Railway wheel tread damage and axle bending stress – Instrumented wheelset measurements and numerical simulations

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

EPFM Analysis of Subsurface Crack Beneath a Wheel Flat Using Dynamic Condition

AbstractDuring running due to frequent braking and suddenly jamming of brakes the Railway wheel skids over rails. This frequent skidding removes large amount of metal from the surface known as Wheel-flat defect. In this paper the wheel-flat and a subsurface crack in the beneath is studied using FEA. If the wheel-flat is not detected early the subsurface crack can originate in the beneath due to inclusion, may leads to fatal accidents. In this study wheel material is taken Elastic-plastic and J-Integral factor has been obtained. The wheel–rail vehicle is modelled as a mass–spring–damper syste

Railway wheel steel behaviour upon thermo-mechanical loadings

Optimised railway maintenance techniques such as rail grinding and milling, or rail repair welding, are vital to more sustainable rail networks. As demands on the railway increases, the need to better understand the material behaviour during local heating events occurring during maintenance is amplified. Other heating events can occur during operation, for instance during severe block braking. This thesis provides insight into thermal damage resulting from these local heating events on railway wheels, which can lead to altered mechanical properties and changed residual stresses. The material behaviour of the ferritic-pearlitic railway wheel steel ER7T was studied during severe block braking (i.e., slow heating and cooling) at peak temperatures varying between 300 \ub0C and 650 \ub0C. The thermal dilatation was restricted to different degrees between free expansion and full restriction. This study thus explores the combined effect of thermal and mechanical cycling on the mechanical properties and material structure. The experimental results from the thermo-mechanical testing were also used to validate a new constitutive material model for use in FE models to predict severe block braking.\ua0 The second part of the thesis explored the effect of rapid heating and cooling events on the microstructure and residual stress state of railway wheel steel. Localised heating using laser scanning with additive manufacturing equipment was compared to the heating done by scanning with laser welding equipment. This study thus investigated the similarities of different rapid heating (high temperature) processes and the effect of process parameter variations. The results can be used to provide insight into the material behaviour of railway steels during local heating events. Furthermore, it can support the development of more accurate simulations for both operation and maintenance processes

INFLUENCE OF CROSSING WEAR ON ROLLING CONTACT FATIGUE DAMAGE OF FROG RAIL

The damage of the frog rail significantly affects the wear of the crossing rail and restricts the passing speed of the train. A geometric 3D modeling of the vehicle passing through the crossing center is particularly concerned with the cumulative wheel-rail contact of the traffic volume. The frog rail wear is simulated to obtain the dynamic change of the impact force of the wheel on the frog rail as the rail wears. By summarizing the existing experimental results of other scholars, it is clear that the important factors, that cause the damage of the frog rail, are vehicle load, friction coefficient, slip roll ratio and shear stress.  This paper combines the theoretical analysis of mechanics and 3D simulation to obtain the position change of the wheel-rail contact point with the wear of the frog rail, and finally compares it with the actual measurement results. It can more accurately predict the area where the maximum damage occurs after a certain amount of traffic for a certain fixed model, the change of wheel-rail contact point at frog rail is simulated with the wear of each component. Through theoretical analysis, the main factors determining frog rail damage were determined. Then evaluate the possible damage area of the frog track and control the prediction range to 5-10 cm, which reduces the detection time and cost. The worst state of distraction will be detected in time to facilitate replacement or polishing. Through further research in this area, the service life of the frog rail can be predicted

CONTRIBUTION TO THE MODELIZATION, ANALYTICAL AND NUMERICAL, OF GENERATION AND PROPAGATION OF VIBRATIONS ORIGINATED BY RAILWAY TRAFFIC. ANALYSIS OF MITIGATION PROPOSALS

Tesis por compendioReal Herráiz, JI. (2015). CONTRIBUTION TO THE MODELIZATION, ANALYTICAL AND NUMERICAL, OF GENERATION AND PROPAGATION OF VIBRATIONS ORIGINATED BY RAILWAY TRAFFIC. ANALYSIS OF MITIGATION PROPOSALS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/52247TESISCompendi

Towards Model-Based Condition Monitoring of Railway Switches and Crossings

Railway switches and crossings (S&C, turnouts) connect different track sections and create a railway network by allowing for trains to change between tracks. This functionality comes at a cost as the load-inducing rail discontinuities in the switch and crossing panels cause much higher degradation rates for S&C compared to regular plain line track. The high degradation rates create a potential business case for condition monitoring systems that can allow for improved maintenance decisions compared to what can be achieved from periodic inspection intervals using measurement vehicles or visual inspection by engineers in track. \ua0To this end, this thesis addresses the development of tailored processing tools for the analysis of measured data from accelerometers mounted adjacent to the crossing transition in crossing panels. With the presented tools, a condition monitoring framework is established. The analysis procedures showed robustness in processing large datasets. The framework includes the extraction of different crossing panel condition indicators for which the interpretation is supported by multi-body simulations (MBS) of dynamic train–track interaction. Additionally, a demonstrator is presented for MBS model calibration to the measured track responses.A particularly important signal processing tool is the development of a novel sleeper displacement reconstruction method based on frequency-domain integration. Using the reconstructed displacements, the track response is separated into quasi-static and dynamic domains based on deformation wavelength regions. This separation is shown to be a promising strategy for independent observations of the ballast condition and the crossing rail geometry condition from a single measurement source. In addition to sleeper acceleration measurements, field measurements have been performed in which crossing rail geometries were scanned. The scanned geometries have been implemented into a MBS software with a structural representation of the crossing panel, where analyses have been performed to relate the concurrently measured accelerations and crossing rail geometries. To address the variation in operational conditions in the MBS environment, a sample of measured wheel profiles was accounted for in the analysis. This MBS study showed that there is a strong correlation between the crossing rail geometry condition, wheel–rail contact force, and crossing condition indicators computed from the dynamic track responses. Contrasting measured and simulated track responses from the six investigated crossing panels showed a good agreement. This observation supports the validity of the simulation-based condition assessment of crossing rail geometry. Based on the work in this thesis, a foundation is set for developing methods for automatic calibration of S&C MBS models and subsequent damage evolution modelling based on operational online condition monitoring data. This development aims to address S&C service life in a digital environment and presents a key component for building a Digital Twin prototype for S&C condition monitoring

