scholarly journals Effect of Dynamic Stiffness of Fasteners on Vibration and Acoustic Radiation of a Ballastless Track

2021 ◽  
Author(s):  
hanwen xu ◽  
jian han ◽  
xinbiao xiao ◽  
xiaolong liu ◽  
moukai liu ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Property ◽  
Acoustic Radiation ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Vertical Direction ◽  
Coupled System ◽  
Fe Method ◽  
Ballastless Track ◽  
Wheel Rolling

Abstract A new model for a single wheel rolling over a metro ballastless track is developed. It is used to carry out the analysis on the effect of dynamic characteristics of fastener on the vibration and noise radiation of the wheel and the track in the vertical direction, under the excitation of the wheel/rail uneven surfaces in detail. In this analysis, a rail is modeled as a Timoshenko beam resting on discrete rubber booted short sleepers, and the sleepers are connected with the slab through linear springs and damping units, the slab is modeled by using the FE method, the fastener is characterized by using the Poynting-Thomson model which takes into account that the stiffness and dumping of the fasteners vary with vibration frequency in their service. The dynamic characteristics of the fastener include the variation of its stiffness and damping with frequency. The analysis considers that the fastener dynamic stiffness increases with the excitation frequency while its damping decreases. The vibration and acoustic radiation of the wheel/track is, to varying degree, affected by the dynamic property of the fastener. The vibration and acoustic radiation of the sleeper and the slab is greatly affected by the dynamic property of the fastener. But the effect of the total noise level of the wheel and the track by the dynamic property of the fastener is not so large because the wheel and rail noise is dominant in the whole analyzed system. These conclusions have certain reference values for the study of the vibration and noise reduction measures of the wheel and track coupled system using the fastening characteristic.

Design and structural performance measurements of a novel multi-cantilever foil bearing

2014 ◽  
Vol 229 (10) ◽  
pp. 1830-1838 ◽  
Author(s):  
Kai Feng ◽  
Xueyuan Zhao ◽  
Zhiyang Guo
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Foil Bearing ◽  
Load Tests ◽  
Stiffness And Damping ◽  
Motion Amplitude

With increasing need for high-speed, high-temperature, and oil-free turbomachinery, gas foil bearings (GFBs) have been considered to be the best substitutes for traditional oil-lubricated bearings. A multi-cantilever foil bearing (MCFB), a novel GFB with multi-cantilever foil strips serving as the compliant underlying structure, was designed, fabricated, and tested. A series of static and dynamic load tests were conducted to measure the structural stiffness and equivalent viscous damping of the prototype MCFB. Experiments of static load versus deflection showed that the proposed bearing has a large mechanical energy dissipation capability and a pronounced nonlinear static stiffness that can prevents overly large motion amplitude of journal. Dynamic load tests evaluated the influence of motion amplitude, loading orientation and misalignment on the dynamic stiffness and equivalent viscous damping with respect to excitation frequency. The test results demonstrated that the dynamic stiffness and damping are strongly dependent on the excitation frequency. Three motion amplitudes were applied to the bearing housing to investigate the effects of motion amplitude on the dynamic characteristics. It is noted that the bearing dynamic stiffness and damping decreases with incrementally increasing motion amplitudes. A high level of misalignment can lead to larger static and dynamic bearing stiffness as well as to larger equivalent viscous damping. With dynamic loads applied to two orientations in the bearing midplane separately, the dynamic stiffness increases rapidly and the equivalent viscous damping declines slightly. These results indicate that the loading orientation is a non-negligible factor on the dynamic characteristics of MCFBs.

A Method of Calculating the Dynamic Characteristics of Rubber Isolator

2013 ◽  
Vol 395-396 ◽  
pp. 1170-1173 ◽  
Author(s):  
Xiao Yan Guo ◽  
Jin Zhi Zhou ◽  
Da Peng Feng ◽  
Hou Min Li
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Property ◽  
Excitation Frequency ◽  
Viscoelastic Model ◽  
Elastic Model ◽  
Frequency Dependency ◽  
Plastic Model ◽  
Filled Rubber ◽  
Relative Errors ◽  
Rubber Isolator

The dynamic property of carbon filled rubber materials is related to pre-load, excitation frequency and amplitude etc. A model by superimposing an elastic model, a viscoelastic model and an elastic-plastic model is presented to model the dynamic property of a rubber isolator. In this paper, this approach is adopted to calculate the dynamic property of a rubber isolator. It is shown that the presented model can predict the amplitude and frequency dependency of a rubber isolator with small relative errors. The validity of this model is verified by experiment. The approach described in this paper can be used in the design and calculation for rubber isolators.

