Simulation research of railway crossings with stiffness control

This research presents the existing problem of railway elements and motor – vehicle road elements at their intersections. The work also concerns issues of designing and constructing railway crossings at the intersections of motor-vehicle and rail transportation. A new conception of vibroisolated railway crossing is introduced, based on the analysis of a discrete-continuous system

Benefits of mechatronically guided vehicles on railway track switches

Conventional rail vehicles struggle to optimally satisfy the different suspension requirements for various track profiles, such as on a straight track with stochastic irregularities, curved track or switches and crossings (S&C), whereas mechatronically-guided railway vehicles promise a large advantage over conventional vehicles in terms of reduced wheel-rail wear, improved guidance and opening new possibilities in vehicle architecture. Previous research in this area has looked into guidance and steering using MBS models of mechatronic rail vehicles of three different mechanical configurations - secondary yaw control (SYC), actuated solid-axle wheelset (ASW) and driven independently-rotating wheelsets (DIRW). The DIRW vehicle showed the best performance in terms of reduced wear and minimal flange contact and is therefore chosen in this paper for studying the behaviour of mechatronically-guided rail vehicles on conventional S&Cs. In the work presented here, a mechatronic vehicle with the DIRW configuration is run on moderate and high speed track switches. The longer term motivation is to perform the switching function from on-board the vehicle as opposed to from the track as is done conventionally. As a first step towards this, the mechatronic vehicle model is compared against a conventional rail vehicle model on two track scenarios - a moderate speed C type switch and a high speed H switch. A multi-body simulation software is used to produce a high fidelity model of an active rail vehicle with independentlyrotating wheelsets (IRWs) where each wheel has an integrated ’wheelmotor’. This work demonstrates the theory that mechatronic rail vehicles could be used on conventional S&Cs. The results show that the mechatronic vehicle gives a significant reduction in wear, reduced flange contact and improved ride quality on the through-routes of both moderate and high speed switches. On the diverging routes, the controller can be tuned to achieve minimal flange contact and improved ride quality at the expense of higher creep forces and wear

Benefits of mechatronically guided vehicles on railway track switches

Conventional rail vehicles struggle to optimally satisfy the different suspension requirements for various track profiles, such as on a straight track with stochastic irregularities, curved track or switches and crossings (S&C), whereas mechatronically-guided railway vehicles promise a large advantage over conventional vehicles in terms of reduced wheel-rail wear, improved guidance and opening new possibilities in vehicle architecture. Previous research in this area has looked into guidance and steering using MBS models of mechatronic rail vehicles of three different mechanical configurations - secondary yaw control (SYC), actuated solid-axle wheelset (ASW) and driven independently-rotating wheelsets (DIRW). The DIRW vehicle showed the best performance in terms of reduced wear and minimal flange contact and is therefore chosen in this paper for studying the behaviour of mechatronically-guided rail vehicles on conventional S&Cs. In the work presented here, a mechatronic vehicle with the DIRW configuration is run on moderate and high speed track switches. The longer term motivation is to perform the switching function from on-board the vehicle as opposed to from the track as is done conventionally. As a first step towards this, the mechatronic vehicle model is compared against a conventional rail vehicle model on two track scenarios - a moderate speed C type switch and a high speed H switch. A multi-body simulation software is used to produce a high fidelity model of an active rail vehicle with independentlyrotating wheelsets (IRWs) where each wheel has an integrated ’wheelmotor’. This work demonstrates the theory that mechatronic rail vehicles could be used on conventional S&Cs. The results show that the mechatronic vehicle gives a significant reduction in wear, reduced flange contact and improved ride quality on the through-routes of both moderate and high speed switches. On the diverging routes, the controller can be tuned to achieve minimal flange contact and improved ride quality at the expense of higher creep forces and wear

Railway track condition assessment at network level by frequency domain analysis of GPR data

