Subjects -> TRANSPORTATION (Total: 214 journals)     - AIR TRANSPORT (9 journals)    - AUTOMOBILES (26 journals)    - RAILROADS (10 journals)    - ROADS AND TRAFFIC (9 journals)    - SHIPS AND SHIPPING (43 journals)    - TRANSPORTATION (117 journals) TRANSPORTATION (117 journals)
 Showing 1 - 53 of 53 Journals sorted by number of followers Journal of Navigation       (Followers: 184) Accident Analysis & Prevention       (Followers: 131) Transportation Research Part A: Policy and Practice       (Followers: 38) Transportation Research Part B: Methodological       (Followers: 38) Urban, Planning and Transport Research       (Followers: 33) Transportation       (Followers: 32) Transportation Research Record : Journal of the Transportation Research Board       (Followers: 29) Transportation Research Part C: Emerging Technologies       (Followers: 29) Journal of Transport and Land Use       (Followers: 27) Transportation Science       (Followers: 26) Journal of Transport Geography       (Followers: 22) European Transport Research Review       (Followers: 22) Nonlinear Dynamics       (Followers: 20) Public Transport       (Followers: 18) International Journal of Sustainable Transportation       (Followers: 18) Cities in the 21st Century       (Followers: 17) Open 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(Followers: 11) International Journal of Crashworthiness       (Followers: 11) Proceedings of the Institution of Mechanical Engineers Part F: Journal of Rail and Rapid Transit       (Followers: 11) International Journal of Physical Distribution & Logistics Management       (Followers: 11) Journal of Transport and Supply Chain Management       (Followers: 10) Journal of Sport & Social Issues       (Followers: 10) Journal of Transportation Safety & Security       (Followers: 9) International Journal of Transportation Science and Technology       (Followers: 9) Travel Behaviour and Society       (Followers: 9) Transportmetrica A : Transport Science       (Followers: 8) Transportation Infrastructure Geotechnology       (Followers: 8) International Journal of Mobile Communications       (Followers: 8) Analytic Methods in Accident Research       (Followers: 8) International Journal of Electric and Hybrid Vehicles       (Followers: 8) Pervasive and Mobile Computing       (Followers: 8) 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(Followers: 4) IEEE Open Journal of Intelligent Transportation Systems       (Followers: 4) Journal of Traffic and Transportation Engineering (English Edition)       (Followers: 4) Transport and Telecommunication       (Followers: 4) Research in Transportation Business and Management       (Followers: 4) Transactions on Transport Sciences       (Followers: 4) Journal of Transportation and Logistics       (Followers: 3) TRANSPORTES       (Followers: 3) Journal of Transportation Security       (Followers: 3) World Electric Vehicle Journal       (Followers: 3) Journal of Big Data Analytics in Transportation       (Followers: 2) Transportation Research Interdisciplinary Perspectives       (Followers: 2) International Journal of Vehicle Systems Modelling and Testing       (Followers: 2) Travel Medicine and Infectious Disease       (Followers: 2) International Journal of Transportation Engineering       (Followers: 2) Sport, Ethics and Philosophy       (Followers: 2) Streetnotes       (Followers: 2) Packaging, Transport, Storage & Security of Radioactive Material       (Followers: 2) Danish Journal of Transportation Research / Dansk Tidsskrift for Transportforskning       (Followers: 1) eTransportation       (Followers: 1) Decision Making : Applications in Management and Engineering       (Followers: 1) Transportation Safety and Environment       (Followers: 1) Journal of Intelligent and Connected Vehicles       (Followers: 1) Logistics       (Followers: 1) International Journal of Ocean Systems Management       (Followers: 1) Asian Transport Studies       (Followers: 1) Romanian Journal of Transport Infrastructure       (Followers: 1) Open Transportation Journal       (Followers: 1) International Journal of Services Technology and Management       (Followers: 1) Synthesis Lectures on Mobile and Pervasive Computing       (Followers: 1) Emission Control Science and Technology       (Followers: 1) Botswana Journal of Technology       (Followers: 1) Transportation Geotechnics       (Followers: 1) Les Dossiers du Grihl       (Followers: 1) Recherche Transports Sécurité       (Followers: 1) Transportmetrica B : Transport Dynamics       (Followers: 1) Transportation Engineering       (Followers: 1) Journal of Public Transportation Maritime Transport Research Communications in Transportation Research IET Smart Cities Journal on Vehicle Routing Algorithms Transportation in Developing Economies Vehicles Periodica Polytechnica Transportation Engineering Transportation Systems and Technology LOGI ? 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Similar Journals
 Journal of Modern TransportationJournal Prestige (SJR): 0.354 Citation Impact (citeScore): 1Number of Followers: 7      Subscription journal ISSN (Print) 2095-087X - ISSN (Online) 2196-0577 Published by SpringerOpen  [228 journals]
• System reliability evaluation of long railway subgrade slopes considering
discrete instability

