scholarly journals Investigating the Effect of Some Train and Track Parameters on Contact-impact Forces in the Vicinity of a Rail Breakage

2019 ◽  
Author(s):  
Mosab Reza Tajalli ◽  
Jabbar Ali Zakeri
Keyword(s):  
Interaction Model ◽  
Element Model ◽  
Contact Forces ◽  
Railway Track ◽  
Dynamic Impact ◽  
Impact Forces ◽  
Risk Increase ◽  
Length Increase ◽  
Train Speed ◽  
Contact Impact

Broken rails or welds are the main causes of derailment in railway networks. Therefore, a wheel-rail interaction model, which precisely estimates contact-impact forces in the presence of broken rails, can have a significant effect on derailment risk reduction. This paper attempts to present contact-impact forces in the vicinity of broken rails by employing a detailed 3D finite element model. The model is verified using a field test carried out on a ballasted railway track. Effects of train speed, gap length, axle load and railpad and ballast characteristics are studied on rail-wheel contact forces as well as on railpad and ballast forces. Results suggest that increasing the train speed from 60 km/h to 110 km/h would increase dynamic impact force from 2.46 to 4.11. It is also observed that increasing axle load results in an increase in the wheel-rail impact forces and in railpad and ballast forces, while leading to a reduced dynamic impact factor. Furthermore, investigating the effect of the track parameters demonstrates that ballast stiffness is the most important characteristic of the track, which has a reverse effect on dynamic impact forces. Moreover, unloading length increase and consequently derailment risk increase is highly sensitive to increasing train speed.

Modeling Expected Wear in Revolute Joints With Clearance in Multibody Mechanical Systems

2007 ◽  
Author(s):  
P. Flores ◽  
J. Ambro´sio ◽  
J. C. P. Claro ◽  
H. M. Lankarani
Keyword(s):  
Research Work ◽  
Contact Forces ◽  
Joint Surface ◽  
Force Model ◽  
Wear Model ◽  
Continuous Contact ◽  
Revolute Joints ◽  
Sliding Motion ◽  
Impact Forces ◽  
Contact Impact

The main goal of this work is to develop a methodology for studying and quantifying the wear phenomenon in revolute clearance joints. In the process, a simple model for a revolute joint in the framework of multibody systems formulation is presented. The evaluation of the contact forces developed is based on a continuous contact force model that accounts for the geometrical and materials properties of the colliding bodies. The friction effects due to the contact in the joints are also represented. Then, these contact-impact forces are used to compute the pressure field at the contact zone, which ultimately is employed to quantify the wear developed and caused by the relative sliding motion. In this work, the Archard’s wear model is used. A simple planar multibody mechanical system is used to perform numerical simulations, in order to discuss the assumptions and procedures adopted throughout this work. Different results are presented and discussed throughout this research work. From the main results obtained, it can be drawn that the wear phenomenon is not uniformly distributed around the joint surface, owing to the fact that the contact between the joint elements is wider and more frequent is some specific regions.

Out-of-Plane Responses of Overspeeding High-Speed Train on Curved Track

2018 ◽  
Vol 18 (11) ◽  
pp. 1850132 ◽  
Author(s):  
Jian Dai ◽  
Kok Keng Ang ◽  
Van Hai Luong ◽  
Minh Thi Tran ◽  
Dongqi Jiang
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Contact Forces ◽  
Railway Track ◽  
High Speed Train ◽  
Track Segment ◽  
Out Of Plane ◽  
Train Speed ◽  
Curved Track ◽  
Design Speed

This paper presents a numerical study on the out-of-plane responses of a high-speed train running on a curved railway track segment using the moving element method. The accuracy and efficiency of the proposed computation model presented herein are compared with available analytical results from the literature and a finite element solver based on a simplified moving load model. Thereafter, a half-railcar moving sprung-mass model and a double-rail track-foundation model are presented to investigate the behavior of a high-speed train traversing a curved track, particularly when the train speed is greater than the design speed of the curved track segment. The results show that the train speed and severity of track irregularity significantly affect the contact forces on the rails. This paper also presents a case of a railcar overturning when the train speed is greater than 2.5 times the design speed of a curved track segment.

