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Vibration characteristics and environmental responses of different vehicle-track-ballast coupling systems in subway operation
Get PDFThe vibration characteristics of two ballast beds are analyzed in this study from five aspects including the amplitude-frequency characteristic curve of foundation reaction. This study also shows that the maximum ground Z vibration level caused by a normal monolithic ballast bed structure is 75 dB. The range of its vibration influence during daytime is approximately 30 m. The maximum ground Z vibration level caused by a rubber floating slab track structure is 52 dB, whereas that caused by a steel spring floating slab track structure is 57 dB. The maximum damping amount in horizontal speed of a rubber floating slab track structure is 74 %, whereas the reduction of vertical ground vibration speed and acceleration is 92 % and 93 %, respectively. The reduction in Z level is 37 %. The horizontal speed reduction in a steel spring floating slab track structure is 71 %, whereas the reduction of ground vertical vibration speed and acceleration is 83 % and 84 %, respectively. The reduction in Z level is 29 %
Reduction of axis acceleration of quarter car suspension using pneumatic actuator and active force control technique
Get PDFThis paper presents the design of a control technique applied to the pneumatic active suspension system of a quarter car model using controller with fuzzy logic embedded in the active force control component. The overall control system is decomposed into two loops. In the main loop the desired force signal is calculated using an active force control strategy with a sugeno fuzzy logic element which is being employed to estimate the mass needed to feed the control loop. A Mamdani fuzzy logic controller is implemented in the outer loop to design a force controller such that the desired force signal is achieved in a robust manner. The resulting control strategy known as fuzzy – active force controller (FLC-AFC) is used to control a nonlinear actuator attached between the sprung mass and the unsprung mass of the quarter car model. The performances of the proposed control method were evaluated and later compared to examine the effectiveness in suppressing the vibration effect of the suspension system. Resulting fuzzy active force control gives better results if compared to the fuzzy logic and the passive suspension system
Design and analysis of a quasi-zero stiffness isolator using a slotted conical disk spring as negative stiffness structure
Get PDFThis paper concerns the characteristics of a novel quasi-zero stiffness (QZS) isolator developed by parallelly combining a slotted conical disk spring with a vertical linear spring. The static characteristics of the slotted conical disk spring as well as the QZS isolator are presented. The configurative parameters are optimized to achieve a wide displacement range around the equilibrium position for which the stiffness has a low value and changes slightly. The overload and underload conditions are taken into account, resulting in a Helmoholtz-Duffing equation. The primary resonance response of the nonlinear system composed by a loaded mass and the QZS isolator are determined by employing the Harmonic Balance Method (HBM) and confirmed with the results of numerical simulation. The frequency response curves (FRCs) are obtained for both force and displacement excitations. The force transmissibility, the absolute displacement and acceleration transmissibility are defined and investigated. The study shows that the overloaded or underloaded system can exhibit linear stiffness, softening stiffness, softening-hardening stiffness and hardening stiffness with the increasing excitation amplitude. The response and the resonance frequency of the system are affected by the excitation amplitude and the offset displacement to the position at which the dynamic stiffness is zero. To enlarge the isolation frequency range and improve the isolation performance, the loaded mass and the excitation amplitude should be suitably controlled
A revised averaging method and general forms of approximate solution for nonlinear oscillator with only polynomial-type displacement nonlinearity
Get PDFIn this paper a revised averaging method is presented, that does not need the detuning factor in the solving procedure. Comparison with the traditional averaging method shows that it has the similar solving procedure and the same result as the primary resonance of the traditional averaging method. Then the nonlinear oscillator with only polynomial-type displacement nonlinearity is studied, and the general forms of the first-order approximate solution by this revised averaging method, and by the traditional averaging method for the super-harmonic resonance and sub-harmonic resonance are established. At last, the Duffing oscillator is investigated as an example, and the comparison of the analytical and numerical results proves the validity and simplicity of the presented method
Establishment of ground vibration prediction model for high-speed trains on embankments
Get PDFA series of field measurement data is used to establish the prediction model of ground vibration induced by Taiwan high-speed trains on embankments. These measurements consist of various possible influence factors, such as train speed, ground shear wave velocity, and structure volume. The characteristics of near-field ground vibration, far-field vibration propagation, and vibration influence distance are then evaluated from these measurement data. The analyses reveal that the near-field ground vibration level mainly depends on train speed and ground shear wave velocity. The influence of structure volume on the vibration level is minor. The far-field vibration propagation is affected by ground shear wave velocity. The analysis results also show that the attenuation coefficient is different for each frequency range. In general, the measured ground vibration in the high frequency range has the highest attenuation coefficient and that in the low frequency range has the lowest. For the vibration influence distance, the rock can propagate the vibration to the farthest distance among all soil types while the sand/silt/clay soils show the shortest. Finally, a specific ground vibration prediction model is established using these characteristics
Rapid optimization of the sound insulation performance of magnesium alloy dash panel based on periodic sound-package structure
