In this paper, we combine engineering and economic methods to estimate the relative maintenance cost of different types of damage on the Swedish rail infrastructure. The engineering method is good at predicting damage from traffic, while the economic method is suitable for establishing a relationship between damage and cost. We exploit the best features of both methods in a two-stage approach and demonstrate its applicability for rail infrastructure charging, based on a sample of 143 track sections comprising about 11,000 km of track. The paper implements for the first time the method previously proposed in Smith et al., whilst also enhancing the method in several respects. We demonstrate how the estimated relative maintenance costs related to different damage mechanisms can be used to calculate the marginal cost of different vehicle types. The results are relevant for infrastructure managers in Europe who wish to differentiate their track access charges such that each vehicle pays its short run-marginal damage cost, which can support more efficient use of the rail infrastructure and influence vehicle design to minimize system costs.

This paper reports on a novel project to develop a fully active, two axle railway vehicle which could provide reduced track forces and noise and improved ride comfort compared with existing vehicles. Computer simulations have been used to tune the suspension components and control systems to ensure good passenger comfort and safe operation even in failed control cases. A prototype of the vehicle has been constructed and tested on a full size roller rig. The test results confirm the computer simulations and demonstrate that for speeds up to 200 km/h and in all failure modes the vehicle was stable and with low track forces and high stability and passenger comfort.

The contact between pantograph and catenary at high speeds suffers from high dynamic contact force variation due to stiffness variations and wave propagation. To increase operational speed on an existing catenary system, especially for soft catenary systems, technical upgrading is usually necessary. Therefore, it is desirable to explore a more practical and cost-saving method to increase the operational speed. Based on a 3D pantograph-catenary finite element model, a parametric study on two-pantograph operation with short spacing distances at high speeds shows that, although the performance of the leading pantograph gets deteriorated, the trailing pantograph feels an improvement if pantographs are spaced at a proper distance. Then, two main positive effects, which can cause the improvement, are addressed. Based on a discussion on wear mechanisms, this paper suggests to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current, to minimise additional wear caused by the leading pantograph. To help implementation and achieve further improvement under this working condition, this paper investigates cases with optimised uplift force on the leading pantograph and with system parameter deviations. The results show that the two positive effects still remain even with some system parameter deviations. About 30% of speed increase should be possibly achieved still sustaining a good dynamic performance with help of the optimised uplift force.

Stiffness variations and wave propagation in the catenary system cause high dynamic variations in the contact force between pantograph and catenary at high operating speeds. In order to increase the operational speed on an existing catenary system, especially on soft catenary systems, technical upgrading is usually required to keep the current collection quality within an acceptable range. Therefore, it is desirable to explore a more practical and cost-saving method to achieve higher operational speed. With the help of a 3D pantograph-catenary finite element (FE) model, a parametric study on two-pantograph operation at short spacing distances is carried out. Results show that although the leading pantograph suffers from deterioration of dynamic performance, the trailing pantograph achieves a better dynamic behaviour by using a proper spacing distance between pantographs. To avoid the additional wear caused by poor dynamic performance on the leading pantograph, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current. In this way, the operational speed of the existing system can be increased while still sustaining a good dynamic performance without large modifications on the existing catenary system.

Trains operating with several pantographs are used in Sweden and other countries. The more complex operational conditions, however, cause additional difficulties, i.e. low quality of current collection, increased mechanical wear and electromagnetic interference, due to the poor dynamic behaviour of the system. In order to address these problems, a three-dimensional model for the computational analysis of the interaction between catenary and pantograph is presented and validated in this paper, and the dynamic behaviour of the multi-pantograph system, based on Swedish soft pantograph/catenary systems, is analysed. Parametric studies are performed to investigate cases with different distances between pantographs and with up to three pantographs in use. The relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, is studied. The results show that an appropriate distance between pantographs and a given type of catenary allow operation on the existing infrastructure with up to three pantographs while maintaining an acceptable dynamic performance at the desired speed.

The Swedish iron ore company LKAB uses freight wagons with three-piece bogies to transport iron ore from its mines in Kiruna and Malmberget to the ports at Luleå and Narvik. A simulation model of the freight wagon is built using the multibody simulation code GENSYS. The objective is to investigate possible sources of rolling contact fatigue (RCF) of the wheels given the high level of observed damage. A parameter study is performed on the effects of vertical track stiffness and viscous damping that occur as a result of seasonal variations of the track condition. Another parameter study is carried out on the influence of the wheel/rail friction coefficient as in winter time the climate is very dry along most parts of the Malmbanan line. The impact of track gauge, track quality and cant deficiency on RCF is also studied. Comparing the calculated and observed RCF locations on wheels, attempts are made to find a relation between wear number and RCF damage. To detect the surface-initiated fatigue a so-called shakedown map is used. It is shown that RCF occurs on the tread of the inner wheels while negotiating curves with below an approximately 450 m radius. It is also shown that cant deficiency can be helpful for the vehicles to negotiate curves and to reduce the risk of RCF, however, on the other hand it may increase the track forces and in severe cases result in flange climbing. Lateral track irregularities and a large track gauge result in small contact areas and can lead to a higher risk of RCF. In cold dry climate conditions, as the water content in air drops significantly, the wheel/rail friction coefficient increases and when the material in the wheel begins to behave in a brittle manner, the risk of RCF is significantly increased, especially when the wear rate is not high enough to remove the initiated cracks.

