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  • 1.
    Roudiere, Elie
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Väg- och spårfordon samt konceptuell fordonsdesign.
    Data analytics and machine learning for railway track degradation: Using Bothnia Line track measurements for maintenance forecasting2024Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this paper, a statistical method is developed to improve predictive maintenance on railway track. The problem tackled is being able to predict when the next maintenance event should take place to guarantee a certain track quality class. To solve the problem, The prediction is made using track measurement data exclusively, with no maintenance history to support the data analysis. The dataset consists of track measurements taken over eleven years and 170 kilometres on the Bothnia line in Northern Sweden. Different track degradation models and machine learning approaches are discussed and implemented. In the end, the tool developed was able to predict track degradation with an error within reasonable bounds of the typical maintenance limit. This will allow an operator to predict the recommended date for the next maintenance event at all locations using only historical track measurements as an input and little to no user intervention on the programme.

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  • 2.
    Chatelais, Léa
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Väg- och spårfordon samt konceptuell fordonsdesign.
    Vehicle dynamics modelling of electromagnetic suspensions for MAGLEV applications2024Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    MAGnetic LEVitation Guidance System (MAGLEV) technology was commercially introduced relatively recently in the guided transport field. It is based on removing the wheels and rails of classic railway systems and supporting and guiding the train with magnets and magnetic forces instead. But, as for conventional railways, those trains need to fulfil dynamic requirements in order to make trains safe and comfortable. The dynamics of a train being mainly influenced by its suspensions characteristics, the magnetic forces generated in MAGLEV systems are of prime importance. Having a model of those systems allows to check the requirements of a certain design, and to consider the influence of different parameters on their fulfilment. This thesis leans on research work on MAGLEV vehicle modelling to model and implement magnetic levitation components in a quarter-car model in order to study the fulfilment of vehicle dynamics requirements. Specifically, the modelled vehicles are based on Electro- Magnetic Suspension (EMS) and Electro-Dynamic Suspension (EDS) (Inductrack) technologies, for which the modelling equations are analysed to study the magnetic force dependencies with physical and operational parameters. Finally, the dynamic requirements are checked in response to a set of track irregularities amplitudes, anda parametric study is carried out to verify the fulfilment of those requirements for other design cases. The results show that it is possible to model and implement simple MAGLEV MBS models for dynamic studies, although it is challenging to model and simulate specific MAGLEV components because of the lack of component specifications or experimental data on track irregularities.

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  • 3.
    Kongpachith, Erik
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Estimating the load weight of freight trains using machine learning2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Accurate estimation of the load weight of freight trains is crucial for ensuring safe, efficient and sustainable rail freight transports. Traditional methods for estimating load weight often suffer from limitations in accuracy and efficiency. In recent years, machine learning algorithms have gained significant attention and use cases within the railway industry due to their strong predictive capabilities for classification and regression tasks. This study aims to present a proof of concept in the form of a comparative analysis of five machine learning regression algorithms: Polynomial Regression, K-Nearest Neighbors, Regression Trees, Random Forest Regression, and Support Vector Regression for estimating the load weight of freight trains using simulation data. The study utilizes two comprehensive datasets derived from train simulations in GENSYS, a simulation software for modeling rail vehicles. The datasets encompasses various driving condition factors such as train speed, track conditions and running gear configurations. The algorithms are trained and evaluated on these datasets and their performance is evaluated based on the root mean squared error and R2 metrics. Results from the experiments demonstrate that all five machine learning algorithms show promising performance for estimating the load weight. Polynomial regression achieves the best result for both of the datasets when using many features of the datasets are considered. Random forest regression achieves the best result for both of the data sets when a small number features of the datasets are considered. Furthermore, it is suggested that the methodical approach of this study is examined on real world data from operating freight trains to assert the proof of concept in a real world setting.