Abstract: Abstract This paper develops a dual-indicator discrete method (DDM) for evaluating the system reliability performance of long soil subgrade slopes. First, they are segmented into many slope sections using the random finite element method, to ensure each section statistically contains one potential local instability. Then, the $$k$$ -out-of- $$n$$ system model is used to describe the relationship between the total number of sections $$n$$ , the acceptable number of failure sections $$m$$ , the reliability of sections $$R_{{{\text{sec}}}}$$ , and the system reliability $$R_{{{\text{sys}}}}$$ . Finally, $$m$$ and $$R_{{{\text{sys}}}}$$ are jointly used to assess the system reliability performance. For cases lacking spatial data of soil properties, a simplified DDM is provided in which long subgrade slopes are segmented by the empirical value of section length and $$R_{{{\text{sec}}}}$$ is substituted by that of cross-sections taken from them. The results show that (1) DDM can provide the probability that the actual number of local instabilities does not exceed a desired threshold. (2) $$R_{{{\text{sys}}}}$$ decreases with increasing $$n$$ or decreasing $$R_{{{\text{sec}}}}$$ ; that is, it is likely to encounter more local instabilities for longer or weaker subgrade slopes. $$n$$ is negatively related to the horizontal scale of fluctuation of soil properties and positively related to the total length of subgrade slopes $$L$$ . (3) When $$L$$ is sufficiently large, there is a considerable opportunity to meet local instabilities even if $$R_{{{\text{sec}}}}$$ is large enough.
PubDate: 2022-06-01

• Stochastic dynamic simulation of railway vehicles collision using
data-driven modelling approach

Abstract: Abstract Using stochastic dynamic simulation for railway vehicle collision still faces many challenges, such as high modelling complexity and time-consuming. To address the challenges, we introduce a novel data-driven stochastic process modelling (DSPM) approach into dynamic simulation of the railway vehicle collision. This DSPM approach consists of two steps: (i) process description, four kinds of kernels are used to describe the uncertainty inherent in collision processes; (ii) solving, stochastic variational inferences and mini-batch algorithms can then be used to accelerate computations of stochastic processes. By applying DSPM, Gaussian process regression (GPR) and finite element (FE) methods to two collision scenarios (i.e. lead car colliding with a rigid wall, and the lead car colliding with another lead car), we are able to achieve a comprehensive analysis. The comparison between the DSPM approach and the FE method revealed that the DSPM approach is capable of calculating the corresponding confidence interval, simultaneously improving the overall computational efficiency. Comparing the DSPM approach with the GPR method indicates that the DSPM approach has the ability to accurately describe the dynamic response under unknown conditions. Overall, this research demonstrates the feasibility and usability of the proposed DSPM approach for stochastic dynamics simulation of the railway vehicle collision.
PubDate: 2022-04-28

• Quantitative detection of locomotive wheel polygonization under
non-stationary conditions by adaptive chirp mode decomposition