A wheel passing a crossing nose: Dynamic analysis under high axle loads using finite element modelling*

2012 ◽  
Vol 226 (6) ◽  
pp. 603-611 ◽  
Author(s):  
Martin Pletz ◽  
Werner Daves ◽  
Heinz Ossberger
Keyword(s):  
Finite Element ◽  
Finite Element Modelling ◽  
Element Model ◽  
Contact Forces ◽  
Element Modelling ◽  
Multiple Contacts ◽  
Load Train ◽  
Proposed Model ◽  
Train Speed ◽  
Axle Loads

A finite element model for the process of a wheel passing a crossing is presented. In the dynamic model, one wheel, the wing rails and the crossing nose (frog) are modelled. The bogie, the complete wheel set and the support of the crossing are represented as a system consisting of masses, springs, dampers and friction-generating elements. The rolling/sliding behaviour between the wheel and crossing is studied using the proposed model. Due to the conical shape of the wheel tread and multiple contacts between the wheel and the crossing parts, sliding occurs during the transition of the wheel from the wing rail to the crossing nose or vice versa. At the same time, an impact occurs that produces high contact forces. The parameters of the model are the train speed and passing direction, the wheel and the crossing geometry, the axle load and the support of the crossing. In this paper, the crossover process is studied for high axle loads and compared with results of simulations using a normal axle load. Further parameters are three train velocities, both directions of passing and different crossing materials. The loading of the crossing nose is calculated for all cases (axle load, train speed and direction) and materials.

scholarly journals Application of the Bezgin Method to estimate dynamic impact forces and judge the conditions for ballast pulverization and slab cracking due to abrupt and rapid changes in railway track profile

2021 ◽  
Author(s):  
Erdem Balcı ◽  
Niyazi Özgür Bezgin
Keyword(s):  
Experimental Studies ◽  
Rate Of Change ◽  
Railway Track ◽  
Rolling Stock ◽  
Structural Domain ◽  
Numerical Techniques ◽  
Dynamic Impact ◽  
Accurate Analysis ◽  
Impact Forces ◽  
Track Stiffness

Dynamic impact forces occur on railway tracks due to the presence of roughness of the track and the wheel and relate to the train speed and the rate of change of roughness. Variations in track profile and track stiffness and variations in wheel circularity are the causes of roughness. Quantification of the dynamic impact forces is not an easy task due to the complexity of the mechanics of the rolling stock interaction with the railway track. A number of experimental studies have led to an understanding of the dynamic impact forces, yielding a set of conservative and case-specific empirical equations. There are also many calculation-intensive numerical techniques, relying on iterative calculations seeking to converge to a state of temporary equilibrium for the analyzed structural domain within small-time increments. These techniques provide detailed and valuable information for the stresses that develop within the many components of the railway track. However, such numerical techniques rely on expensive computational tools that require experienced users to apply and interpret their results. The sheer amount of representative structural and material data input required to define the analyzed structural domain of the railway track properly is also an important task to accomplish in order to conduct a meaningful analysis. The second author developed a simple analytical method that can provide an accurate analysis for the dynamic impact forces on any railway track relying on track stiffness as the only mechanical railway track parameter. This paper introduces an ongoing study led by the second author and provides an insight into how a designer or a track maintainer can apply the Bezgin Method to estimate dynamic impact forces that may occur in rail-ends and within turnouts. This paper will also discuss how one can judge the conditions for ballast pulverization or slab cracking should these conditions exist.

Variation of Track Response to Wheel Forces with Bogie Axle Spacing: Apparent Track Stiffness and its Influence on Dynamic Impact Forces on Railway Tracks

2021 ◽  
pp. 036119812110624
Author(s):  
Erdem Balcı ◽  
Niyazi Özgür Bezgin ◽  
Mohamed Wehbi
Keyword(s):  
Analytical Study ◽  
Mechanical Characteristics ◽  
Numerical Study ◽  
Railway Track ◽  
Dynamic Impact ◽  
Transition Zones ◽  
Railway Tracks ◽  
Impact Forces ◽  
Track Stiffness ◽  
New Perspective

