Vibration Of Car Body Research Articles

Dynamic characteristics of high-speed railway vehicle with axle box bearing faults

Based on the motion characteristics of axle box bearings and taking high-speed railway vehicles as the research object, a vertical dynamic model of 17-DOF car body-bogie-axle box bearings-wheel set is proposed. Aiming at the surface fault of axle box bearing, the New-Mark fast numerical integration method is used to simulate and analyze. The dynamic characteristics of railway vehicle under early failure of axle box bearing on inner ring and outer ring raceway surface are studied. The vibration characteristics of axle box bearings under different fault degrees and different vehicle speeds (axle box bearing speed) are analyzed. The changes of vehicle dynamic performance and vibration characteristics under fault evolution are discussed. The analysis results show that the vibration of car body and bogie is little affected by the early fault of axle box bearing; with the deepening of the fault degree, the vertical vibration acceleration and displacement of axle box bearing are increasing; with the increase of vehicle speed, the motion state of axle box bearing undergoes a change from periodic motion, quasi-periodic motion to chaotic motion. Finally, the dynamic simulation results of axle box bearing fault evolution in high-speed vehicle system are validated on the experimental platform. The research work has certain reference value for vehicle condition tracking and monitoring.

A Survey of Suspension Component Specifications and Vehicle Vibration Measurements in an Operational Railway System

Primary and secondary suspensions are essential in railway vehicles. In this study, the specifications of suspension components were discussed in detail by referring to the component procurement documents to ensure satisfactory ride quality. These specifications were compared with those obtained from simulations and measurements of an operational railway system through a transverse vehicle model using the equations of motion derived from the Lagrange equation. The equivalent rail stiffness and damping were also derived. Results showed that the stiffness should be altered according to the vehicle’s load, i.e., the number of passengers on board. The secondary suspension stiffness could be determined based on the specification. The primary suspension stiffness was 26% higher than the upper limit of the specification with a load of full-seated passengers. According to the maintenance instructions, a 7-Hz low-pass filter (LPF) was used for car body vibration measurements. It is suggested that the cutoff frequency of the LPF had to be increased to 9 Hz at least for suspension defect diagnoses. Furthermore, a smartphone with a gravity sensor could also be used for measuring car body vibrations. A sampling rate of 100 Hz could obtain the desired results, which could be an effective and efficient method for vibration analyses.

A three-dimensional analytical model and parameter determination method of the elastic vibration of a railway vehicle carbody

ABSTRACT Reducing railway vehicles’ three-dimensional (3D) elastic vibration is needed to improve passenger comfort. This paper presents a 3D analytical model and parameter determination method for the elastic vibration of a carbody. The carbody is modelled as a simple box-type structure consisting of an anisotropic 3D elastic body treated as a continuous system. This model can express complicated 3D elastic vibration (such as lateral–vertical coupled vibration) with fewer degrees of freedom and at a lower computational cost than the detailed finite element model. A model parameter determination method using particle swarm optimisation was also proposed. Application to a Shinkansen-type test vehicle showed good agreement between measured and calculated results with a maximum natural frequency differences of the targeted six elastic vibration modes within 0.86%, indicating the effectiveness of the proposed model and parameter determination method.

Modelling rubber dynamic stiffness for numerical predictions of the effects of temperature and speed on the vibration of a railway vehicle car body

Using a viscoelastic model containing a temperature spectrum and a friction model, a nonlinear model of rubber elements has been developed and verified. It takes into account the correlation between temperature, vibration frequency, and vibration amplitude, its parameters are identified by conducting static tests and dynamic mechanical thermal analysis. Then, it is used in a dynamic model for high-speed railway vehicles containing suspended under-chassis equipment (UCE). The coupling between the vibrations of the car body and UCE that considers the temperature-dependent characteristics of the rubber elements is studied, and trends for the modal vibrational energy of the UCE and car body are identified. The results indicate that the decrease in the ambient temperature significantly increases the dynamic stiffness of the rubber elements, which impairs their function. It also generates more intense UCE vibrations and increases the vibrational energy of the low-frequency (first-order vertical bending and diamond-shaped deformation) modes of the car body, thus degrading the ride quality assessed via the Sperling index. At extremely high ambient temperature (around 40 °C), the dynamic stiffness and damping coefficient of rubber elements decreases, thus weakening the damping effect and increasing the vibration amplitudes of the car body and UCE. Considering the dynamic stiffness of the rubber elements at 20 °C as a reference, the dispersion of their dynamic stiffness should be maintained within the range [−20%, 50%] at temperatures between −30 and 40 °C to ensure good ride quality of the vehicle at running speeds above 300 km/h.

