Computer simulation techniques can be used to quantify the effects of changes to railway vehicle ... more Computer simulation techniques can be used to quantify the effects of changes to railway vehicle and track parameters and the likelihood of derailment. Using this knowledge the precise effects of possible changes to vehicle and track standards can be evaluated. In this paper these tools have been used to analyse the nature of the interaction of vehicles running over twisted track.
The dynamic behavior of vehicle and track systems is studied in the presence of an insulated rail... more The dynamic behavior of vehicle and track systems is studied in the presence of an insulated rail joint through a two-dimensional vehicle-track coupling model. The track system is described as a finite length beam resting on a double layer discrete viscous-elastic foundation. The vehicle is represented through a half car body and a single bogie. These sub-systems are solved independently and coupled together through a Hertzian contact model, where the irregularity caused by the rail joint is modelled as a second order polynomial. A parametric study is carried out in order to understand the influence by the main track and vehicle parameters to the P1 and P2 peak forces. Finally, the results in terms of P2 force from the present model have been compared not only with measured values but also with both other simulated and analytical solutions and an excellent agreement between these values has been found.
Accurate modelling of railway ballasted track dynamics is an important issue for a variety of app... more Accurate modelling of railway ballasted track dynamics is an important issue for a variety of applications such as the assessment of wheel/rail contact force and critical speed of the vehicle. Track design and assessment against safety and stability criteria can now rely on a number of advanced and validated dynamic models. However, there is a large range of different models that can be used to predict ballasted track dynamics. They vary from fast and simple rigid multi-body models as used in commercial Multibody System approach (MBS) vehicle dynamics calculations, to more complex and expensive three-dimensional (3D) Finite Element (FE) models. This paper investigatesthe influence of different modelling options up to 2000 Hz for characterising ballasted track dynamics with the aim of providing guidelines for simplifying the model and summarising the advantages and limitations of each option. Five different models, a two-degrees-of-freedom (2 dof) multi-body track model, 2D FE model,...
This paper details the field-testing approach and results of thermite welds used in railway appli... more This paper details the field-testing approach and results of thermite welds used in railway applications. Rail steels made from R260 grades are welded by two different processes: the standard process according to the European standards, and a recent technology. Welds are introduced in the same testing location to ensure comparable loading conditions in the aim of studying their degradation behaviours. The total testing-period is 6 months. During the in-service period, the surface hardness of the running band, in the welded area, is recurrently measured. For an accurate assessment of field results, a vehicle/track interaction (VTI) model evaluated the expected dynamic loads induced by the initial vertical irregularities. The simulations show that the highest dynamic load at the wheel/rail contact happens at the location of the maximum absolute gradient, in accordance with previous research. Particularly, dipped welds show relatively high dynamic forces inducing a high loss of the tra...
Multi-body system models of two typical UK railway locomotives running on a range of curves have ... more Multi-body system models of two typical UK railway locomotives running on a range of curves have been simulated in ADAMS/Rail and the predicted wheel-rail contact forces have been used to generate stresses using two ABAQUS finite element models. The predicted forces were validated against test measurements from one site on the UK rail network. The first ABAQUS model represents a global length of railway track with ballast and sleepers. The second model is a more detailed 3 dimensional contact model that includes a section of wheel running on a length of rail. This method allows integration between the two software packages, with dynamic forces from the vehicle simulation being transferred to the FE models. The global track model predicts the bending stresses in the rail while the wheel-rail contact model predicts the contact stresses in the rail head. This information can then be used to develop an understanding of the process of rolling contact fatigue, crack initiation and crack g...
Running characteristics’ of rolling stock are assessed using a process defined in EN 14363. Track... more Running characteristics’ of rolling stock are assessed using a process defined in EN 14363. Track geometry is an essential parameter for this. This contribution describes methods for dealing with track geometry in the assessment process and some proposals for an improvement. Different types of track geometry characterisation are assessed on their effectiveness in describing the running characteristics in a regression model. The test data gathered in Dynotrain is used for this. Multiple regression is proposed to be used as a method to transform test data from one set of track geometry conditions to another set. This allows the quantification of the influence of track geometry on the vehicle’s running behaviour.