Track stiffness is an important parameter that affects railway track response. Axle spacing influences the response of the track to wheel forces and has an effect on track stiffness. Track response to train wheels within a bogie or between neighboring bogies vary in relation to their mutual interference, depending on the mechanical characteristics of the layers composing the track, axle spacing and bogie spacing. This interference affects the force-deflection characteristic of the railway track under a wheel. Dynamic impact forces caused by track and wheel roughness relate to track stiffness. Therefore, everything else being the same, two trains with different bogie spacing may generate different dynamic impact forces on the railway track. As a result, the accumulated damage to a railway track over time can relate not only to cumulative tonnage but also to the axle spacing of the trains operating on the railway track. Through superposition of the estimated track deflections by the beam-on-elastic-foundation theorem and looking at it from a new perspective, this paper discovers a set of relations between the variations of track stiffness with bogie axle spacing. The paper introduces a new concept of apparent track stiffness and hypothesizes that dynamic impact forces on the railway tracks relate to axle spacing. The paper then presents a numerical study and an analytical study that analyzes wheel and track interaction along stiffness transition zones for different values of axle spacing and shows that bogie axle spacing has an effect on dynamic impact forces on railway tracks.

scholarly journals Contact Impact Forces at Discontinuous 2-DOF Vibroimpact

2016 ◽  
Vol 1 (1) ◽  
pp. 183-196 ◽  
Author(s):  
V.A. Bazhenov ◽  
O.S. Pogorelova ◽  
T.G. Postnikova
Keyword(s):  
Continuation Method ◽  
Excitation Amplitude ◽  
Contact Forces ◽  
Bifurcation Points ◽  
Strongly Nonlinear ◽  
Impact Forces ◽  
Discontinuous Bifurcation ◽  
Contact Impact ◽  
Vibroimpact System ◽  
The Impact

AbstractDynamic behaviour of contact impact forces in strongly nonlinear discontinuous vibroimpact system is studying. Contact impact force is one of the most significant vibroimpact system characteristics. We investigate the 2-DOF vibroimpact system by numerical parameter continuation method in conjunction with shooting and Newton-Raphson methods. We simulate the impact by nonlinear contact interactive force according to Hertz’s contact law. This paper is the continuation of the previous works [1,2]. We have determined the instability zones and bifurcations points for loading curves [1] and frequency-amplitude response [2] under variation of excitation amplitude and frequency. In this paper we investigate the behaviour of contact forces at bifurcation points particularly at discontinuous bifurcation points where set-valued Floquet multipliers cross the unit circle by jump that is their moduli becoming more than unit by jump. It is phenomenon unique for nonsmooth systems with discontinuous right-hand side. We observe also the contact forces increase at nT -periodical multiple impacts regimes. We also learn the change of contact forces behaviour when the impact between system bodies became the soft one due the change of system parameters.

Proposal and Application of a New Technique to Forecast Railway Track Damage Because of Track Profile Variations

2019 ◽  
Vol 2673 (4) ◽  
pp. 568-582
Author(s):  
Mohamed Wehbi ◽  
Niyazi Özgür Bezgin
Keyword(s):  
Decomposition Method ◽  
Wavelet Decomposition ◽  
Impact Force ◽  
Railway Track ◽  
Dynamic Impact ◽  
Railway Tracks ◽  
Impact Forces ◽  
Profile Variation ◽  
Damage Data ◽  
A New Technique

This paper presents a new technique to estimate dynamic impact forces on railway tracks that develop because of variations in track profile. The approach presented uses a wavelet decomposition method to systematically define the irregular profile variation of a rough track length in relation to regular wavelet functions. These functions provide the regular profile variation parameters to estimate the dynamic impact forces using a new method proposed by Bezgin. This paper begins with an introduction of the proposed Bezgin Method and two equations developed by this method to estimate dynamic impact force factors that develop along descending track profiles, followed by the presentation of the wavelet decomposition method to represent the irregular variations in rough track profiles by wavelet functions. The paper then presents three case studies that involve track profile and stiffness measurements and track damage data collection along three railway tracks in the United Kingdom and continues with the applications of the wavelet decomposition method to the measured variations in the track profiles. The equations developed by the Bezgin Method then make use of the processed profile data to estimate the dynamic impact force factors along the railway tracks. The paper ends by correlating the estimated dynamic impact force factors to the damage data collected along the tracks and shows that there is a relation between the observed track damage and the estimated dynamic impact force factors. The proposed technique has, therefore, the potential applications to assess railway track conditions and forecast railway track damage.