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  • 4.
    Matz, Christian
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Väg- och spårfordon samt konceptuell fordonsdesign.
    Development and implementation of a tram line performance model2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wiener Linien’s tram network is one of the largest and busiest of its kind worldwide. Maintaining and improving the Level of Service (LoS) is one of the major tasks of the operations division. To direct these improvements efficiently to lines and sections of lines in need, tram line performance needs to be assessed. In this master thesis a Python-based model is developed to assess tram line performance using ideal operational constraints. Furthermore, the model is capable of computing the energy consumption for this optimal case.The tool computes Undisturbed Optimal Travel Times (UOTTs) which serve as a benchmark for tram line performance. Therefor it builds on track alignment data (curves and radii, gradients and switches), speed restriction data and a set of optimal parameters (no traffic, constant acceleration, etc.). Furthermore, train resistance, curve speeds and vehicle type are taken into consideration. These parameters are investigated and selected based on literature studies, interviews with employees of Wiener Linien, as well as field tests.Finally, the model results are compared to real world data for evaluation. A discussion of the results regarding further applications and improvements is performed.

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  • 5.
    Olsson, Emma
    KTH, School of Engineering Sciences (SCI).
    Tåg eller flyg för tjänsteresor inom Europa2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Arbetets mål var att jämföra tåg och flyg som färdsätt för tjänsteresor inom Europa.Detta genom att jämföra farkosternas restider, koldioxidutsläpp och biljettkostnader.Syftet var att presentera en metod för att jämföra resor som företag eller organisationerskulle kunna använda vid beslut av färdmedel. Arbetet innehåller först en litteraturstudieav tidigare forskning och sedan en analys av fem olika europeiska tjänsteresmål. Femresmål undersöktes: Oslo, Köpenhamn, Berlin, London och Bordeaux. För varje resmålundersöktes tågets respektive flygets koldioxidutsläpp, restidskostnad och biljettkostnad.Sedan infördes en optimeringsalgoritm för att väga samman dessa parametrar som enkostnad TI (Travel Impact Cost).

    Resultatet var att tåget hade lägst kostnad TI för fyra utav fem resor och därmed utifrånoptimeringsalgoritmen borde väljas. Endast till London hade flyget lägre kostnad TI.Flygets koldioxidutsläpp för resor utanför Skandinavien var mellan 5,3-10,3 gånger högrerespektive tågresa. Flygresor inom Skandinavien hade koldioxidutsläpp som var 71-140gånger högre än tåget. Restiden var längre för tåget för samtliga resor men skillnadenvar liten för resor inom Skandinavien.

    Slutsatsen var att det finns goda möjligheter för företag och organisationer att väljatåg för tjänsteresor inom Skandinavien. Detta då skillnaden i koldioxidutsläpp varbetydande medan skillnaden i restid var förhållandevis liten. För tjänsteresor utanförSkandinavien bör även faktorer som inte undersökts i denna rapport inkluderas vid beslutav färdmedel.

     

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  • 6.
    Schick, Bastian
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    A Digital Test Bench for Pneumatic Brakes2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master’s thesis covers the structuring and implementation of a digital testbench for the air brake system of freight trains. The test bench will serveto further improve the existing brake models at Transrail Sweden AB. Theseare used for the optimised calculation of train speed profiles by the DriverAdvisory System CATO. This work is based on the research of the technicalbackground, as well as the methodical approach to physical modelling anda modular implementation of the test bench. It gives full flexibility for thesimulation of customised train configurations using the European UIC brakesystem. Train length and vehicle arrangement can be adapted to the user’sspecific needs. For example, the test bench could be used for the simulation ofa train with distributed power. The system parameters are stored in a vehiclelibrary for the convenient generation of train configurations. This vehiclelibrary is freely expandable.The simulation is based on an equivalent electric circuit model which iscompleted with nozzle flow modelling. This model involves monitoring themain pipe, brake cylinder and reservoir pressure. Linear approximation is usedto obtain braking forces for the individual wagons and for the whole train. Thedepiction of the brake system behaviour is mostly accurate in the operationalscenarios, which is validated with measurement data. Additional calibrationis required for further reduction of the simulation errors and an extension ofthe model’s domain of validity. The test bench is developed by incrementaland iterative modelling and prepared for further improvements and variations,for example the adaption to the American AAR system variant.The presented work can also be used as a basis for similar implementationssuch as driving simulators. The methods are transferable to other applicationsof modular simulation.

