze the effect of structure parameter disturbance on the dynamic characteristics of a hydropower station powerhouse. A vibration model with a head-cover system is established, and then the general disturbance problem analysis methods are discussed. Two new formulae based on two types of disturbances are developed from existing methods. The correctness and feasibility of these two formulae are validated by analyzing the hydropower station powerhouse vibration model. The appropriate calculation method for disturbance of the hydropower station powerhouse vibration dynamic characteristics is derived.