scholarly journals An Investigation into the Modeling Methodology of the Coil Spring

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Liangcheng Dai ◽  
Maoru Chi ◽  
Hongxing Gao ◽  
Jianfeng Sun
Keyword(s):  
Mass Distribution ◽  
Dynamic Characteristics ◽  
Dynamic Stiffness ◽  
Railway Vehicle ◽  
Spring Model ◽  
Coil Spring ◽  
Railway Vehicles ◽  
Equivalent Models ◽  
Laboratory Test Results ◽  
Exciting Frequency

The coil spring is an important element in the suspension system of railway vehicles, and its structural vibration caused by the mass distribution can deteriorate the dynamic performance of the vehicle. However, the coil spring is usually modelled as a simple linear force element without considering the dynamic characteristics in multibody dynamic simulations of railway vehicles. To integrate the dynamic characteristics of the coil spring into the simulation, three equivalent dynamic models of the coil spring are established by treating the coil spring as multimass spring series, Timoshenko beam, and flexible spring, respectively. The frequency-sweep method is applied to obtain the dynamic response of the proposed models of coil spring, and the accuracy of the models’ results has been compared and verified by the laboratory test. Results show that all of these three equivalent models can reflect the influence of the spring mass distribution on its dynamic responses. Compared with the mass-spring series and beam element equivalent models, the flexible spring model can better reflect the dynamic stiffness and stress of the coil spring changing with the exciting frequency. Thus, the flexible spring model proposed in this paper is more applicable to railway vehicle system dynamics and the fatigue analysis.

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.

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

2017 ◽  
Vol 232 (4) ◽  
pp. 1103-1120 ◽  
Author(s):  
Wonhee You ◽  
Hyukbin Kwon ◽  
Joonhyuk Park ◽  
Yujeong Shin
Keyword(s):  
Dynamic Characteristics ◽  
Wind Tunnel Test ◽  
Simulation Software ◽  
Scale Model ◽  
Railway Vehicle ◽  
Wind Gust ◽  
Railway Vehicles ◽  
Wind Gusts ◽  
Pitch Moment ◽  
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.

Experimental Investigation of Dynamic Normal Characteristics of Machined Joint Surfaces

2000 ◽  
Vol 122 (4) ◽  
pp. 393-398 ◽  
Author(s):  
W. P. Fu ◽  
Y. M. Huang ◽  
X. L. Zhang ◽  
Q. Guo
Keyword(s):  
Experimental Investigation ◽  
Dynamic Characteristics ◽  
Static Pressure ◽  
Dynamic Stiffness ◽  
Relative Displacement ◽  
Test Range ◽  
Joint Surfaces ◽  
Exciting Frequency ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping

This paper presents an experimental investigation on the normal dynamic characteristics of several machined joint surfaces, i.e., the varying principle of the normal dynamic stiffness and damping with exciting frequency, relative displacement and static pre-load under different joint conditions, including joint materials, mediums, machining methods and surface roughness, etc.. The joint parameters are extracted from experimental data by establishing the theoretical model of the joint surfaces, and the mechanism is analyzed qualitatively. The studied results show that, in the test range of this paper, the stiffness and damping coefficient of the joint surfaces increase with the static pre-load; the stiffness for a dry joint is independent of the exciting frequency, while the damping coefficients for both a dry and an oiled joint decrease with the exciting frequency; little relative displacement has no marked effect on the dynamic characteristics. The amount of influence of exciting frequency and static pressure is related to the joint conditions. [S0739-3717(00)00804-7]

scholarly journals Simulation of Energy Absorption Performance of the Couplers in Urban Railway Vehicles during a Heavy Collision

Machines ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 91
Author(s):  
Sunghyun Lim ◽  
Yong-hyeon Ji ◽  
Yeong-il Park
Keyword(s):  
Reaction Force ◽  
Crash Test ◽  
Railway Vehicle ◽  
Buffer System ◽  
Railway Vehicles ◽  
Hydraulic Shock Absorber ◽  
Coupling Buffer ◽  
Absorption Performance ◽  
Different Characteristics ◽  
The Impact

