Papers by Keyword: Vibration Attenuation

Abstract: Phononic crystals (PCs) have the ability to have phononic bandgaps dependent on the acoustic properties of its constituent materials (i.e., mass, elasticity). Forming a 1D periodic variation using a viscoelastic material allow the PC to have more wave vibration attenuation in the longitudinal direction. In this study, the low transmission zones and the vibration attenuation properties of a one-dimensional PC subjected to flexural vibration was evaluated experimentally. Results were presented in the form of frequency response functions and showed the flexural low-frequency zones starting at 500 Hz with three zones in the 16kHz range.

Abstract: Beams in lightweight truss structures are subject to axial and lateral loads that may lead to undesired structural vibration or failure by buckling. The axial and lateral forces may be transferred via the truss supports that offer possibilities for state control of single beams and larger structures. In earlier own studies, the concept of a piezo-elastic support for active buckling control and resonant shunt damping has been investigated. An elastic spring element is used to allow a rotation in the beam's bearing in any plane perpendicular to the beam's longitudinal axis. The rotation is laterally transferred to an axial displacement of piezoelectric stack transducers that are either used to generate active lateral forces for active buckling control or to attenuate vibrations with a resonant shunt. In this paper, the model verification and validation of the elastic properties of the piezo-elastic support for passive and active structural control of beams with circular cross-section is presented. The rotational and lateral spring element stiffness is investigated numerically and experimentally and the existing models are updated in the verification process. The model is validated by comparing the numerical results and experimental ability for vibration attenuation.

Abstract: Through site test, the paper conducts site test to vertical vibration accelerations when a train passes through steel rails and tunnel walls at a steel spring floating slab track section and a general track section in the tunnel of Yizhuang Line of Beijing Metro. The paper also conducts comparative analysis of the accelerations in time domain and frequency domain. It is shown in results that the vibration acceleration level of the steel spring floating slab track in time domain is reduced by 22 dB in tunnel walls in comparison with the general track; in the frequency domain, the vibration effect is gradually increased with frequency increase and reaches the optimal effect in medium-high frequency. The maximum vibration attenuation quantity of frequency division reaches up to 40 dB; and the maximum Z weighted vibration acceleration level is reduced by 22 dB.

Abstract: In this paper a new type of semi-active vibration absorber has been developed. The vibration absorber consists of mass block, cantilever beam, magnet lock system, vibration and distance sensors, controller and servo motor. The mass block is fixed on the tip of cantilever beam, and the control process is driven by a servo motor and a transmit gears. Portion of cantilever was cut in form of gear tracks, which can be driven by servo motor through transmit gear to regulate the length of the cantilever beam, and the natural frequency of absorber will also be regulated. After the mass locates in right position (i.e. the natural frequency of absorber is in assigned condition), the magnetic lock will clamp the cantilever beam. The design has the benefit of simplified control system, and extra unknown vibration modes will be averted. A fabrication prototype of the proposed semi-active vibration absorber is constructed and tested to demonstrate the application and modeling of the new cantilever beam damper. By performing the experimental work, the semi-active vibration control system is designed not only for reduce vibration level in resonant condition, but also considered for vibration attenuation in non-resonant conditions.

Abstract: A novel three-phase (ceramic, epoxy resin and decoupling material) piezoelectric composite with multi-element in parallel connection has been developed by using dice-fill technology. This kind of composite consists of a large number of elements which can be seen as a single-sound radiation source. The space between elements is determined via a precise method of calculation. The ceramic elements are then cut using precision machinery to achieve exact results. A kind of decoupling material has been developed to decrease the cross coupling effect between elements. The vibration velocity curves of active elements and close elements were measured using a Scanning Laser Vibrometer (Polytec PSV-400). The results indicated that the decoupling materials induced in multi-element composites have a good decoupling effect. Vibration attenuations between adjacent elements are larger than 31 dB at resonance frequency.

Abstract: In order to analyze the damping effect of high-elastic damping fastener on rail transit viaduct, Ls Dyna software was use to analyze rail and viaduct vertical vibration under different fastener damping constant. Fasteners with no damping constant and different damping constant are built in finite element model with rail transit viaduct, and the acceleration simulation results of them are compared to find damping effect on rail transit viaduct vibration transmission. The results indicate that the damping characteristic can attenuate vibration produced by wheel rail impact, however as the fastener damping constant are only parts of the whole damping system of the rail transit viaduct, the damping constant is not as better as its increment. The paper attempts to provide advice for employment of damping fastener in excessive vibration region of urban mass transit.

Abstract: In this paper, the possibility of applying non-obstructive particle damping (NOPD) into the vibration attenuation for heavy-duty machine tool was analyzed and the experimental study on the characteristics of damping vibration attenuation was then carried out. First, the finite-element model for heavy planer type milling machine was built and then the stress state excited by the cutting force in the presence of the holes for filling particles located in the stand column was calculated. Secondly, based on the experiment, the acceleration time-domain waveform and the frequency response function (FRF) between NOPD application and the traditional solid cast-iron column of the planer type milling machine were obtained. Finally it is indicated that NOPD can effectively reduce the amplitude of vibration of heave-duty machine tool and has a good damping effect. Meanwhile, it has some additional effects, such as cost reduction, energy conservation and emission reduction.

Abstract: In cantilever beam system, through the experimental method to study vibration reduction mechanism of particle collision damper. The filling rate of particle damping agent in damper is 40%, added the damper with different diameter impacters and different kinds of particle damping agent in combinations ways, the cantilever beam system obtained the varying vibration reduction, according to the quality of vibration reduction, analyzed the joined impacters and particle damping agent influence of vibration attenuation rule. Experimental results show that damper added impacters and particle damping agent can dramatically reduce the maximum amplitude of cantilever beam system in resonant frequency, and can effectively restrain vibration of cantilever beam system.

Abstract: This study presents an experimental characterization of cork storage modulus used to model the vibration response of bars built using alternate layers of cork and steel. In the experimental setup, the specimen was suspended from a fixed support by two thin lines while a shaker was suspended from a mobile support by metallic chains. The shaker was connected to the bar specimen through a force transducer imposing a dynamical deformation that propagates through the specimen. An accelerometer in the opposite extremity of the bar measures the corresponding vibration response and the cork storage modulus is then obtained from the first peak of this frequency response. The proposed methodology successfully characterized the storage modulus of the cork material used in the multilaminated periodic bars. The results obtained illustrate a satisfactory correlation between

Abstract: A grinding wheel spindle with squeeze film damper—SFD is designed based on squeeze film damping theory and relevant grinding experiments have been performed. Experimental results indicate that the rationality of design for SFD can make the vibration of the grinding wheel spindle is reduced by 25%. The precision of hole machining is improved by 20%. At the same time, work efficiency of the grinder can be raised about 15%. So it has very important research value and wide application prospect in the field of machining.