Rail Inclination Research Articles

Причины возникновения и развития дефектов рельсов в кривых на участках обращения поездов повышенной массы и длины

Purpose: determine the causes of defects in rails in areas of circulation of trains of increased weight and length through modeling the operation of rails in curved sections of the railway track using digital twins. Methods: t study the influence of various factors on rail wear in curved sections of the track, software systems were used ased on the numerical solution of differential equations for the movement of rolling stock and the operation of the railway track under the train. To determine the stresses in the rails in order to predict the development of contact-fatigue defects, dynamic calculations using the finite element method were used. Results: it was revealed that in order to reduce rail wear in a curved section of the track in sections with predominantly freight traffic, the elevation of the outer rail must be calculated based on the actually realized speeds of freight trains. It has been established that at the moment the influence of the amount of rail inclination on rail wear has not been sufficiently studied. As an analysis of the position of the rails at various inclines has shown, for the curve under consideration it is most advisable to use a 1/30 inclination within the limits of a circular curve and with a 1/20 to 1/30 inclination within the transition curve. To reduce the likelihood of contact-fatigue defects occurring in such areas, it is necessary to provide for the implementation of measures to lubricate the side working edge of the outer rail thread and the rolling surface of the inner rail thread within the entire curve. Practical importance: the research results indicate the need to revise the approach to calculating the elevation of the outer rails in curves with heavy freight train traffic. The possibility of extending the service life of rails by revising the system for planning and implementing work on lubricating and grinding rails in curves in areas where trains of increased mass and length operate

Compliance Modeling and Kinetostatic Analysis of a Generalized 3-PSS Compliant Parallel Micro-Motion Platform.

In order to expand the range of motion performance of the 3-PSS-compliant parallel micro-motion platform, a variable inclination angle of the mechanism's guide rails was introduced to construct a category of generalized 3-PSS compliant parallel micro-motion platforms with distinct configurations (exhibiting different motion performances) but identical motion patterns (three translational degrees of freedom). The compliance and kinetostatics of such micro-motion platform are modeled and analyzed. Firstly, the compliance model is established based on the coordinate transformation method. Then, simplifying the micro-motion platform into a spring system, the kinetostatic model in terms of input force-output displacement is established based on the compliance model using the compliance matrix method. For practical application considerations, the kinetostatic model in terms of input displacement-output displacement is further derived based on the input force-output displacement model. Then, the correctness of the established compliance model and kinetostatic model is successively verified through finite element simulation. Finally, using two specified motion trajectories (spatial spiral trajectory and planar circular trajectory) as examples, an analysis is conducted on the influence of guide rail inclination angle variations on the kinetostatic performance of the micro-motion platform. This analysis serves as guidance for the rational design of such micro-motion platforms.

Simulation Analysis of the Influence of Changes in Track Parameters on Running Safety of a Rail Vehicle

The contemporary striving for increased speed in rail transport, with simultaneous requirements in terms of travel comfort, makes the safety of rail vehicles one of the priorities in the process of passenger rail transport. It is obvious that safety in this case is determined by: the technical condition of the vehicle, the condition of the railway infrastructure and the conditions of cooperation between the railway vehicle and the track. Railway vehicles running safety tests can be carried out on-line, in real operating conditions, and off-line with the use of mathematical models and simulation methods. The on-line research does not assess the impact of the parameter characterizing the track geometry, i.e., rail inclination, on the driving safety, and the deviation of the shape of wheel and rail running surfaces from the nominal dimensions is rarely diagnosed and taken into account in the tests. The considerations in this article are devoted to the discussion of the effects on the safety of a rail vehicle, resulting from possible changes in the inclination of the rails and deviations of the rail profile from the nominal dimensions. The research, the results of which are presented in the article, were carried out using off-line methods for the wheelset, using mathematical models, but taking into account the forces resulting from the interactions of the bogie frame and the railway wagon body and the real track geometry.

