This thesis aims at systematically studying the possibilities of minimising devastatingconsequences of high-speed derailments by appropriate measures and features in thetrain design, including the running gear. The course of events immediately afterderailments is studied with respect to whether the train stays upright and close to thetrack centre line or deviates laterally with probably serious consequences. There is abelief in the railway community that some trains can better cope with derailment thenothers, although this superiority is apparently hard to quantify.Firstly, an empirical database has been established containing as much relevantinformation as possible of past incidents and accidents occurred at higher speeds due tomechanical failure close to the interface between the running gear and the track, as wellas other causes that ultimately brought the train into a derailed condition. Although nevertwo derailments are the same, certain patterns appeared to crystallise after analysing thecourse of events immediately after the failure based on the descriptions available in eachincident or accident report. Ultimately, this led to that several critical vehicle parameterscould be distinguished as capable to influence the outcome of a derailment.Secondly, two of the critical vehicle features found in the first stage have been subject todetailed analysis by means of multi-body system (MBS) simulations. The first phase ofthe computer simulation program focused on studying the tendency of a wheelset toderail as a result of an axle journal failure on the outside of the wheel. The prederailmentcomputer simulation model has been validated with good results for twoauthentic Swedish events of axle journal failure.Thereafter, one of the newly found critical vehicle feature, the wheelset mechanicalrestrictions relative to the bogie frame, have been extensively studied on an X 2000power unit and trailer car model. The results show that a vertical mechanical restrictionof the wheelset relative to the bogie frame of approximately 50 to 60 mm is capable ofkeeping the wheelsets on the rails after an axle journal failure, for the studied conditions.An axle mounted brake disc constitutes the second critical vehicle feature that has thepotential to favourably influence the sequence of events in cases of wheel flangeclimbing. A minimal range of geometrical parameters for which the rail would safely fillthe gap between the brake disc and the wheel has been calculated.The third and last part of the thesis establishes the prerequisites necessary in order tostudy the remaining of the critical vehicle parameters found in the first part, whichrequires complete MBS simulations of derailed vehicles rolling on track structures, i.e.concrete sleepers. To accomplish this task, hysteresis data for the force as function ofconcrete material indentation, are aimed to be acquired by means of finite element (FE)simulations. Therefore, the intended FE model of wheel-concrete sleeper impact issubjected to a tentative validation procedure. A good agreement is observed whencomparing the FE model results with an authentic accident in terms of concrete sleeperindentation. Furthermore, preliminary results in terms of a wheelset tendency to reboundafter concrete sleeper impact are presented. / QC 20101125

This thesis presents a theoretical application of multibody dynamics with unilateral contact to model the interaction of the damping element in a freight train suspension, the friction wedge, with the bolster and the side frame. The objective of the proposed approach is to produce a stand-alone model that can better characterize the interaction between the bolster, the friction wedge, and the side frame subsystems. The new model allows the wedge four degrees of freedom: vertical displacement, longitudinal (between the bolster and the side frame) displacement, pitch (rotation about the lateral axis), and yaw (rotation about the vertical axis). The new model also allows for toe variation. The stand-alone model shows the capability of capturing dynamics of the wedge which were not possible to simulate using previous models. The inclusion of unilateral contact conditions is integral in quantifying the behavior during lift-off and the stick-slip phenomena. The resulting friction wedge model is a 3D, dynamic, stand-alone model of a bolster-friction wedge-side frame assembly. The new stand-alone model was validated through simulation using simple inputs. The dedicated train modeling software NUCARS® has been used to run simulations with similar inputs and to compare — when possible — the results with those obtained from the new stand-alone MATLAB friction wedge model. The stand-alone model shows improvement in capturing the transient dynamics of the wedge better. Also, it can predict not only normal forces going into the side frame and bolster, but also the associated moments. Significant simulation results are presented and the main differences between the current NUCARS® models and the new stand-alone MATLAB models are highlighted. / Master of Science

