► Development of innovative model for the wear prediction at the wheel–rail interface. ► Multibody simulations are used to study the dynamics of the vehicle. ► Contact points and contact forces at ...the wheel–rail interface are evaluated by a fully 3D contact model. ► The model has been validated by means of experimental data provided by Trenitalia.
The prediction of the wear at the wheel–rail interface is a fundamental problem in the railway field, mainly correlated to the planning of maintenance interventions, vehicle stability and the possibility of researching specific strategies for the wheel and rail profile optimization. In this work the Authors present a model specifically developed for the evaluation of the wheel and rail profile evolution due to wear, whose layout is made up of two mutually interactive but separate units: a vehicle model for the dynamic analysis and a model for the wear estimation. The first one is made up of two parts that interact online during the dynamic simulations: a 3D multibody model of the railway vehicle implemented in Simpack Rail (a commercial software for the analysis of multibody systems) and an innovative 3D global contact model (developed by the Authors in previous works) for the detection of the contact points between wheel and rail and for the calculation of the forces in the contact patches (implemented in C/C++ environment). The wear model, implemented in the Matlab environment, is mainly based on experimental relationships found in literature between the removed material and the energy dissipated by friction at the contact. It starts from the outputs of the dynamic simulations (position of contact points, contact forces and global creepages) and calculates the pressures inside the contact patches through a local contact model (FASTSIM algorithm); then the material removed due to wear is evaluated and the worn profiles of wheel and rail are obtained. This approach allows the evaluation of both the quantity of removed material and its distribution along the wheel and rail profiles in order to analyze the development of the profiles shape during their lifetime.
The whole model is based on a discrete process: each discrete step consists in one dynamic simulation and one profile update by means of the wear model while, within the discrete step, the profiles are supposed to be constant. The choice of an appropriate step is fundamental in terms of precision and computational load. Moreover the different time scales characterizing the wheel and rail wear evolution require the development of a suitable strategy for the profile update: the strategy proposed by the Authors is based both on the total distance traveled by the considered vehicle and on the total tonnage burden on the track. The entire model has been developed and validated in collaboration with Trenitalia S.p.A. and Rete Ferroviaria Italiana (RFI), which have provided the technical documentation and the experimental results relating to some tests performed with the vehicle DMU Aln 501 Minuetto on the Aosta-Pre Saint Didier line.
The last decade observed a significant research effort directed towards maneuverability and safety of mobile robots such as smart wheelchairs. The conventional electric wheelchair can be equipped ...with motorized omnidirectional wheels and several sensors serving as inputs for the controller to achieve smooth, safe, and reliable maneuverability. This work uses the decentralized algorithm to control the motion of omnidirectional wheelchairs. In the body frame of the omnidirectional wheeled wheelchair there are three separated independent components of motion including rotational motion, horizontal motion, and vertical motion, which can be controlled separately. So, each component can have its different sub-controller with a minimum tracking error. The present work aims to enhance the mobility of wheelchair users by utilizing an application to control the motion of their attained/unattained smart wheelchairs, especially in narrow places and at hard detours such as 90˚ corners and U-turns, which improves the quality of life of disabled users by facilitating their wheelchairs' maneuverability. Two approaches of artificial intelligent-based controllers (PD-Fuzzy-P and GA-PID controllers) are designed to optimally enhance the maneuverability of the system. MATLAB software is used to simulate the system and calculate the Mean Error (ME) and Mean Square Error (MSE) for various scenarios in both approaches, the results showed that the PD-Fuzzy-P controller has a faster convergence in trajectory tracking than the GA-PID controller. Therefore, the proposed system can find its application in many areas including transporting locomotor-based disabled individuals and geriatric people as well as automated guided vehicles.
Wheel wear is a natural phenomenon of wheel-rail rolling contact during vehicle operation. The non-uniform wear in lateral and circumferential directions is normally occurred on wheels. The lateral ...non-uniform wear will lead to the unexpected hollow wear which can cause flange to flange vibration at low-frequency band, and the circumferential non-uniform wear will result in the vertical vibration which is the originate from the polygon phenomenon. These two forms of wear are coupled to each other on wheels and affect the dynamic behaviours of wheel-rail system. In this paper, a wheel-rail contact dynamics model which includes the 3D geometric shape of wheel profile is established and employed to vehicle system dynamics. The results show that the contact mechanical properties of wheel-rail are greatly affected by the 3D wheel profile. The low-frequency vibration of wheelset caused by hollow wear and the high-frequency vibration by polygonised wear are coupled, which increase the vibrational acceleration of wheel-rail system and even made for the main problem of the periodic separation of wheel and rail and aggravate the wear of wheel polygon.