Abstract: Abstract Wheel polygonal wear is a common and severe defect, which seriously threatens the running safety and reliability of a railway vehicle especially a locomotive. Due to non-stationary running conditions (e.g., traction and braking) of the locomotive, the passing frequencies of a polygonal wheel will exhibit time-varying behaviors, which makes it too difficult to effectively detect the wheel defect. Moreover, most existing methods only achieve qualitative fault diagnosis and they cannot accurately identify defect levels. To address these issues, this paper reports a novel quantitative method for fault detection of wheel polygonization under non-stationary conditions based on a recently proposed adaptive chirp mode decomposition (ACMD) approach. Firstly, a coarse-to-fine method based on the time–frequency ridge detection and ACMD is developed to accurately estimate a time-varying gear meshing frequency and thus obtain a wheel rotating frequency from a vibration acceleration signal of a motor. After the rotating frequency is obtained, signal resampling and order analysis techniques are applied to an acceleration signal of an axle box to identify harmonic orders related to polygonal wear. Finally, the ACMD is combined with an inertial algorithm to estimate polygonal wear amplitudes. Not only a dynamics simulation but a field test was carried out to show that the proposed method can effectively detect both harmonic orders and their amplitudes of the wheel polygonization under non-stationary conditions.
PubDate: 2022-04-13

• On dynamic analysis method for large-scale
train–track–substructure interaction

Abstract: Abstract Train–track–substructure dynamic interaction is an extension of the vehicle–track coupled dynamics. It contributes to evaluate dynamic interaction and performance between train–track system and its substructures. For the first time, this work devotes to presenting engineering practical methods for modeling and solving such large-scale train–track–substructure interaction systems from a unified viewpoint. In this study, a train consists of several multi-rigid-body vehicles, and the track is modeled by various finite elements. The track length needs only satisfy the length of a train plus boundary length at two sides, despite how long the train moves on the track. The substructures and their interaction matrices to the upper track are established as independent modules, with no need for additionally building the track structures above substructures, and accordingly saving computational cost. Track–substructure local coordinates are defined to assist the confirming of the overlapped portions between the train–track system and the substructural system to effectively combine the cyclic calculation and iterative solution procedures. The advancement of this model lies in its convenience, efficiency and accuracy in continuously considering the vibration participation of multi-types of substructures against the moving of a train on the track. Numerical examples have shown the effectiveness of this method; besides, influence of substructures on train–track dynamic behaviors is illustrated accompanied by clarifying excitation difference of different track irregularity spectrums.
PubDate: 2022-03-18

• Aerodynamic characteristics of a high-speed train crossing the wake of a
bridge tower from moving model experiments

Abstract: Abstract In a strong crosswind, the wake of a bridge tower will lead to an abrupt change of the aerodynamic forces acting on a vehicle passing through it, which may result in problems related to the transportation safety. This study investigates the transient aerodynamic characteristics of a high-speed train moving in a truss girder bridge and passing by a bridge tower in a wind tunnel. The scaled ratio of the train, bridge, and tower are 1:30. Effects of various parameters such as the incoming wind speed, train speed, and yaw angle on the aerodynamic performance of the train were considered. Then the sudden change mechanism of aerodynamic loads on the train when it crosses over the tower was further discussed. The results show that the bridge tower has an apparent shielding effect on the train passing through it, with the influencing width being larger than the width of the tower. The train speed is the main factor affecting the influencing width of aerodynamic coefficients, and the mutation amplitude is mainly related to the yaw angle obtained by changing the incoming wind speed or train speed. The vehicle movement introduces an asymmetry of loading on the train in the process of approaching and leaving the wake of the bridge tower, which should not be neglected.
PubDate: 2022-03-05

• Polyurethane grouting materials with different compositions for the
treatment of mud pumping in ballastless track subgrade beds: properties
and application effect

Abstract: Abstract Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines, reduce the smoothness of the railway lines, and seriously affect the comfort and safety of the trains. Due to their good mechanical properties, two-component polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping. To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping, we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios, to determine an optimal composition ratio of the raw materials. Then, we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio. The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area, coordinating the dynamic response between the track structure and the subgrade bed. Thus, the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.
PubDate: 2022-02-15