Previous work in the Railway Technology Laboratory at Virginia Tech focused on better capturing the dynamics of the friction wedge, modeled as a 3D rigid body. The current study extends that work to a half-truck model treated as an application of multibody dynamics with unilateral contact to model the friction wedge interactions with the bolster and the sideframe. The half-truck model created in MATLAB is a 3D, dynamic, multibody dynamics model comprised of four rigid bodies: a bolster, two friction wedges, and a sideframe assembly. The model allows each wedge four degrees of freedom: vertical displacement, longitudinal displacement (between the bolster and sideframe), pitch (rotation around the lateral axis), and yaw (rotation around the vertical axis). The bolster and the sideframe have only the vertical degree of freedom. The geometry of these bodies can be adjusted for various simulation scenarios. The bolster can be initialized with a pre-defined yaw (rotation around the vertical axis) and the sideframe may be initialized with a pre-defined pitch/toe (rotation around the lateral axis). The multibody dynamics half-truck model simulation results have been compared with results from NUCARS®, an industry standard train modeling software, for similar inputs. The multibody dynamics models have also been extended to a variably damped full-truck model and a variably damped half-truck warping model. These models were reformulated to react dynamically to simulated truck warp inputs. The ability to better characterize truck warping properties can prevent train roll over and derailments from truck hunting. In a quarter-truck variably damped configuration the effects of a curved wedge surface has also been explored. Actual friction wedges have surfaces which are slightly curved, this iteration in the multibody dynamics friction wedge modeling attempts to draw one step closer to actual friction wedge geometry. This model lays the ground work for a contact dependant wedge wearing model based on material properties and tribology. / Master of Science

This diploma thesis deals with rail undercarriage of stacker/reclaimer used in thermal power plants. The paper focuses on a conceptual framework of two-track bogie rail undercarriage and on a calculation of maximal load of undercarriage wheels within operational processes. The results are used for a design of two-wheel driven bogie and its main parts. The next part of the thesis presents finite element method analysis of a designed bogie along with a projection drawing. The diploma thesis was elaborated in cooperation with a company NOEN a. s.

The diploma thesis deals with the design of a magnetorheological damper with a short response time of the damping force for the bogie of a rail vehicle. The largest component, which slows down the response, is the eddy currents generated in the piston group of the MR damper. A rapid onset of damping force is achieved by using a shape approach in magnetic circuit design. The shape approach increases the distance that the eddy currents must travel, and therefore it helps to reduce them. The shape approach is realized by grooving the core and the shell of the MR damper. The proposed fast version of the MR damper is measured on a hydraulic pulsator and its results show a sufficient time response of the damping force. This response does not exceed 8 ms for the primary onset of the damping force. The new fast design of the MR damper combines the greatest advantages of the technology and enables to meet new requirements for damping elements in the rolling stock chassis.

The current thesis work is based on fatigue testing of welded structures which is completed in collaboration with Volvo CE. Improvement of the technology and customers demands for higher quality products with lower price makes the VCE to invest on the product development projects. One of the projects in VCE focuses on the weight and production cost optimization of the bogie beam on the hauler. The present project is a completion of the previous project with the objective of the fatigue testing of the bogie beam of the hauler under oscillating loads for verification of the expected fatigue life assessed with FEM. In the process of this work, an existing test rig is modified. The strains over the beam are measured through strain gauges mounted on the beam. The simulated model, the stresses and strains are investigated. The fatigue life is evaluated with different fatigue assessment methods. Finally, the outcomes of all the methods for fatigue investigation of the beam are compared and verified. / Detta examensarbete, som utförts för Volvo CE, behandlar utmattningsprov av svetsade konstruktioner. Teknikutveckling och förändrade kundkrav på högre kvalitet till en lägre kostnad är drivkrafter för Volvo CE att investera i produkt- och metodutvecklingsprojekt, som exempelvis det aktuella projektet att optimera vikt och tillverkningskostnad för boggi-balkar till dumprar. Detta projekt är en fortsättning av ett tidigare arbete som hade som mål att verifiera utmattningslivslängden för en boggibalk till en dumper predikterad med FEM, genom att utmattningsprova balken för oscillerande last. Som en del av projektet modifieras en existerande provningsrigg. Töjningar på balken mats med ett antal töjningsgivare monterade på balken. Spännings och töjningfrån den simulerade modellen analyseras och utmattningslivslängden jämförs för olika metoder för att prediktera utmattning. Slutligen jämförs och veriferas dessa metoder.

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. / En flerkroppssimulering genomfördes med hjälp av Simpack med syfte att undersöka gångegenskaperna hos ett järnvägsslipfordon, med boggi som nyligen utvecklats av Ganz. Huvudsyftet bakom simuleringarna var att förutspå - och underlätta godkännandet av fordonets acceptanskrav samt underlätta pågående utveckling.  En flerkroppsmodell konstruerades och de mest kritiska kraftbärande elementen undersöktes - och verifierades separat med hjälp av tester. Säkerhetsaspekterna kring urspårning undersöktes utifrån både europeiska och australiska standarder. Fordonets gångstabilitet bedömdes med både standard - samt bred spårviddsvarianter. Fordonets svängningsegenskaper bestämdes genom att genomföra beräkningar av flexibilitetskonstanten både numeriskt och analytiskt.  En parameterstudie genomfördes för fordonets primära vertikala dämpare med avsikt att evaluera empiriskt valda dämpare samt optimera prestanda. Resultaten visar att dämpningskoefficienten avsevärt kan minskas samtidigt som acceptabel rullningsförmåga behålls, vilket därmed förlänger dämparens livstid. Installation av girdämpare är inte nödvändigt, baserat på stabilitetsundersökningar, dock behålls fästen på boggi-prototypen för att möjliggöra framtida monteringar av sådana element.