Investigating high rail side wear in urban transit track through numerical simulation and field monitoring

One of the major track issues in urban rail transit is the rail side wear, especially at the high rail on sharp curves. The mechanism of rail side wear is very complex and has not been fully understood. This study attempts to characterize the progressive development of high rail side wear in a transit track with heavy traffic. A numerical vehicle-track model is developed based on multi-body dynamics and the modified Archard wear formula and is used to perform a parametric analysis. The side wear development trend observed in the field is in good agreement with the results calculated from the numerical mode. According to the results obtained from this study, the side wear during the life-cycle of the high rail can be approximately characterized into three stages: 1) Stage I, rail wear initiates at the gauge side corner; 2) Stage II, side wear propagates linearly; 3) Stage III, side wear propagates exponentially. The parametric analysis suggests that three maintenance activities may ease the development rate of the high rail side wear in Stage III. These include increasing the rail inclination, adjusting the track gauge on time, and restoring the rail profile of the low rail.

Numerical simulation of rail surface-initiated rolling contact fatigue in the switch panel of railway turnouts

Considering the complex characteristics of the track structure in railway turnouts, it is difficult and also expensive to experimentally study rail damages; therefore, numerical methods are an effective alternative. This study presents a numerical method to simulate rail surface-initiated rolling contact fatigue in the switch panel of railway turnouts. This method includes simulation of the vehicle–turnout wheel–rail dynamic interaction, analysis of the wheel–rail multipoint non-Hertzian rolling contact that considers the relative motion between the switch and stock rails, and calculation of the accumulated rail surface-initiated rolling contact fatigue. The accumulated rail surface-initiated rolling contact fatigue after the vehicles passed a turnout switch panel 80 times (the average number of vehicles running on the Chinese high-speed railway lines per day) in the through route with facing move was simulated based on this procedure. The result showed that the maximum surface-initiated rolling contact fatigue damage of the switch rail and the stock rail was 1.57 × 10−2 and 0.62 × 10−2, respectively. Surface-initiated rolling contact fatigue in the switch rail mainly occurred at the gauge angle, and in the stock rail it mainly occurred at the center of the rail. In addition, the influence of track parameters (rail inclination, track gauge, and friction coefficient) is analyzed. The friction coefficient influenced the rail surface-initiated rolling contact fatigue. When the coefficient exceeded 0.3 in particular, the rail rolling contact fatigue damage increased sharply. Hence, suitable friction control measures should be taken during rail maintenance in order to mitigate the rail surface-initiated rolling contact fatigue damage, e.g. by keeping the wheel–rail friction coefficient below 0.3.

레일 경좌에 따른 고속철도 차륜답면형상의 접촉파라미터 분석

레일 경좌에 따른 고속철도 차륜답면형상의 접촉파라미터 분석

Investigation of the formation of corrugation-induced rail squats based on extensive field monitoring

Rail squats originate from a number of sources, such as corrugations, indentations and welds. A five-year continual field monitoring study was performed on squats induced by corrugations. This study indicated that a small black depression formed at the corrugation under wheel-rail dynamic forces, and then, a primary crack typically initiated on the gauge side edge of the depression. Subsequently, the crack began to propagate in the rail surface in a U shape toward the gauge side in both the traffic direction and the opposite-traffic direction and into the rail toward the field side at an angle of approximately 20°. Rail inclination could influence the crack initiation location and propagation path. The geometry of the black squat depression was initially elliptical, and then, its edge followed the U-shaped cracking path as it grew. The squats turned into a kidney-like shape, typically with a U-shaped crack. Tensile stress likely led to the squat crack initiation and propagation. This cracking phenomenon and mechanism are analogous to the ring/cone crack formation of brittle materials under sphere-sliding contact. As the squats grew further, a ridge formed in the middle part of the depression, and an I-shaped crack appeared at this ridge due to the impact of the wheels. This process eventually led to two-lung-shaped mature squats, typically with a Y-shaped crack. The findings of this paper provide insight into the formation of rail squats.