This paper gives an overview of the state of the art of modelling and simulation of freight wagons. The main focus of the paper is to analyse the impact of freight wagons operation on track and whe ...

Wheel reprofiling costs for freight vehicles are a major issue in Sweden, reducing the profitability of freight traffic operations and therefore hindering the modal shift needed for achieving reduced emissions. In order to understand the damage modes in freight vehicles, uniform wear prediction with Archard's wear law has been studied in a two-axle timber transport wagon, and simulation results have been compared to measurements. Challenges of wheel wear prediction in freight wagons are discussed, including the influence of block brakes and switches and crossings. The latter have a major influence on the profile evolution of this case study, so specific simulations are performed and a thorough discussion is carried out.

As part of the European Commission project ‘SUSTRAIL’ the authors together with other industry and academic partners are designing a freight vehicle optimised for the carriage of high value, low density, time sensitive products. A review of potential engineering innovations has been carried out and a vehicle is being designed based on optimised parameters for this combination of innovative technologies including radial steering, disk braking and optimised bogie frame structure. The results of the selection and optimisation of the running gear are presented heretogether with an assessment of the potential improvement in running behaviour and its impact on the railway system.

Wheel profile evolution has a large influence on track and wheelset related maintenance costs. It influences important parameters such as equivalent conicity or contact point positioning, which will affect the dynamic behavior of the vehicle, in both tangent track and curve negotiation. High axle loads in freight wagons may increase both the wheel wear and the damage caused by vehicles with both new and already worn profiles. A common profile in Europe is the S1002 profile, developed for rail inclination 1/40. In Sweden rail inclination is 1/30, so contact conditions might not be optimal. The presented work uses Archard’s wear law to analyze the profile wear evolution in a two axle freight vehicle with Unitruck running gear on the Swedish network. This wear calculation methodology has been successfully used to predict uniform wear in passenger vehicles. First, the vehicle model has been optimized in order to improve the speed of the wear simulations. Experimental measurements of wheel profiles have been performed in order to validate the simulations. The conclusion is that the wear methodology successfully used to predict uniform wheel wear in passenger vehicles cannot be directly applied for the calculation of wheel profile evolution in high tonnage freight vehicles. The influence of block brakes or switches and crossings cannot be dismissed when calculating uniform wheel wear in these cases.

Wheel reprofiling accounts for a considerable amount of the maintenance costs forfreight wagons in Sweden, and the causes can be divided mainly in three groups:wheel flats, shelling and uniform wear. In this paper the development of uniformwheel wear in a two-axle freight vehicle is studied. This wagon with Unitruckrunning gear had a major modification in the suspension elements in 2005 whichhighly reduced flange wear. The method developed at KTH for uniform wearcalculation is applied on both old and new simulation models. The influence offreight wagon specific characteristics on the wear development is also analysed, i.e.high axle load and friction damping elements.

The current collection using more than one pantograph is needed in railway operation to provide power to non-electrically connected traction units and, in some cases, to reduce current density on the collector strips that heavily influences the wear on the contacting bodies. The multiple current collection may become a critical condition due to the mechanical disturbances produced on the trailing pantographs by the interaction between the first pantograph and the catenary. The present-day evolution of pantograph preload regulating systems, exploiting pressure-controlled servo-valves driven by electronic units, allows a diversification of the preloads of front and rear pantographs. In this work, a suitable solution to improve multiple pantograph collection quality is analysed by the use of a lower mean force on the leading pantograph aimed at reducing the oscillations of contact wire the trailing pantograph is subjected to. This would improve the current collection quality of the trailing pantograph, and could be pursued even admitting a slight worsening of front pantograph's performances.

The Previous freight wagon model developed at KTH is able to explain many of the phenomena observed in tests. In some cases. however, simulated and measured running behaviour differ. Therefore, in this paper, a new simulation model is presented and validated with on-track test results. The performance of standard two-axle freight wagons is investigated. The most important parameters for the running:behaviour of the vehicle are the suspension characteristics. The variation in characteristics between different wagons is large due to geometrical tolerances of the components, wear, corrosion, moisture or other lubrication. The influence of the variation in suspension characteristics and other Parameters oil the behaviour of the wagon on tangent track and in curves is discussed. Finally, suggestions for improvements of the system are made.