Vibration control of high-speed trains self-excitation under-chassis equipment by HSLDS vibration isolators

To minimize the self-excitation effects of the equipment on the carbody, a high static and low dynamic stiffness (HSLDS) vibration isolator is proposed by connecting a negative stiffness unit and a positive linear stiffness spring in parallel. The nonlinear stiffness of the HSLDS isolator can be designed according to the needs of any target stiffness curve. A vibration test is applied to obtain the vibration acceleration of the under-chassis equipment. A rigid-flexible coupling multi-body dynamic model of a high-speed train is established which considers the elastic vibration of the carbody and the self-excitation of the under-chassis equipment based on the tested result. Different connection methods of the under-chassis equipment including rigid hanging, vibration isolation theory (VIT) hanging, dynamic vibration absorber (DVA) hanging and HSLDS hanging are applied and their effects on the carbody vibration and ride quality are investigated. The simulation results reveal that the proposed HSLDS vibration isolator can effectively isolate the self-excitation of the under-chassis equipment from the carbody and enhance the ride quality of the high-speed train.

Research on Causes and Countermeasures of Abnormal Flexible Vibration of Car Body for Electric Multiple Units

Research on Causes and Countermeasures of Abnormal Flexible Vibration of Car Body for Electric Multiple Units

Piezoelectric Energy Harvesting Based on Vertical Vibration of Car Body Induced by Road Surface Roughness

This paper presents the analysis of a cantilevered piezoelectric energy harvester (PEH) under the random vibration excitation of the car body. A two degree-of-freedom (2-DOF) quarter car model is established. The Matlab/Simulink simulation software is used to analyze the dynamic response of the car body under the random road excitation. The transient analysis of the PEH is carried out using ANSYS software to obtain the time-dependent voltage, current and power outputs of the PEH. The root mean square (RMS) power is used to evaluate the electricity generation of the PEH. The effect of the load resistance, the car speed, and the road surface roughness on RMS power are studied. The results show that it exists the optimal load resistance to achieve the maximum RMS power output for the vibration-based PEH. When the road surface roughness is constant, the increase of the car speed can induce the increase of the RMS power of the PEH. When the car speed is constant, higher RMS power outputs of the PEH can be achieved by increasing road surface roughness coefficient.

Study on the Vibration Suppression Method of Urban Railway Vehicles Based on a Composite Dynamic Vibration Absorber

To reduce the bounce and the pitch vibration of carbody, a vertical dynamic model for urban rail vehicles is established to analyze the vibration response of the carbody in the low frequency range. In this paper, different methods of single-degree-of-freedom dynamic vibration absorber to suppress the vibration for carbody are investigated. The limits of single-degree-of-freedom dynamic vibration absorber to the vibration reduction effect of carbody are pointed out. After that, the design of a composite dynamic vibration absorber including a double oscillator structure is introduced. A vibration discreteness index is used to evaluate dynamic vibration absorbers with various designs for the vibration damping performance. Finally, the vibration reduction performance of the composite dynamic vibration absorber is verified by Sperling’s riding index. The results demonstrate that the performance of the single degree of freedom dynamic vibration absorber attached to a carbody may increase the vibration within a partial scope, when the peak frequency of vibration is far away from the design frequency. The installation of the composite dynamic vibration absorber vibration provides gentler running experience for passengers.

A Novel Prediction Model for Car Body Vibration Acceleration Based on Correlation Analysis and Neural Networks

This paper aims to create a prediction model for car body vibration acceleration that is reliable, effective, and close to real-world conditions. Therefore, a huge amount of data on railway parameters were collected by multiple sensors, and different correlation coefficients were selected to screen out the parameters closely correlated to car body vibration acceleration. Taking the selected parameters and previous car body vibration acceleration as the inputs, a prediction model for car body vibration acceleration was established based on several training algorithms and neural network structures. Then, the model was successfully applied to predict the car body vibration acceleration of test datasets on different segments of the same railway. The results show that the proposed method overcomes the complexity and uncertainty of the multiparameter coupling analysis in traditional theoretical models. The research findings boast a great potential for application.

Carbody vibrations of high-speed train caused by dynamic unbalance of underframe suspended equipment

The effect of dynamic unbalance of the underframe suspended rotational equipment on the flexible vibrations of the carbody has become a major concern for high-speed trains. It is known from the field tests that the dynamic unbalance has a significant influence on carbody vibrations, especially the local flexible vibration, which leads to a decrease in the passenger ride comfort and may even cause structural damage to the carbody. A vertical mathematic model considering the carbody flexibility and the underframe suspended equipment is first set up, and then a three-dimensional dynamic model for a rigid–flexible coupled vehicle system is established. The effect mechanism of the dynamic unbalance on carbody flexible vibration is extensively studied, and the efficient measures to reduce the carbody flexible vibrations are proposed. The theoretical and simulation models are verified by comparing with a field test conducted on a newly designed high-speed railway. The results show that decreasing the unbalanced mass of the rotational equipment can reduce the carbody vibrations. Moreover, the use of elastic suspension for the underframe equipment can isolate the vibration transmission to the carbody. Both the theory of dynamic vibration absorber and dynamic unbalance should be considered to optimize reasonable suspension parameters, especially the suspension location and the suspension frequency.