Applications and Estimate Comparisons of Bezgin–Kolukırık Equations for Dynamic Impact Forces Because of Wheel Flats with Numerical Analysis Estimates and Instrumented Track Measurements

2020 ◽  
Vol 2674 (10) ◽  
pp. 199-214
Author(s):  
Niyazi Özgür Bezgin ◽  
Cengiz Kolukırık
Keyword(s):  
Numerical Methods ◽  
Impact Force ◽  
Hertzian Contact ◽  
Rolling Stock ◽  
Dynamic Impact ◽  
Impact Reduction ◽  
Impact Forces ◽  
Wide Range ◽  
Train Speed ◽  
Wheel Flat

Bezgin–Kolukırık equations (K’B3 and K'B3,H) are the last group of seven analytical equations based on the Bezgin Method. The method is based on the law of conservation of energy, rules of kinematics and a new concept, impact reduction factor, that describes the development of dynamic impact forces because of track and wheel roughness. K'B3 and K’B3,H estimate dynamic impact force factors because of wheel flats. K'B3,H includes the effect of Hertzian contact deformation on dynamic impact force factors. The proposed equations require up to six parameters to yield estimates. These parameters are: wheel diameter, wheel flat length, train speed, static wheel force transferred to the rail based on the tributary mass of the wheel, equivalent system stiffness of railway track and rolling stock, and length of Hertzian contact interface between wheel and rail. These equations empower users with the ability to estimate the highest values of the dynamic impact force factors because of wheel flats by manual calculations that yield realistic estimates comparable with estimates from advanced numerical methods and measurements obtained from instrumented test tracks. This paper presents the proposed Bezgin–Kolukırık equations followed by their application on hypothetical track and rolling stock conditions presenting a wide range of values for track and rolling stock stiffness, static wheel force, wheel diameters, train speed and wheel flat lengths. Estimates from the proposed equations are compared with the estimates of advanced numerical methods and experimental measurements from two previous papers.

Modeling Vibration-Induced Tire-Pavement Interaction Noise in the Mid-frequency Range

2020 ◽  
Author(s):  
Sterling McBride ◽  
Ricardo Burdisso ◽  
Corina Sandu
Keyword(s):  
Sound Intensity ◽  
Element Model ◽  
Dominant Frequency ◽  
Contact Forces ◽  
Surface Velocity ◽  
New Wave ◽  
Normal Surface ◽  
Radiated Noise ◽  
Physical Effects ◽  
Effects Of Rotation

ABSTRACT Tire-pavement interaction noise (TPIN) is one of the main sources of exterior noise produced by vehicles traveling at greater than 50 kph. The dominant frequency content is typically within 500–1500 Hz. Structural tire vibrations are among the principal TPIN mechanisms. In this work, the structure of the tire is modeled and a new wave propagation solution to find its response is proposed. Multiple physical effects are accounted for in the formulation. In an effort to analyze the effects of curvature, a flat plate and a cylindrical shell model are presented. Orthotropic and nonuniform structural properties along the tire's transversal direction are included to account for differences between its sidewalls and belt. Finally, the effects of rotation and inflation pressure are also included in the formulation. Modeled frequency response functions are analyzed and validated. In addition, a new frequency-domain formulation is presented for the computation of input tread pattern contact forces. Finally, the rolling tire's normal surface velocity response is coupled with a boundary element model to demonstrate the radiated noise at the leading and trailing edge locations. These results are then compared with experimental data measured with an on-board sound intensity system.

scholarly journals A new time-delayed periodic boundary condition for discrete element modelling of railway track under moving wheel loads

2021 ◽  
Vol 23 (4) ◽  
Author(s):  
Huiqi Li ◽  
Glenn McDowell ◽  
John de Bono
Keyword(s):  
Boundary Condition ◽  
Periodic Boundary Condition ◽  
Periodic Boundary ◽  
Discrete Element ◽  
Contact Forces ◽  
Railway Track ◽  
Discrete Element Modelling ◽  
Fixed Boundary ◽  
Element Modelling ◽  
New Time

Abstract A new time-delayed periodic boundary condition (PBC) has been proposed for discrete element modelling (DEM) of periodic structures subject to moving loads such as railway track based on a box test which is normally used as an element testing model. The new proposed time-delayed PBC is approached by predicting forces acting on ghost particles with the consideration of different loading phases for adjacent sleepers whereas a normal PBC simply gives the ghost particles the same contact forces as the original particles. By comparing the sleeper in a single sleeper test with a fixed boundary, a normal periodic boundary and the newly proposed time-delayed PBC (TDPBC), the new TDPBC was found to produce the closest settlement to that of the middle sleeper in a three-sleeper test which was assumed to be free of boundary effects. It appears that the new TDPBC can eliminate the boundary effect more effectively than either a fixed boundary or a normal periodic cell. Graphic abstract

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