A method to introduce the simulation in the railway certification process is described in this st... more A method to introduce the simulation in the railway certification process is described in this study. Since the track / vehicle system is non-linear, and since critical situations (rare events) are considered, the modelling of the excitations (running conditions for example) must be very precise and representative. These are moreover related to poorly determined parameters which can vary along the track and during the life cycle of the system : the friction coefficient for example depends on the weather conditions; the rail profile depends on the radius of the track, as well as on tonnage. In order to have a relevant certification, the method proposed thus insists on the introduction of the variability in the simulation and presents a sensitivity analysis.
Railway track support conditions are known to deeply affect the dynamic performance of vehicle-tr... more Railway track support conditions are known to deeply affect the dynamic performance of vehicle-track interaction, influencing the state of the track system both in the short and in the long term. Exactly how much and how is not precisely understood and the notion of track stiffness, although thought to be a key parameter of the track quality, is currently not being monitored systematically. This paper seeks to analyse the influence on the ballast behaviour of track vertical stiffness and especially its spatial non-uniformity, using available experimental data measured at different sites. Mathematical models are developed and the effectiveness of applying under sleeper pads is also investigated. Finally, an iterative procedure based on Guerin’s settlement law is used to take into account the long-term behaviour of the ballast. Such models can help to understand mitigation solutions as well as predicting track quality evolution over time.
ABSTRACT Running characteristics of rolling stock are assessed using a process defined in EN 1436... more ABSTRACT Running characteristics of rolling stock are assessed using a process defined in EN 14363. Track geometry is an essential parameter for this. This contribution describes methods for dealing with track geometry in the assessment process and some proposals for an improvement. Different types of track geometry characterisation are assessed on their effectiveness in describing the running characteristics in a regression model. The test data gathered in Dynotrain is used for this. Multiple regression is proposed to be used as a method to transform test data from one set of track geometry conditions to another set. This allows the quantification of the influence of track geometry on the vehicle's running behaviour.
This poster, providing an overview of the Spectrum freight bogie, was presented at the Railway En... more This poster, providing an overview of the Spectrum freight bogie, was presented at the Railway Engineers Forum (REF) Technical Seminar held at the Institution of Civil Engineers on the 15th June 2015.
A discretely supported track model was built in multibody dynamic software VI-Rail. The model was... more A discretely supported track model was built in multibody dynamic software VI-Rail. The model was first compared against the default continuously supported track model and an in-house built finite element model. A plain line case with a short wavelength irregularity was used and a good agreement between the three models was achieved. A full turnout model including both through and divergent routes was then built. A detailed model of a UK passenger coach was used for the vehicle-track interaction simulations. The main focus of this paper is to compare different approaches to model the track, highlighting the capabilities of the selected methodology and give an insight into the influence of model approaches in the S&C panels.
Developing resilient and reliable switches and crossings is one of the key challenges of the rail... more Developing resilient and reliable switches and crossings is one of the key challenges of the railways for the future. Understanding the detailed interaction between the railway vehicle and the track is paramount in order to develop sustainable railway track components. In this paper, an investigation is carried out on the relative movement between the switch and stock rails under dynamics loading and the effect of their relative connection on the wheel/rail interface and the vehicle-track response. To do this, a multibody dynamics software track model is modified and compared to the default approach of using one solid rail profile throughout the switch-stock rail assembly. The results show that significant differences are present when the relative motion between switch and stock rail is accounted for. A sensitivity analysis on the modelling approach and rail-pad stiffness properties is also considered, showing that in comparison there is relatively much less variation based on track support properties. It is concluded that to accurately predict the dynamic behaviour of vehicle and track in switches it is crucial to account for the relative connection between the switch and stock rail and model them as two independent rail bodies.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit
The performance of switches and crossings compared with plain line is complicated by the presence... more The performance of switches and crossings compared with plain line is complicated by the presence of movable parts, changing rail geometry and non-uniformities in the composite and/or trackbed stiffness. These features lead to complex vehicle–track interactions and higher maintenance costs. The trackbed stiffness is the least well-controlled engineering property. A greater variability in trackbed stiffness leads to higher differential trackbed settlement and associated poorer track quality. At switches and crossings, changes in trackbed stiffness are exacerbated by changing rail properties which also contribute to changes in the overall composite track stiffness. This work focuses on the role of variations in stiffness on the performance of switches and crossings. Field measurements of bearer displacement were carried out using geophones at a switch and crossing equipped with under sleeper pads. The vehicle–switch and crossing interaction was modelled using a multi-body system and f...