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  • 7.
    Prifer, David
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Dynamic Simulation and Suspension Optimization for a Heavy Duty Railway Bogie2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A multi-body simulation study was undertaken to investigate the running behavior of a rail grinder vehicle with newly developed Ganz bogies. The main purpose of the simulations was to forecast and support the vehicle acceptance tests and support the ongoing development.

    A multi-body model was built in Simpack and the most critical force elements were isolated and validated by tests. Derailment safety was assessed based on both European and Australian standards. The vehicle's running stability was carried out for both standard (1435mm) and broad gauge (1676mm) versions. Vehicle sway characteristics were determined through the calculation of flexibility coefficient both numerically and analytically.

    A parametric study for primary vertical damper was undertaken to assess the empirically selected dampers and optimize the performance. The results show that the damping coefficient can be greatly reduced while maintaining acceptable running behavior, thus the lifetime of dampers can be increased. Based on stability investigations, yaw damper installation is not necessary, though the bracketry for the possibility of later installation will remain on the prototype bogie.

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  • 8.
    de Leeuw, Bente
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Improving the validation of a railway vehicle model in the virtual certification process2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Before vehicles can be placed in service it has to complete an authorisation process. At the moment,this process is largely depended on tests. This is, however, an expensive and long process. With new technologies and improved simulations this process can be shortened and the costs can be lowered. The validation of a vehicle model, however, is often limited by the available data. Often the measured rail profiles are not available and thus a new UIC60 profile is used for the simulations. The railway track often has been used and showssigns of wear and damages, therefore research has been done to investigate the influence of the rail profiles on the validation of a railway vehicle model. The current methods of validation in the European norm are used to compare simulated values with forces and accelerations available from vehicle measurements. In the first step,25 track sections with different curve radii have beensimulated with a measured rail profile every 100 meters. In the next step, the same sections have been simulated by using the standard UIC60 rail profile. The results show that the use of measured rail profiles does have a positive influence on the outcome of simulation.

    In the final step, one single narrow curve has been simulated to show the effect of standard and worn rail profiles. Four different wear stages of the rail profile are simulated and compared to the available vehicle measurements available. These simulations show that the use of a medium worn rail profile gives the most accurate value.

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  • 9.
    Chen, Shaoyao
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Modified train wheel wear calculation for fast calculation2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis, a modified wear calculation method is developed to calculate the train wheel wear, which can give less precise but faster results compared to the classic wear calculation method. This modified method is developed based on the classic wear calculation method developed by Jendel, which uses Hertz theory and Kalker’s simplified theory to calculate the contact variables and uses Achard theory to calculate the wear volume in an iterative manner. Compared with the classic method, this modified wear calculation method does not execute the multibody simulation (MBS) at each wear step, instead, it executes MBS by different strategies, for example, does MBS only at the first wear step or does it at every several wear steps. This way, a look-up table is utilised to store the contact variables from MBS and when no MBS is executed, the variables stored in the look-up table would be used to calculate the wear.In order to make the implementation of the modified wear calculation method possible, a contact point detection program is developed in this research. Significantly, this contact point detection program considers the material flexibility and can detect multiple contact points, which makes it very precise. It uses the pressure distribution calculated by Winkler theory as a weighting function to consider the material flexibility. In terms of multiple contact points detection, the gap between wheel and rail is regarded as a function, and the derivative relationship of the function is used to detect multiple contact points. Results from the modified wear calculation method are compared with results from the classic wear calculation method. The effects of different strategies are discussed, and the analysis of the error source is carried out in this work.This modified wear calculation method could be used for predicting the wear condition of the wheel when a quick result with only moderate precision is needed. 

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  • 10.
    Niedecken, Timon
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Optimized maintenance budget planning for DB Cargo locomotives2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Deutsche Bahn Cargo AG (DB Cargo) is a German line haul provider for the European Rail Transport Market. The more than 1500 locomotives owned by the company receive frequent maintenance for all their components. The many components of course have many different life cycles, costs and time needed for maintenance in the workshop. One of the tasks for the department “Operative Locomotives and Budget Planning Germany” (L.CBA 22) is to create a budget plan for the locomotive maintenance with a high quality of prediction. Because a change in maintenance procedures is currently ongoing, the budgeting process needs to be adjusted to keep the quality of prediction high without exceeding available time needed to create the budget plan.To do so, a tool consisting of excel files with queries, macros, in cell calculations as well as pivot table visualization is being created. Although not finished until now, it already facilitates some processes of the budgeting procedure.