The aim of this study is to analyze how wheel wear affects the wheel reprofiling and service life and evaluate if these aspects can be improved by a new optimal wheel profile design. The NSGA-II ...multi-objective optimization algorithm was used to generate three optimal wheel profiles that are used alongside the current BRA profile for this analysis. After the optimization process, wear simulation was done to verify if the profiles performance will be maintained over time and to analyze how the worn profile shape affects reprofiling and service life. To quantify this, the worn profiles are used to simulate the reprofiling process in order to estimate the wheel's expected service life according to the wheels geometric tolerances. For this railway, an increase of at least 17% of service life can be expected by reducing the hollow wear maintenance limit from 3 mm to 2.5 mm while an increase of at least 29% can be expected from changing the limit from 3 mm to 2 mm.
•Wear and reprofile simulation for data acquisition.•Large hollow wear values leads to decreased wheel life.•Large hollow wear worsens wheel reprofiling efficiency.•Improved wheel profile creation method.•Increase in wheel life by lowering permissible hollow wear limit.
On the sloping section of a train service line located in mountainous areas, idling and skidding of the wheels caused by leaves that fall on the railhead in autumn often occurs, and this hinders the ...scheduled operation of the train. Although countermeasures such as spraying sand or ceramic particles onto the contact zone of wheel/rail are adopted, the effect is insufficient in late autumn. For clarifying the mechanism of the decrease in the adhesion between the wheel and the rail based on fallen leaves and acquiring information useful for practical implementation of countermeasures, the authors conducted a vehicle running test with driving and braking operations on a test line to investigate the occurrence of wheel slipping/sliding under various railhead states such as dry/wet leaves and dry/wet black accretion films, as well as the adhesion coefficient between the wheel and the rail when dry/wet black accretion films exist on the railhead. The results clarified that the wheel slipping/sliding was likely to occur under wet conditions, in particular frequently occur while wet black accretion films exist on the railhead, and then a low adhesion coefficient was recognized under the same conditions. Regarding the black accretion film formation process, the authors reproduced by a rail cooling device which can simulate atmospheric temperature in mountain area, and clarified that the tannin contained in the crushed fallen leaves has a reaction with steel comment of rail under wet (condensation, frost, light rain etc.) conditions and then black tannin iron was generated and adhere to the railhead. The countermeasure of wheel slip/slide should be focused on how to prevent the formation of the black accretion films or remove the black accretion films in the future work.
•The adhesion coefficient decreases significantly, and wheels tend to slip or slide when a black accretion film made from crushed leaves adheres to the rail surface and becomes wet.•Wheel slip or slide occurs in area surrounded by many trees and also in areas far from trees, due to the transcription of the black accretion film to a far place.•The slip and slid caused by falling leaves are due to the black accretion film formed on the rail surface. In particular, this phenomenon easily occurs in wet conditions.
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•Rail-wheel analysis of the train.•Real time monitoring and detection of the train wheel passage using optical sensor fiber Bragg grating sensor.•Positions of grating sensors ...installed on the rail.•Time domain and frequency spectrum analysis for the strain data induced on the rail when train passes by, to detect wheel flats.•Reflection spectrum analysis for good wheel and bad wheel of a passenger train.
Wheel flats are a key source of issues in railway systems, as they generate significant wear on both the infrastructure and the train carriages. Flat zones on the wheel tread are created by the wheel sliding unintentionally on the rail. They can cause serious damage to the train and accidents, so identifying worn wheels is critical for human safety and rail transit. The purpose of this study is to present the real-time implementation of fiber Bragg grating sensors on rail tracks and to investigate the train's flat wheel status. By considering passenger train running at speed 70kmph, it has been monitored for 35 sec in the interrogator. Real time analysis of strain induced in the rail was calculated and it has been found from the sensor reading there is peak value of strain of the order of 303.4 µɛ which implies that wheel flatness is present whereas for normal wheel strain value is minimal up to 173.23 µɛ. By collecting experimental strain data simulation has been done and shift in peak wavelength at 1550.804 nm and reflectivity obtained was 89.3% for flat wheel. Simulation result shows that there is a remarkable wavelength shift for the flat wheel and normal wheel from the Bragg center wavelength.