Railway vehicles are generally operated by connecting several vehicles in a row. Mechanisms connecting railway vehicles must also absorb front and rear shock loads that occur during a train’s operation. To minimize damage, rail car couplers are equipped with a buffer system that absorbs the impact of energy. It is difficult to perform a crash test and evaluate performance by applying a buffer to an actual railway vehicle. In this study, a simulation technique using a mathematical buffer model was introduced to overcome these difficulties. For this, a model of each element of the buffer was built based on the experimental data for each element of the coupling buffer system and a collision simulation program was developed. The buffering characteristics of a 10-car train colliding at 25 km/h were analyzed using a developed simulator. The results of the heavy collision simulation showed that the rubber buffer was directly connected to the hydraulic shock absorber in a solid contact state, and displacement of the hydraulic buffer hardly occurred despite the increase in reaction force due to the high impact speed. Since the impact force is concentrated on the vehicle to which the collision is applied, it may be appropriate to apply a deformation tube with different characteristics depending on the vehicle location.

scholarly journals Analysis of the dynamic characteristics of downsized aerostatic thrust bearings with different pressure equalizing grooves at high or ultra-high speed

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110180
Author(s):  
Ruzhong Yan ◽  
Haojie Zhang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Rotation Speed ◽  
Dynamic Stiffness ◽  
Simulation Method ◽  
Perturbation Amplitude ◽  
Thrust Bearings ◽  
Supply Pressure ◽  
Ultra High Speed ◽  
Air Film

This study adopts the DMT(dynamic mesh technology) and UDF(user defined functions) co-simulation method to study the dynamic characteristics of aerostatic thrust bearings with equalizing grooves and compare with the bearing without equalizing groove under high speed or ultra high speed for the first time. The effects of air film thicness, supply pressure, rotation speed, perturbation amplitude, perturbation frequency, and cross section of the groove on performance characteristics of aerostatic thrust bearing are thoroughly investigated. The results show that the dynamic stiffiness and damping coefficient of the bearing with triangular or trapezoidal groove have obvious advantages by comparing with that of the bearing without groove or with rectangular groove for the most range of air film thickness, supply pressure, rotation speed, perturbation amplitude, especially in the case of high frequency, which may be due to the superposition of secondary throttling effect and air compressible effect. While the growth range of dynamic stiffness decreases in the case of high or ultra-high rotation speed, which may be because the Bernoulli effect started to appear. The perturbation amplitude only has little influence on the dynamic characteristic when it is small, but with the increase of perturbation amplitude, the influence becomes more obvious and complex, especially for downsized aerostatic bearing.

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.

scholarly journals Effect of Rail Vehicle–Track Coupled Dynamics on Fatigue Failure of Coil Spring in a Suspension System

2021 ◽  
Vol 11 (6) ◽  
pp. 2650
Author(s):  
Sunil Kumar Sharma ◽  
Rakesh Chandmal Sharma ◽  
Jaesun Lee
Keyword(s):  
Mathematical Model ◽  
Fatigue Fracture ◽  
Suspension System ◽  
Railway Vehicle ◽  
Coil Spring ◽  
Internal Resonances ◽  
Rail Vehicle ◽  
Rail Vehicles ◽  
Stress Result ◽  
Wheel Track

In a rail vehicle, fatigue fracture causes a significant number of failures in the coil spring of the suspension system. In this work, the origin of these failures is examined by studying the rail wheel–track interaction, the modal analysis of the coil springs and the stresses induced during operation. The spring is tested experimentally, and a mathematical model is developed to show its force vs. displacement characteristics. A vertical 10-degree-of-freedom (DOF) mathematical model of a full-scale railway vehicle is developed, showing the motions of the car body, bogies and wheelsets, which are then combined with a track. The springs show internal resonances at nearly 50–60 Hz, where significant stresses are induced in them. From the stress result, the weakest position in the innerspring is identified and a few guidelines are proposed for the reduction of vibration and stress in rail vehicles.

scholarly journals A new vertical dynamic model for railway vehicle with passenger-train-track coupling vibration

2019 ◽  
Vol 234 (1) ◽  
pp. 134-146
Author(s):  
Yuewei Yu ◽  
Leilei Zhao ◽  
Changcheng Zhou
Keyword(s):  
Dynamic Model ◽  
Railway Vehicle ◽  
Train Track ◽  
Passenger Train ◽  
Railway Vehicles ◽  
Vertical Coupling ◽  
Track System ◽  
Coupling Dynamic ◽  
Train System ◽  
Coupling Dynamic Model

