<p>Numerical procedures for reliable wheel and rail wearprediction are rare. Recent development of simulationtechniques and computer power together with tribologicalknowledge do however suggest computer aided wear prediction.The objective of the related research field at the RoyalInstitute of Technology (KTH) is to arrive at a numericalprocedure able to simulate profile evolution due to uniformwear to a degree of accuracy sufficient for application tovehicle dynamics simulation. Such a tool would be useful formaintenance planning as well as optimisation of the transportsystem and its components.</p><p>The research contribution accounted for in this thesisincludes, in addition to a literature review, refinement ofmethods applied to uniform wheel wear simulation by inclusionof braking and improvement of the contact model. Further atentative application to uniform rail wheel simulation has beenproposed and tested.</p><p>The first part addresses issues related to braking andwheel-rail contact conditions in the context of wheel wearsimulation. The KTH approach includes Archard’s wear modelwith associated wear maps, vehicle dynamics simulation andrailway network definition. In previous work at KTH certainvariations in operating conditions have been accounted forthrough empirically estimated average scaling factors. Theobjective of the current research is to be able to include suchvariations in the set of simulations. In particular theinfluence of disc braking and varying friction and lubricationconditions are investigated. Both environmental factors likemoist and contamination and deliberate lubrication need to beconsidered. As part of the associated contact analysis theinfluence of tangential elastic deformation of the contactingsurfaces on the sliding velocity has been separatelyinvestigated and found to be essential in case of partial slipcontact conditions.</p><p>In the second part validation of the improvements related towheel wear simulation is addressed. Disc braking has beenincluded in the simulation set and a wear map for moist contactconditions based on recent tribometer tests has been draftedand tested. It has been shown that the previously used brakingfactor accounts for the combination of the contributions fromsurface elasticity and braking. Good agreement withmeasurements from the Stockholm commuter service is achieved.It is concluded that the model improvements accounted for aresufficient for adequate simulation of tread wear but thatfurther development of the flange / gauge corner contactmodelling may be needed.</p><p>In the final part a procedure for simulation of rail wearand corresponding profile evolution has been formulated. Asimulation set is selected defining the vehicles running on thetrack to be investigated, their operating conditions, andcontact parameters. Several variations of input data may beincluded together with the corresponding occurrenceprobability. Trial calculations of four non-lubricated curveswith radii from 303 m to 802 m show qualitatively reasonableresults in terms of profile shape development and difference inwear mechanisms between gauge corner and rail head. The wearrates related to traffic tonnage are however overestimated. Itis believed that model refinements in terms of environmentalinfluence and contact stress calculation are useful to improvethe quantitative results.</p> / QC 20100531

The link suspension is the most prevailing suspension system for freight wagons in Central and Western Europe. The system design is simple and has existed for more than 100 years. However, still its characteristics are not fully understood. This thesis investigates the dynamic performance of freight wagons and comprises five parts: In the first part a review of freight wagon running gear is made. The different suspension systems are described and their advantages and disadvantages are discussed. The second part focuses on the lateral force-displacement characteristics of the link suspension. Results from stationary measurements on freight wagons and laboratory tests of the link suspension characteristics are presented. To improve the understanding of various mechanisms and phenomena in link suspension systems, a simulation model is developed. In the third part the multibody dynamic simulation model is discussed. 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, a new simulation model is presented and validated against 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. A majority of the traffic related track deterioration cost originates from freight traffic. With heavier and faster freight trains the maintenance cost is likely to increase. In the fourth part the possibility to improve ride comfort and reduce track forces on standard freight wagons with link suspension is discussed. The variation of characteristics in link suspension running gear is considerable and unfavourable conditions leading to hunting are likely to occur. Supported by on-track tests and multibody dynamic simulations, it is concluded that the running behaviour of two-axled wagons with UIC double-link suspension as well as wagons with link suspension bogies (G-type) can be improved when the running gear are equipped with supplementary hydraulic dampers. Finally in the fifth part the effects of different types of running gear and operational conditions on the track deterioration marginal cost — in terms of settlement in the ballast, component fatigue, wear and RCF — is investigated. Considerable differences in track deterioration cost per produced ton-km for the different types of running gear are observed. Axle load is an important parameter for settlement and component fatigue. Also the height of centre of gravity has significant influence on track deterioration, especially on track sections with high cant deficiency or cant excess. / QC 20100802

Numerical procedures for reliable wheel and rail wearprediction are rare. Recent development of simulationtechniques and computer power together with tribologicalknowledge do however suggest computer aided wear prediction.The objective of the related research field at the RoyalInstitute of Technology (KTH) is to arrive at a numericalprocedure able to simulate profile evolution due to uniformwear to a degree of accuracy sufficient for application tovehicle dynamics simulation. Such a tool would be useful formaintenance planning as well as optimisation of the transportsystem and its components. The research contribution accounted for in this thesisincludes, in addition to a literature review, refinement ofmethods applied to uniform wheel wear simulation by inclusionof braking and improvement of the contact model. Further atentative application to uniform rail wheel simulation has beenproposed and tested. The first part addresses issues related to braking andwheel-rail contact conditions in the context of wheel wearsimulation. The KTH approach includes Archard’s wear modelwith associated wear maps, vehicle dynamics simulation andrailway network definition. In previous work at KTH certainvariations in operating conditions have been accounted forthrough empirically estimated average scaling factors. Theobjective of the current research is to be able to include suchvariations in the set of simulations. In particular theinfluence of disc braking and varying friction and lubricationconditions are investigated. Both environmental factors likemoist and contamination and deliberate lubrication need to beconsidered. As part of the associated contact analysis theinfluence of tangential elastic deformation of the contactingsurfaces on the sliding velocity has been separatelyinvestigated and found to be essential in case of partial slipcontact conditions. In the second part validation of the improvements related towheel wear simulation is addressed. Disc braking has beenincluded in the simulation set and a wear map for moist contactconditions based on recent tribometer tests has been draftedand tested. It has been shown that the previously used brakingfactor accounts for the combination of the contributions fromsurface elasticity and braking. Good agreement withmeasurements from the Stockholm commuter service is achieved.It is concluded that the model improvements accounted for aresufficient for adequate simulation of tread wear but thatfurther development of the flange / gauge corner contactmodelling may be needed. In the final part a procedure for simulation of rail wearand corresponding profile evolution has been formulated. Asimulation set is selected defining the vehicles running on thetrack to be investigated, their operating conditions, andcontact parameters. Several variations of input data may beincluded together with the corresponding occurrenceprobability. Trial calculations of four non-lubricated curveswith radii from 303 m to 802 m show qualitatively reasonableresults in terms of profile shape development and difference inwear mechanisms between gauge corner and rail head. The wearrates related to traffic tonnage are however overestimated. Itis believed that model refinements in terms of environmentalinfluence and contact stress calculation are useful to improvethe quantitative results. / QC 20100531