Study of fatigue crack initiation location of wheel and rail under rolling contact using finite element method

The rail transit system is widely used for freight and passenger transportation. Due to the fact that its economic worthiness and high safety mode. Maintenance and damage prevention of wheel and rail are important factors affecting the safety of the system. The previous studies show that the most damage of wheel and rail is fatigue cracking, which is caused by the contact stress resulting from wheel and rail interaction. This article presents the study of the fatigue crack initiation location of wheel and rail under rolling contact at the wheel speed of 80 km/h using Finite Element Method (FEM). The three dimensional finite element models were created using the UIC60E1 wheel profile and BS100 rail profile. The Dang Van criteria was applied to analyse the fatigue crack initiation location in case of the wheel's position was changed along the rail lateral direction while the rail inclination angle was also varied at 0, 1/40, 1/30 and 1/20, respectively. The analysing results show that the fatigue crack initiation, determined by the Dang Van stress ratio, tends to increase when the wheel is moved from gauge side to field side. Additionally, the fatigue crack damage is likely to decrease when the rail inclination increases up to the inclination of 1/30 and the fatigue crack initiation locations were found underneath the wheel and rail surfaces. The obtained result can be a primary guideline for maintenance planning.

Design of high-speed turnouts and crossings

Recently, the new ways to improve the railway switches and crossings have been sought, as the railway transport increases its operating speed. The expectation of these adjustments is to decrease the dynamic load, which usually increases together with velocity, and this influences the comfort of the vehicle passage, the wear of the structural parts and the cost of maintenance. These adjustments are primarily the turnout elements such as the optimized geometry of the turnout branch line by means of transition curves application, which minimizes the lateral acceleration during the vehicle passage through the track curve. The rail inclination is solved either by means of inclination in fastening system, or by machining of the rail head shape, because this ways of adjustment retain the wheel-rail interaction characteristics along the whole length of the turnout. Secondly, it is the crossing with movable part, which excludes the interruption of the running surface and optimization of the railway stiffness throughout the whole turnout length as well. We can see that the different stiffness along the turnout influences the dynamic load and it is necessary to optimize the discontinuities in the stiffness along the whole length of the turnout. For this purpose, the numeric modeling is carried out to seek the areas with the highest stiffness and subsequently, the system of stiffness optimization will be designed.

Numerical analysis of the effect of track parameters on the wear of turnout rails in high-speed railways

In this study, a numerical procedure is developed to predict the wear of turnout rails, and the effect of track parameters is investigated. The procedure includes simulation of the dynamic interaction between the train and the turnout, the rolling contact analysis, and the wear model. The dynamic interaction is simulated with the validated commercial software Simpack that uses a space-dependent model of a railway turnout. To reproduce the actual operating conditions of a railway turnout, stochastic variations in the input parameters are considered in the simulation of the dynamic interaction. The rolling contact is analyzed with the semi-Hertzian method and improved FASTSIM algorithm, which enable the contact model to deal with situations of multipoint contact and nonelliptic contact. Based on the Archard’s wear law, the wear model requires the calculation of normal/tangential stresses and a relative slide on the contact patches. The numerical procedure is performed for the selected sections of the vehicle, which runs through the railway turnout in the diverging route. By using the numerical procedure, the effect of track parameters (track gage, rail inclination, and friction coefficient) on the wear of turnout rails is analyzed. The results show that the wear of the front wheelset is more serious than the wear of the rear wheelset for a single vehicle. The degree of wear of switch rails is more severe than that of the stock rails and the difference is more obvious for the front wheelset of the switch rails. The wear of switch rails is mainly concentrated on the rail gage corner, while the wear of stock rails is mainly concentrated on the rail crown. For the analysed CN60-1100-1:18 turnout and the high-speed vehicle CRH2 in China, the rail wear rate could be slowed down by increasing the track gage and decreasing the rail inclination. Alternatively, the rail wear rate could be slowed by decreasing the friction coefficient; however, the variation of wear depth is quite small for friction coefficients that are larger than 0.3.

Dynamics and stability analysis of a freight wagon subjective to the railway track and wheelset operational conditions

Abstract In order to enhance railway freight bogie dynamic behavior, a proposal is made for varying the axle box clearances. In essence it introduces nonlinear effects and plays an important role for the bogie dynamic performance. This research involves investigation on the effects of axle box clearances, variation of the wheel-rail friction coefficient and the track curve radius on rail vehicle nonlinear critical speed. Bifurcation diagrams and system dynamic behavior are calculated. Possibility for chaotic solutions and the effect of axle box clearances on bogie curving are also studied. Rail vehicle specifications and the track related parameters originate from real operational conditions. The effects of axle box clearances on wheel wear are examined. The consequences of wheel-rail profile geometry, contact point distribution for various rail inclinations on vehicle curving are considered. The results are debated and recommendations are proposed to improve the vehicle dynamic performance.

