DMTI

In railway applications, the estimation of wear at the wheel-rail interface is an important field of study, mainly correlated to the planning of maintenance interventions, vehicle stability and the possibility of carrying out specific strategies for the wheel profile optimization. In this work the authors present a model for the evaluation of wheel and rail profile evolution due to wear specifically developed for complex railway networks. The model layout is made up of two mutually interactive but separate units: a vehicle model (composed of the multibody model and the global contact model) for the dynamical analysis and a model for the wear evaluation (composed of the local contact model, the wear evaluation procedure and the profile update strategy). The authors propose a statistical approach for the railway track description to study complex railway lines in order to achieve general significant accuracy results in a reasonable time: in fact the exhaustive simulation of the vehicle dynamics and of wear evolution on all the railway network turn out to be too expensive in terms of computational effort for each practical purpose. The wear model has been validated in collaboration with Trenitalia S.P.A and RFI, which have provided the technical documentation and the experimental data relating to some tests performed on a scenario that exhibits serious problems in terms of wear: the vehicle ALn 501 "Minuetto" circulating on the Aosta-Pre Saint Didier Italian line.

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The accurate estimation of the axle loads and the correct detection of overloads and imbalances, represent a primary concern for railways management companies, since they are strictly related to traffic safety and maintenance planning of the track. Weigh in Motion (WIM) systems aim at the dynamic weighing of railway vehicles through a reasonable number of measurement stations placed along the track. Such systems may overcome disadvantages in terms of costs and traffic management exhibited by conventional static weighing systems. In this paper the authors present an innovative algorithm for high speed WIM applications to estimate the wheel loads of trains by means of indirect track measurements. The formulation of the algorithm is quite general and it can be customized for several track measurements; consequently it can be employed in different typologies of measurement stations. The WIM algorithm processes the set of experimental physical quantities chosen as track inputs by means of estimation procedures based on least square (LSQ) minimization techniques. The vertical loads on the train wheels are computed from the measurements according to the assumption that the effects of the single wheel loads on the track are approximately superimposable. The whole WIM architecture has been developed in cooperation with Ansaldo STS and ECM SpA.

The modelling and the reduction of wear due to wheel-rail interaction is a fundamental aspect in the railway field, mainly correlated to running stability and safety, maintenance interventions and costs. In this work the authors present two innovative wheel profiles, specifically designed with the aim of improving the wear and stability behaviour of the standard ORE S1002 wheel profile matched with the UIC60 rail profile canted at 1/20 rad, which represents the wheel-rail combination adopted in Italian railway line. The two wheel profiles, conventionally named CD1 and DR2, have been developed by the authors in collaboration with Trenitalia S.p.A. The CD1 wheel profile has been designed with the purpose of spreading the contact points in the flange zone on a larger area in order to reduce wear phenomena and having a constant equivalent conicity for small lateral displacements of the wheelset with respect to the centred position in the track. The DR2 wheel profile is instead designed in order to guarantee the same kinematic characteristics of the matching formed by ORE S1002 wheel profile and UIC60 rail profile with laying angle a p equal to 1/40 rad, widely common in European railways and characterized by good performances in both wear and kinematic behaviour. Wheel profiles evolution has been calculated through a wear model developed and validated by the authors in previous works with experimental data relative to the Italian Aosta-Pre Saint Didier railway line. This model comprises two mutually interactive units: a vehicle model for the dynamic simulations and a model for the wear assessment. 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 crucial in terms of precision and computational effort: the particular strategy adopted in the current work has been chosen for its capacity in representing the non-linear wear evolution and for the low computational time required. In the present research the investigated trainset is the passenger vehicle ALSTOM ALn 501 ''Minuetto'', which is usually equipped with the standard ORE S1002 wheel profile and UIC60 rail profile canted at 1/20 rad in Italian railways. The entire model has been simulated on a virtual track specifically developed to represent a statistical description of the whole Italian line. The data necessary to build the virtual track and the vehicle model were provided by Trenitalia S.p.A. and Rete Ferroviaria Italiana (RFI). Both the innovative wheel profiles developed in this research activity for the UIC60 rail with cant 1/20 rad have proven to work fine in terms of resistance to wear if compared with the old ORE S1002 wheel profile.

This paper mainly focuses on the development of efficient three-dimensional (3D) models of TPJBs, able to in parallel simulate both the rotor dynamics behaviour and lubricant supply plant. The proposed modelling approach tries to obtain a good compromease between the typical accuracy of standard 3D models and the high numerical efficiency of simpler and less accurate models. In this work, the whole model has been developed and validated in collaboration with Nuovo Pignone General Electric S.p.a. which provided the required technical data. In particular, the experimental data are referred to a suitable lube oil console system, built at the GE testing center located in Massa-Carrara (MS, Italy) for the verification of such components.

