• Korean Journal of Materials Research
• /
• v.4 no.5
• /
• pp.502-509
• /
• 1994

New damping measurement equipment was designed using the dynamic strain gage and high speed analog to digital signal 12 bit converter and compared it with existing equipment. The damping properties of general material and high damping material were also studied by this machine. The SDC (specific damping capacity) was measured with various heat treatment condition, initial vibration amplitude and internal stress. The vibration amplitude of high damping material is decreased within nearly less than 0.4 second after applying the initial forced vibration. But that of general material is still vibrating at the same time. After furnace-cooling heat treatment, SDCmax of Fe-lGwt.%Cr system was more than 40% and that of Fe-5.5wt.%Al alloy was more than 30% after air-cooling heat treatment. Upon increasing of initial vibration amplitude, it is detected the migration of SDCmax into the region of small vibraton amplitude. Damping capacity is decreased rapidly as the internal stress Increases. Damping measurement equipment in the present study was ahln to give the more accurate results of damping properties in the small vibration amplitude region.

• Journal of KSNVE
• /
• v.3 no.1
• /
• pp.29-37
• /
• 1993

This study is concerned about the impact type damper for effectively restraining the high vibration amplitude in the resonance regions. The theoretical analysis is based on the assumption that the impacts occur twice per cycle at an equal time interval. Simple but reasonable approximations have been derived for the optimum collision clearance and maximum amplitude ratio. Using the impact dampers which is rigidly attached to the primary vibration system, we have experimented for mass ratios and restitution coefficients. The experimental results are in good agreement with theoretical results.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.12
• /
• pp.1950-1959
• /
• 2001

An active control of the vibration transmitted by longitudinal load in flight control system is investigated numerically. The flight control system is modeled as a finite, thin shell cylinder with constant thickness. A vibration source is generated by exterior monopole source. Distributed piezoelectric actuator is used to control of the vibration. Thin shell theory is used to formulate the numerical models. The amplitude of vibration at discrete location and power transmission are minimized by analytical optimization method. Genetic algorithm is used as numerical optimization method to search optimal actuator position and size which amplitude of vibration is minimized.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.4 no.4
• /
• pp.225-230
• /
• 2000

Recent building structures are superior in its ability but they are light and flexible, and so have problems of vibration. In general, the serviceability of RC slabs was known to be good against vibration because of its hardness. However, recent high-rise apartment slabs are mostly light and long, the serviceability of RC slabs due to vibration could be a problem. In this paper, a basic investigation about vibration problems of RC slabs was performed. Basic information and its influence on vibrations of RC slabs were revealed. Also, its serviceability against vibration was examined. Many tests were conducted on existing building located in Chung-Nam area. As a results, damping ratio, natural frequency, acceleration amplitude and displacement amplitude which were used to examine serviceability of the RC slabs were obtained. These results on the test building proved that its serviceability conditions were satisfied to meet the code against vibration.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.9-12
• /
• 2001

An active control of the vibration transmitted by longitudinal load in flight control system is investigated numerically. The flight control system is modeled as a finite, thin shell cylinder with constant thickness. A vibration source is generated by exterior monopole source. Distributed piezoelectric actuator is used to control of the vibration. Thin shell theory is used to formulate the numerical models. The amplitude of vibration at discrete location and power transmission are minimized by analytical optimization method. Genetic algorithm is used as numerical optimization method to search optimal actuator position and size which amplitude of vibration is minimized.

