Per-Anders Jönsson

Implications of the operation of multiple pantographs on the soft catenary systems in Sweden

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.

New simulation model for freight wagons with UIC link suspension

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 on the behaviour of the wagon on tangent track and in curves is discussed. Finally, suggestions for improvements of the system are made.

Adoption of different pantographs’ preloads to improve multiple collection and speed up existing lines

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 pantographs performances.

Experimental and theoretical analysis of freight wagon link suspension

Abstract Link suspension is the most prevailing suspension system for two-axle freight wagons and still frequently used for four-axle freight wagons in central and western Europe. The system design is simple and has existed for more than 100 years. However, still, the characteristics are not fully understood. This article focuses on the lateral characteristics of the link suspension. First, results from stationary measurements on freight wagons and laboratory tests on single links are presented. Then, a simulation mathematical model is proposed. Finally, the influence of various parameters on the link characteristics is investigated. With the developed simulation model, many of the stability problems of link suspension running gears can be explained, but further research is needed to fully understand the characteristics and to be able to recommend improvements. From the tests, it also becomes obvious that the characteristics of different links can vary significantly from each other depending on age and maintenance status.

CaPaSIM statement of methods

In the present paper, the method for calculation of the dynamic pantograph–catenary interaction developed by the Royal Institute of Technology and the Swedish National Rail/Road administration (Trafikverket) is described and the results of the benchmark exercise are discussed. The method is based on the commercial Finite Element software ANSYS. The geometry of the catenary and pantograph is defined in a pre-processor, BARTRAD, developed by Trafikverket, and is automatically translated into an ANSYS model. Basically all types of catenary systems could be handled as well as different types of non-linearity. There are both 2D and 3D versions of the code existing. The results achieved in this first stage of the benchmark are well in line with the results from the other partners in the benchmark study

Influence of switches and crossings on wheel profile evolution in freight vehicles

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 Archards 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.

Influence of link suspension characteristics variation on two-axle freight wagon dynamics

The link suspension is the most prevailing suspension system for freight wagons in central and western Europe. Link suspension systems have strong non-linear characteristics including a hysteresis loop. The loop exhibits usually three characteristic sections with different tangential stiffnesses. The actual contact geometry of the links and end bearings has a significant influence on the characteristics. By wear in ordinary service, the contact geometry changes considerably, thus causing the characteristics to change. In summary, it appears that the link suspension characteristics are very sensitive to several factors, being hard to control in the real world of freight wagon operations. The various stiffnesses and hysteresis loops are found to have a strong influence on the ride qualities of vehicles. This paper presents non-linear multibody simulations investigating these matters. As long as the characteristics cannot be controlled within closer limits than found in this study, there is a strong need for the sensitivity analysis to be made, both in predictive multibody simulations of vehicle dynamics as well as for verification and acceptance tests.

On the Implementation of an Auxiliary Pantograph for Speed Increase on Existing Lines

ABSTRACT 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.

Wheel damage on the Swedish iron ore line investigated via multibody simulation

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.

Use of Archard’s Wear Law for the Calculation of Uniform Wheel Wear of High Tonnage Freight Vehicles

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.Copyright