In order to further reveal the vertical random vibration characteristics of railway vehicles, using the system engineering method, taking the passenger, the train system, and the track system (ballast track) as a unified whole, a passenger-train-track vertical coupling dynamic model is established, and the vibration differential equations of the model are derived. In the model, passengers are regarded as a single-degree-of-freedom system attached to the bottom of the carriage, the train system is represented as a 10-degree-of-freedom multi-rigid body model, the track system is regarded as the infinite long Euler beam model with three layers of continuous elastic point support, and the Hertz nonlinear elastic contact theory is applied to the wheel and rail coupling relationship. Based on this, the time-domain numerical solution of the passenger-train-track vertical coupling dynamic model is given by using Newmark- β implicit integration algorithm, and the correctness of the model is verified by the real vehicle test. This study can provide some theoretical basis for the design of railway vehicles and provide fundamentals for the coordinated control and system optimization of railway vehicle ride comfort.

A Fractional Derivative Model for Rubber Spring of Primary Suspension in Railway Vehicle Dynamics

2017 ◽  
Vol 3 (3) ◽  
Author(s):  
Dawei Zhang ◽  
Shengyang Zhu
Keyword(s):  
Fractional Derivative ◽  
Degrees Of Freedom ◽  
Excitation Frequency ◽  
Coupled System ◽  
Dynamic Responses ◽  
Viscous Force ◽  
Railway Vehicle ◽  
Spring Model ◽  
The Difference ◽  
Amplitude Dependency

This paper presents a nonlinear rubber spring model for the primary suspension of the railway vehicle, which can effectively describe the amplitude dependency and the frequency dependency of the rubber spring, by taking the elastic force, the fractional derivative viscous force, and nonlinear friction force into account. An improved two-dimensional vehicle–track coupled system is developed based on the nonlinear rubber spring model of the primary suspension. Nonlinear Hertz theory is used to couple the vehicle and track subsystems. The railway vehicle subsystem is regarded as a multibody system with ten degrees-of-freedom, and the track subsystem is treated as finite Euler–Bernoulli beams supported on a discrete–elastic foundation. Mechanical characteristic of the rubber spring due to harmonic excitations is analyzed to clarify the stiffness and damping dependencies on the excitation frequency and the displacement amplitude. Dynamic responses of the vehicle–track coupled dynamics system induced by the welded joint irregularity and random track irregularity have been performed to illustrate the difference between the Kelvin–Voigt model and the proposed model in the time and frequency domain.

Design, Analysis and Test of Multi-Stage Crashworthiness Energy Absorbing Device for Railway Vehicles

2019 ◽  
Author(s):  
Haifeng Hong ◽  
Hongtao Liu ◽  
Ziwen Fang ◽  
Kefei Wang ◽  
Jianran Wang ◽  
...  
Keyword(s):  
Railway Vehicle ◽  
Test Results ◽  
Railway Vehicles ◽  
Multi Stage ◽  
Element Simulation ◽  
Sufficient Energy ◽  
Stage 4 ◽  
Third Stage ◽  
Energy Absorbing ◽  
Stage 1

Abstract An anti-collision and energy absorbing device is generally placed at the front end of railway vehicles to provide controlled collapse and sufficient energy absorbing capacity. In the conventional way, the energy absorbing device is usually designed as an integrated part of the carbody that can’t be easily replaced nor maintained after crash. To increase the maintainability and energy absorbing capacity of the energy absorbing device, a Multi-stage Crashworthiness Energy Absorbing Device has been developed, in which the first-stage and the second-stage energy absorbing units can be replaced or repaired under the collision that is not severe enough to initiate the third-stage energy absorbing unit. The Crashworthiness Energy Management (CEM) has four stages: coupler energy absorbing components (stage 1), honeycomb in the sliding center anti-climber (stage 2), metal peeling tubes mounted at the back of the fixed anti-climber (stage 3) and the structural components in the cab area (stage 4). By comparing the simulation results and test results, it is concluded that the finite element simulation model can provide dependable and accurate prediction for collision behaviors. Based on the design, simulation and test data, a safe, reliable and maintainable Multi-stage Crashworthiness Energy Absorbing Device has been verified and validated, which can provide valuable reference for researchers and engineers in the crashworthiness and railway vehicle industry.

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