Finite element analysis of railway track under vehicle dynamic impact and longitudinal loads

Impact loads caused by flat spots on railcar wheels impose a major maintenance burden on railroads and can cause severe damage to both railcar and rail track components. In addition, the increasing tractive power of locomotives leads to significant increase in the longitudinal load demand in railway tracks. The capacity of longitudinal restraint of existing rail fastening system and its dependency on track parameters affects the future design of rail fastening system. This thesis focuses on investigating numerically these two problems using finite element (FE) method. An FE model with multiple crossties and their accompanying fastening systems is developed and utilized in this study after being validated using field data. The results of the impact load study indicate that impact loading consists of direct wheel impact loads and track system vibration induced impact loads. Both of these impact mechanisms are sensitive to the parameters considered in this study, including the stiffness of rail pad and the speed of train. It is observed that rail pad with a moderate stiffness provides the most effective impact attenuation. Furthermore, impact load is found to increase with increasing train speed. On the other hand, the study conducted on longitudinal track loads focused on investigating the effects of wheel acceleration, elastic modulus of clips, rail-to-railpad coefficient of friction (COF), and crosstie spacing on the distribution of longitudinal force in the rail fastening system. The FE model results suggest that a coefficient of friction (COF) of 0.65 is most efficient in maximizing the longitudinal restraint per railseat. Additionally, a crosstie spacing of 24 inches can lead to a desired distribution of longitudinal force

Wheel-rail contact force measurement. A comparison between distance laser and strain gauges measuring technology

The development of this PhD thesis is focus on the wheel/rail contact force measurement on a 1 : 10 scaled railway vehicle. To that end, the author has designed and manufactured a dynamometric wheelset instrumented with several sensors for the direct measurement of forces applied on the instrumented wheel. Two di erent technologies have been used for the wheelset instrumentation: On the one hand, a set of strain gauges measure the radial strains experienced by the wheel-web when a lateral load is applied on the wheel. On the other hand, three high precision lasers have been installed on the axel that measure the lateral de ection experienced by the wheel due to the applied lateral loads. Normal contact forces are measured independently throughout the de ection experienced by the primary suspension. This is also measured with laser distance sensors. After being instrumented, the wheelset has been submitted to a calibration process. A calibration test bench where controlled loads can be applied to the wheelset has been also designed and manufactured. Finally the instrumented wheelset has been installed on the scaled vehicle and tested on a 5 inches wide scale track. The force measurements obtained in the experiments with both set of sensors have been compared with numerical results drawn from a computational model of the vehicle. A novel procedure to measure the track irregularities applied to the scaled track has been also include as part of this thesis.El desarrollo de esta tesis se centra en la medici on experimental de fuerzas de contacto rueda carril en un veh culo ferroviario a escala 1 : 10. Para ello, el autor ha dise~nado y fabricado un eje dinamom etrico instrumentado con multiples sensores para la medici on directa de las fuerzas aplicadas en las ruedas. Para la instrumentaci on del sistema se han utilizado dos tecnolog as distintas: Por un lado se dispone de un conjunto de bandas extensom etricas que miden las deformaciones radiales experimentadas por el velo de la rueda debidas a la carga lateral aplicada en la misma. Por otro lado se han instalado tres l aseres de alta precisi on que miden la de exi on experimentada por la rueda debidas tambi en a las cargas lateral aplicadas. Las fuerzas normales a las que se ve sometida la rueda son calculadas a trav es de la medici on de la de exi on experimentada por la suspensi on primaria del veh culo, siendo tambi en medida mediante sensores de distancia l aser. Tras la instrumentaci on el eje dinamom etrico ha sido sometido a un proceso de calibraci on, para el cual se ha dise~nado y fabricado un banco de pruebas a escala donde puden aplicarse cargas al eje de forma controlada y conocer la respuesta de los sensores. Finalmente el mencionado eje dinamom etrico ha sido instalado en el veh culo a escala y su funcionamiento ha sido probado en una v a a escala de 5 inches de ancho. En los experimentos realizados se han contrastado las mediciones de fuerzas realizadas por ambos sensores y comparado con resultados num ericos obtenidos de un modelo multicuerpo de simulaci on del veh culo. Como parte de esta tesis se incluye tambi en la descripci on del novedoso proceso de auscultaci on y c alculo de irregularidades realizado en del trazado ferroviario a escala