  • 11.
    Dang, Ngoc Thúy Vy
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    The Effect of High Wheel Impact Load on the Rail Reliability - a Case Study at Bodsjön2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study focuses on the reliability of railway track in the relation with high loads resulted from wheel damages, where higher (dynamic) vertical wheel loads are expected from trains with damaged wheels. The Swedish Transport Administration (Trafikverket) has monitored and recorded data of rail defects and breaks. This data is important for the risk evaluation and management process, in order to obtain a balance between the maintenance costs and availability and quality of service for the railway transportation. To detect wheel damages in advance, Wheel Impact Loads (WIL) are measured and recorded by Wheel Impact Load Detectors (WILD), which are installed along the Swedish railway network, currently at 29 locations. Additionally, to detect defects and breakages in rails, Ultrasonic Testing (UT) is a common non-destructive testing method used by Trafikverket. In this project, a case study is conducted to examine statistically the frequency of rail defects and rail breaks after trains with high WILs, which exceed 350 kN, continued to operate in a defined area during the winter of 2019/20 at Bodsjön. The case study compares the data of WILD at Bodsjön and UT of the nearby track sections, 211 and 212, over a period of five years, from 2016 to 2020. Rail reliability levels are examined based on the absolute frequencies of rail defects detected by UT and the normalised ones per kilometre of UT-checked track, as well as the severity levels of those rail defects. The severity levels are denoted from the highest to the lowest, as 1a/ 1v/ 1m, 2b and 3i, based on the derailment risks and the priority of maintenance. It is observed that the extremely high WILs in the winter 2019/2020 has coincided with the more severe rail defects found by the following UT in 2020. Furthermore, the dominant rail defect type is found as squats. By studying the frequency of squats and their locations along the defined track sections, it is shown that there is a similar trend in the frequencies of squats and the high WILs. While, the effect of the high WILs’ magnitudes onto the occurrence of squats is undefined. However, the correlation between the frequencies and magnitudes of high WILs and the rail reliability levels could not be determined from this case study due to the limitations in the data collections. The current way of data collections for WILs, wheel damage types and rail defects are discussed for future works. Lastly, the statistics shows that the level of rail reliability of the area defined in the case study is considered as acceptable, considering the recent national levels that have been reported in the annual reports on rail defects. This gives the basis for the possibility of reviewing the permissible power level and proposing a new alert limit value of WIL. Nevertheless, considering the recommendation of The International Union of Railways (UIC) for the international railway sections, the implementation of the increased alert limit of WIL shall be examined carefully, with a future pilot study in railway sections that are not used for international traffic.

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  • 12.
    Flodin, Jesper
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Investigate the track gauge widening on the Iron-ore line and suggest maintenance limits2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Iron ore export remains a major player in the Swedish economy to date, with 90% of all iron ore produced in Europe stemming from the relatively small northern country. A large amount of this ore is transported from the mines to harbours for world-wide freight on railways. On such railway is the SwedishIron-ore Line running from Kiruna to Riksgränsen, connecting to the Norwegian Ofoten line which continues to Narvik. The line has the highest permissible axle-load in Europe at 30 tonnes, which poses challenges in its own. Historically, damage on the high rail of curves have been problematic, butremedies introduced in the form of wear adapted rail profiles has brought light to a new issue. Lowrail spalling damage, caused by rolling contact fatigue (RCF) has been problematic on the line, as it reduces the life of the rails and increases maintenancecosts. It is believed that a major factor to this damage is the track gauge width. The current limit values for maintenance of the track gauge is set at 1450mm, a figure derived from empirical studies. It is therefore the wish of the infrastructure manager Trafikverket to investigate the effect the gaugewidth has on this RCF induced damage, in order to review current maintenance practices. By applying current state of the art in rail vehicle dynamics simulations and contact mechanics, the current maintenance limit has been investigated.The outcome of said investigation has yielded a foundation of support for the current maintenance limit, as it closely aligns with where damage is calculated to form at a significantly higher rate than at lower gauges.