Dynamic Characteristics Analysis of Axle Box Spring by FEM

2013 ◽  
Vol 712-715 ◽  
pp. 1535-1540
Author(s):  
Li Liu ◽  
Wei Hua Zhang ◽  
Dong Li Song
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Excitation Frequency ◽  
Railway Vehicle ◽  
Helical Spring ◽  
Working Stress ◽  
Characteristics Analysis ◽  
In Series ◽  
Spring Method

Axle box spring of railway vehicle is the structure of helical spring in series with rubber pad to reduce working stress of helical spring and absorb high-frequency vibration. Rubber pad model was built. Static and dynamic characteristics were researched in axial and radial directions. The results show that the static stiffness of rubber pad decreases with the increase of radial displacement and increases distinctly with the increase of the amount of compression; The dynamic stiffness of rubber pad increases with the decrease of the excitation force in the case of the same excitation frequency and decreases with the decrease of the frequency in the case of the same excitation displacement. Axle box spring method was established and the amplitude-frequency curve of dynamic stiffness of the spring was presented. The results provide a theoretical basis to research the dynamic performance of railway vehicle.

Experimental Analysis of the Dynamic Characteristics of a Foil Thrust Bearing

2014 ◽  
Author(s):  
Franck Balducchi ◽  
Mihai Arghir ◽  
Romain Gauthier
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Analysis ◽  
Dynamic Models ◽  
Thrust Bearing ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Test Rig ◽  
Equivalent Damping ◽  
Start Up ◽  
Foil Thrust Bearing

The paper deals with the experimental analysis of the dynamic characteristics of a foil thrust bearing (FTB) designed following the specifications given by NASA in 2009. The start-up characteristics of the same foil bearing were investigated in a recently published paper. The test rig used for start-up measurements was adapted for dynamic measurements. The paper presents the test rig in detail as well as its identified dynamic models. Measurements of the dynamic characteristics of the bump foil structure were performed for static loads comprised between 30 N and 150 N while measurements for the FTB were performed at 35 krpm for 30 N, 60 N and 90 N. Excitation frequencies were comprised between 150 Hz and 750 Hz. Results showed that the dynamic stiffness of the FTB increase with excitation frequency while the equivalent damping decreases. Both stiffness and damping increase with the static load but are smaller at 35 krpm compared to 0 rpm.

Experimental Analysis of the Dynamic Characteristics of a Foil Thrust Bearing

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Franck Balducchi ◽  
Mihai Arghir ◽  
Romain Gauthier
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Analysis ◽  
Gas Turbines ◽  
Thrust Bearing ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Equivalent Damping ◽  
Start Up ◽  
And Performance ◽  
Foil Thrust Bearing

This paper deals with the experimental analysis of the dynamic characteristics of a foil thrust bearing (FTB) designed according to specifications given by NASA scientists in 2009 (Dykas et al., 2009, “Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications,” ASME J. Eng. Gas Turbines Power, 131(1), p. 012301). The present work details the new configuration of the same test rig that was used to test start-up characteristics of the aforementioned bearing (Balducchi et al., 2013, “Experimental Analysis of the Start-Up Torque of a Mildly Loaded Foil Thrust Bearing,” ASME J. Tribol., 135(3), p. 031703). The rig has been reconfigured to test dynamic characteristics. The dynamic characteristics of the bump foil structure were measured for static loads comprised between 30 N and 150 N while measurements for the FTB were performed at 35 krpm for 30 N, 60 N, and 90 N. Excitation frequencies were comprised between 150 Hz and 750 Hz. Results showed that the dynamic stiffness of the FTB increase with excitation frequency while the equivalent damping decreases. Both stiffness and damping increase with the static load but are smaller at 35 krpm compared to 0 rpm.

Experimental Analysis of Dynamic Characteristic for Automatic Tensioner

2014 ◽  
Vol 915-916 ◽  
pp. 49-52
Author(s):  
Xiang Kun Zeng
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Analysis ◽  
Angular Displacement ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Excitation Amplitude ◽  
Loss Angle ◽  
Load Torque ◽  
Dynamic Performances ◽  
Stiffness Loss

Experimental method and parameters to investigate the dynamic performances of an automatic tensioner are discussed. Parameters to evaluate the dynamic performances of a tensioner include dynamic stiffness, loss angle and equivalent viscous coefficient. Dynamic stiffness and loss angle can be measured directly, and the equivalent viscous coefficient can be calculated by torque-angular displacement loop which identified with the parameters including dynamic stiffness, loss angle, pre-load torque, pre-load angular displacement, excitation amplitude and excitation frequency. In this paper, the influences of excitation amplitude, excitation frequency and pre-load torque on the dynamic characteristics of tensioner are measured and investigated.

Experimental Study of Dynamic Characteristics and Model Parameter Identification of Tensioner

2014 ◽  
Vol 988 ◽  
pp. 332-337
Author(s):  
Hong Yun Wang ◽  
Xiang Kun Zeng ◽  
Ji Yong Zhao
Keyword(s):  
Parameter Identification ◽  
Nonlinear Model ◽  
Dynamic Characteristics ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Identification Method ◽  
Serpentine Belt ◽  
Drive Systems ◽  
Set Up ◽  
Stiffness And Damping

Tensioners play a predominant role in the dynamic behavior of serpentine belt drive systems. The experimental set-up was carried out to study the dynamic characteristics of tensioner. Experimental results illustrate that tensioner shows hysteresis nonlinear dynamic characteristics, and dynamic stiffness and damping of slip motion of up stroke of tensioner are related to excitation frequency and amplitude. The first differential nonlinear model of tensioner was determined, and the parameter identification method of the model was introduced. The accurate of the nonlinear model and effectiveness of the parameter identification method was validated.