3호선 실제선로 조건에서의 레일경좌 변화에 따른 철도차량 주행안전성 해석

It is very hard to analyze the train derailment safety quantitatively at the curved section because of the diversified affect parameters including the complex interaction between wheel and rail, the train conditions such as the shape of wheel, suspension system, the track conditions such as the radius of curve, cant, transition curve, and the operation conditions, etc. Two major factors related to the running safety of railway vehicle are classified as the railway vehicle and the track condition. In this study, when the railway vehicle passing through curves of actual track condition of subway line NO.3 in seoul (<TEX>$Yeonsinnae{\leftrightarrow}Gupabal$</TEX>), the effect that has influence on running safety depending on rail inclination. The analysis result of 1/40 rail inclination condition is more favorable on running safety than other rail inclination conditions because derailment coefficient and wheel unloading ratio are the lowest.

Switch panel design based on simulation of accumulated rail damage in a railway turnout

A methodology for numerical prediction of accumulated rail damage in railway turnouts is presented. Based on simulation of dynamic vehicle-track interaction followed by a discretisation of the conditions in each wheel-rail contact, distributions of rail wear are calculated by the Archard model of sliding wear, while surface initiated rolling contact fatigue (RCF) damage is evaluated by the Palmgren–Miner rule and an index building on shakedown theory. Partial slip in the wheel-rail contacts and variable amplitude loading are considered. For freight traffic in the diverging route, the influence of rail inclination and switch rail elevation on damage in the switch panel is investigated in a demonstration example. Two-point contact situations with one contact on the switch rail and one on top of the stock rail induce relative motion and slip between wheel and rail leading to high energy dissipation. In agreement with field observations, it is concluded that wear is the dominating damage mechanism on the gauge side of the switch rail while the risk for RCF is higher on the crowns of the switch and stock rails. For accurate prediction of rail life for given combinations of wheel/rail materials and traffic conditions, the methodology needs to be calibrated by field measurements.

Modeling wear and rolling contact fatigue: Parametric study and experimental results

A recently developed simulation model is used to study wear and rolling contact fatigue crack initiation. The model is capable of predicting the damage pattern observed in a full-scale test-rig experiment with respect to crack initiation and wear under conformal contact conditions. The crack initiation model assesses the propensity for rolling contact fatigue crack initiation at the surface of rails based on the combined assessment of the rolling contact stresses and the plastic shear strain distribution in a near-surface layer. Crack initiation is not necessarily linked to low wear rates. If favorable microstructural crack paths away from the surface exist, crack initiation can also take place in parts of the rail where high wear rates are observed. The parametric study shows that an increasing angle of attack of the wheel and an increasing coefficient of friction lead to an increase in the profile height change at the gauge corner of the rail. Likewise, the effective stress for crack initiation at the gauge corner of the rail increases with both an increasing angle of attack and an increasing coefficient of friction, but it is insensitive with respect to small changes in the rail inclination under test rig conditions.

Sensitivity analysis of the wheel–rail normal contact on the basis of continuous factors

The exact characterization of the wheel–rail normal contact situations is essential for its wear, fatigue, and guidance analysis. To simulate this contact, numerous input parameters are required. Many of them have to be estimated. The aim of this sensitivity analysis was to investigate the direct effects and interactions of the input parameters on the contact pressure distribution of a freight wagon wheel on a straight track. For this purpose, a finite element model was parametrized in such a way that all the parameters were continuous. This research demonstrates that the output parameters of the wheel–rail contact simulations have a broad deviation and the input variable with the most influence on the contact form and position is the lateral displacement of the wheelset. Nevertheless, the profile shape of the wheel and rail, the wheel radius, and the relative wheel–rail inclination are important input parameters as well, and also need to be considered for exact simulations of the wheel–rail contact. On the other hand, the deviation of material parameters of wheel and rail steel can be neglected.

