Influence of railway wheel tread damage and track properties on wheelset durability – Field tests and numerical simulations
Doctoral thesis, 2023
Wheel tread damage leading to high magnitudes of vertical wheel–rail contact forces is a major cause of train delays in the Swedish railway network, particularly during the coldest months of the year. According to regulations, vehicles generating wheel–rail impact loads exceeding the limit values must be taken out of service for wheel maintenance. This may lead to severe traffic disruptions and associated high costs. On the other hand, increased wheel‒rail impact loads cause elevated stress levels in wheels, axles and bearings and may shorten the life of track components, resulting in higher costs for vehicle and track maintenance. Thus, alarm limits should provide a balance between preventing operational failures and minimising the number of stopped trains.
The aim of this thesis is to enhance the understanding of the consequences of wheel tread damage and to identify better means of addressing them. To achieve this aim, the ability of numerical simulations to investigate different operational scenarios is crucial. A versatile and cost-efficient method to simulate the vertical dynamic interaction between a wheelset and a railway track, accounting for generic distributions and shapes of wheel tread damage, has therefore been extended and improved. The dynamic coupling between the two contact points (one on each wheel) via the wheelset axle and via the rails and sleepers is accounted for. Post-processing steps to evaluate fatigue impact at critical positions in the wheelset have been developed.
The applied simulation models have been calibrated and verified by extensive field tests. Measurement campaigns with two different Swedish passenger trains have been carried out. In the first field test, impact loads generated by a wheelset with severe tread damage were measured. Measurements and simulations have been used to illustrate how wheel–rail loads and fatigue impact depend on the three-dimensional shape of the tread damage. The effects of speed and travelling direction of the vehicle, position in the sleeper bay where the defect strikes the rail, lateral position of the wheelset, and track stiffness on wheel–rail contact forces and wheelset durability have been investigated.
In the second long-term field test, axle stresses have been monitored using an instrumented wheelset on a passenger train in revenue traffic. By post-processing of test results, statistical models of stress spectra for different stretches of the Swedish rail network were obtained. Moreover, the parameters describing such models have been related to track characteristics in terms of the presence of curves, switches & crossings and irregularities in track geometry. This allowed to develop numerical routines to evaluate wheelset durability depending on operational parameters. These studies are used to initiate a discussion on improved wheelset maintenance procedures.
The aim of this thesis is to enhance the understanding of the consequences of wheel tread damage and to identify better means of addressing them. To achieve this aim, the ability of numerical simulations to investigate different operational scenarios is crucial. A versatile and cost-efficient method to simulate the vertical dynamic interaction between a wheelset and a railway track, accounting for generic distributions and shapes of wheel tread damage, has therefore been extended and improved. The dynamic coupling between the two contact points (one on each wheel) via the wheelset axle and via the rails and sleepers is accounted for. Post-processing steps to evaluate fatigue impact at critical positions in the wheelset have been developed.
The applied simulation models have been calibrated and verified by extensive field tests. Measurement campaigns with two different Swedish passenger trains have been carried out. In the first field test, impact loads generated by a wheelset with severe tread damage were measured. Measurements and simulations have been used to illustrate how wheel–rail loads and fatigue impact depend on the three-dimensional shape of the tread damage. The effects of speed and travelling direction of the vehicle, position in the sleeper bay where the defect strikes the rail, lateral position of the wheelset, and track stiffness on wheel–rail contact forces and wheelset durability have been investigated.
In the second long-term field test, axle stresses have been monitored using an instrumented wheelset on a passenger train in revenue traffic. By post-processing of test results, statistical models of stress spectra for different stretches of the Swedish rail network were obtained. Moreover, the parameters describing such models have been related to track characteristics in terms of the presence of curves, switches & crossings and irregularities in track geometry. This allowed to develop numerical routines to evaluate wheelset durability depending on operational parameters. These studies are used to initiate a discussion on improved wheelset maintenance procedures.
