Effect of Disabled Fastening Systems and Ballast on Vehicle Derailment

2006 ◽  
Vol 129 (2) ◽  
pp. 217-229 ◽  
Author(s):  
Xinbiao Xiao ◽  
Xuesong Jin ◽  
Zefeng Wen
Keyword(s):  
Degrees Of Freedom ◽  
Great Influence ◽  
Contact Forces ◽  
Railway Vehicle ◽  
Vertical Force ◽  
Nonlinear Creep ◽  
Wheel Load ◽  
Creep Theory ◽  
Normal Contact ◽  
Contact Points

The effect of disabled fastening systems and ballast on railway vehicle derailment is investigated by developing a nonsymmetrical coupled vehicle/track model. In the model a half passenger car is considered, and modeled with a multi-body system with 18 degrees of freedom, which runs on a tangent track at a constant speed. The tangent track is modeled as two elastic beams by discrete nonsymmetrical supporters modeling fastening systems, sleepers, and ballasts. The normal contact forces between wheels and rails are described by Hertzian elastic contact theory, and the tangential forces by the nonlinear creep theory of Shen et al. (Proceedings of the 8th IAVSD Symposium, Cambridge, MA, pp. 591–605). In the numerical analysis, the disabled rail fastening, rail pad, and ballast, on one and two sides of the track are, respectively, considered. Through a detailed analysis, derailment coefficients and the track state variations are obtained. The derailment coefficients are defined as the ratio of the lateral force to the vertical force of the wheel and rail (indicated by L∕V), duration of L∕V, and rate of the wheel load reduction (indicated by ΔV∕V), respectively. The variations of the contact points on the wheel treads, the track gauge, the track cross-level, and rail turnover angle are present in the paper. The numerical results obtained indicate that the failure of rail supports has a great influence on the vehicle running safety.

Influence of the Wheel and Rail Interpolation Scheme on the Contact Evaluation in Railway Dynamics

2005 ◽  
Author(s):  
J. Pombo ◽  
J. Ambro´sio
Keyword(s):  
Three Dimensional ◽  
Contact Forces ◽  
Railway Vehicle ◽  
Interpolation Scheme ◽  
Normal Contact ◽  
Contact Points ◽  
Rail Vehicles ◽  
Direct Measurements ◽  
Spatial Geometry ◽  
Conventional Rail

The dynamic behavior of the railway vehicles is strongly influenced by the complex interaction between the wheels and rails. In conventional rail vehicles the wheelsets are assembled with two wheels that are not free to rotate independently. Hence, their treads are profiled in order to allow them to negotiate curves without slipping. The dynamics of guidance depends on the wheel-rail contact forces resultant from the vehicle interaction with the track. In this work a methodology for the accurate geometric description of track models is proposed in the framework of multibody dynamics. It includes the representation of the track spatial geometry and its irregularities. The wheel and rail surfaces are parameterized with a formulation that allows using any wheel and rail profiles obtained from direct measurements or design requirements. A methodology is proposed to find online the coordinates of the contact points between wheel and rail surfaces, even for the most general three dimensional motion of the wheelset. A formulation for the description of the normal contact forces, which result from the wheel-rail interaction, is also presented. The tangential creep forces in the wheel-rail contact area are evaluated using: Kalker linear theory; Heuristic force method; Polach formulation. All methodologies proposed here are implemented in a general multibody code. The advantages and drawbacks of the computational tool are discussed with emphasis on the influence of the interpolation scheme used to parameterize the wheel and rail profiles. The discussion is supported through the dynamic analysis of the wheelset of the railway vehicle ML95 on a straight track.

Modeling Two-Point Wheel/Rail Contacts Using Constraint and Elastic-Force Approaches

2002 ◽  
Author(s):  
Ahmed A. Shabana ◽  
Khaled E. Zaazaa ◽  
Jose´ L. Escalona ◽  
Jalil R. Sany
Keyword(s):  
Contact Problem ◽  
Degrees Of Freedom ◽  
Point Contact ◽  
Elastic Force ◽  
Contact Forces ◽  
Force Model ◽  
Arc Length ◽  
Normal Contact ◽  
Contact Points ◽  
Constraint Approach