The railway track system is a crucial infrastructure for the transportation of people and goods in modern societies. With the increase in railway traffic, the availability of the track for monitoring and maintenance purposes is becoming significantly reduced. Therefore, continuous non-destructive monitoring tools for track diagnoses take on even greater importance. In this context, Ground Penetrating Radar (GPR) technique results yield valuable information on track condition, mainly in the identification of the degradation of its physical and mechanical characteristics caused by subsurface malfunctions. Nevertheless, the application of GPR to assess the ballast condition is a challenging task because the material electromagnetic properties are sensitive to both the ballast grading and water content. This work presents a novel approach, fast and practical for surveying and analysing long sections of transport infrastructure, based mainly on expedite frequency domain analysis of the GPR signal. Examples are presented with the identification of track events, ballast interventions and potential locations of malfunctions. The approach, developed to identify changes in the track infrastructure, allows for a user-friendly visualisation of the track condition, even for GPR non-professionals such as railways engineers, and may further be used to correlate with track geometric parameters. It aims to automatically detect sudden variations in the GPR signals, obtained with successive surveys over long stretches of railway lines, thus providing valuable information in asset management activities of infrastructure managers

The effect of railway local irregularities on ground vibration

The environmental effects of ground-borne vibrations generated due to localised railway defects is a growing concern in urban areas. Frequency domain modelling approaches are well suited for predicting vibration levels on standard railway lines due to track periodicity. However, when considering individual, non-periodic, localised defects (e.g. a rail joint), frequency domain modelling becomes challenging. Therefore in this study, a previously validated, time domain, three-dimensional ground vibration prediction model is modified to analyse such defects. A range of different local (discontinuous) rail and wheel irregularity are mathematically modelled, including: rail joints, switches, crossings and wheel flats. Each is investigated using a sensitivity analysis, where defect size and vehicle speed is varied. To quantify the effect on railroad ground-borne vibration levels, a variety of exposure–response relationships are analysed, including: peak particle velocity, maximum weighted time-averaged velocity and weighted decibel velocity. It is shown that local irregularities cause a significant increase in vibration in comparison to a smooth track, and that the vibrations can propagate to greater distances from the line. Furthermore, the results show that step-down joints generate the highest levels of vibration, whereas wheel flats generate much lower levels. It is also found that defect size influences vibration levels, and larger defects cause greater vibration. Lastly, it is shown that for different defect types, train speed effects are complex, and may cause either an increase or decrease in vibration levels

A New Switch and Crossing Design: Introducing the Back to Back Bistable Switch

A new track swtich and crossing (S&C), the back to back bistable (B2B) switch, is proposed that has shown potential to significantly reduce the wheel/rail contact forces through the switch due to its more continuous wheel/rail contact interface and more uniform track stiffness arising from the elimination of the crossing nose. This offers a major reduction on maintenance cost of future S&Cs. The paper explains the concept and identifies the design guidelines for a current layout and uses vehicle/turnout dynamic modelling to predict wheel rail forces through a switch to identify performance improvements relative to a conventional S&C. Both multi-body simulation (MBS) and Finite Element (FE) model have been developed to account for dynamic and thermal analysis. The new design has shown improvements in lateral and vertical wheel-rail contact forces and less relative rail displacements due to thermal effect compared to the conventional S&C

The Development of modelling tools for railway switches and crossings

Network Rail records indicate that approximately 24% of the total track maintenance and renewal budgets are spent on railway switches and crossings (S&C), which account for only 5% of the total main line track mileage. S&C complexities also introduce a degree of risk, which must be adequately managed to ensure a safe and reliable network. In recent years, risk mitigation fell short, resulting in some high profile incidents at S&C. A recent derailment investigation uncovered knowledge gaps within the UK rail industry, including the understanding of S&C degradation. This PhD research project was therefore initiated to investigating modelling tools for S&C wheel-rail interaction and degradation. A new wheel-rail contact detection routine has been developed and validated using existing software and a novel experimental technique using thermal imagery. Existing techniques were then integrated to enable the prediction of normal and tangential contact stresses whilst also simulating wear accumulation. To improve accuracy for long-term S&C damage, a combined tool for assessing non-Hertzian normal contact stresses and multiple modes of S&C degradation was sought. A novel 2.5D boundary element model capable of simulating wheel-rail contact detection, surface and sub-surface elastic and elastic-plastic stress analysis and dynamic material response is presented. Superior computational effort is also achieved, illustrating further the feasibility of such an approach. To conclude, a three-dimensional dynamic finite element model of a railway wheel passing through a cast manganese crossing has also been developed. For the first time, a tool capable of simulating both dynamic contact forces and corresponding plastic material response has been used to discover flaws within existing designs of UK cast manganese crossings. This approach has enabled immediate recommendations for asset improvement to be provided to Network Rail and gives the UK rail industry more scientific insight into the optimal design of railway crossings.Open Acces