Computer simulation techniques can be used to quantify the effects of changes to railway vehicle ... more Computer simulation techniques can be used to quantify the effects of changes to railway vehicle and track parameters and the likelihood of derailment. Using this knowledge the precise effects of possible changes to vehicle and track standards can be evaluated. In this paper these tools have been used to analyse the nature of the interaction of vehicles running over twisted track.
The dynamic behavior of vehicle and track systems is studied in the presence of an insulated rail... more The dynamic behavior of vehicle and track systems is studied in the presence of an insulated rail joint through a two-dimensional vehicle-track coupling model. The track system is described as a finite length beam resting on a double layer discrete viscous-elastic foundation. The vehicle is represented through a half car body and a single bogie. These sub-systems are solved independently and coupled together through a Hertzian contact model, where the irregularity caused by the rail joint is modelled as a second order polynomial. A parametric study is carried out in order to understand the influence by the main track and vehicle parameters to the P1 and P2 peak forces. Finally, the results in terms of P2 force from the present model have been compared not only with measured values but also with both other simulated and analytical solutions and an excellent agreement between these values has been found.
Accurate modelling of railway ballasted track dynamics is an important issue for a variety of app... more Accurate modelling of railway ballasted track dynamics is an important issue for a variety of applications such as the assessment of wheel/rail contact force and critical speed of the vehicle. Track design and assessment against safety and stability criteria can now rely on a number of advanced and validated dynamic models. However, there is a large range of different models that can be used to predict ballasted track dynamics. They vary from fast and simple rigid multi-body models as used in commercial Multibody System approach (MBS) vehicle dynamics calculations, to more complex and expensive three-dimensional (3D) Finite Element (FE) models. This paper investigatesthe influence of different modelling options up to 2000 Hz for characterising ballasted track dynamics with the aim of providing guidelines for simplifying the model and summarising the advantages and limitations of each option. Five different models, a two-degrees-of-freedom (2 dof) multi-body track model, 2D FE model,...
This paper details the field-testing approach and results of thermite welds used in railway appli... more This paper details the field-testing approach and results of thermite welds used in railway applications. Rail steels made from R260 grades are welded by two different processes: the standard process according to the European standards, and a recent technology. Welds are introduced in the same testing location to ensure comparable loading conditions in the aim of studying their degradation behaviours. The total testing-period is 6 months. During the in-service period, the surface hardness of the running band, in the welded area, is recurrently measured. For an accurate assessment of field results, a vehicle/track interaction (VTI) model evaluated the expected dynamic loads induced by the initial vertical irregularities. The simulations show that the highest dynamic load at the wheel/rail contact happens at the location of the maximum absolute gradient, in accordance with previous research. Particularly, dipped welds show relatively high dynamic forces inducing a high loss of the tra...
Multi-body system models of two typical UK railway locomotives running on a range of curves have ... more Multi-body system models of two typical UK railway locomotives running on a range of curves have been simulated in ADAMS/Rail and the predicted wheel-rail contact forces have been used to generate stresses using two ABAQUS finite element models. The predicted forces were validated against test measurements from one site on the UK rail network. The first ABAQUS model represents a global length of railway track with ballast and sleepers. The second model is a more detailed 3 dimensional contact model that includes a section of wheel running on a length of rail. This method allows integration between the two software packages, with dynamic forces from the vehicle simulation being transferred to the FE models. The global track model predicts the bending stresses in the rail while the wheel-rail contact model predicts the contact stresses in the rail head. This information can then be used to develop an understanding of the process of rolling contact fatigue, crack initiation and crack g...
Running characteristics’ of rolling stock are assessed using a process defined in EN 14363. Track... more Running characteristics’ of rolling stock are assessed using a process defined in EN 14363. Track geometry is an essential parameter for this. This contribution describes methods for dealing with track geometry in the assessment process and some proposals for an improvement. Different types of track geometry characterisation are assessed on their effectiveness in describing the running characteristics in a regression model. The test data gathered in Dynotrain is used for this. Multiple regression is proposed to be used as a method to transform test data from one set of track geometry conditions to another set. This allows the quantification of the influence of track geometry on the vehicle’s running behaviour.