Get PDFIn order to improve the sound insulation performance of the magnesium alloy dash panel at medium and low frequency, the FE-SEA hybrid method was employed to numerically calculate the sound transmission loss of the dash panel, which was subsequently compared with the experimental result and eventually proved the feasibility of this numerical method. Subsequently, through analysis on the modal contribution, the speed vibration modes at the natural frequencies were extracted, and the key sound-transmission areas were identified. Through combined considerations of both the vibration-isolating and the sound-absorbing characteristics, the parallel periodic sound-package structure was proposed, whose basic theory was deduced by reference to phononic crystals. Moreover, a reverberation box was designed and manufactured so as to test the sound transmission loss of specimens with small sectional dimensions, such as the periodic sound-package structure, and the reliability of the predicting method was simultaneously verified. Additionally, manually weaving the parameters of the periodic sound-package structure could maximally improve its sound insulation characteristic, and changing the traditional parallel structure into the staggered and skewed laying manner could upgrade the vibration-isolating and sound-absorbing effect. Finally, this noise-reducing scheme was applied to the magnesium alloy dash panel, where in the medium and low frequency noise was rapidly optimized
Stress and vibration of a viscoelastic damping isolator under impact loading
Get PDFThere are different types of isolators which include rubber type, coil spring type, slide and rotating type and there are different types of dampers which include viscous type, oil type, and try friction type. Both isolators and dampers are common used to reduce vibration caused by forging or stamping process. However, a new way to reduce the vibration of the punch press is viscoelastic damping isolator (VDI) which can be widely used in manufacturing, electricity and gas supply, construction, transportation and warehousing, and other industries. This study analyzes a VDI composed by partitions, damping fluid, steel springs and level adjusters. Different numbers of the partitions are welded on upper and lower rectangular steel plates, respectively. Up to 150 tons of weight of the punching machines supported by steel springs which are placed at the edges between the square upper/lower plates. Screw types of level adjusters are placed between lower plate and thick steel base to tune the horizontal level of the isolator. High viscosity damping fluid is filled in the space between interlacing partitions around 60 % of the height of the VDI. Punching induced impact energy is dissipated by shear deformation between the damping fluid and partitions. This study uses 3D graphing software and finite element method (FEM) to investigate the dynamic characteristic of the damping isolator after impacted by the puncher. The normal mode analysis of the VDI is obtained. The isolator is settled within 0.3 seconds after 300.000 N of shock impact and satisfies industrial specification of large punchers with loading frequency of 100 cycles per min
The defect detection in glass materials by using discrete wavelet packet transform and artificial neural network
Get PDFIn this study, a method based on impact tests was designed in order to determine undamaged and broken glasses. By means of using an impact pendulum, impact was applied on glasses and the generated sounds were transferred to the computer using a microphone. The sound signals were decomposed into 128 components by using Discrete Wavelet Packet Transform (DWPT) at the seventh level. 16 of the 128 components that characterized the properties of undamaged and broken glasses were chosen as inputs for the designed Artificial Neural Network (ANN). The designed ANN model was tested with real-time simulation, and it was observed that the proposed method could determine undamaged and broken glasses with high precision. This method, which is based on analyzing the sounds generated after the impact, can detect defects that the conventional visual methods can detect; however, it can also be used as supplement to these methods
Influence of imbalance force angular position to vertical and horizontal rotors rolling bearings defects diagnostics
Get PDFInstead of using the traditional periodical diagnostics, modern technological machinery has increasingly been using monitoring systems based on acceleration transducers of mechanical vibrations. Although, oftentimes it is difficult to identify rolling bearing faults, even if constantly monitoring and analyzing the machinery vibration acceleration or vibration velocity FFT spectra or their cascades. We usually run into such problems when analyzing gravity based technological processes (separators, diffusion machinery) in vertical machinery observations. This is because the angular position of imbalance mass varies often in this type of machinery, which causes the inner ring race fault in the bearing. This article describes the comparative experimental research data between the vertical and horizontal axis rotors. The test rig consists of the disk fixed onto the end of the shaft; the deep groove rolling bearing 6004-2Z/C3 with inner ring race defect is mounted behind the support. Throughout the experiment tests, the angular position of imbalance mass and inner ring race local defect is switched from 00 to 3600, each 450 angular step value. The study is carried out both with rotor axis oriented vertically and horizontally. In order to simplify the data being analyzed and to quantifiably assess the diagnostic experiments of vertical and horizontal rotor defects, statistical processing parameter called “Defect Visibility Ratio” (DVR) is being designed. Through the use of this statistical parameter, the defect-detection capabilities of rotor with bearing inner ring race fault can be determined quantifiably
Development of vibrating bracelet for the actuation of the blood circulation at capillaries
Get PDFAccording to Katsuzo Nishi proposed capillarity exercise based on limbs vibrations the equipment to compensate obstruction of blood circulation is proposed. This equipment is composed from the vibrating bracelet for disable people and simplify exercise execution for healthy people as well. A need to create small size and low voltage device was identified. Previous studies have showed that it is recommended to avoid high frequencies because of possible harm for human. According to this requirements two high RPM, small size and low voltage motors were chosen. The rotors unbalances are working in beating regime, which increases the excentrical forces actuating human limbs. After processing gathered data proper frequencies for vibrating bracelet were chosen