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  • 13.
    Öhnander, Fred
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    An Attempt Towards FE-Modelling of Fracture Propagation in Railway Wheels2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The demand for higher velocities and heavier axle loads for freight trains leads to higher forces on the railway wheels which in turn lead to an increase in stresses on and below the surface of the wheel-rail contact. By time, this induces wear on the wheels which consequently lead to higher maintenance costs and in some cases accidents. The ability to predict the evolution of wheel profiles due to uniform wear has been demonstrated with a rather accurate precision in most operational conditions. These wear models are based on wear coefficients and since they are not usually valid for real operational conditions, the models are generally calibrated against real-life scenarios in order to adjust the coefficients from test conditions to real-life lubrication conditions. This engineering approach can be useful in prediction of wear in systems where the materials and contact conditions do not vary. However, when addressing material development focused on reducing specific damage modes, the approach is of limited use because the obtained wear coefficients are not directly related to material properties. Therefore, attempts towards developing physical fracture propagation models that relates to the contact conditions and material properties have been made. The purpose has been to retrieve vital information about where a fracture initiates and how it propagates. In the long run, it is of great interest to be able to attain information about how a material particle is removed from the contact surface. Studies for this type of model was done in the 70’s and 80’s mainly with pin-disk experiments but has not been utilized in the specific field of wheel-rail contact. The thesis is part of the FR8RAIL project arranged by the European rail initiative Shift2Rail. Literature studies have been the basis for the thesis in order to gain vital insights into fracture mechanics and other related fields. The physical fracture propagation models have been constructed in the FE software Abaqus with the implementation of the XFEM. For the 2D model, the fracture initiates at the top of the implanted inclusion when the friction coefficient is  and propagates upwards a few elements. For , the fracture initiates at the right surface boundary where the pressure distribution and traction is applied. The fracture propagation angle increases relative to the surface as the friction coefficient value is increased. The fracture for the 3D model extends broader compared to the 2D model at the top of the inclusion in the case of . The fracture initiates at the same surface location as for the 2D model for . The fracture propagation is however non-existent due to convergence problems. The FE-models constructed are initial steps towards analysing the fracture propagation and closely related phenomena for a railway freight wheel in detail. At the end of the thesis, the simplified models give mainly information about the fracture initiation, propagation and its patterns. From this first phase, further adjustments and improvements can take place in order to eliminate the margins of error. In the long run, fully integrated models with further implementations such as detailed microstructure for the contact conditions, plastic behaviour for the material, and complete three-dimensional models can finally be employed.

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    An Attempt Towards FE-Modelling of Fracture Propagation in Railway Wheels
  • 14.
    Firdaus, Alfi Hadi
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    System-wide LCC Calculation for Novel Brake Block Material in Nordic Condition2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the main issues of cast-iron block brake material is high noise. Nowadays, train operators tend to change the brake block material from cast-iron to composite material. However, composite block brake materials are likely to produce more wear than cast-iron block brakes, degrading the dynamic behavior of the vehicle on the track. Therefore, comparison of the dynamic behavior and the maintenance cost of each block brake material of the train has been performed. The dynamic behavior is analyzed using GENSYS software and the maintenance cost analysis is done by using the Universal Cost Model developed in the EU project Roll2Rail. The iron ore train that operates in Malmbanan has been used as the simulation model. One-wheel profile before changing the block brake material before 2010 and two-wheel profiles after changing the block brake material after 2010 have been used for simulation. Certain radii, cant, vehicle speeds and wheel-rail friction coefficients has been taken into consideration in the simulations. After that, the wheel and track maintenance costs have been taken into consideration for analyzing the Universal Cost Model. The simulation results show that the wheel profiles after changing the block brake material possess higher risk of RCF than wheel profile before changing the brake block material. The UCM calculation show that the wheel profile after changing brake material leads to higher track maintenance costs, 9.3% higher for new1 and 2.8% higher for new2 wheel profiles, compared to the worn wheel profile before changing brake material. Moreover, The UCM calculation show that the wheel profile after changing brake material leads to higher wheel maintenance costs, 1.04% higher for new1 and 4.3% higher for new2 wheel profiles, compared to the worn wheel profile before changing brake material. The total of maintenance cost also shows that the wheel profile after changing brake material leads to higher maintenance costs, around 2-4%, compared to the worn profile before changing brake material. 