• Rail temperature variation under heavy haul operations

Abstract: Abstract There currently does not exist in industry a reliable method for the detection of rail foot flaws. Like their head-based counterparts, foot flaws result in broken rail with potentially catastrophic consequences. A proposed area of research for the detection of these flaws is thermography, a non-contact method of measuring and analysing infrared emissions from an object under test. In industry, active excitation thermography is the most common, requiring an excitation source. This paper will present a temperature measurement system and a method of transient temperature extraction from the running rails for the effects of a passing train to evaluate heat transfer in the practical rail environment. The outcomes of these results will provide future direction in the development of a rail heat transfer model and determine if train passage provides enough active excitation for a thermography-based detection technique.
PubDate: 2022-02-11

• Dynamic characteristics of a switch and crossing on the West Coast main
line in the UK

Abstract: Abstract Railway switches and crossings constitute a small fraction of linear track length but consume a large proportion of the railway track system maintenance budget. While switch and crossing (S&C) faults rarely prevent trains from running, switches and crossings are the source of many faults and need continual attention. On the rare occasions when trains are prevented from running the cost of the disruption is very high. Condition monitoring of the point operating equipment that moves the switchblades has been in use for many years but condition monitoring of the state of the switch in terms of the support and mechanical damage as trains pass over has only recently started to become possible. To this end, it is important to understand the correlation between S&C faults and sensor data that can detect those faults. This paper assesses some of the data collected from multiple sensors variously positioned on and around a switch and crossing on the UK mainline for a few days of normal train operation. Accelerometers, geophones, and strain gauges were installed at the locations where they were anticipated to be most useful. Forces at the load transfer point on the crossing nose were estimated from two separate strain gauge bridges and possible use of acceleration on the crossing is discussed. Correlations between different data are analysed and assessed and correlation between peak estimated load transfer forces and accelerations is presented. Based on the analysis, conclusions are drawn about the different types of dynamic information around S&Cs that can be obtained from a variety of sensor types.
PubDate: 2022-01-29

• Recycled materials in railroad substructure: an energy perspective

Abstract: Abstract Given that the current ballasted tracks in Australia may not be able to support faster and significantly heavier freight trains as planned for the future, the imminent need for innovative and sustainable ballasted tracks for transport infrastructure is crucial. Over the past two decades, a number of studies have been conducted by the researchers of Transport Research Centre (TRC) at the University of Technology Sydney (UTS) to investigate the ability of recycled rubber mats, as well as waste tyre cells and granulated rubber to improve the stability of track substructure including ballast and subballast layers. This paper reviews four applications of these novel methods, including using recycled rubber products such as CWRC mixtures (i.e., mixtures of coal wash (CW) and rubber crumbs (RC)) and SEAL mixtures (i.e., mixtures of steel furnace slag, CW and RC) to replace subballast/capping materials, tyre cells reinforcements for subballast/capping layer and under ballast mats; and investigates the energy dissipation capacity for each application based on small-scale cyclic triaxial tests and large-scale track model tests. It has been found that the inclusion of these rubber products increases the energy dissipation effect of the track, hence reducing the ballast degradation efficiently and increasing the track stability. Moreover, a rheological model is also proposed to investigate the effect of different rubber inclusions on their efficiency to reduce the transient motion of rail track under dynamic loading. The outcomes elucidated in this paper will lead to a better understanding of the performance of ballast tracks upgraded with resilient rubber products, while promoting environmentally sustainable and more affordable ballasted tracks for greater passenger comfort and increased safety.
PubDate: 2022-01-27

• Traction power substation balance and losses estimation in AC railways
using a power transfer device through Monte Carlo analysis

Abstract: Abstract The high dynamic power requirements present in modern railway transportation systems raise research challenges for an optimal operation of railway electrification. This paper presents a Monte Carlo analysis on the application of a power transfer device installed in the neutral zone and exchanging active power between two sections. The main analyzed parameters are the active power balance in the two neighbor traction power substations and the system power losses. A simulation framework is presented to comprise the desired analysis and a universe of randomly distributed scenarios are tested to evaluate the effectiveness of the power transfer device system. The results show that the density of trains and the relative branch length of a traction power substation should be considered in the evaluation phase of the best place to install a power transfer device, towards the reduction of the operational power losses, while maintaining the two substations balanced in terms of active power.
PubDate: 2022-01-17

