Experimental and numerical simulation of wheel-rail adhesion and wear using a scaled roller rig and a real-time contact code

The work shows the use of a scaled roller rig to validate a real time wheel-rail contact code developed to study the wheel rail adhesion and the wear evolution. The code allows the profiles to change at each time step in order to take into account the material loss due to the wear process. The contact code replicates a testing machine composed of a roller rig with a prototype of a single suspended wheelset pressed onto it with a variable load. The roller rig, developed at Politecnico di Torino, is used to validate and optimize the contact code referring to experimental data directly measured in real time. The test bench, in fact, allows measurement of specific kinematical quantities and forces that are elaborated by the real-time code in order to produce numerical results for comparison with the experimental ones. This approach can be applied both to the determination of wheel-rail adhesion and to the wear process. The test rig is also equipped with a laser profilometer that allows measurement of the wheel and rail profiles with a very high accuracy

A Novel Analytical Method to Calculate Wheel-Rail Tangential Forces and Validation on a Scaled Roller-Rig

The study of railway dynamic strongly depends on the estimation of the tangential forces acting between wheel and rail. Simulation of the dynamical behaviour of railway vehicles is often performed using multibody codes, and the calculation of the contact forces must be efficient and accurate, even if the contact problem is strongly nonlinear. Therefore, the contact problem is still of great interest for researchers. This work proposes an analytical and efficient algorithm to calculate wheel-rail tangential forces. The proposed method is compared with the most commonly used algorithms under different conditions. In addition, experimental tests are performed on a scaled prototype on roller-rig to demonstrate that the method can be easily adjusted using experimental results. The benefit of the proposed method is to provide an analytical and fast solution, able to obtain accurate results and to allow corrections based on empirical evidence

UN ALGORITMO DI CONTATTO RUOTA-ROTAIA PER L'IMPIEGO IN SISTEMI DI CALCOLO IN TEMPO REALE

Nello studio del comportamento dinamico dei veicoli ferroviari uno degli aspetti di maggiore rilevanza è il problema della determinazione delle forze scambiate al contatto ruota-rotaia. Questo problema è tuttora oggetto di studi che da un lato cercano di ottenere risultati di maggiore accuratezza e dall'altro cercano di ridurre i tempi di calcolo. Il lavoro illustra i risultati ottenuti con l'algoritmo di contatto sviluppato presso il Politecnico di Torino, denominato RTCONTACT; questo codice, che è un'evoluzione dell'algoritmo CONPOL, è il risultato di lunghe attività di ricerca, le versioni precedenti sono state utilizzate in cosimulazione con codici MBS e in ambiente Matlab® per simulare il comportamento di veicoli ferroviari. Il codice è stato sviluppato anche basandosi su risultati sperimentali ottenuti da banco prova "Roller-Rig". In questo lavoro si illustrano le principali caratteristiche del codice e si presentano confronti con altri codici numerici, pubblicazioni e normative per i risultati di maggiore interesse per il contatto ruota-rotai

Design and Simulation of a Railway Vehicle for the Transport of People with Reduced Mobility

One of the most important aspects of the design activity of passenger railway vehicles is the optimization of the comfort level that is often in contrast with other requirements, such as low weight, to reduce energy consumption, and high and flexible seating capacity. Due to the coach weight reduction, the car body structure becomes more susceptible to structural vibrations that affect the passenger comfort. In modern vehicles, seats are important elements to achieve the desired comfort, but in order to design and estimate the actual comfort level, the whole system must be considered, including the track excitations, a vehicle detailed dynamic model, and the coach and the seat flexibility. This paper describes a numerical model of a double-deck vehicle developed using a MB code that considers measured track irregularities, a detailed vehicle model, and a transfer function of the seat obtained by experimental tests on an optimized seat. In order to make the numerical model more realistic, the coach has been modeled as a flexible body to consider the effect of its natural frequencies. The work has been performed within the "CARITAS" project, whose aim is the design of a high comfort vehicle for people with reduced mobility

Monitoring systems for railways freight vehicles

Monitoring systems are a key tool to improve the safety of railway vehicles and to support maintenance activities. Their on-board application on railway vehicles is currently well established on newly built passenger vehicles, while their use on freight vehicles is not yet sufficiently widespread. This is due to the complex management of the operating procedures of the freight wagons, to the substantial impact of the cost of these systems compared to the cost of the wagon and to the common lack of electrification on freight wagons. This work illustrates the characteristics of a monitoring system developed at Politecnico di Torino and previously installed on freight vehicles and operationally tested as regards the detection of accelerations and temperatures as diagnostic parameters. This system has been improved by adding diagnostics of the vehicle braking system, in order to detect anomalies during braking operations and to support maintenance procedures. The activity described in the present work aims to identify, beyond the specific diagnostic system that has been implemented, the basic characteristics that a modern monitoring system, intended to be installed on railway freight wagons, should feature. The new version of the monitoring system that has been developed at Politecnico di Torino has been preliminarily tested on a scaled roller-rig in order to monitor the braking system even in abnormal operating conditions, which would be difficult to reproduce safely on a real vehicle. The monitoring system is equipped with an axle generator capable of autonomously supporting its operation, and it is also provided with a diagnostic information processing system and communication protocols to send outside this information

Dynamical Effects of the Increase of the Axle Load on European Freight Railway Vehicles

The development of an efficient freight railway system requires minimizing the travel time and maximizing the load capacity of trains. This objective can be achieved through three different strategies which can be adopted separately or in synergy. These strategies substantially consist of improvement of the load capacity of a single vehicle, increase in the train length, and increment of the vehicle velocity. The option to adopt simultaneously all three strategies is possible only when operating on dedicated infrastructures and specifically designing the vehicles and the track. This work shows the effect of the increment of the axle load, over the actual Italian limitation, on the most important indicators defined by the UIC regulation to homologate the vehicles. The calcula-tions have been performed on a high-quality real track using a numerical model of a vehicle based on the Y25 bogie. In order to take into account higher axle loads, the vehicle primary suspension has been redesigned. The results show that an increment of the axle load is feasible until an axle load of 32.5 ton if speed is limited to 80 km/h, or until 30 ton if speed is limited to 120 km/h

Interposition Arthroplasty Versus Hematoma and Distraction for the Treatment of Osteoarthritis of the Trapeziometacarpal Joint

Various surgical techniques were reported with excellent result for the treatment of trapeziometacarpal joint arthritis. However, the best treatment option was not defined yet

monitoring of railway freight vehicles using onboard systems

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