| 1. |
- Brouzoulis, Jim, 1984, et al.
(författare)
-
Orbital friction welding of steel bars – heat generation and process modelling
- 2023
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications. - : SAGE Publications. - 1464-4207 .- 2041-3076. ; 237:8, s. 1715-1724
-
Tidskriftsartikel (refereegranskat)abstract
- Welding of rails in the field is usually associated with a large heat input, which results in a large heat-affected zone (HAZ), which in turn may impair the welded rail head and decrease its service life. An innovative orbital friction welding (OFW) process with an intermediate eccentrically oscillating disk is proposed, and a demonstrator has been constructed. This enables welding of rails, which have a non-symmetric cross-sectional area and must be stationary during welding. The process is characterized by low heat input, creating a narrow HAZ, and low welding deformations. A thermo-mechanical finite element model is developed to determine suitable process parameters to create a narrow HAZ. A phenomenological model for heat generation during friction welding is developed for pearlitic rail steel with parameters calibrated from rotary friction welding experiments on pipes. The temperature dependence of the friction coefficient in the interface is established. Pilot tests with the demonstrator OFW machine on bars with a quadratic cross section showed that preheating will be required to guarantee a fully pearlitic weld zone. This was verified by the simulations of the thermo-mechanical finite element model.
|
|
| 2. |
- Kabo, Elena, 1972, et al.
(författare)
-
Rolling contact fatigue assessment of repair rail welds
- 2018
-
Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems (CM2018). - 2590-0609. - 9789461869630 ; , s. 450-456
-
Konferensbidrag (refereegranskat)abstract
- A repair welding procedure is numerically simulated. To validate the numerical model, analyses of the temperature evolution are compared to full-scale test results. Further simulations are then carried out to evaluate the residual stress formation during welding and how the residual stress field is influenced by subsequent wheel passages. The influence of residual stresses from welding and the subsequent residual stress redistribution during operations on the risk of rolling contact fatigue (RCF) is discussed and analyzed. It is found that high tensile stresses are formed during welding, however these shake down substantially during subsequent operations. The influence on RCF is found to be moderate on the surface and somewhat more severe in a layer at the bottom of the repair weld. In addition to residual stresses, there is also a risk that welding introduces material defects and alters material properties. The influence of such phenomena on RCF are discussed.
|
|
| 3. |
- Kabo, Elena, 1972, et al.
(författare)
-
Rolling contact fatigue assessment of repair rail welds
- 2019
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 436-437
-
Tidskriftsartikel (refereegranskat)abstract
- A repair welding procedure is numerically simulated. To validate the numerical model, analyses of the temperature evolution in a repaired rail are compared to existing full-scale test results. Thermomechanical simulations are carried out to evaluate the residual stress formation during welding and how the residual stress field is influenced by subsequent wheel passages during operations. The risk of rolling contact fatigue (RCF) is analysed and results discussed. It is found that tensile stress magnitudes resulting from welding decrease substantially during rolling contact loading. The influence of the residual stresses on RCF is found to be minor on the surface and somewhat more severe in a layer at the bottom of the repair weld. In addition to residual stresses, there is also a risk that welding introduces material defects and alters material properties. The influence of these factors on the risk of RCF is discussed.
|
|
| 4. |
- Maglio, Michele, 1993, et al.
(författare)
-
Digitalisation of condition monitoring data as input for fatigue evaluation of wheelsets
- 2019
-
Ingår i: Proceedings of the XIX International Wheelset Congress.
-
Konferensbidrag (refereegranskat)abstract
- A field test in which a train was run at different speeds over an impact load detector is described. One of the wheelsets in the train had severe wheel tread damage. The results are presented and the relation between the speed of the train and the magnitude of the impact loads registered for the two wheels is discussed. The defects on the wheel tread have been studied and scanned by means of 3D laser and their characteristics are described. An in-house software for the simulation of dynamic wheel–rail interaction has been improved by including the possibility to account for the cross-coupling of the two wheels within the same wheelset. The contact algorithm and a possible implementation of discrete defects in the in-house software are discussed. The in-house software gives, among other possible outputs, the maximum dynamic loads occurring at both wheels of the wheelset. To show an example of the utility of such information, fatigue analyses for the axle are performed for the different running conditions used during the field tests. The impact loads measured on the day of the tests are given as input to the fatigue analyses.
|
|
| 5. |
- Maglio, Michele, 1993
(författare)
-
Influence of railway wheel tread damage and track properties on wheelset durability – Field tests and numerical simulations
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 6. |
- Maglio, Michele, 1993, et al.