Two approaches are commonly used for solving the problem of wheel/rail contact in railroad dynamics. The first is the elastic approach in which the wheel is assumed to have six degrees of freedom with respect to the rail. The normal contact forces are defined using Hertz’s contact theory or in terms of assumed stiffness and damping coefficients. The second approach is the constraint approach in which nonlinear kinematic contact constraint equations are introduced, leading to a model in which the wheel has five degrees of freedom with respect to the rail. It is the objective of this investigation to present a new formulation for the wheel/rail contact problem based on the elastic force approach. Crucial to the success of any elastic force formulation for wheel/rail contact problem is the accurate prediction of the location of the contact points. To this end, features of multibody formulations that allow introducing arbitrary differential equations are exploited in this investigation in order to obtain a good estimate of the rail arc length traveled by the wheel set. In the formulation presented in this paper, four surface parameters are used to describe the wheel and the rail surfaces each with arbitrary geometry. In order to determine the location of the points of contact between the wheel and the rail, a first order differential equation for the rail arc length is introduced and is integrated simultaneously with the multibody equations of motion of the wheel/rail system. The method presented in this paper allows for multiple points of contact between the wheel and the rail by using an optimized search for all possible contact points. The normal contact forces are calculated and used with non-linear expressions for the creepages to determine the creep forces. The paper also discusses two different procedures for the analysis of the two-point contact in the wheel/rail interaction. Numerical results obtained using the elastic force model are presented and compared with the results obtained using the constraint approach.

Estimation of Graphite Dust Production in a Pebble-Bed Type Nuclear Reflector

2014 ◽  
Author(s):  
Ji-Ho Kang ◽  
Eung Seon Kim ◽  
Seungyon Cho
Keyword(s):  
Adhesive Wear ◽  
Cell Model ◽  
Estimation Method ◽  
Unit Cell ◽  
Contact Forces ◽  
Dust Explosion ◽  
Dust Production ◽  
Pebble Bed ◽  
Normal Contact ◽  
Contact Points

In this study, an estimation method of graphite dust production in the pebble-bed type reflector region of Korean HCSB (Helium-Cooled Solid Breeder) TBM (Test Blanket Module) in the ITER (International Thermonuclear Experimental Reactor) project using FEM (Finite Element Method) was proposed and the amount of dust production was calculated. A unit-cell model of uniformly arranged pebbles was defined with appropriate thermal and mechanical loadings. A commercial FEM program, Abaqus V6.10 was used to model and solve the stress field under multiple contact constraints between pebbles in the unit-cell. Resulting normal contact forces and slip distances on contact points were applied into the Archard adhesive wear equation to calculate the amount of graphite dust. The friction effect on contact points was investigated. The calculation result showed that the amount of graphite dust production was estimated to 2.22∼3.67e−4 g/m3 which was almost linearly proportional to the friction coefficient. The analysis results will be used as the basis data for the consecutive study of dust explosion.

Modelling and evaluation of the hunting behaviour of a high-speed railway vehicle on curved track

2018 ◽  
Vol 233 (2) ◽  
pp. 220-236 ◽  
Author(s):  
Vivek Kumar ◽  
Vikas Rastogi ◽  
PM Pathak
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Critical Speed ◽  
Transportation Network ◽  
Graph Model ◽  
Railway Vehicle ◽  
Physical Damage ◽  
Creep Theory ◽  
High Speed Railway ◽  
Hunting Behaviour

Nowadays, rail transport is a very important part of the transportation network for any countries. The demand for high operational speed makes hunting a very common instability problem in railway vehicles. Hunting leads to discomfort and causes physical damage to carriage components, such as wheels, rails, etc. The causes of instability and derailment should be identified and eliminated at the designing stage of a train to ensure its safe operation. In most of the earlier studies on hunting behaviour, a simplified model with a lower degree of freedom were considered, which resulted in incorrect results in some instances. In this study, a complete bond graph model of a railway vehicle with 31 degrees of freedom is presented to determine the response of a high-speed railway vehicle. For this purpose, two wheel–rail contacts grounded on a flange contact and Kalker’s linear creep theory are implemented. The model is simulated to observe the effects of suspension elements on the vehicle’s critical hunting velocity. It is observed that the critical hunting speed is extremely sensitive to the primary longitudinal and lateral springs. Other primary and secondary springs and dampers also affect the critical speed to some extent. However, the critical hunting velocity is insensitive to vertical suspension elements for both the primary and secondary suspensions. Also, the critical speed is found to be inversely related to the conicity of the wheel.

