• Title/Summary/Keyword: 진동효과

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A Novel Cooling Method by Acoustic Streaming Induced by Ultrasonic Resonator (초음파 진동자에 의해 유도된 음향유동을 이용한 첨단 냉각법)

  • 노병국;이동렬
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.3
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    • pp.217-223
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    • 2003
  • A novel cooling method induced by acoustic streaming generated by ultrasonic vibration at 30㎑ is presented. Ultrasonic vibration is obtained by piezoelectric devices and the maximum vibration amplitude of 50 m is achieved by including a horn, mechanical vibration amplifier in the system and making the complete system resonate. To investigate the enhancement of heat transfer capability of acoustic streaming, the temperature variations of heat source and air in the vicinity of heat source are measured in real-time. It is observed that acoustic streaming is instantly induced by ultrasonic vibration, resulting in the significant temperature drop due to the bulk air flow caused by acoustic streaming. In addition, it is observed that the cooling effect on the heat source is maximized when the gap between the ultrasonic vibrator and heat source coincides with the multiples of half-wavelength of the ultrasonic wave. This fact results from the resonance of the sound wave. The theoretical analysis of the dependence on the gap is also accomplished and verified by experiment. The advantage of the proposed cooling method by acoustic streaming is noise-free due to the ultrasonic vibration and maintenance-free because of the absence of moving parts. Moreover. This cooling method can be utilized to the nano and micro-electro mechanical systems, where the fan-based conventional cooling method can not be employed.

Analysis of Vibration Suspension Device for Trailer in Agricultural Products (농산물 수송 트레일러의 현가장치 진동 분석)

  • Hong, Jong-Ho;Lee, Seong-Beom;Park, Won-Yeob;Kim, Seong-Yeob;Wu, Yong-Gun
    • Journal of Bio-Environment Control
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    • v.21 no.4
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    • pp.437-444
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    • 2012
  • This study was aimed to minimized the impact force and vibration transmitted to transporting agricultural product from the power tiller trailer by installing vibration absorption device. The vibration absorbable trailer (I) mounted with leaf spring suspension and shock absorber was developed and compared on vibration absorption performance with the existing trailer (E) equipped no vibration absorption device. In order to identify the vibration absorption effect of the trailer developed in this study, the vibration accelerations, occurred during driving on paved road with loading 360 kg of pear, were measured and analyzed using FFT analyzer. The magnitude of average vibration acceleration was decreased highly for the improved trailer mounted with vibration absorption device in comparing with existing trailer in the frequency range under 60 Hz and under 80 Hz. And similar vibration absorption effect was represented for the improved trailer in all frequency range. Especially, in the frequency range between 40 Hz and 80 Hz, the magnitude of vibration acceleration for the improved trailer was decreased with 1/3 times in comparing with existing trailer. So, the transporting loss including damage of agricultural product could be decreased highly by using the improved vibration absorbable trailer mounted with leaf spring suspension and shock absorber simultaneously, designed in this study.

Nonlocal elasticity effects on free vibration properties of sigmoid functionally graded material nano-scale plates (S형상 점진기능재료 나노-스케일 판의 자유진동 특성에 미치는 비국소 탄성 효과)

  • Kim, Woo-Jung;Lee, Won-Hong;Park, Weon-Tae;Han, Sung-Cheon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.2
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    • pp.1109-1117
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    • 2014
  • We study free vibration analysis of sigmoid functionally graded materials(S-FGM) nano-scale plates, using a nonlocal elasticity theory of Eringen in this paper. This theory has ability to capture the both small scale effects and sigmoid function in terms of the volume fraction of the constituents for material properties through the plate thickness. Numerical solutions of S-FGM nano-scale plate are presented using this theory to illustrate the effect of nonlocal theory on natural frequency of the S-FGM nano-scale plates. The relations between nonlocal and local theories are discussed by numerical results. Further, effects of (i) power law index (ii) nonlocal parameters, (iii) elastic modulus ratio and (iv) thickness and aspect ratios on nondimensional frequencies are investigated. In order to validate the present solutions, the reference solutions are compared and discussed. The results of S-FGM nano-scale plates using the nonlocal theory may be the benchmark test for the free vibration analysis.

