• Journal of KSNVE
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• v.22 no.4
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• pp.28-32
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• 2012

Condition-based maintenance on wind turbines not only involves maintenance, but also encompasses servicing, inspection, measurement and evaluation of the condition of the unit. The current condition can be evaluated on the basis of machine-specific overall vibration values. Until now, overall vibration values had not been defined for wind turbines. In fact, ISO 10816-3 explicitly excludes wind power plants. The new VDI 3834 closes this gap shown in Sheet 1: Vibration values for wind turbines up to 3 MW. In addition to the new VDI 3834 is the ISO 10816-21 in preparation. The author of the article Dr. Edwin Becker is the nominated expert for Germany.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1097-1104
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• 2008

Working condition is one of the most important factors in precision working. In this study, we optimized the vibration acceleration of working progress direction using RSM(response surface methodology) by table of orthogonal array. RSM was well adapted to make analytic model for minimizing vibration acceleration, created the objective function and saved a great deal of computational time. Therefore, it is expected that the proposed optimization procedure using RSM can be easily utilized to solve the optimization problem of working condition. The experimental results of the surface roughness and vibration acceleration showed the validity of the proposed working condition of side wall end-milling as it can be observed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.879-881
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• 2008

The construction noise and vibration is a serious social problem in the downtown. This results in many expenses and delays of construction process because of the satisfactory settlement of popular complaints. In this study, we analyze the dispute mediation cases on the damages of construction noise and vibration and the noise and vibration condition in construction sites by using questionnaire surveys.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.85-91
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• 2006

Recently, the reduction of electromagnetic vibration and noise of a capacitor motor (CRM) has become a very important subject from the standpoint of environmental improvement. Therefore, the authors have studied the characteristics of the dominant electromagnetic vibration of the CRM under load condition. In this paper, the effects of slot combination and skewed slot on the dominant electromagnetic vibration of a CRM under load condition are discussed both theoretically and experimentally. As a result, the characteristics of the dominant electromagnetic vibration for the slot combination and the reduction effect of the skewed slot on the electromagnetic vibration are clarified for a 4-pole CRM.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.8
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• pp.720-725
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• 2011

Most ultrasonic vibration cutting tools are operated at the resonance condition of the longitudinal vibration of the structure consisting of booster, horn and bite. In this study, a transverse vibration tool with beam shape is designed to utilize the vibration characteristics of the beam. Design point of the transverse vibration tool is to match the resonance frequency of the bite to the frequency of the signal to excite the piezoelectric element in the booster. The design process to match the natural frequency of the longitudinal vibration mode of the horn and that of the transverse vibration mode of the bite is presented. Dimensions of the horn and bite are searched by trend analysis through which the standard shapes of the horn and bite are determined. After the dimensions of each component of the cutting tool consisting of booster, horn and bite are determined, the assembled structure was experimentally tested to verify that true resonant condition is achieved and proper vibrational displacement are obtained to ensure that enough cutting force is generated.

• Journal of Environmental Impact Assessment
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• v.22 no.4
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• pp.381-387
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• 2013

In order to improve the environmental vibration, it is necessary to method for not only reduce the vibration source, but also control the vibration path. In this study, we used borebole for estimate the vibration reduction. And also, we analyzed displacement and vibration velocity caused by the position of borehole as well as the condition of borehole in ground structure. Visual FEA(Finite Element Analysis) program was used in this numerical analysis. The results are as follows : The displacement magnitude and X, Y direction displacement were represented to different results due to the condition and position of borehole, and were represented to the lowest values when the position of borehole is the most close condition from the vibration source. And also, the vibration velocity was decreased as using borebole in ground structure. The isolation efficiency of the vibration was calculated to maximum 18.40% when borehole was established to the most close position from the vibration source and the receive point.