A method to introduce the simulation in the railway certification process is described in this st... more A method to introduce the simulation in the railway certification process is described in this study. Since the track / vehicle system is non-linear, and since critical situations (rare events) are considered, the modelling of the excitations (running conditions for example) must be very precise and representative. These are moreover related to poorly determined parameters which can vary along the track and during the life cycle of the system : the friction coefficient for example depends on the weather conditions; the rail profile depends on the radius of the track, as well as on tonnage. In order to have a relevant certification, the method proposed thus insists on the introduction of the variability in the simulation and presents a sensitivity analysis.
Railway track support conditions are known to deeply affect the dynamic performance of vehicle-tr... more Railway track support conditions are known to deeply affect the dynamic performance of vehicle-track interaction, influencing the state of the track system both in the short and in the long term. Exactly how much and how is not precisely understood and the notion of track stiffness, although thought to be a key parameter of the track quality, is currently not being monitored systematically. This paper seeks to analyse the influence on the ballast behaviour of track vertical stiffness and especially its spatial non-uniformity, using available experimental data measured at different sites. Mathematical models are developed and the effectiveness of applying under sleeper pads is also investigated. Finally, an iterative procedure based on Guerin’s settlement law is used to take into account the long-term behaviour of the ballast. Such models can help to understand mitigation solutions as well as predicting track quality evolution over time.
ABSTRACT Running characteristics of rolling stock are assessed using a process defined in EN 1436... more ABSTRACT Running characteristics of rolling stock are assessed using a process defined in EN 14363. Track geometry is an essential parameter for this. This contribution describes methods for dealing with track geometry in the assessment process and some proposals for an improvement. Different types of track geometry characterisation are assessed on their effectiveness in describing the running characteristics in a regression model. The test data gathered in Dynotrain is used for this. Multiple regression is proposed to be used as a method to transform test data from one set of track geometry conditions to another set. This allows the quantification of the influence of track geometry on the vehicle's running behaviour.
This poster, providing an overview of the Spectrum freight bogie, was presented at the Railway En... more This poster, providing an overview of the Spectrum freight bogie, was presented at the Railway Engineers Forum (REF) Technical Seminar held at the Institution of Civil Engineers on the 15th June 2015.
A discretely supported track model was built in multibody dynamic software VI-Rail. The model was... more A discretely supported track model was built in multibody dynamic software VI-Rail. The model was first compared against the default continuously supported track model and an in-house built finite element model. A plain line case with a short wavelength irregularity was used and a good agreement between the three models was achieved. A full turnout model including both through and divergent routes was then built. A detailed model of a UK passenger coach was used for the vehicle-track interaction simulations. The main focus of this paper is to compare different approaches to model the track, highlighting the capabilities of the selected methodology and give an insight into the influence of model approaches in the S&C panels.
Developing resilient and reliable switches and crossings is one of the key challenges of the rail... more Developing resilient and reliable switches and crossings is one of the key challenges of the railways for the future. Understanding the detailed interaction between the railway vehicle and the track is paramount in order to develop sustainable railway track components. In this paper, an investigation is carried out on the relative movement between the switch and stock rails under dynamics loading and the effect of their relative connection on the wheel/rail interface and the vehicle-track response. To do this, a multibody dynamics software track model is modified and compared to the default approach of using one solid rail profile throughout the switch-stock rail assembly. The results show that significant differences are present when the relative motion between switch and stock rail is accounted for. A sensitivity analysis on the modelling approach and rail-pad stiffness properties is also considered, showing that in comparison there is relatively much less variation based on track support properties. It is concluded that to accurately predict the dynamic behaviour of vehicle and track in switches it is crucial to account for the relative connection between the switch and stock rail and model them as two independent rail bodies.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit
The performance of switches and crossings compared with plain line is complicated by the presence... more The performance of switches and crossings compared with plain line is complicated by the presence of movable parts, changing rail geometry and non-uniformities in the composite and/or trackbed stiffness. These features lead to complex vehicle–track interactions and higher maintenance costs. The trackbed stiffness is the least well-controlled engineering property. A greater variability in trackbed stiffness leads to higher differential trackbed settlement and associated poorer track quality. At switches and crossings, changes in trackbed stiffness are exacerbated by changing rail properties which also contribute to changes in the overall composite track stiffness. This work focuses on the role of variations in stiffness on the performance of switches and crossings. Field measurements of bearer displacement were carried out using geophones at a switch and crossing equipped with under sleeper pads. The vehicle–switch and crossing interaction was modelled using a multi-body system and f...
Uploads
Papers by Yann Bezin