Hunting Stability Analysis of a New High-Speed Railway Vehicle Model Moving on Curved Tracks

2007 ◽  
Author(s):  
Yung-Chang Cheng ◽  
Sen-Yung Lee
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Lateral Displacement ◽  
Creep Model ◽  
Railway Vehicle ◽  
Nonlinear Creep ◽  
Car Body ◽  
Suspension Parameters ◽  
Virtual Boundary ◽  
Hunting Stability

A new dynamic model of railway vehicle moving on curved tracks is proposed. In this new model, the motion of the car body is considered and the motion of the tuck frame is not restricted by a virtual boundary. Based on the heuristic nonlinear creep model, the nonlinear coupled differential equations of the motion of a fourteen degrees of freedom car system, considering the lateral displacement and the yaw angle of the each wheelset, the truck frame and the car body, moving on curved tracks are derived in completeness. To illustrate the accuracy of the analysis, the limiting cases are examined. In addition, the influences of the suspension parameters on the critical hunting speeds evaluated via the linear and the nonlinear creep models respectively are studied. Furthermore, the influences of the suspension parameters on the critical hunting speeds evaluated via the fourteen degrees of freedom car system and the six degrees of freedom truck system, which the motion of the tuck frame is restricted by a virtual boundary, are compared.

Stability Analysis of High-Speed Railway Vehicle Based on Multibody Dynamics Analysis

2013 ◽  
Vol 392 ◽  
pp. 156-160
Author(s):  
Ju Seok Kang
Keyword(s):  
Stability Analysis ◽  
Multibody Dynamics ◽  
High Speed ◽  
Equations Of Motion ◽  
Contact Forces ◽  
Design Parameters ◽  
Railway Vehicle ◽  
Dynamics Analysis ◽  
Contact Points ◽  
The Stability

Multibody dynamics analysis is advantageous in that it uses real dimensions and design parameters. In this study, the stability analysis of a railway vehicle based on multibody dynamics analysis is presented. The equations for the contact points and contact forces between the wheel and the rail are derived using a wheelset model. The dynamics equations of the wheelset are combined with the dynamics equations of the other parts of the railway vehicle, which are obtained by general multibody dynamics analysis. The equations of motion of the railway vehicle are linearized by using the perturbation method. The eigenvalues of these linear dynamics equations are calculated and the critical speed is found.

Effect of the Wheel Geometric Design on the Nonlinear Dynamics of Railroad Vehicles

2005 ◽  
Vol 128 (5) ◽  
pp. 1130-1140 ◽  
Author(s):  
Ahmed A. Shabana ◽  
Mahmoud Tobaa ◽  
Khaled E. Zaazaa
Keyword(s):  
Nonlinear Dynamics ◽  
Simple Model ◽  
Single Point ◽  
Contact Forces ◽  
Geometric Properties ◽  
Normal Contact ◽  
Railroad Vehicles ◽  
Contact Points ◽  
Contact Constraint ◽  
Wheel Profile

The effect of the geometry of a wheel profile that allows only a single point of contact with the rail is investigated in this study. The local geometric properties of this profile are compared with the local geometric properties of a profile that allows for two-point contacts in order to understand the basic differences between the two profiles. A simple model is first used to examine the effect of the profile geometry on the stability and nonlinear dynamics of a suspended wheel set. The results obtained using this simple model show that the geometry of the wheel profile can significantly alter the critical speed. A computational approach is then used to investigate and quantify the effect of the wheel geometry wheel on the dynamics and stability of railroad vehicles. Two methods, the contact constraint and elastic formulations, are used. The contact constraint method employs nonlinear algebraic kinematic constraint equations to describe the contact between the wheel and the rail. The contact kinematic constraints, which eliminate one degree of freedom and do not allow for wheel/rail separation, are imposed at the position, velocity and acceleration levels. The system equations of motion are expressed in terms of the generalized coordinates and the nongeneralized surface parameters. In the formulations based on the elastic approach, the wheel has six degrees of freedom with respect to the rail, and the normal contact forces are defined as a function of the penetration using Hertz’s contact theory or using assumed stiffness and damping coefficients. In the elastic approach that allows for wheel/rail separation, the locations of the contact points are determined by solving a set of algebraic equations. The distribution of the contact forces resulting from the use of the two profiles that have different geometric properties is investigated using the two methods. Numerical results are presented for a full railroad vehicle model and the effect of the wheel profile on the vehicle stability is investigated.