• Journal of Biosystems Engineering
• /
• v.6 no.1
• /
• pp.1-14
• /
• 1981

A laboratory model test was carried out with a newly designed model to figure out the vibration characteristics of the vibratory tillage tool according to the method of forced vibration, i.e., horizontally and vertically forced vibrations. The results are summarized as follows: 1. The reduction ratios of the draft force of the vibratory blade were 14.2-42.6% for the case where the vibration was forced parallel to the travelling direction of the blade, and 15-54.5% for the vertically forced vibration. And it was thought that the method of vertically forced vibration was preferable to the reduction of the draft force. 2. The ratio of the draft force of a vibratory blade to that of a static one could be represented as a function of V/At. It was found to be possible to reduce the draft force by taking a lower value of (V/Af) and this meant that the effictiveness of tillage practice using the vibratory system would be limited. 3. The torque to the main rotating shaft to vibrate the model blade increased frequency and amplitude. This tendency varied according to the physical properties of tested soil. In case of horizontally forced vibration, the torque was 8~34% less than in case of vertically forced vibration. 4. With the increase of frequency, the total power requirement increased linearly, and also the portion of oscillating power requirement in the total power tended to increase. The magnitude of the total power requirement was 1.4-13 times greater than that of a static one for the case of horizontal vibration, and 1.5-15 times greater for the case of vertical vibration. It was thought that the horizontal vibration of the blade was preferable to the vertical vibration in view of the power requirement. 5. A linearity was found between the amplitude of moment oscillogram and magnitude of oscillating acceleration. Only positive values of moment occurred when the blade was forced to vibrate vertically, but negative values occurred in rarity in the case of amplitude A3 when the blade was forced to vibrate horizontally.

• Geomechanics and Engineering
• /
• v.5 no.3
• /
• pp.223-240
• /
• 2013

In the present study an attempt was made to predict the complex nonlinear parameters of the soil-pile system subjected to the vertical vibration of rotating machines. A three dimensional (3D) finite element (FE) model was developed to predict the nonlinear dynamic response of full-scale pile foundation in a layered soil medium using ABAQUS/CAE. The frequency amplitude responses for different eccentric moments obtained from the FE analysis were compared with the vertical vibration test results of the full-scale single pile. It was found that the predicted resonant frequency and amplitude of pile obtained from 3D FE analysis were within a reasonable range of the vertical vibration test results. The variation of the soil-pile separation lengths were determined using FE analysis for different eccentric moments. The Novak's continuum approach was also used to predict the nonlinear behaviour of soil-pile system. The continuum approach was found to be useful for the prediction of the nonlinear frequency-amplitude response of full-scale pile after introducing the proper boundary zone parameters and soil-pile separation lengths.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2000.11c
• /
• pp.533-542
• /
• 2000

Instrumentation and technologies are described for determining the vibration response characteristics of the pear with frequency range 5 to 320Hz. The computer program for controlling the vibration exciter and the function generator and for measuring the vibration response characteristics of the pear was developed. Mechanical properties such bioyield deformation, rupture deformation and apparent elastic modulus etc. were compared with the vibration response characteristics of the pear. The resonant frequency of the pear ranged from 53 to 102Hz and the amplitude at resonance was between 1.08 and 2.48g-rms. The resonant frequency and amplitude at resonance decreased with the increase of the sample mass, and they were slightly affected by mechanical properties such as bioyield deformation and rupture deformation. Regression analysis was performed among the relatively high correlated parameters from the results of correlation coefficient analysis.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.245-250
• /
• 2000

Recent building structures are superior in its ability but they are light and fiexible, and so have problems of vibration. In general, the serviceability of RC slabs was known to be good against vibration because of its hardness. However recent high-rise apartment slabs are mostly light and long, the serviceability about vibration problems of RC slabs was performed. Basic information and its influence on vibrations of RC slabs were revealed. Also, its serviceability against vibration was examined. Many tests were conducted on existing building located in Chung-Nam area. As a results, damping ratio, natural frequency, acceleration amplitude and displacement amplitude which were used to examine serviceability of the RC slabs were obtained. These results on the test building proved that its serviceability conditions were satified to meet the code against vibration.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.3 s.96
• /
• pp.329-333
• /
• 2005

This paper is concerned with the measurement of low-frequency vibrations of structures using the image processing method. To measure the vibrations visually, the measurement system consists of a camera, an image grabber board, and a computer. The specific target installed on the structure is used to calculate the vibration of structure. The captured image is then converted into a pixel-based data and then analyzed numerically. The limitation of the system depends on the image capturing speed and the size of image. In this paper, we propose the methodology for the vibration measurement using the image processing method. The method enables us to measure the displacement directly without any contact. The current resolution of the vibration measurement is limited to sub centimeter scale. However, the frequency bandwidth and resolution can be enhanced by a high-speed and high-resolution image processing system.