• 한국공간구조학회논문집
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• 제17권1호
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• pp.93-100
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• 2017

With increasing number construction of high-rise building which has about 40 to 60 floors there have been many kinds of problem which related with usage from vibration. To predict response acceleration, it is important to assess correct natural frequency. However, due to the noise of MEMS sensor, it is difficult to measure dynamic characteristic such as natural frequency when measuring ambient vibration using MEMS sensor within cell phone. Therefore, a comparative analysis on vibration measuring applications was performed after measuring ambient vibration of 2 skyscrappers which have height between 133.5~244.3m that are located in Seoul and Observation tower using I-jishin APP with noise reduction function of MEMS sensor in order to verify the effectiveness of low noise type vibration measurement APP.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.383-386
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• 2005

Low frequency heavy-weight impact noise is the most irritating noise in Korean high-rise reinforced concrete apartment buildings. This low frequency noise is generated by foot traffic due to the fact that Koreans do not wear shoes at home. The transmission of the noise is facilitated by a load bearing wall structural system without beams and columns which is used in these buildings. In order to control low frequency heavy-weight impact noise, floating floors using isolation materials such as glass-wool mat and poly-urethane mat are used. However, it was difficult to control low frequency heavy-weight impact sound using isolation material. In this study, reinforcement of concrete slab using beams and plate was conducted. Using the FEM analysis, the effect of concrete slab reinforcement using FRP(fiber-glass reinforced plastic) on the bang machine impact vibration acceleration level and sound were conducted at the standard floor impact sound test building. The $3{\sim}4dB$ floor impact vibration acceleration level and impact sound pressure level were reduced and the natural frequency of slabs were changed.

• 한국정밀공학회지
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• 제31권8호
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• pp.697-703
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• 2014

This paper is study of solving vibration problem occurred in moving hand of wafer transfer robot in semiconductor manufacturing line. Long settling time for decreasing vibration makes low production rate, and moreover the excessive vibration of hand sometimes breaks the wafer in a cassette. The ways of reducing the moving speed and changing the type of motion profile did not help for lessening vibration. Therefore, we analyzed the mechanical property of the hand such as natural frequency, and frequency component of the motion profile currently used in the manufacturing line. In several conditions of motion profile, we found the best condition of which the frequency component in near of natural frequency of the hand is minimal and this induced small vibration in moving hand. The results were verified theoretically and experimentally using frequency analysis.

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.957-965
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• 2013

This paper deals with analytical methods for low frequency and high frequency brake squeal noise on brake-rear caliper. In order to improve low frequency and high frequency squeal noise, we take survey caliper bracket shape parameters and housing shape parameters. Besides, using the combination of bracket and housing parameter were surveyed. Thus, using the combination of bracket Alt_05 and housing Alt_45 specifications, instability analysis and brake dynamo test were carried out. Based upon the two models, low and high frequency squeal noise of base model were improved. But, for 6.0 kHz frequency noise, which is not improved, it needs to additionally study on instability analysis and combination of the other brake components.

• Smart Structures and Systems
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• 제6권5_6호
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• pp.661-673
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• 2010

This paper presents recent developments in an extremely compact, wireless impedance sensor node (the WID3, $\underline{W}$ireless $\underline{I}$mpedance $\underline{D}$evice) for use in high-frequency impedance-based structural health monitoring (SHM), sensor diagnostics and validation, and low-frequency (< ~1 kHz) vibration data acquisition. The WID3 is equipped with an impedance chip that can resolve measurements up to 100 kHz, a frequency range ideal for many SHM applications. An integrated set of multiplexers allows the end user to monitor seven piezoelectric sensors from a single sensor node. The WID3 combines on-board processing using a microcontroller, data storage using flash memory, wireless communications capabilities, and a series of internal and external triggering options into a single package to realize a truly comprehensive, self-contained wireless active-sensor node for SHM applications. Furthermore, we recently extended the capability of this device by implementing low-frequency analog-to-digital and digital-to-analog converters so that the same device can measure structural vibration data. The compact sensor node collects relatively low-frequency acceleration measurements to estimate natural frequencies and operational deflection shapes, as well as relatively high-frequency impedance measurements to detect structural damage. Experimental results with application to SHM, sensor diagnostics and low-frequency vibration data acquisition are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 합동춘계학술대회 논문집 전기물성,응용부문
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• pp.189-190
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• 2008

