1,721,067 research outputs found
kit di adattamento per un gruppo mozzo ruota, gruppo mozzo ruota provvisto di tale kit e relativo metodo di smontaggio
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Using multi-core architectures to solve the wheel-rail contact problem
No full textThe forces exchanged between wheel and the rail are fundamental in order to study the railway vehicle dynamic. These forces arise from the non linear combination of profile contact and friction and their calculation can be performed using iterative methods which require important calculation time. Simulation of railway vehicle dynamic takes therefore large calculation time or simplified contact models are needed. This becomes critical especially in case of real time simulation. Recent development of CPU based on multi-core processor makes possible to distribute the calculation of contact forces and the vehicle dynamic problem over different cores, reducing the calculation time. This work describes the strategies adopted to perform parallel distributed calculation starting from the RTCONTACT code, developed at Politecnico di Torino during the last years. According to the proposed approach, the contact problem is solved using one core for each wheel, while one or more cores can be used to solve the vehicle dynamics. An example of application of the contact code, distributed on different cores, is shown during evaluation in a real-time environment of the wheel and roller profile evolution on a scaled roller-rig
Real Time Implementation of a Traction Control Algorithm on a Scaled Roller Rig
No full textTraction control is a very important matter in railway vehicle dynamics. Its optimization allows improvement of the performance of a locomotive by working close to the limit of adhesion. On the other hand, in case the adhesion limit is surpassed, the wheels are subjected to heavy wear and there is also a big risk that vibrations in the traction occur. Similar considerations can be made in the case of braking. The development and optimization of a traction/braking control algorithm is a complex activity, because it is usually performed on a real vehicle on the track, where many uncertainties are present due to environmental conditions and vehicle characteristics. This work shows the use of a scaled roller rig to develop and optimize a traction control algorithm on a single wheelset. Measurements performed on the wheelset are used to estimate the optimal adhesion forces by means of a wheel/rail contact algorithm executed in real time. This allows application of the optimal adhesion forc
Long train simulation using a multibody code
No full textThe work deals with the simulation of long trains in traction condition using a multibody code. The proposed approach consists of the use of mixed models of detailed and simplified vehicle sub-models in order to allow the simulation of the longitudinal dynamic of the entire train, and the analysis of the wheel/rail forces for the detailed sub-models. In this way, it is possible to investigate the effect of the longitudinal efforts on the wheel/rail forces and, more specifically, on the vehicle safety. The vehicle and track configuration is taken from the Benchmark on longitudinal dynamic of trains proposed by the Central Queensland University
Analisi parametrica numerico/sperimentale della stabilita' di un carrello ferroviario su roller rig
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Multibody simulation of vehicles interactions in freight trains during curving and braking operations
No full textDetermination of wheel-roller friction coefficient on roller rigs for railway applications
No full textRailway technology is strongly influenced by the friction coefficient between wheel and rail. Friction plays a key role in many aspects of railway dynamic such as derailment, wear, noise, stability and is the most important factor to be considered in traction and braking problems. The railway system is based on the interaction of the profiles of wheel and rail, and their relative motion is subject to the presence of friction, which produces tangential forces acting on the vehicle and determining its dynamic behaviour. In case of traction and braking, the presence of friction is adopted in order to generate the required traction and braking force, and the study of friction in this field is indicated as adhesion and it is fundamental to define the vehicle performance. Since the railway system is subjected to the environmental effects, the friction coefficient can vary due to the presence of contamination, such as water, rust or weaves on the rail surface. The determination of the friction coefficient is usually obtained through complex and expensive experimental tests performed on the track using a real vehicle. Those tests are mandatory to verify the vehicle safety especially when active system are adopted to control traction and braking (WSP). An alternative to the use of test on the track, is the adoption of test on a roller-rig, a dynamic track simulator where the track is replaced by rollers. The roller rig allows to recreate in a laboratory environment test conditions comparable with the track, but with better repeatability, lower costs and higher safety. Both full scale or scaled similitude prototypes can be used on roller rig, and this strategy was adopted since the beginning of the 19th century to study traction by Carter. In the present work, a simple and efficient laboratory methodology for the estimation of the value of static friction coefficient on roller-rig is proposed. An accurate determination of the static friction coefficient is mandatory when a roller rig is adopted to study adhesion, wear or vehicle dynamic, in order to be able to perform different tests in known initial condition
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