scholarly journals Development of a Model for the Prediction of Wheel and Rail Wear in the Railway Field

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
M. Ignesti ◽  
L. Marini ◽  
E. Meli ◽  
A. Rindi
Keyword(s):  
Fundamental Problem ◽  
Point Of View ◽  
Contact Forces ◽  
Dynamical Analysis ◽  
Railway Vehicle ◽  
Technical Documentation ◽  
Wear Model ◽  
Contact Points ◽  
Rail Wear ◽  
Dynamical Simulations

The wear prediction at the wheel-rail interface is a fundamental problem in the railway field, mainly correlated to the planning of maintenance interventions, vehicle stability, and the possibility of researching strategies for the design of optimal wheel and rail profiles from the wear point of view. The authors in this work present a model specifically developed for the evaluation of the wheel and rail wear and of the wheel and rail profiles evolution. The model layout is made up of two mutually interactive parts: a vehicle model for the dynamical analysis and a model for the wear estimation. The first one is a 3D multibody model of a railway vehicle where the wheel-rail interaction is implemented in a C/C++ user routine. Particularly, the research of the contact points between wheel and rail is based on an innovative algorithm developed by authors in previous works, while normal and tangential forces in the contact patches are calculated according to the Hertz and Kalker’s global theory, respectively. The wear model is mainly based on experimental relationships found in literature between the removed material by wear and the energy dissipated by friction at the contact. It starts from the outputs of the dynamical simulations (position of contact points, contact forces, and global creepages) and calculates the pressures inside the contact patches through a local contact model; then, the material removed by wear is evaluated and the worn profiles of wheel and rail are obtained. In order to reproduce the wear evolution, the overall mileage traveled by the vehicle is divided into discrete steps, within which the wheel and rail profiles are constant; after carrying out the dynamical simulations relative to one step, the profiles are updated by means of the wear model. Therefore, the two models work alternately until completing the whole mileage. Moreover, the different time scales characterizing the wheel and rail wear evolutions require the development of a suitable strategy for the profile update; the strategy proposed by the authors is based both on the total distance traveled by the vehicle and on the total tonnage burden on the track. The entire model has been developed and validated in collaboration with Trenitalia S.p.A. and Rete Ferroviaria Italiana (RFI), which have provided the technical documentation and the experimental results relating to some tests performed with the vehicle DMU Aln 501 Minuetto on the Aosta-Pre Saint Didier line.

Influence of rail flexibility in a wheel/rail wear prediction model

2016 ◽  
Vol 231 (1) ◽  
pp. 57-74 ◽  
Author(s):  
Javier F Aceituno ◽  
Pu Wang ◽  
Liang Wang ◽  
Ahmed A Shabana
Keyword(s):  
Prediction Model ◽  
Rigid Body ◽  
Contact Point ◽  
Three Dimensional ◽  
Contact Forces ◽  
Wear Model ◽  
Material Loss ◽  
Wear Prediction ◽  
Contact Points ◽  
Rail Wear

The aim of this paper is to study the influence of rail flexibility when a wheel/rail wear prediction model that computes the material loss based on an energy approach is used. The wheel/rail wear model used in this investigation is a simplified combined wear hypothesis that is based on the frictional energy loss in the contact patch. In order to account for wear and its distribution in a profiled wheel surface, the contact forces, creepages and location of the wheel/rail contact points are first calculated using a fully nonlinear multibody system (MBS) and three-dimensional contact formulations that account for the rail flexibility. The contact forces, creepages and contact point locations are defined as nonlinear functions of the rail deformations. These nonlinear expressions are used in the wear calculations. The wear distribution is considered to be proportional to the normal force in the contact area. Numerical simulations are first performed in order to compare between the results obtained using the simplified wheel/rail wear model and the results obtained using Archard’s wear model with a focus on sliding when the track is modeled as a rigid body. This simplified wear model is then used in the simulation of the MBS vehicle model in the case of a flexible body track, in which the rails are modeled using the finite element floating frame of reference approach and modal reduction techniques. The effect of the rail deformation on the wear results are examined by comparing these results with those obtained using the rigid-body track model.