This study was investigated a possibility of fault of glass insulator due to vibration on high-speed railway. The proper vibration of 1-glass insulator have many frequency band and high amplitude showed in high frequency than low frequency. The proper vibration of strut tube insulator was lowest 170Hz, highest 1.5kHz. The field signal amplitude of viaduct and open route were biggest moment pantograph of high-speed rail. The surface vibration(V3) amplitude of strut tube insulator was biggest. From the FFT analysis of viaduct and open route, the strut tube insulator effect by vertical vibration was big, the frequency was 82.5Hz and 105Hz, respectively. However, in comparison with the proper vibration of strut tube insulator, the resonance was not observed. Although the amplitude of insulator is high, the possibility of fault is low because the glass insulator deterioration by the accumulation of vibration do not happen.

• 소음진동
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• 제9권1호
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• pp.85-96
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• 1999

For ASME Code pumps in nuclear power plants, inservice test is required to assess the operational readiness in accordance with ASME code and related regulations. The objective of this study therefore, is to develop the technical background of the degradation of pump performances and conditions due to low flow rate operation. In addition. the detection techniques of pump operating conditions are to be developed to enhance the safety and economy of nuclear power plants. A test loop consisted of pump, motor. water tank, flow rate measurements and piping system with flow control devices was established for this study. Two typical pumps, 1-stage volute pump and 3-stage turbine pump, were selected and the test was performed upon two major point of views ; i.e., pump discharge pressure pulsations analysis and pump vibration spectrum analysis. From the test results, it is concluded that (1) the pump vibration affected by the natural frequency of operating pump is significant in the low frequency zone (around 1 Hz) : the vibration amplitude. especially. is an important factor during low flow rate operation. and shall be monitored to ensure that it is within the limit of ASME OM code Part 6, (2) the vibration frequency and pump discharge pressure are affected by vane pass frequency and running speed, (3) the wave phenomena due to the compressiblity of water is anticipated during low flow rate operation. and the pump system shall be designed to prevent it and. finally, (4) the technical background of the degradation of pump performances and conditions due to low flow rate operation is provided.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.297-300
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• 2005

This paper presents vibration control of an engine mount for a passenger vehicle utilizing ER fluid and piezoelectric actuator. The proposed engine mount can be isolated the vibration of wide frequency range with many types of amplitude. The main function of ER fluid is to attenuate vibration for low frequency with large amplitude, while the piezoelectric actuator is activated in hish frequency range with small amplitude. A mathematical model of the engine mount is derived using Hydraulic model and mechanical model. After formulating the governing equation of motion, then field-dependent dynamic stiffness of the engine mount is evaluated for various engine speed and excitation amplitude conditions. Then robust controller is designed to attenuate vibration of wide range frequency component. Computer simulation is undertaken in order to evaluate the vibration control performance such as transmissibility magnitude in frequency domains.

• 산업경영시스템학회지
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• 제30권4호
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• pp.71-77
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• 2007

In this study, reactions of central nervous systems working against different conditions of forced frequency and acceleration were measured and analyzed. The experiment are conducted with health men. The steady vibration conditions of forced frequency (0.315m/s2-1.0Hz, 0.315m/s2-10Hz and 10Hz-1.0m/s2) are used and the waves of EEG (Electroencephalogram) are measured. As a result, this paper shows that the ${\alpha}-wave$ of frontal lobe transfers from low to high frequency band under the vibration environment. Additionally, the average frequency of ${\alpha}-wave$ is higher under the vibration than under non-vibration environment. In the case of forced frequency of 1.0Hz-0.315m/s2, the feeling with the vibration are nearly same compared with the non-vibration condition. But in the case of 10Hz-1.0m/s2, uncomfortable feeling increased compared with the non-vibration condition. This study also shows the relationship between fluctuation slop and feeling. From this study, it is found that the effect of vibration on human depends on acceleration characteristics. Highly accelerating vibration is more harmful to human.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.612-617
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• 2000

This paper describes the experience gained from the treatments for prevention of blade failure occurred in the low-pressure turbine. Some cracks due to high cycle fatigue were found at the blades in low-pressure turbines after long time operation. Such failure was mainly caused by the resonance of the blade with the vane passing frequency excitation. If a natural frequency of the blade exists near the excitation frequency, a resonant vibration can occur and leads to a large amount of stress which may cause fatigue failures in turbine blades. To avoid the resonance of the blade, some modifications have been performed and full-scaled mockup testing has been done to confirm the verification for modification. Test result shows that enlarging the span cover is very useful to change the natural frequency of the grouped blades effectively.