• Problems, assumptions and solutions in locomotive design, traction and
operational studies

Abstract: Abstract Locomotive design is a highly complex task that requires the use of systems engineering that depends upon knowledge from a range of disciplines and is strongly oriented on how to design and manage complex systems that operate under a wide range of different train operational conditions on various types of tracks. Considering that field investigation programs for locomotive operational scenarios involve high costs and cause disruption of train operations on real railway networks and given recent developments in the rollingstock compliance standards in Australia and overseas that allow the assessment of some aspects of rail vehicle behaviour through computer simulations, a great number of multidisciplinary research studies have been performed and these can contribute to further improvement of a locomotive design technique by increasing the amount of computer-based studies. This paper was focused on the presentation of the all-important key components required for locomotive studies, starting from developing a realistic locomotive design model, its validation and further applications for train studies. The integration of all engineering disciplines is achieved by means of advanced simulation approaches that can incorporate existing AC and DC locomotive designs, hybrid locomotive designs, full locomotive traction system models, rail friction processes, the application of simplified and exact wheel-rail contact theories, wheel-rail wear and rolling contact fatigue, train dynamic behaviour and in-train forces, comprehensive track infrastructure details, and the use of co-simulation and parallel computing. The co-simulation and parallel computing approaches that have been implemented on Central Queensland University’s High-Performance Computing cluster for locomotive studies will be presented. The confidence in these approaches is based on specific validation procedures that include a locomotive model acceptance procedure and field test data. The problems and limitations presented in locomotive traction studies in the way they are conducted at the present time are summarised and discussed.
PubDate: 2022-01-08

• Railway ground vibration and mitigation measures: benchmarking of best
practices

Abstract: Abstract Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their residents. Among the different sources, the one coming from the rail transit system will play a central concern in the following years due to its sustainability. Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry. This paper aims to describe and compare the different mitigation systems existing and reported in literature through a comprehensive state of the art analysis providing the performance of each measure. First, an introduction to the ground-borne vibration and noise generated from the wheel-rail contact and its propagation through the transmission path is presented. Then, the impact and the different ways of evaluating and assessing these effects are presented, and the insertion loss indicator is introduced. Next, the different mitigation measures at different levels (vehicle, track, transmission path and receiver) are discussed by describing their possible application and their efficiency in terms of insertion loss. Finally, a summary with inputs of how it is possible to address the future of mitigation systems is reported.
PubDate: 2022-01-08

• Experimental investigation on vibration characteristics of the
medium–low-speed maglev vehicle–turnout coupled system

Abstract: Abstract The steel turnout is one of the key components in the medium–low-speed maglev line system. However, the vehicle under active control is prone to vehicle–turnout coupled vibration, and thus, it is necessary to identify the vibration characteristics of this coupled system through field tests. To this end, dynamic performance tests were conducted on a vehicle–turnout coupled system in a medium–low-speed maglev test line. Firstly, the dynamic response data of the coupled system under various operating conditions were obtained. Then, the natural vibration characteristics of the turnout were analysed using the free attenuation method and the finite element method, indicating a good agreement between the simulation results and the measured results; the acceleration response characteristics of the coupled system were analysed in detail, and the ride quality of the vehicle was assessed by Sperling index. Finally, the frequency distribution characteristics of the coupled system were discussed. All these test results could provide references for model validation and optimized design of medium–low-speed maglev transport systems.
PubDate: 2021-12-30

performance

Abstract: Abstract The type of subgrade of a railroad foundation is vital to the overall performance of the track structure. With the train speed and tonnage increase, as well as environmental changes, the evaluation and influence of subgrade are even more paramount in the railroad track structure performance. A geomechanics classification for subgrade is proposed coupling the stiffness (resilient modulus) and permanent deformation behaviour evaluated by means of repeated triaxial loading tests. This classification covers from fine- to coarse-grained soils, grouped by UIC and ASTM. For this achievement, we first summarize the main models for estimating resilient modulus and permanent deformation, including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters. This is followed by the procedure required to arrive at the geomechanical classification and rating, as well as a discussion of the influence of environmental factors. This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.
PubDate: 2021-12-05

