Papers by Keyword: Vibration Isolation

Abstract: Besides the underground, the second common type of public transport is the tram. Tram lines in Moscow city center, as well as in other cities in Russia, are being renovated and reconstructed. Vibration of the railway track travels through the ground to the foundation of buildings adjacent to tram lines, causing high vibration and structure-borne noise levels inside them. The article presents result of a vibration isolation system analysis and design for a building, located in 37m of the two-lanes tram line. Prior to design procedure, field measurements were made and vibration levels inside the building were recorded. The vibration isolation system design included calculation of soil pressure on the isolation pad and subsequent estimation of the elastomeric pad dynamic modulus. Using this data, the eigenfrequecny of vibration isolation system was derived and its efficiency calculated. After the system maintenance, measurements were made to check the system’s performance. During the measurements acceleration of isolated part of the building and the ground surface were synchronously measured and transfer function derived.

Abstract: The paper is devoted to the idea of metamaterials with quasi-zero stiffness for vibration isolation. Metametarials may provide special and unique properties of materials. In this area it is possible to use the principles of systems with quasi-zero stiffness. Such nonlinear deformation of material provides low stiffness at a certain point. Hence low natural frequency and high efficiency of vibration isolation can be obtained. An analytical study was done. Computer modeling shows a big enough margin of safety and also proves the existence of force characteristic with quasi-zero stiffness. The calculation has shown that the metamaterial has natural frequency lower than 1 Hz and optimum load 2 tons per m². An experimental prototype has been made for further study.

Abstract: In the work the problem of designing of mechatronic discrete systems have been studied for new possibilities of utilization of negative vibration isolation elements. Systems have cascade form and contains the piezo stack actuator and an external electric network connected to the mechanical discrete part. The main focus of the paper is given to the parameters related with negative damping, comparison of usage them based on dynamical flexibilities functions and study on constrains and limitations coming from potential practical application point of view. The new approach is related with placing the issue of negative value damping elements inside the synthesis process. Elements that can exhibits negative value, have been identified and found after distribution of dynamical characteristics, during creation of the mechanical displacement model.

Abstract: When power equipments are suspended under the under-frame of a rail train vehicles, dynamic and vibration characteristics of the car body will be changed. In order to study suspended parameters of the car body dynamic system, the vertical dynamic coupling model of rigid car body and power equipment under different exciting force was established. Results showed: when the exciting force of suspended power equipment is zero, the elastic suspension stiffness and damping can be designed according to the principle of Dynamic Vibration Absorber (DVA); when the exciting force acting on the rigid car body is zero, the vibration isolation problem of equipment is consistent to the base isolation problem, a good vibration isolation effect can be obtained as; when the body and power equipment simultaneously be excited, vibration absorbing and isolation must be simultaneously designed: the DVA is meet on at first, when ,the suspension isolation system appeared two different frequency peaks, but only , a good vibration isolation can be obtained for suspension system.

Abstract: This paper provides a starting point for further study in the domain of analysis of the behavior of the pendulum absorber systems in dynamic regime. Thus, one can determine an optimal configuration of the pendulum absorber system to ensure the efficiency for the dynamic isolation for the entire domain of variation of excitation.

Abstract: A molecular spring isolator which consists of water and hydrophobic zeolites as working medium is investigated. When the isolator undergoes periodic excitation, water intrudes into hydrophobic pores of zeolites depending on the external pressure and extrudes from the pores as hydraulic pressure decreases. As a result, molecular spring absorbs, releases and dissipates mechanism energy. To obtain the stiffness properties of molecular spring isolator, the mechanics modal of water column intruding into a hydrophobic pore is established utilizing force equilibrium. Subsequently, the process of water infiltrating large numbers of hydrophobic pores is explored. Then the quasi-static experiment is carried out to validate the theoretical modal. It is found that the molecular spring exhibits high static and low dynamic stiffness. Finally, the effect of quantity of zeolites and temperature on stiffness of molecular spring is investigated experimentally.

Abstract: In order to improve the vibration isolation performance of engine mount, a new type of magneto-rheological semi-active mount with multiple inertia tracks is designed based on the existing magneto-rheological semi-active mount . The mechanical model is established according to the mount. The expression of the dynamic stiffness and damping lag angle is deduced, then the dynamic characteristics is simulated in the simulation software. At the same time, verify this model correct by the experiments.

Abstract: In the first part of my paper, a vibration model has been put forward for studying the self-synchronization of a vibrating system by two-motor driven with isolation frame. The self-synchronization motion implementation and the stability condition of self-synchronization motion is obtained by the Routh-Hurwitz criterion. Zhao C Y ^{[ 1 ,2 ]} developed self-synchronization of the duel-motor and four-motor driven vibrating system by modified average method. S everal methods were used to analyze the self-synchronous motion verifying the self-synchronization of two motors. Wang D G used the computer to simulate the process of self-synchronization, and the results showed that the synchronization of vibrating system came true in either speed or phase to enable the system to be in a good self-synchronization state ^{[ 3 ]} . Balthazar ^{[ 4 ,5 ]} studied the self-synchronization of four motors having limited power supply and mounted on a flexible structural frame support.

Abstract: The idea of self-synchronization vibrating system comes from the phenomenon of synchronization. In the 1960s, Blekhman^[1,2] proposed the self-synchronization theory of vibrating system driven by two induction motors. When the structure parameters of the two motors met the requirements, the system could operate synchronously. Blekhman^[3] also found that even if the rotating speed and the angular phase difference of the two eccentric rotors were being disturbed or one of the motors was powered off, the system could still operate synchronously. The small parameter methods were applied to a number of problems by R.F. Nagaev^[4]. It can lead to better understanding of the self-synchronization theory. Wen Bang-chun^[5] applied self-synchronization theory to engineering and established a branch of the vibration utilization engineering, and numerous self-synchronous vibrating machines were invented.

Abstract: The article studies the energy method for determining loss factor due to hysteretic damping in systems of vibration and seismic isolation. Typical measure of damping is, where φ is the phase angle between stress and strain sinusoids [1], or damping constant δ ( [2, 3]). Both of these parameters are acquired through experimental investigations for each type of boundary conditions or element’s cross section. Proposed energy method is capable of loss factor ψ determination for different types of beams based on only one experimental investigation. This method is used in the paper to determine the damping ratio of elastic element in vibration isolation system of precision equipment.