Low frequency vibration control of railway vehicles based on a high static low dynamic stiffness dynamic vibration absorber

In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom (2DOF) low frequency dynamic vibration absorber (DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density (PSD) and ride quality of the car body are calculated based on the pseudo excitation method (PEM) and covariance algorithm, respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness (HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved.

Research Topics on Railway Vehicle Dynamics

Engineering research subjects relating railway vehicle dynamics are described as a literature survey in this paper. Research works concerning to the motion of wheelset; pantograph-catenary interaction; aerodynamic relating problems on the vehicle; and application of control techniques are introduced firstly as the most distinctive subjects of railway vehicle dynamics. The topics on safety assessment and ride comfort evaluation are also dealt with since those are important research area in railway dynamics as public transportation system. The subject concerning to carbody elastic vibration, which is important relating to ride comfort, is also described. The effect of passengers on the elastic vibration of carbody has been introduced as the interesting (and something surprising) topic. The focuses in the literature survey are particularly on the research works from Japan, in this paper.

Study on Improving the Ride Comfort in Railway Vehicles Using Anti-Bending Dampers

The paper researches the possibility to reduce the bending vibrations in the railway vehicle carbody and to improve the ride comfort via a new passive type method. This would involve the fitting of the vehicle with dampers, called anti-bending dampers, fixed to the longitudinal beams of a carbody underframe. The efficiency of this method is made visible in the results derived from numerical simulations developed on the basis of a rigid-flexible coupled vehicle model. The introduction of the anti-bending dampers is seen as a significant reduction in the bending vibration of the carbody. Similarly, a relevant improvement of the ride comfort at the centre of the carbody, at high velocities. This efficiency mainly depends on the damping constant of the anti-bending damper.

Damage Degree Detection of Cracks in a Locomotive Gear Transmission System

The gear transmission system is a vital component of the locomotive bogie. During locomotive operation, the damage to the gear transmission system spreads rapidly and affects the locomotive’s operational safety. In this paper, a method is proposed to detect the degree of tooth root crack damage. First, a dynamic locomotive model with a gear transmission is built, and the vertical acceleration of the locomotive subsystem (car body, bogie frame, wheelset, and motor) vibrations is obtained under various degrees of tooth root crack damage on the gear transmission system. By comparing the characteristics of those signals, the subsystem that is more sensitive to the effect of the tooth root crack is found. The characteristic parameters of the sensitive subsystem are calculated, and a multidimensional characteristic parameter matrix is established. The multidimensional characteristic parameter matrix is optimized and reduced by principal component analysis (PCA). Using the Grey relational analysis method, the degree of tooth root crack damage is detected. The proposed method demonstrates the ability to recognize the degree of tooth root crack damage.

Coupling vibration research on Vehicle-bridge system

The vehicle-bridge coupling system forms when vehicle running on a bridge. It will generate a relatively large influence on the driving comfort and driving safe when the vibration of the vehicle is bigger. A three-dimensional vehicle-bridge system with biaxial seven degrees of freedom has been establish in this paper based on finite numerical simulation. Adopting the finite element transient numerical simulation to realize the numerical simulation of vehicle-bridge system coupling vibration. Then, analyze the dynamic response of vehicle and bridge while different numbers of vehicles running on the bridge. Got the variation rule of vertical vibration of car body and bridge, and that of the contact force between the wheel and bridge deck. The research results have a reference value for the analysis about the vehicle running on a large-span cabled bridge.

Integration of car-body flexibility into train–track coupling system dynamics analysis

ABSTRACTThe resonance vibration of flexible car-bodies greatly affects the dynamics performances of high-speed trains. In this paper, we report a three-dimensional train–track model to capture the flexible vibration features of high-speed train carriages based on the flexible multi-body dynamics approach. The flexible car-body is modelled using both the finite element method (FEM) and the multi-body dynamics (MBD) approach, in which the rigid motions are obtained by using the MBD theory and the structure deformation is calculated by the FEM and the modal superposition method. The proposed model is applied to investigate the influence of the flexible vibration of car-bodies on the dynamics performances of train–track systems. The dynamics performances of a high-speed train running on a slab track, including the car-body vibration behaviour, the ride comfort, and the running safety, calculated by the numerical models with rigid and flexible car-bodies are compared in detail. The results show that the car-body flexibility not only significantly affects the vibration behaviour and ride comfort of rail carriages, but also can has an important influence on the running safety of trains. The rigid car-body model underestimates the vibration level and ride comfort of rail vehicles, and ignoring carriage torsional flexibility in the curving safety evaluation of trains is conservative.