• Dynamic analysis of traction motor in a locomotive considering surface
waviness on races of a motor bearing

Abstract: Abstract The traction motor is the power source of the locomotive. If the surface waviness occurs on the races of the motor bearing, it will cause abnormal vibration and noise, accelerate fatigue and wear, and seriously affect the stability and safety of the traction power transmission. In this paper, an excitation model coupling the time-varying displacement and contact stiffness excitations is adopted to investigate the effect of the surface waviness of the motor bearing on the traction motor under the excitation from the locomotive-track coupled system. The detailed mechanical power transmission path and the internal/external excitations (e.g., wheel–rail interaction, gear mesh, and internal interactions of the rolling bearing) of the locomotive are comprehensively considered to provide accurate dynamic loads for the traction motor. Effects of the wavenumber and amplitude of the surface waviness on the traction motor and its neighbor components of the locomotive are investigated. The results indicate that controlling the amplitude of the waviness and avoiding the wavenumber being an integer multiple of the number of the rollers are helpful for reducing the abnormal vibration and noise of the traction motor.
PubDate: 2021-12-01

• Seismic analysis of high-speed railway irregular bridge–track system
considering V-shaped canyon effect

Abstract: Abstract To explore the effect of canyon topography on the seismic response of railway irregular bridge–track system that crosses a V-shaped canyon, seismic ground motions of the horizontal site and V-shaped canyon site were simulated through theoretical analysis with 12 earthquake records selected from the Pacific Earthquake Engineering Research Center (PEER) Strong Ground Motion Database matching the site condition of the bridge. Nonlinear seismic response analyses of an existing 11-span irregular simply supported railway bridge–track system were performed under the simulated spatially varying ground motions. The effects of the V-shaped canyon topography on the peak ground acceleration at bridge foundations and seismic responses of the bridge–track system were analyzed. Comparisons between the results of horizontal and V-shaped canyon sites show that the top relative displacement between adjacent piers at the junction of the incident side and the back side of the V-shaped site is almost two times that of the horizontal site, which also determines the seismic response of the fastener. The maximum displacement of the fastener occurs in the V-shaped canyon site and is 1.4 times larger than that in the horizontal site. Neglecting the effect of V-shaped canyon leads to the inappropriate assessment of the maximum seismic response of the irregular high-speed railway bridge–track system. Moreover, engineers should focus on the girder end to the left or right of the two fasteners within the distance of track seismic damage.
PubDate: 2021-11-12

• Deep learning-based fault diagnostic network of high-speed train secondary
suspension systems for immunity to track irregularities and wheel wear

Abstract: Abstract Fault detection and isolation of high-speed train suspension systems is of critical importance to guarantee train running safety. Firstly, the existing methods concerning fault detection or isolation of train suspension systems are briefly reviewed and divided into two categories, i.e., model-based and data-driven approaches. The advantages and disadvantages of these two categories of approaches are briefly summarized. Secondly, a 1D convolution network-based fault diagnostic method for high-speed train suspension systems is designed. To improve the robustness of the method, a Gaussian white noise strategy (GWN-strategy) for immunity to track irregularities and an edge sample training strategy (EST-strategy) for immunity to wheel wear are proposed. The whole network is called GWN-EST-1DCNN method. Thirdly, to show the performance of this method, a multibody dynamics simulation model of a high-speed train is built to generate the lateral acceleration of a bogie frame corresponding to different track irregularities, wheel profiles, and secondary suspension faults. The simulated signals are then inputted into the diagnostic network, and the results show the correctness and superiority of the GWN-EST-1DCNN method. Finally, the 1DCNN method is further validated using tracking data of a CRH3 train running on a high-speed railway line.
PubDate: 2021-10-20