Dynamic Property Analysis of Rubber Absorber in Rail Fastenings of Different Force Condition

2012 ◽  
Vol 226-228 ◽  
pp. 877-880
Author(s):  
Shu Wei Wang ◽  
Yan Yun Luo ◽  
Li Li ◽  
Yan Liu
Keyword(s):  
Dynamic Property ◽  
Dynamic Stiffness ◽  
Testing Machine ◽  
Excitation Frequency ◽  
Least Square Method ◽  
Excitation Amplitude ◽  
Least Square ◽  
Model Parameters ◽  
Nonlinear Dynamic Model ◽  
Stiffness And Damping

This paper studies the dynamic property of rubber absorber in rail fastening by electro-hydraulic testing machine. Two different types of rail fastening are tested. In one fastening the rubber component is in compressed condition (RCRF). While in another the rubber is in sheared (RSRF). A nonlinear dynamic model of rubber absorber in rail fastening is proposed. The model parameters are obtained by the least square method. The accuracy of the obtained model is verified by measured result. The two results are in good agreement. The dynamic stiffness and damping are analyzed, and the results show that dynamic stiffness and damping are closely related to the frequency and amplitude of excitation. Nonlinear characteristic becomes greater with increasing excitation amplitude for the both rail fastenings. For different excitation frequency, the vibration reduction effect of RSRF is more stable than that of RCRF.

scholarly journals Estimation of Dynamic Characteristics of a Spring-Mass-Beam System

2007 ◽  
Vol 14 (4) ◽  
pp. 271-282 ◽  
Author(s):  
Ding Zhou ◽  
Tianjian Ji
Keyword(s):  
Dynamic Characteristics ◽  
Coupled System ◽  
Frequency Equation ◽  
Fe Method ◽  
Beam System ◽  
Parametric Studies ◽  
Internal Forces ◽  
Frequency Coupling ◽  
The Galerkin Method ◽  
Two Degree Of Freedom

This paper presents an approximate solution for the analysis of the dynamic characteristics of a spring-mass-beam system. The spring-mass can be distributed or concentrated on a beam, which can represent a crowd or an individual on a beam. The analysis is based on the fact that a spring-mass-beam system can be modeled approximately as a series of two degree-of-freedom (TDOF) systems and the frequency coupling occurs mainly at the first TDOF system. The Galerkin method is used to derive the frequency equation of the TDOF system. Static beam functions of a beam with distributed and concentrated spring-masses are developed for the solutions, in which the effect of the magnitude and position of the mass of the spring-mass on the beam is considered. Using a set of simple formulae, the first pair of coupled frequencies and the corresponding mode can be obtained. The mass and stiffness factors in the TDOF system are tabled for engineering applications. For verification and use of the proposed method, a case of human-structure interaction is analysed using the proposed method and FE method. Parametric studies show that using the proposed functions, not only the first pair of natural frequencies but also the mode and internal forces of the coupled system can be obtained with high accuracy.

scholarly journals Study on dynamic characteristics of leaf spring system in vibration screen

2021 ◽  
pp. 146134842110229
Author(s):  
Jiacheng Zhou ◽  
Chao Hu ◽  
Ziqiu Wang ◽  
Zhengfa Ren ◽  
Xiaoyu Wang ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Vertical Direction ◽  
Maximum Amplitude ◽  
Exciting Force ◽  
Mode Shapes ◽  
Leaf Spring ◽  
Amplification Factors ◽  
Simulation And Experiment ◽  
Exciting Forces ◽  
Spring System

By studying dynamic characteristics of the leaf spring system, a new elastic component is designed to reduce the working load and to a certain extent to ensure the linearity as well as increase the amplitude in the vertical and horizontal directions in vibration screen. The modal parameters, amplitudes, and amplification factors of the leaf spring system are studied by simulation and experiment. The modal results show that the leaf spring system vibrates in horizontal and vertical directions in first and second mode shapes, respectively. It is conducive to loosening and moving the particles on the vibration screen. In addition, it is found that the maximum amplitude and amplification factor in the horizontal direction appear at 300 r/min (5 Hz) while those in the vertical direction appear at 480 r/min (8 Hz), which are higher than those in the disc spring system. Moreover, the amplitude of the leaf spring system increases proportionally with the increase of exciting force while the amplification factors are basically the same under different exciting forces, indicating the good linearity of the leaf spring system. Furthermore, the minimum exciting force occurs in the leaf spring system under the same amplitude by comparing the exciting force among different elastic components. The above works can provide guidance for the industrial production in vibration screen.

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