(författare)
-
Influence of railway wheel tread damage on wheel–rail impact loads and the durability of wheelsets
- 2023
-
Ingår i: Railway Engineering Science. - 2662-4745 .- 2662-4753. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic wheel–rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds. Based on laser scanning, the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle–track interaction to calibrate and verify a simulation model. The relation between the magnitude of the impact load and various operational parameters, such as vehicle speed, lateral position of wheel–rail contact, track stiffness and position of impact within a sleeper bay, is investigated. The calibrated model is later employed in simulations featuring other forms of tread damage; their effects on impact load and subsequent fatigue impact on bearings, wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed. The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear, and for general assessment of the severity of different types of railway wheel tread damage.
|
|
| 7. |
|
|
| 8. |
- Maglio, Michele, 1993
(författare)
-
Influence of wheel tread damage on wheelset and track loading – Field tests and numerical simulations
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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, in particular during the coldest months of the year. According to regulations, vehicles generating contact forces exceeding the limit value for allowed wheel–rail impact loads must be taken out of service for wheel maintenance. This may lead to severe traffic disruptions and higher costs. Increased wheel‒rail impact loads also 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. Wheel tread irregularities also lead to increased levels of rolling noise, impact noise and ground-borne vibration. The aim of the thesis is to enhance the understanding of wheel tread damage and its consequences and to identify better means of addressing them. To achieve this aim, the ability for 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 wheelset (comprising two wheels, axle and any attached equipment for braking and power transmission) and track with two discretely supported rails are described by three-dimensional finite element (FE) models. The dynamic coupling between the two wheel‒rail contacts (one on each wheel) via the wheelset axle and via the sleepers and ballast is considered. The simulation of dynamic vehicle–track interaction is carried out in the time domain using a convolution integral approach, while the non-linear wheel–rail normal contact is solved using Kalker’s variational method. Non-symmetric wheelset and track designs, as well as non-symmetric distributions of wheel tread damage or rail irregularities can be studied. Based on Green’s functions, a post-processing step has been developed to compute time-variant stresses at locations in the wheelset axle which are prone to fatigue. In an extensive parameter study, wheel–rail impact loads and axle stresses have been computed for different shapes and sizes of wheel tread damage. The simulations need to be calibrated and validated by tests. To this end, field tests with two different Swedish passenger trains with severe wheel tread damage have been carried out. Time histories of numerically evaluated axle stresses have been compared to measured data from an instrumented wheelset. Simulations have been used to demonstrate that variations in rail roughness level, and the angular position of a strain gauge with respect to that of a discrete wheel tread defect, may lead to a significant influence on predicted axle stresses. Developed numerical routines to predict stresses at critical locations in the wheelset from condition monitoring data will improve understanding and possibilities to handle wheel tread deteriorations. A discussion on future applications in terms of improved wheelset maintenance procedures is initiated.
|
|
| 9. |
- Maglio, Michele, 1993, et al.
(författare)
-
Prediction of axle fatigue life based on field measurements
- 2022
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To facilitate the adoption of a condition-based maintenance approach for railway axles, more knowledge regarding operational loading is needed. In the present work, statistical distributions on axle stresses for revenue vehicles have been derived. To this end, raw strain spectra have been gathered during field measurements using an instrumented telemetry mounted on a powered axle running within the Swedish railway network. Strain spectra are transformed into bending stress spectra which are used to estimate the statistical distributions of axle stresses for different track sections. Both the derived stress spectra and the estimated statistical distributions are used as input to fatigue life analyses. In these analyses, Wöhler (stress–cycle) curves estimated for varying axle surface conditions (which can be related to different axle maintenance conditions) are used to predict axle lives. The proposed method allows to rapidly post-process data obtained during field tests, to quantify indications on the health status of track and of the wheelset from these, and to estimate resulting fatigue life. This would aid in asset management by enhanced status characterisation, improved inspection and maintenance planning, and enhanced possibilities to follow-up any non-conformities.
|
|
| 10. |
- Maglio, Michele, 1993, et al.
(författare)
-
Railway wheel tread damage and axle bending stress – Instrumented wheelset measurements and numerical simulations
- 2022
-
Ingår i: International Journal of Rail Transportation. - : Informa UK Limited. - 2324-8386 .- 2324-8378. ; 10:3, s. 275-297
-
Tidskriftsartikel (refereegranskat)abstract
- A combination of instrumented wheelset measurements and numerical simulations of axle bending stresses is used to investigate the consequences of evolving rolling contact fatigue (RCF) damage on a passenger train wheelset. In a field test campaign, stresses have been monitored using a wheelset with four strain gauges mounted on the axle, while the evolution of wheel tread damage (out-of-roundness) has been measured on regular occasions. The strain signals are post-processed in real time and stress variations are computed. Based on a convolution integral approach, the measured wheel out-of-roundness has been used as input to numerical simulations of vertical dynamic wheelset–track interaction and axle stresses. Simulated and measured axle stresses are compared for cases involving combinations of low or high levels of rail roughness and the measured levels of RCF damage. The study enhances the understanding of how wheel tread damage and track quality influence axle stress amplitudes.
|
|