• Safety evaluation of a vehicle–bridge interaction system using the
pseudo-excitation method

Abstract: Abstract A method for analysing the vehicle–bridge interaction system with enhanced objectivity is proposed in the paper, which considers the time-variant and random characteristics and allows finding the power spectral densities (PSDs) of the system responses directly from the PSD of track irregularity. The pseudo-excitation method is adopted in the proposed framework, where the vehicle is modelled as a rigid body and the bridge is modelled using the finite element method. The vertical and lateral wheel–rail pseudo-excitations are established assuming the wheel and rail have the same displacement and using the simplified Kalker creep theory, respectively. The power spectrum function of vehicle and bridge responses is calculated by history integral. Based on the dynamic responses from the deterministic and random analyses of the interaction system, and the probability density functions for three safety factors (derailment coefficient, wheel unloading rate, and lateral wheel axle force) are obtained, and the probabilities of the safety factors exceeding the given limits are calculated. The proposed method is validated by Monte Carlo simulations using a case study of a high-speed train running over a bridge with five simply supported spans and four piers.
PubDate: 2021-10-19

• Numerical simulation and optimization of aerodynamic uplift force of a
high-speed pantograph

Abstract: Abstract Aiming at the problem that aerodynamic uplift forces of the pantograph running in the knuckle-downstream and knuckle-upstream conditions are inconsistent, and their magnitudes do not satisfy the corresponding standard, the aerodynamic uplift forces of pantographs with baffles are numerically investigated, and an optimization method to determine the baffle angle is proposed. First, the error between the aerodynamic resistances of the pantograph obtained by numerical simulation and wind tunnel test is less than 5%, which indicates the accuracy of the numerical simulation method. Second, the original pantograph and pantographs equipped with three different baffles are numerically simulated to obtain the aerodynamic forces and moments of the pantograph components. Three different angles for the baffles are −17°, 0° and 17°. Then the multibody simulation is used to calculate the aerodynamic uplift force of the pantograph, and the optimal range for the baffle angle is determined. Results show that the lift force of the baffle increases with the increment of the angle in the knuckle-downstream condition, whereas the lift force of the baffle decreases with the increment of the angle in the knuckle-upstream condition. According to the results of the aerodynamic uplift force, the optimal angle of the baffle is determined to be 4.75° when the running speed is 350 km/h, and pantograph–catenary contact forces are 128.89 N and 129.15 N under the knuckle-downstream and knuckle-upstream operating conditions, respectively, which are almost equal and both meet the requirements of the standard EN50367:2012.
PubDate: 2021-10-06

• Rail RCF damage quantification and comparison for different damage models

Abstract: Abstract There are several fatigue-based approaches that estimate the evolution of rolling contact fatigue (RCF) on rails over time and built to be used in tandem with multi-body simulations of vehicle dynamics. However, most of the models are not directly comparable with each other since they are based on different physical models even though they shall predict the same RCF damage at the end. This article studies different approaches to quantifying RCF and puts forward a measure for the degree of agreement between them. The methodological framework studies various steps in the RCF quantification procedure within the context of one another, identifies the ‘primary quantification step’ in each approach and compares results of the fatigue analyses. In addition to this, two quantities—‘similarity’ and ‘correlation’—have been put forward to give an indication of mutual agreement between models. Four widely used surface-based and sub-surface-based fatigue quantification approaches with varying complexities have been studied. Different operational cases corresponding to a metro vehicle operation in Austria have been considered for this study. Results showed that the best possible quantity to compare is the normalized damage increment per loading cycle coming from different approaches. Amongst the methods studied, approaches that included the load distribution step on the contact patch showed higher similarity and correlation in their results. While the different approaches might qualitatively agree on whether contact cases are ‘damaging’ due to RCF, they might not quantitatively correlate with the trends observed for damage increment values.
PubDate: 2021-09-27

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