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  • 15.
    Martin, Michael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    The Effect of Geometrical Contact Input to Wheel-Rail Contact Model2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wheel-rail contact is an important aspect of railway, the forces transferred between the wheel and rail are the one that guide, brake, or accelerate the train, and that is why the understanding of the contact between wheel and rail is an interesting research topic. In this master thesis wheel-rail contact model named ANALYN is used to see the effect of the different geometrical input, like undeformed distance, relative longitudinal curvature, and relative lateral curvature calculation affect the contact patch estimation formed at the wheel-rail contact. 

    In the process, a geometrical contact search code is made to find the contact point between wheel and rail for certain lateral displacement, yaw angle, and roll angle of the wheelset. The codes used to calculate the three geometrical inputs are also prepared, with two methods are prepared for each input. The results that generated from combination of the geometrical contact search and geometrical input preparation are used as the input to ANALYN.

    The results showed that different geometrical input calculations do affect the shape of the contact patch, with the calculation of lateral curvature being the most important since it affects the shape of the contact patch greater than other geometrical inputs. It is also shown that taking yaw angle into account in the contact search will affect the shape of the contact patch.

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  • 16.
    Prevolnik, Robin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On estimating the risk of wheel damage for wagons with paper rolls considering various dynamic conditions2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Hector Rail AB is a Swedish line haul provider for the European Rail Transport Market. On one of their lines, Hector Rail transports large cylinder-shaped paper rolls of different sizes from Holmsund to Skövde, and compressed recycled paper back to Holmsund, with Y25 bogie wagons. The wheels of these wagons experience surface initiated rolling contact fatigue, RCF, which is increasing the maintenance cost. In a collaboration with KTH Royal Institute of Technology a study of the risk of developing RCF cracks when comparing different track qualities, load cases, speeds, curves and wheel-rail friction coefficients as well as the consideration of wear is carried out.

    The difference in surface initiated RCF when applying the different input parameters is analysed. The location along the track where the wheels are likely to initiate RCF is calculated, as well as the location of RCF on the wheels. The model also provides the curve characteristics that are most likely to initiate RCF on the wheels. This tool can be used for optimising and further streamlining the operation for freight traffic on this (or any other) line with respect to wheel damages and planned maintenance.

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  • 17.
    Larsson, Kristina
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Wheel damage and maintenance of SCA Skog wagons2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the SCA Skog wagon fleet run by Hector Rail, wheel damages are a serious problem all year. The goal of this work is to find out why, and what changes can be made to decrease them. For comparison, Hector Rail does run the same sgnss type wagons for two other customers (Stora Enso and SCA Logistics), and those are much less damaged. This makes it possible to compare the different attributes of the customers’ wagon traffics to single out the influencing factors. The SCA Skog damages are almost only wheel flats. In Stora Enso there are a few wheel flats while in SCA Logistics there is almost none. Wheel flats can only occur if a wheelset is blocked in a moving vehicle. That could however be due to a few different reasons.

    Studying data from workshops and automatic detectors, it was found that most flats occur in the ends of the trains. Some other patterns were that the inner wheelsets on wagons had less flats, and Stora Enso wagons temporarily moved to the SCA Skog network had less flats too. Therefore, the similarities and differences between these networks are studied and classified regarding their influence on wheel damage, and several different actions are suggested afterwards to decrease the number of flats. For the flats in the ends of the train is the remedy to teach the drivers the second, but better, driver valve RHZE2. Another remedy for the same purpose is to implement an end-of-train device that measures air pressure in the end of the train. That the inner wheelsets cope better is probably because one of two brake blocks there cannot freeze to the wheel. Therefore one action is to prevent running with frozen brake blocks by for example moving the train back and forth at red light. Lastly, when it comes to the Stora Enso wagons they probably break free from ice easier as they are heavier, so an extra wall added on the SCA Skog wagons might improve the situation.