Follower Effect of the Axisymmetric Shells under External Pressure (축대칭 쉘 구조물에 작용하는 외압의 부가효과)

  • Hwang, Chul-Sung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.8 no.1
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    • pp.195-202
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    • 2004
  • The shell due to the effect of initial normal pressures on the shell surface was based on the assumption that the directions of the pressures are always normal to the undeformed shell surface, and that the change in the surface area of the shell is negligible. But the fact that the pressure are always normal to the deforming surface leads "follower force". The follower effect in the analysis can significantly alter the solution for natural frequency and buckling load as compared to the case when the direction of the pressures are assumed to be normal to the uniform shell surface. The expression for the part of strain energy contribution from normal pressure due to the effect of follower force was derived and added to the element stiffness matrix of axisymmetric shell. In the case of increasing external pressure, the natural frequencies decrease until one of them reaches zero. Theoretically the smallest applied load that reduces the frequency of any mode to zero, will have same magnitude as that of the buckling load. In order to determine the bucking load of the shell a few sets of frequencies are computed and the results considering the follower effects are well with the exact solution while the case without that are quite different. But in case of hemispherical dome, there are little difference in buckling pressure between with and without the effect of follower force.

Adaptive Multi-mode Vibration Control of Composite Beams Using Neuro-Controller (신경망 제어기를 이용한 복합재 보의 다중 모드 적응 진동 제어)

  • Yang, Seung-Man;Rew, Keun-Ho;Youn, Se-Hyun;Lee, In
    • Composites Research
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    • v.14 no.1
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    • pp.39-46
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    • 2001
  • Experimental studies on the adaptive multi-mode vibration control of composite beams have been performed using neuro-controller. Neuro-controllers require too much computational burden, which blocks wide real-time applications of neuro-controllers. Therefore, in this paper, an adaptive notch filter is proposed to separate a vibration signal into each modal vibration signal. Two neuro-controllers with fewer weights are connected to the corresponding modal signals to generate proper modal control forces. The vibration controls using the adaptive notch filter and neuro-controllers have been performed for two specimens. A and B, which have different natural frequencies because of different positions of tip masses. Significant vibration reduction has been observed in both cases. The vibration control results show that the present neuro-controller has good adaptiveness under the system parameter variations.

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Semiactive Control for Structural Vibration Mitigation (구조물 진동 저감을 위한 반능동 제어)

  • Changki Mo;Jaesoo Lee
    • Journal of KSNVE
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    • v.11 no.1
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    • pp.96-103
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    • 2001
  • Past research has repeatedly demonstrated the fact that hydraulic semiactive systems, if operated Properly, can provide levels of control authority in structural vibration control systems that are comparable to a fully active hydraulic damper. The performance of the semiactive system when used to provide vibration mitigation for a laboratory test structure is described in this paper Numerical and experimental verification of the effectiveness of the proposed bistate controller which relies on a Lyapunov approach that seeks to dissipate the energy of the system is also presented. The results based on the bistate control are compared with those of two different control strategies. The work indicates that hydraulic semiactive actuator provides a reliable, and inexpensive means of achieving structural control.

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Vibration Control of Flexible Structures Using ER Dampers (ER 댐퍼를 이용한 유연구조물의 진동제어)

  • 최승복;이재홍
    • Journal of KSNVE
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    • v.8 no.2
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    • pp.313-323
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    • 1998
  • This paper addresses a sliding mode control of vibration in a flexible structure using ER(electro-rheological) dampers. A clamped-clamped flexible structure system supported by two short columns is considered. Three ER dampers to be operated in shear mode are designed on the basis of Bingham model of the arabic gum-based ER fluid, and attached to the flexible beam structure. After deriving the governing equation of motion and associated boundary conditions, a sliding mode controller is formulated to effectively suppress the vibration of the beam structure caused by sinusoidal and random excitations. In the formulation of the controller, parameter variations such as natural frequency deviation are treated to take into account the robustness of control system. The effectiveness of the proposed control system is confirmed by both simulation and experimental results.