• Tribology and Lubricants
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• v.33 no.4
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• pp.141-147
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• 2017

The vibration data of bearings are very useful for monitoring and determining the condition of the bearings. The defect frequencies of ball bearings have been used for monitoring there condition. However, it is not easy to verify the defect frequencies as the wear progress. Therefore there is a need for an easy method to monitor the damages of bearings in real-time and to observe the variations in vibration characteristics as the wear progress. In this study, a bearing test equipment is constructed to diagnose the damage of bearings. The friction coefficient and vibration data are measured by using a torque sensor and an acceleration sensor, and the correlation between the measured data is analyzed to diagnose the condition of the bearing. We reached the following conclusions from the results. When the ball surface, inner and outer rings of a ball bearing are damaged, the friction coefficient increases to over 0.02 with an adhesion on the surface. Moreover this damage occurs more quickly with an increase in the number of revolutions. In the vibration characteristics, the amplitude of vibration wave appears high with an increase in the friction coefficient. In the high frequency range between 1000 and 2000 Hz, a wide range of frequency components with high amplitude occurs continuously irrespective of the number of revolutions.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.143-156
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• 2021

Rail transit lines usually pass through many complicated topographies in mountain areas. The influence of inclined bedrock on the train-induced soil vibration response was investigated. Model tests were conducted to comparatively analyze the vibration attenuation under inclined bedrock and horizontal bedrock conditions. A three-dimension numerical model was built to make parameter analysis. The results show that under the horizontal bedrock condition, the peak velocity in different directions was almost the same, while it obviously changed under the inclined bedrock condition. Further, the peak velocity under inclined bedrock condition had a larger value. The peak velocity first increased and then decreased with depth, and the trend of the curve of vibration attenuation with depth presented as a quadratic parabola. The terrain conditions had a significant influence on the vibration responses, and the inclined soil surface mainly affected the shallow soil. The influence of the dip angle of bedrock on the peak velocity and vibration attenuation was related to the directions of the ground surface. As the soil thickness increased, the peak velocity decreased, and as it reached 173% of the embedded pile length, the influence of the inclined bedrock could be neglected.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.3
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• pp.1-7
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• 2011

The analysis shows that the vibration is one of the main reasons of turbine failure. Especially, the problems caused by vibration occur right after retrofit of the turbine-generator and restarting the turbine. Through the case study of high vibration caused by after the turbine trip and restart, turbine vibration was identified to be influenced by startup condition. Turbine startup at high casing temperature right after unscheduled turbine trip cause radial expansion in rotor by contraction in axial direction, while casing continues to contract by steam flowing into casing. Consequently, gap between rotor and casing decrease until to metal contact to cause high vibration. Through the case study of high vibration of turbine-generator system after generator retrofit, it was identified that generator replacement could cause high vibration in turbine-generator system if the influence of generator replacement on entire system was not considered properly. To prevent startup delay caused by high vibration, it is important to keep the gaps at the design standard and start the turbine after thermal equilibrium.

• International Journal of Highway Engineering
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• v.15 no.6
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• pp.93-101
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• 2013

PURPOSES : The rumble strip installed at the highway near the tollgate has the purpose to reduce the vehicle velocity or prevent sleepiness by awakening people to the danger. These rumble strip has different vibration decibel from the rumble strip shapes, resulting in some fatigue damage to human because a driver suffers from a lot of stress and displeasure. In this connection, the objective of this paper is to analyze the vibration decibel perceived by a driver in the vehicle under some conditions. METHODS : The vibration decibel conveyed from the tire can be analyzed. The frequency analysis methods were used according to DFT (Discrete Fourier Transform) analysis, FFT (Fast Fourier Transform) analysis, CPB (Constant Percentage Bandwidth) analysis. But the frequency analysis method in this paper is the 1/24 OCT(Octave) band analysis because of the convenience of the analysis and the overall vibration amplitude along the frequency. RESULTS : By using the results of the vibration decibel after analyzing the 1/24 OCT band analysis, these results can be compared from some conditions (e.g., rumble strip shape, uniform velocity of a vehicle, road condition, mass of a vehicle). As a result, the numerical values of decibel are not directly proportional to the vehicle velocity. CONCLUSIONS : At the condition that a vehicle is passing by the rumble strip, the value of a vibration decibel at the rumble strip of the cylinder shape is smaller than the rumble strip of rectangular shape regardless of the rumble strip depth and width. At the mass condition, the more a vehicle is massive, the more the vibration decibel increases. At the road condition, the vibration decibel at the wet road is smaller than the value at dry road condition.