The number of operating high-speed trains in China is around 2800 today and 179,200 wheels are under maintenance in one reprofiling period. To help researchers to understand the evolution of the ...wheel profile and improve the reprofiling strategy of the wheels, this study predicts the development of wheel profiles on a high-speed train as function of mileage and compare simulated worn wheel profiles with measured ones. The methodology includes transient multi-body dynamic simulation, wheel-rail contact calculation and wear calculation with Archard's model. Calibrated by analysing measurements of worn S1002CN profiles and performing parameters sensitivity study in the wear model, the model is then used to predict the development of a recently designed wheel profile, called S1002CN-RF. The simulation results for S1002CN and S1002CN-RF show that the predicted wheel profiles coincide with the measured ones. Wear prediction of another high-speed wheel profile (LMA) validates that the vehicle performance with respect to wear could be further improved compared to using S1002CN or S1002CN-RF. Finally, the influence of track alignment and operating speed is investigated. The wear increases with the speed increasing up to 300 km/h, but stays almost constant with a further speed increase from 300 to 400 km/h.
For a railway vehicle moving over a series of floating-slab (FS) tracks with identical spans at a constant speed, track-induced resonance on the railway vehicle could occur when any of the ...frequencies of the FS track coincides with any of those implied by the wheel loads. Under this condition, the wheel-rail interaction will be aggravated and the ride comfort of railway vehicles will be deteriorated. This paper presents an experimental and numerical investigation of the mechanism and countermeasures for the resonant response of a metro vehicle induced by eccentric wheels travelling on FS tracks. The characteristics of the resonant response of the metro vehicle are revealed through the field tracking tests. A vehicle-track model considering the FS tracks and eccentric wheels is developed to analyse the resonant mechanism. Several countermeasures, including optimal design of FS track structure and elimination of wheel eccentric wear, are proposed to restrain the resonant vibration. The results show that the resonance caused by the eccentric wheels moving over FS tracks is the root causes for the ride comfort reduction of the metro vehicle. The field tests validate that re-profiling eccentric wheels can significantly eliminate the resonance phenomenon and enhance vehicle dynamics performances.
Creating grooves in the surface of grinding wheels for the purposes of modifying their performance properties has been a subject of academic interest since the late 1970s. Recently, this area of ...investigation has increased in popularity, with around half of all papers on the subject being published in the last decade. The advantages of grooved grinding wheels over conventional wheels have been well documented across the literature: decreased specific energy of machining, decreased process forces, and decreased process temperatures. However, there remains some debate over the disadvantages of grooved wheels over conventional wheels, namely, increased wheel wear and increased surface roughness. This paper presents a literature review of state-of-the-art grinding wheel grooving processes for vitrified bond grinding wheels, along with a proposed update to the nomenclature surrounding grinding wheel grooves. The advantages and disadvantages of several grooving methods are then discussed and areas of future research are suggested.
•A five DOF vehicle dynamics model based on a Uni-Tire model is established.•Sliding mode control algorithm is utilized at engine speed dragged up phase.•A feedforward with robust feedback controller ...is applied at synchronization phase.•HIL bench is built to validate effectiveness of proposed control strategy.
When the four-wheel-drive hybrid electric vehicle (HEV) equipped with a dry dual clutch transmission (DCT) is in the mode transition process from pure electrical rear wheel drive to front wheel drive with engine or hybrid drive, the problem of vehicle longitudinal jerk is prominent. A mode transition robust control algorithm which resists external disturbance and model parameter fluctuation has been developed, by taking full advantage of fast and accurate torque (or speed) response of three electrical power sources and getting the clutch of DCT fully involved in the mode transition process. Firstly, models of key components of driveline system have been established, and the model of five-degrees-of-freedom vehicle longitudinal dynamics has been built by using a Uni-Tire model. Next, a multistage optimal control method has been produced to realize the decision of engine torque and clutch-transmitted torque. The sliding-mode control strategy for measurable disturbance has been proposed at the stage of engine speed dragged up. Meanwhile, the double tracking control architecture that integrates the model calculating feedforward control with H∞ robust feedback control has been presented at the stage of speed synchronization. Finally, the results from Matlab/Simulink software and hardware-in-the-loop test both demonstrate that the proposed control strategy for mode transition can not only coordinate the torque among different power sources and clutch while minimizing vehicle longitudinal jerk, but also provide strong robustness to model uncertainties and external disturbance.
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