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An Analysis on Performance Test of TLD and MTLD Using Shaking Table (진동대를 이용한 TLD와 MTLD의 성능실험에 대한 분석)

  • You, Jang-Youl;Song, Chang-Hyun;You, Ki-Pyo;Kim, Young-Moon
    • Proceeding of KASS Symposium
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    • 2008.05a
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    • pp.139-144
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    • 2008
  • Experimental studies using tuned liquid damper(TLD) and multiple tuned liquid damper(MTLD), which are passive control devices consisting of a rigid tank filed with liquid, are used to suppress vibration of structures. This TLD and MTLD are attributable to several potential advantage -low costs, easy; easy to install in existing structures: effective even for small amplitude vibrations. For this, we conducted shaking table experiments for two natural frequencies (0.44Hz, 0.55Hz) according to the excitation amplitude(1mm, 3mm, 5mm, 10mm, 20mm) So, the majority of studies suggested optimized natural frequence and excitation amplitude for control devices.(TLD and MTLD type : circle, rectangular) As the analysis result, we verified vibration reduction effects of a MTLD by analyzing the performance experiment of TLD and MTLD

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A Study on Forced Vibration Tests on a Structure with Stud Type of Vibration Control Damper (스터드형 진동제어 강재댐퍼가 장착된 3층 강구조 골조의 강제진동실험에 관한 연구)

  • Lee, Seung-Jae
    • Journal of Korean Association for Spatial Structures
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    • v.6 no.2 s.20
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    • pp.115-121
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    • 2006
  • In recent years vibration control damper made of low yield point steel is expected to play an important role in controlling structural vibration induced earthquake and wind. But their dynamic characteristics and energy dissipation effects on the whole structure model are not clarified. In this paper, firstly, we presents the results of cyclic tests on low yield steel dampers. Secondly, forced vibration tests on existence three stories steel structure model with low yield point steel dampers are presented. Lastly, it is estimated energy amount which is dissipated through the hysteresis dampers by using two types of analytical models, hysteresis model and equivalent linear model.

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Semi-active control of elastically supported floating slab vibration excited by the moving train mass (열차 운행 중 발생하는 탄성지지 슬라브 진동의 반능동 제어)

  • Lee, Gyu-Seop;Jang, Seung-Yeop;Baek, Jae-Ho;Park, Sang-Gon;Han, Hyun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.678-678
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    • 2009
  • 환경 소음,진동 개선의 측면에서 철도 레일 하부로 전달되는 진동 및 구조소음을 효과적으로 차단하기 위하여 국내에서도 탄성지지 구조의 플로팅 슬라브를 적용하는 경우가 증가하고 있다. 플로팅 슬라브 구조설계에 있어 주안점은 슬라브 자체 중량에 비하여 열차 중량과 열차 주행간에 발생하는 동하중이 2$\sim$3배 이상 높아 열차 주행 안정성을 고려해야 하는 점이며 열차의 고속화 경향에 따라 동하중의 증가는 더욱 커지고 있다. 특히, 열차의 구조 동특성과 동하중의 주파수 특성을 고려할 경우 슬라브 구조의 동적 설계변수(고유진동수, 감쇠비 등) 결정이 매우 제한되고 있음을 고려하면 탄성지지부의 감쇠 및 강성의 가변 특성의 부여는 매우 중요하다 할 수 있다. 본 연구에서는 MR 댐퍼와 MR 방진고무 등의 반능동 소재를 사용하여 열차 주행간에 발생하는 탄성지지 슬라브의 진동을 제어하는 시뮬레이션을 수행함으로써 적용 가능성을 확인하고자 한다.

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