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.

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.

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

2009 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten ◽  
Brian Marquis ◽  
Erik Curtis ◽  
Magdy El-Sibaie ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Contact Element ◽  
Contact Forces ◽  
Simulation Code ◽  
Vehicle Performance ◽  
Normal Contact ◽  
Advantages And Disadvantages ◽  
High Speed Trains

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

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.

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.

scholarly journals A Study on the Dynamics of Spatial Mechanisms With Frictional Spherical Clearance Joints

2017 ◽  
Vol 12 (5) ◽  
Author(s):  
Filipe Marques ◽  
Fernando Isaac ◽  
Nuno Dourado ◽  
António Pedro Souto ◽  
Paulo Flores ◽  
...  
Keyword(s):  
Friction Force ◽  
Contact Process ◽  
Contact Forces ◽  
Force Model ◽  
Spherical Joint ◽  
Normal Contact ◽  
Clearance Joints ◽  
Dissipative Term ◽  
Contact Points ◽  
Spatial Mechanisms

An investigation on the dynamic modeling and analysis of spatial mechanisms with spherical clearance joints including friction is presented. For this purpose, the ball and the socket, which compose a spherical joint, are modeled as two individual colliding components. The normal contact-impact forces that develop at the spherical clearance joint are determined by using a continuous force model. A continuous analysis approach is used here with a Hertzian-based contact force model, which includes a dissipative term representing the energy dissipation during the contact process. The pseudopenetration that occurs between the potential contact points of the ball and the socket surface, as well as the indentation rate play a crucial role in the evaluation of the normal contact forces. In addition, several different friction force models based on the Coulomb's law are revisited in this work. The friction models utilized here can accommodate the various friction regimens and phenomena that take place at the contact interface between the ball and the socket. Both the normal and tangential contact forces are evaluated and included into the systems' dynamics equation of motion, developed under the framework of multibody systems formulations. A spatial four-bar mechanism, which includes a spherical joint with clearance, is used as an application example to examine and quantify the effects of various friction force models, clearance sizes, and the friction coefficients.

A Study on the Dynamics of Spatial Mechanisms With Frictional Spherical Clearance Joints

2016 ◽  
Author(s):  
Filipe Marques ◽  
Fernando Isaac ◽  
Nuno Dourado ◽  
António Pedro Souto ◽  
Paulo Flores ◽  
...  
Keyword(s):  
Friction Force ◽  
Contact Process ◽  
Contact Forces ◽  
Force Model ◽  
Spherical Joint ◽  
Normal Contact ◽  
Clearance Joints ◽  
Dissipative Term ◽  
Contact Points ◽  
Spatial Mechanisms

An investigation on the dynamic modeling and analysis of spatial mechanisms with spherical clearance joints including friction is presented. For this purpose, the ball and the socket which compose a spherical joint are modeled as two individual colliding components. The normal contact-impact forces that develop at the spherical clearance joint are determined by using a continuous force model. A continuous analysis approach is used here with a Hertzian based contact force model, which includes a dissipative term representing the energy dissipation during the contact process. The pseudo-penetration that occurs between the potential contact points of the ball and the socket surface, as well as the indentation rate play a crucial role in the evaluation of the normal contact forces. In addition, several different friction force models based on the Coulomb’s law are revisited in this work. The friction models utilized here can accommodate the various friction regimens and phenomena that take place at the contact interface between the ball and the socket. Both the normal and tangential contact forces are evaluated and included into the systems’ dynamics equation of motion, developed under the framework of multibody systems formulations. A spatial four bar mechanism, which includes a spherical joint with clearance, is used as an application example to examine and quantify the effects of various friction force models, clearance sizes, and the friction coefficients.

A Three-Dimensional Dynamic Model for Railway Vehicle–Track Interactions

2018 ◽  
Vol 13 (7) ◽  
Author(s):  
Xianmai Chen ◽  
Xiangyun Deng ◽  
Lei Xu
Keyword(s):  
Dynamic Models ◽  
Three Dimensional ◽  
Contact Forces ◽  
Railway Vehicle ◽  
Time Integral ◽  
Proposed Model ◽  
Rigid Contact ◽  
Linearized Model ◽  
Pseudo Excitation ◽  
Force Equilibrium

In light of two wheel–rail contact relations, i.e., displacement compatibility and force equilibrium, a newly developed three-dimensional (3D) model for vehicle–track interactions is presented in this paper. This model is founded on the basis of an assumption: wheel–rail rigid contact. Unlike most of the dynamic models, where the interconnections between the vehicle and the track entirely depend on the wheel–rail contact forces, the subsystems of the vehicle and the tracks in the present study are effectively united as an entire system with interactive matrices of stiffness, damping and mass by the energy-variational principle and wheel–rail contact geometry. With wheel–rail nonlinear creepage/equivalent stiffness, this proposed model can derive dynamic results approaching to those of vehicle-track coupled dynamics. However, it is possible to apply a relatively large time integral step with numerical stability in computations. By simplifying into a linearized model, pseudo-excitation method (PEM) can be theoretically implemented to characterize the dominant vibration frequencies of vehicle-track systems due to random excitations. Finally, a trail method is designed to achieve the wheel climbing derailment process and a full derailment case where the bottom of the wheel flange has completely reached the rail top to form a complete derailment is presented.

Experimental Study of Normal Contact Force Between a Rolling Pneumatic Tyre and a Single Asperity

2017 ◽  
Vol 09 (06) ◽  
pp. 1750081 ◽  
Author(s):  
Yuan-Fang Zhang ◽  
Julien Cesbron ◽  
Hai-Ping Yin ◽  
Michel Bérengier
Keyword(s):  
Contact Force ◽  
Numerical Models ◽  
Force Transducer ◽  
Contact Forces ◽  
Exterior Surface ◽  
Normal Contact ◽  
Single Asperity ◽  
Direct Measurements ◽  
Time Signals ◽  
Force Signal

This paper proposes a novel experimental test apparatus that permits direct measurements of tyre/asperity normal contact forces under rolling conditions without interfacial layer. A reduced-sized pneumatic tyre is set rolling on the exterior surface of a cylindrical test rig simulating a smooth road surface except a single asperity of simple geometric shape connected to an embedded force transducer. Distinct asperity geometries lead to similar shapes of force signal but different magnitudes whose relationships with the indentation have exponents close to those in classical analytical solutions. By analyzing the time signals of the contact force and their frequency contents for different rolling speeds, the quasi-static nature of the contact, commonly assumed in numerical models, is verified.

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