On the Influence of Contact Geometry on Grasp Stability

2008 ◽  
Author(s):  
Gert A. Kragten ◽  
Just L. Herder ◽  
A. L. Schwab
Keyword(s):  
Contact Stiffness ◽  
Contact Geometry ◽  
Contact Forces ◽  
Minor Effect ◽  
Dynamic Simulations ◽  
Normal Contact ◽  
Contact Points ◽  
Grasp Stability ◽  
The Stability ◽  
A Minor

This paper demonstrates that the predicted grasp stability is highly sensitive to only small changes in the character of the contact forces. The contribution of the geometry and stiffness at the contact points to the grasp stability is investigated by a planar grasp with three contact points. Limit cases of zero and infinite contact curvatures, and finite to infinite contact stiffnesses are considered. The stability is predicted based on the approach of Howard and Kumar [1], and verified with multibody dynamic simulations. For rigid objects and fingers with only normal contact stiffness, the grasp stability is dominated by the contact geometry, whereas the local contact stiffness and preload have a minor effect. Furthermore, grasps with pointed finger tips are more likely to be stable than grasps with flat finger tips.

Computer Simulation of the Response of a Railway Vehicle Carbody

2002 ◽  
Author(s):  
M. Senthil Kumar ◽  
P. M. Jawahar
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Contact Forces ◽  
Railway Vehicle ◽  
Lateral Stiffness ◽  
Lateral Vibration ◽  
Kutta Method ◽  
Nonlinear Mathematical Model ◽  
Rail Vehicle ◽  
Runge Kutta Method

In this paper, a nonlinear mathematical model has been constructed by deriving the equations of motion of a Rail Vehicle carbody using Newton’s law. The nonlinear formula is used to evaluate the wheel rail contact forces. The nonlinear profile of wheel and rail are taken into account. Also the lateral stiffness of the track is taken into consideration. The equations of motion are derived for (a) Carbody with conventional wheelset (b) Carbody with unconventional wheelset (independently rotating wheels). For lateral vibration, 17 degrees of freedom are considered. The degrees of freedom represent lateral and yaw movements of 4 wheelsets and lateral, yaw and roll movements of the bogie and carbody. These equations of motion are transformed into a form suitable for numerical differential equation by Runge Kutta method. In the interest of computing economy, certain approximations have been introduced for calculating the creep forces. Sample results are given for a model of a typical railway vehicle used by the Indian Railways. The lateral dynamic response of the railway vehicle carbody for both conventional and unconventional wheelset has been analysed.

Running Safety and Comfort Analysis of Railway Vehicles Moving on Curved Tracks

2014 ◽  
Vol 14 (04) ◽  
pp. 1450004 ◽  
Author(s):  
Yung-Chang Cheng ◽  
Chin-Te Hsu
Keyword(s):  
Degrees Of Freedom ◽  
Lateral Displacement ◽  
Equations Of Motion ◽  
Creep Model ◽  
Railway Vehicle ◽  
Nonlinear Creep ◽  
Running Safety ◽  
Comfort Index ◽  
Vertical Displacements ◽  
Index Formulas

Using a heuristic linear creep model, this study derives the governing differential equations of motion for the railway vehicle traveling on curved tracks. The railway vehicle is modeled as a car system with 27 degrees-of-freedom (DOFs), taking into account the lateral and vertical displacements, roll and yaw angles of the wheelsets and truck frames, as well as the lateral displacement, roll and yaw angles of the car body. The effects of railway vehicle speeds on the derailment quotients and offload factors related to running safety are evaluated by both the linear and nonlinear creep models for various radii of curved tracks. Using the Sperling and modified Sperling index formulas, the effects of railway vehicle speeds on lateral riding quality and comfort are illustrated for the two models with various radii of curved tracks. Furthermore, the effects of railway vehicle speeds on the lateral Sperling comfort index of the 27-DOF car model are presented and compared for various suspension parameters. Finally, the acceptable region for riding quality and comfort are drawn.

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