dynamic wheel–rail interaction
axle stresses
railway wheel tread damage
wheelset durability
instrumented wheelset
rail vehicle maintenance
wheel–rail impact loads
Lecture Hall HC2, Hörsalsvägen 14, Campus Johanneberg, Chalmers
Opponent: Professor Giorgio Donzella, University of Brescia, Italy
Author
Michele Maglio
Chalmers, Mechanics and Maritime Sciences (M2), Dynamics
Wheel–rail impact loads and axle bending stress simulated for generic distributions and shapes of discrete wheel tread damage
Journal of Sound and Vibration,; Vol. 502(2021)
Journal article
Railway wheel tread damage and axle bending stress – Instrumented wheelset measurements and numerical simulations
International Journal of Rail Transportation,; Vol. 10(2022)p. 275-297
Journal article
Railway wheelset fatigue life estimation based on field tests
Fatigue and Fracture of Engineering Materials and Structures,; Vol. 45(2022)
Journal article
M. Maglio, E. Kabo, A. Ekberg. Relating the influence of track properties to axle load spectra through onboard measurements
M. Maglio, T. Vernersson, J.C.O. Nielsen, A. Ekberg, E. Kabo. Influence of railway wheel tread damage on wheel–rail impact loads and the durability of wheelsets
Have you ever heard a repetitive (and maybe annoying) noise, something like a rhythmic “thump thump thump thump”, while travelling on a train or on a city tram? Then the vehicle you were travelling on might have been affected by a wheel flat and the noise you heard was the wheel making repeated impacts with the rail.
Wheel flats are just one of many possible defects which can occur on the wheel tread, the surface of the wheel which is in contact with the rail. Wheel flats can form when the train is running with a frozen brake that causes the wheel to slide on the rail. They are therefore not uncommon in the Swedish railway system during winter time.
Other commonly occurring forms of tread damage are surface cracks. The contact forces between the wheel and the rail – especially the friction forces – cause these cracks. Again, the winter climate plays an unfavourable role, as the dry air causes high friction and melting snow can penetrate inside the cracks where it lubricates the crack faces and thereby contributes to crack growth. An example of a railway wheel with a severe form of rolling contact fatigue damage can be seen on the cover of this thesis.
Some of the most significant consequences of tread damage are discussed in this thesis. In particular, damaged wheel which periodically bump onto the rail do not only generate noise but also higher contact forces between the wheel and the rail. These forces can lead to additional damage on both the wheels and the rail. This will lead to a need for more maintenance and may in extreme cases pose threats to passenger safety. To prevent this, wheels with "too large" defects are stopped. But this will cause traffic delays.
It is therefore vital to be able to achieve more knowledge on which wheel tread damage is "too large" so that trains must be stopped, which is so large that the wheels have to be reprofiled, and which damage can just be ignored. One way to do so is to arrange full-scale field tests. However, railway tests are very expensive and difficult to arrange. Therefore, numerical simulations are necessary. In this work, some simulation methods aimed at predicting wheel–rail contact forces, and wheel, axle and bearing damage caused by operations with wheels having different types of tread damage are presented. The results of these studies will contribute to improved regulations and maintenance practices for wheels with tread defects.
Wheel flats are just one of many possible defects which can occur on the wheel tread, the surface of the wheel which is in contact with the rail. Wheel flats can form when the train is running with a frozen brake that causes the wheel to slide on the rail. They are therefore not uncommon in the Swedish railway system during winter time.
Other commonly occurring forms of tread damage are surface cracks. The contact forces between the wheel and the rail – especially the friction forces – cause these cracks. Again, the winter climate plays an unfavourable role, as the dry air causes high friction and melting snow can penetrate inside the cracks where it lubricates the crack faces and thereby contributes to crack growth. An example of a railway wheel with a severe form of rolling contact fatigue damage can be seen on the cover of this thesis.
Some of the most significant consequences of tread damage are discussed in this thesis. In particular, damaged wheel which periodically bump onto the rail do not only generate noise but also higher contact forces between the wheel and the rail. These forces can lead to additional damage on both the wheels and the rail. This will lead to a need for more maintenance and may in extreme cases pose threats to passenger safety. To prevent this, wheels with "too large" defects are stopped. But this will cause traffic delays.
It is therefore vital to be able to achieve more knowledge on which wheel tread damage is "too large" so that trains must be stopped, which is so large that the wheels have to be reprofiled, and which damage can just be ignored. One way to do so is to arrange full-scale field tests. However, railway tests are very expensive and difficult to arrange. Therefore, numerical simulations are necessary. In this work, some simulation methods aimed at predicting wheel–rail contact forces, and wheel, axle and bearing damage caused by operations with wheels having different types of tread damage are presented. The results of these studies will contribute to improved regulations and maintenance practices for wheels with tread defects.
Subject Categories
Mechanical Engineering
Applied Mechanics
Areas of Advance
Transport
ISBN
978-91-7905-764-0
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5230
Publisher
Chalmers
Lecture Hall HC2, Hörsalsvägen 14, Campus Johanneberg, Chalmers
Opponent: Professor Giorgio Donzella, University of Brescia, Italy