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    fulltext
  • 18.
    Doulgerakis, Emmanouil
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Influence of Switches and Crossings on Wheel Wear of a Freight Vehicle2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Turnouts (Switches & Crossings) are important components in railway networks,

    as they provide the necessary flexibility for train operations by allowing trains to

    change among the tracks. But the turnout’s geometry with discontinuity in rail

    profiles and lack of transition curve causes additional wear both on track and on

    vehicle.

    The main goal of this MSc thesis is to investigate the influence of turnouts on wheel

    wear of a freight vehicle. This will be obtained by simulations in the commercial

    MBS software GENSYS. The wheel-rail contact is modelled according to Hertz’s

    theory and Kalker’s simplified theory, with the FASTSIM algorithm, and the wear

    calculations are performed according to Archard’s law.

    Wheel wear is estimated by considering variations in parameters which have effect

    on wheel-rail contact. All these variations are common in daily rail operation, and

    they are caused by it,

    i.e. worn wheel profiles, worn crossing nose and different

    stiffness of the stock and the switch rails at the beginning of the turnout. Moreover,

    the wheel wear is calculated for both possible directions which a vehicle can run,

    the diverging and the straight direction of the turnout. Especially for the straight

    direction, various running speeds have been tested as the speed limit when the

    vehicle follows the straight direction is higher than for the diverging part.

    Running with worn wheel profiles has the greatest impact in terms of increasing the

    wheel wear, especially on the outer part of wheel tread. In addition, the worn crossing

    nose results in increased wheel wear in this area. The results of the simulations

    concerning the different stiffness showed that the wheel wear caused by the contact

    of wheel and stock rail increases whereas the wear caused by the contact with the

    switch rail is kept at about the same level or decreases. It is concluded that turnouts

    have a significant impact on wheel wear, mainly because of the discontinuity in rail

    geometry and all the investigated parameters increase this impact. Moreover, great

    differences in wear values for areas close to each other are observed, mainly because

    of the wear coefficient values chosen in Archard’s wear map.

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    2013-Doulgerakis
  • 19.
    Sánchez Arandojo, Adrián
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    On validation of a wheel-rail wear prediction code2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the past years, several tools have been developed to try predicting wheel and rail

    wear of railway vehicles in an e-cient way. In this MSc thesis a new wear prediction

    tool developed by I.Persson is studied and compared with another wear prediction tool,

    developed by T.Jendel, which has been already validated and is in use since several years

    ago. The advantages that the new model gives are simpler structure, the consideration of

    wear as a continuous variable and that all the code is integrated in the same software.

    The two models have the same methodology until the part of the wear calculations

    and the post-processing. Wheel-rail geometry functions and time domain simulations are

    performed with the software GENSYS.

    In the simulation model the track and the vehicle are dened as well as other important

    properties such as vehicle speed and coe-cient of friction. Three simple tracks are used:

    tangent track, R=500 m curve with a cant of ht=0.15 m on the outer rail and R=1000 m

    curve with a cant of ht=0.1 m on the outer rail. The model is assumed to be symmetric so

    just outer (first and fourth axle) and inner (second and third axles) wheels are considered.

    During the vehicle-track interaction, the normal and tangential problems are solved.

    The wheel-rail contact is modelled according to Hertz's theory and Kalker's simplied

    theory with the help of the algorithm FASTSIM. Then wear calculations are performed

    according to Archard's wear law. It is applied in dierent ways, obtaining wear depth

    directly in Jendel's and wear volume rate in Persson's model.

    Jendel's model is rstly analyzed. Its specifc methodology is briefly explained and

    modications are performed on the code to make it work as similar as possible to Persson's

    model. Also parameters regarding the distance in which wear calculations are taken, the

    discretization of the width of the wheel and the discretization of the contact patch are

    analyzed.

    The methodology of Persson's model is also studied, most of all the performance of the

    post-processing which is one of the keys to the code. The parameters analyzed in this code

    are the ones regarding a statistical analysis performed during the post-processing and the

    discretization of the contact patch.

    Finally the comparisons between the wear depth obtained for both models are carried

    out. The discrepancies between the models are explained with the parameters analyzed

    and the dynamic behaviour of both models. Also a theoretical case is used as reference for

    comparison.

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    2013-Sanchez_Arandojo-wear_code_validation
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