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.

On Solvability of Multibody Contact Problems

2007 ◽  
Author(s):  
Alexander P. Ivanov
Keyword(s):  
Contact Problem ◽  
Equations Of Motion ◽  
Sufficient Conditions ◽  
Contact Problems ◽  
Point Of View ◽  
Contact Forces ◽  
Empty Intersection ◽  
Contact Points ◽  
Whole Space ◽  
Multibody Contact

The paper is devoted to dynamic multi-rigid-body contact problems with dry friction. It is known that such problem may have multiple solutions or none solution (so-called Painleve´ paradoxes). A great deal of works concerning overcoming of the paradoxes was published last century, but general conditions of existence and uniqueness were not derived yet. We consider systems with a finite numbers of contact points with well-defined contact directions and Coulomb friction. The equations of motion contain unknowns of two kinds: the accelerations and the contact forces. According to the friction law, some of these variables vanish, and remaining ones can be treated as a coordinate system in the space of the generalized forces. Thus, this space splits to a finite number of regions with different coordinates. From a geometrical point of view, the solvability of the multi-contact problem means that the union of these regions equals to the whole space. Furthemore, the solution is unique ⇔ any pair of regions has empty intersection, and the coordinates within any region are defined uniquely. We present some algebraic conditions, which are equivalent to these geometric properties. Therefore, necessary and sufficient conditions of correct solution to multibody contact problem are obtained for the first time. A number of mechanical examples are considered to illustrate new results.

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.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

Periodic Response of a Link Coupling With Clearance

1989 ◽  
Vol 111 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Y. S. Choi ◽  
S. T. Noah
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Solution Procedure ◽  
Contact Forces ◽  
Steady State Response ◽  
Algebraic Equations ◽  
State Response ◽  
Contact Points ◽  
Integration Schemes ◽  
Nonlinear Algebraic Equations

The nonlinear, steady-state response of a displacement-forced link coupling with clearance with finite stiffness is determined. The solution procedure is derived from satisfying the boundary conditions at the contact points and then solving the resulting nonlinear algebraic equations by setting the duration of contact as a parameter. This direct approach to determining periodic solutions for systems with clearances with finite stiffness is substantially more efficient than numerical integration schemes. Results in terms of contact forces and durations of contact are pertinent to fatigue and wear studies. Parametric relations are presented for effects of the variation of damping, stiffness, exciting displacement, and gap length on the dynamic behavior of the link pair.

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.

scholarly journals Repeatability Analysis of Overconstrained Kinematic Coupling Using a Parallel-Mechanism-Equivalent Model

2020 ◽  
Author(s):  
Jianzhong Ding ◽  
Xueao Liu ◽  
chunjie wang
Keyword(s):  
Parallel Mechanism ◽  
Sampling Method ◽  
Contact Forces ◽  
Equivalent Model ◽  
Parallel Mechanisms ◽  
Kinematic Coupling ◽  
Contact Points ◽  
Prismatic Joints ◽  
Type Coupling ◽  
Additional Support

Abstract A novel method for repeatability analysis of overconstrained kinematic coupling using a parallel-mechanism-equivalent-model is proposed. An overconstrained Kelvin-type coupling with one additional support is introduced and used for method illustration. Contact forces of the overconstrained coupling under preload are computed with Moore-Penrose inverse and the deformations are obtained using the Hertz theory. The couping is equivalently modeled as a 7-SPS parallel mechanism, spherical joints of which represent the centers of the supporting balls and the contact points, respectively, and prismatic joints are used to simulate the deformations. Therefore, pose error of the coupling arisen from preload is analyzed using the well-appraised incremental method for forward kinematics analysis of parallel mechanisms. The uncertainties of the preload are discussed and a boundary-sampling method is proposed for repeatability analysis. The main contribution of this study lies in that the proposed parallel-mechanism-equivalent-model and the boundary-sampling method greatly simplify the repeatability analysis of overconstrained kinematic couplings. Finally, the proposed methods are validated by case study.

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