Volvo Construction Equipment is highly regarded for robust products, but with an increasing competition in their market, development of the product portfolio is more important than ever. One step being carried out is to reduce losses in powertrains and increase the fuel efficiency for solutions such as articulated haulers and wheel loaders. This would eventually lower the fuel costs and emissions for the end customer. With this development, Volvo CE could strengthen their position in the market while also contributing to reducing the construction industry's environmental impact. By investigating the front bogie axle of the recently introduced hauler, Volvo A60H, important information about possible reductions and the distribution of the current losses were found. The investigation focused on a front bogie axle, but some of the results are applicable for other applications such as wheel loaders as well, since a lot of the technology in the axles are similar. A conceptual study was performed where completely new ideas were generated, such as implementing a dry sump system in the axle, as well as ideas for improving the subcomponents currently found in the axle. Two cases were presented for the evaluation of concepts, one with a fully loaded dump body and low speeds, and one with an unloaded dump body and a wider speed interval. The concepts were later evaluated using calculation tools such as MATLAB and a Simulink-model was created for the losses in the axle. When combining concepts that reduces load dependent losses, a potential reduction of 64% of the axle's total losses was achieved for the case with a full dump body. The largest improvement found for the load independent losses was 8% with an unloaded hauler and the highest speed investigated, 50 km/h. A dry sump system improves the axle's efficiency with 45% in optimal working conditions, but was found to lower the efficiency at other conditions. Room for improvement of axle losses currently exists both for load dependent and load independent losses. The evaluation performed pointed towards the load dependent losses being the largest influence on the total losses, even with an unloaded dump body and high speeds. This is an interesting observation since a lot of work at Volvo CE has revolved around reducing the load independent losses since these are easier to affect with different lubrication levels and rotational speeds. A test methodology for load dependent losses should be implemented in order to validate the results of this thesis work, and also to aid further development at Volvo CE.

This thesis aims at systematically studying the possibilities of minimizing devastating consequences of high-speed rail vehicle derailments by appropriate measures and features in the train design including the running gear. Firstly, an empirical database is established containing as much relevant information as possible of past incidents and accidents that have occurred at substantial running speeds due to mechanical failure close to the interface between the running gear and the track. Other causes that ultimately brought the train in a derailed condition are also covered. Although various accidental circumstances make each derailment a unique event, certain patterns appear to emerge which lead to several critical vehicle parameters capable of influencing the outcome of a derailment or preventing a derailment to occur. Secondly, the possibility of preventing wheel climbing derailments after an axle journal failure is studied by implementing mechanical restrictions between wheelsets and bogie frame. In this respect, a multi body system (MBS) computer model is developed to account for such an axle failure condition, which is successfully validated on the basis of two authentic passenger car events. In order to study the overall post-derailment vehicle behaviour, in particular the wheelsets’ vertical motion and lateral deviation on sleepers, a comprehensive MBS post-derailment module is developed and implemented in the commercially available software GENSYS. The model detects wheel-sleeper impact conditions and applies valid force resultants calculated through linear interpolation based on a pre-defined look-up table. The table was constructed through exhaustive finite element (FE) wheel to concrete sleeper impact simulations utilising the commercially available software LS-DYNA. The MBS post-derailment module has been validated successfully in several stages, including a correct prediction of the derailing wheelset’s trajectory over ten consecutive sleepers in comparison with an authentic passenger vehicle derailment event. An extensive simulation analysis on the feasibility of utilizing alternative substitute guidance mechanisms attached to the running gear on rail vehicles is presented, as means of minimizing the lateral deviation. Three low-reaching guidance mechanisms attached onto the running gear (bogie frame, brake disc and axle journal box) are analysed in terms of geometrical parameters for a successful engagement with the rail in order to prevent large lateral deviations after twelve different derailment scenarios. Three conventional coupled passenger trailing cars are investigated in terms of lateral deviation and vehicle overturning tendency after derailments on tangent and curved track. This is performed as a function of various vehicle design features and parameters such as: maximum centre coupler yaw angle, carbody height of centre of gravity, coupler height and additional running gear features. In a similar manner, the articulated train concept is investigated in terms of the post-derailment vehicle behaviour as a function of different inter-carbody damper characteristics and running gear features. / QC 20100701

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