Spectral analysis of accelerations measured on a passenger car as a fault-detection technique

This paper presents a dynamic simulation study of a passenger car. The passenger car is equipped with a standard Polish bogie 25ANa. The bogie 25ANa has been designed by Ryszard Suwalski [1]. Spectral analyzes performed to detect damage to the vehicle suspension. In studies used a multi-body, dynamic calculation system SIMPACK 9.5. All analysis presented here are based on the standard wheel-rail profile combination S1002/UIC60, the rail inclination 1/40. The accelerations from the dynamic simulation used to calculate and create spectral markers. Spectra calculated using the Fourier transform

Track loading limits and cross-acceptance of vehicle approvals

The requirements for track loading limits are one of the main barriers to simple cross-acceptance of vehicles where rolling stock that is already operating successfully in one (or more) networks has to be retested before it can be approved for operation on another network. DynoTRAIN Work Package 4 studied this area in order to determine whether the additional requirements were justified, or if the process could be made much cheaper and simpler without increasing the risk of track deterioration for the networks. The review of national requirements identified modified criteria and limit values for track forces in some member states; however, these can be obtained from additional analysis of the normal test results with no new tests required. The influence of design rail inclination has also been found not to be significant, provided a realistic range of wheel–rail contact conditions are included in the tests. For line speeds greater than or equal to 160 km/h, the current standards for track construction across the member states appear to be similar. On lower speed lines in some countries, a ‘weaker’ track condition may require a lower limit on one of the vehicle assessment parameters. Track dynamics modelling has shown that the vehicle assessment parameters used in international standards are suitable for use in cross-acceptance for track forces. The use of multiple regression analysis allows the estimated maximum value for relevant parameters to be evaluated for different target conditions and then compared with the appropriate limit value, or with values for existing, comparable vehicles. Guidance has also been provided on the relevant parameters to consider when developing operating controls for different types of track deterioration.

A multi-national survey of the contact geometry between wheels and rails

The project DynoTRAIN, which was funded under the European Seventh Framework Programme, was set-up in order to close the open points in the Technical Specification of Interoperability (TSI) of the trans-European rail system. The project was divided in seven work packages. The focus in work package 3 (WP 3) was the contact geometry between wheels and rails. More general information about the DynoTRAIN project is given in the foreword of this special edition. WP 3 was split into several tasks. In the first and second tasks worn wheel and rail profiles were collected. Since the wear behaviour of wheels and rails depends (among other factors) on bogie design, operating conditions, rail inclination and curve radius, a large number of wheel and rail profiles were investigated in order to obtain a representative picture of the contact conditions on the trans-European network. The wheel and rail profiles were analysed in terms of equivalent conicity, which is an important indicator for the running stability of railway vehicles. Based on the collected data, reference profiles for wheels and rails were defined for the calculation of conicity maps. The reference wheel and rail profiles act as a sort of coordinate (scaling) system for the conicity maps. The conicity maps were calculated from selected wheel and rail profiles that had the same frequency distribution as the whole sample. The conicity maps were calculated for different speed categories and for wheels operating on networks with rail inclinations of 1/20 and 1/40. Finally, limit values of the equivalent concity for the authorization of vehicles and in-service limits for tracks were derived from these conicity maps. This approach enabled the open point ‘equivalent conicity’ in the TSI: Locomotives and Passenger Rolling Stock and TSI: Infrastructure to be closed.

1D11 Running Safety Analysis of Railway Vehicle depending on Rail Inclination Change on Actual Track Conditions(Vehicles-Dynamics)

1D11 Running Safety Analysis of Railway Vehicle depending on Rail Inclination Change on Actual Track Conditions(Vehicles-Dynamics)

Calculating the Contact Stress Resulting from Lateral Movement of the Wheel on Rail by Applying Hertz Theory

This article has tried to review the maximum contact stresses in the contact area of the wheel and rail as a result of lateral movement of the wheel on rail by taking advantage from Hertz theory. Since wheel movement on rail is accompanied by lateral movement due to wheel profile conisity, so the contact point of wheel and rail is not constant and the contact stresses are therefore changeable in every single moment. Since the shape of rail profile and rail inclination, wheel diameter and the mechanical properties of the wheel and rail are effective on the stresses of contact area, these parameters have been studied by applying Hertz theory. This article aims to calculate the contact stresses in different parts on the wheel surface by using Hertz theory.