Reduction of vertical abnormal vibration in carbodies of low-floor railway trains by using a dynamic vibration absorber

A field test on the dynamic performance of a 100% low-floor railway train with five cars was conducted, and a vertical vibration at around 8 Hz was mainly studied for the background of the research. The vibration around 8 Hz, defined as the abnormal vertical vibration, was proved to be due to the pitching motion of the carbodies, which significantly affected the dynamic performance of the vehicle with a maximum increase of 0.309 in the vertical Sperling index. The dynamic vibration absorber theory was applied to reduce the abnormal vibration of carbodies to around 8 Hz by building a vertical mathematic model and a three-dimensional dynamical simulation model. The results of the theoretical analysis show that the stiffness of the articulated device between carbodies is the reason for the pitching motions at around 8 Hz, and the stiffness significantly affects the main frequency of the vertical vibration of carbodies. What’s more, the application of dynamic vibration absorber theory on low-floor railway trains can reduce the vertical abnormal vibration effectively. Yet, reasonable suspension parameters are needed; otherwise, the vibration of carbodies, including the mass ratio, the suspension frequency, the damping ratio, and the suspended location would be aggravated. Optimal suspension parameters of the dynamic vibration absorber system were used in the simulation model, and the result shows a good agreement with the numerical results; the attached dynamic vibration absorber system on carbodies significantly reduces the vibration of carbodies at around 8 Hz. However, it should be noted that the dynamic vibration absorber is only effective at high-speed stage (beyond 40 km/h) where the pitching motion of carbodies is obvious; this conclusion is consistent with the results of the field test.

Ride comfort enhancement in railway vehicle by the reduction of the car body structural flexural vibration

The paper approaches the issue of reduction in the vertical bending vibrations of the railway vehicle carbody and the ride comfort enhancement at high velocities, starting from the prospect of isolating the vibrations by the best possible selection of the passive suspension damping in the vehicle. To this purpose, the examination falls on the influence of the vertical suspension damping upon the vibrations regime of the vehicle at the bending resonance frequency and upon the ride comfort. The results of the numerical simulations regarding the frequency response of the carbody acceleration and the comfort index will be therefore used. A value of the secondary suspension damping can be thus identified that will provide the best ride comfort performance. Similarly, the ride comfort can be increased by raising the primary suspension damping ratio.

Influence of long-wavelength track irregularities on the motion of a high-speed train

ABSTRACTVertical track irregularities over viaducts in high-speed rail systems could be possibly caused by concrete creep if pre-stressed concrete bridges are used. For bridge spans that are almost uniformly distributed, track irregularity exhibits a near-regular wave profile that excites car bodies as a high-speed train moves over the bridge system. A long-wavelength irregularity induces low-frequency excitation that may be close to the natural frequencies of the train suspension system, thereby causing significant vibration of the car body. This paper investigates the relationship between the levels of car vibration, bridge vibration, track irregularity, and the train speed. First, this study investigates the vibration levels of a high-speed train and bridge system using 3D finite-element (FE) transient dynamic analysis, before and after adjustment of vertical track irregularities by means of installing shimming plates under rail pads. The analysis models are validated by in situ measurements and on-board measurement. Parametric studies of car body vibration and bridge vibration under three different levels of track irregularity at five train speeds and over two bridge span lengths are conducted using the FE model. Finally, a discontinuous shimming pattern is proposed to avoid vehicle suspension resonance.

Effect of wind gusts on the dynamics of railway vehicles running on a curved track

Due to global warming, there is an increasing number of wind gusts that affect the stability of railway vehicles. A railway vehicle running on a curved track during a wind gust is subjected to multiple forces simultaneously, which include the centrifugal force and forces exerted by the wind gust and cant, and they significantly affect the vehicle’s dynamic characteristics as well as its safety. The forces increase the vibration of carbodies and the risk of derailment and overturning of cars; the effect is worse on irregular tracks. In order to review the phenomenon in detail, a 1/20 scale model of a railway vehicle was built to measure the aerodynamic coefficients in five directions—side force, lift force, roll moment, pitch moment, and yaw moment—through a wind tunnel test. The data collected were applied as external forces to a full-scale railway vehicle model traveling on a curved track. Using a multibody simulation software program, SIMPACK, a railway vehicle was modeled, which was then used in the simulation of the dynamic characteristics and safety of vehicles while traveling on a curved track during a wind gust. Using the actual measured track data from the curved zone, a comparison was made on the dynamic characteristics of the car traveling, with and without a wind gust, on a curved track with a railway curve radius of 599 m; also, the difference was analyzed with the direction of the wind gust blowing from inside and toward the center of curvature. The results showed that in the presence of a wind gust blowing from outside the curvature with an average speed of 25 m/s it is advisable to stop train services on grounds of safety.