In the case of rotating machinery, for a long time most of studies has focused on a single form of vibration, hence flexural and torsional vibrations were usually studied in a separate way. Current design trends for rotating equipment (higher power transmission and efficiency by reducing weight and increasing operating speeds) set the assumption on treating flexural and torsional vibrations by separate and decoupled analysis much less accurate. This coupling usually exists, as it is caused by the most common malfunction conditions. Moreover, complex distributed inertial elements connected to the shaft may determine the coupling of flexural and lateral vibrations as well. In the paper, the authors present an accurate, innovative and fully coupled model for the evaluation of the dynamic behaviour of multi-rotor systems that has been conceived with the goal of investigating the flexural-torsional interaction in rotor vibrations. The model, based on a finite element (FE) rotordynamics formulation with 6 DOFS for each node, is able to deal with long rotors characterised by complex topology, such as rotor with distributed inertias or connected simultaneously in several points. The rotor test case studied in the present research activity is a flywheel masses test bench for railway brakes. The effectiveness of the model in predicting the critical behaviour of the considered rotor system has been tested by means of experimental vibration data resulting from dedicated vibration tests campaign, performed in collaboration with Politecnico di Milano to assess the dynamical of the behavior of the machine.

The modelling and the reduction of wear due to wheel-rail contact represents a crucial issue in railway applications, mainly correlated to safety, maintenance interventions and definition of strategies aimed at wheel profile optimization. A model for evaluating wheel and rail profile evolution due to wear developed for complex railway networks is presented in this paper. The model layout is composed of two mutually interacting but separate parts: a vehicle model (composed of multibody model and global contact model) for the dynamical simulations and a unit for wear computation (composed of the local contact model, the wear evaluation procedure and the profile update strategy). In order to achieve general significant accuracy results in reasonable computational effort, a suitable statistical approach for the railway track description is used, aimed at studying complex railway lines: in fact, the exhaustive analysis of vehicle dynamics and wear evolution on all the railway network is too expensive in terms of computational time for each practical purpose. The wear model has been validated in collaboration with Trenitalia S.P.A and RFI, which have provided technical documentation and experimental data relative to some tests performed on a environment exhibiting serious problems in terms of wear: the vehicle ALn 501 Minuetto operated on the Aosta-Pre Saint Didier Italian line.

In railway applications, the wear estimation at the wheel-rail contact is an important field of study, mainly correlated to the planning of maintenance interventions, vehicle stability and the possibility to carry out specific strategies for the wheel profile optimization. In this work the Authors present a model for the evaluation of the wheel and rail profile evolution due to wear specially developed for complex railway networks. The model layout is made up of two mutually interactive but separate units: a vehicle model for the dynamical analysis and a model for the wear evaluation. To study complex railway lines the Authors also proposed a new statistical approach for the railway track description in order to achieve general significant accuracy results in a reasonable time. The wear model has been validated in collaboration with Trenitalia S.P.A and Rete Ferroviaria Italiana (RFI), which have provided the technical documentation and the experimental data relating to some tests performed on a scenery that exhibits serious problems in terms of wear: the vehicle DMU ALn 501 Minuetto circulating on the Aosta-Pre Saint Didier Italian line.

The estimation of the axle loads of running railway vehicles in motion is an important topic in the management of railway networks, basically for purposes of safety and maintenance interventions on the track. To this aim, through a reasonable number of specialized measurement stations, the axle load of the vehicles circulating in a railway network can be easily estimated without any significant consequence on the railway traffic. In this work the authors present the development of an innovative algorithm for WIM systems aimed at estimating, by means of track measurements, the axle loads of a generic train composition. The formulation of the proposed algorithm is quite general and it can work on different sorts of track measurements (rail shear, rail bending, vertical forces on the sleepers as well as on a combination of them); consequently it can find application in different typologies of measurement stations. The set of experimental physical quantities chosen as inputs are properl...

The paper deals with the experimental characterization of different 280 mm diameter tilting pad journal bearings for turbomachines using a dedicated test rig. The test articles were a 5-pad Direct Lube Rocker Pivot bearing, a 5-pad Flooded Rocker Pivot bearing, and a 4-pad Flooded Ball and Socket Pivot bearing. The three bearings were tested in their specific design range of operating conditions. Their static and dynamic behavior was investigated as a function of different operating parameters. In particular, the assumed journal center eccentricity and pads temperature were measured, and the power loss determined as a function of angular speed for different static loads. Dynamic stiffness and damping coefficients were determined as a function of excitation frequency for different speeds and loads. The experimental results were compared showing the influence of the operating parameters, configuration, and oil supply.

The development of an efficient Weigh-In-Motion (WIM) system, with the aim of estimating the axle loads of railway vehicles in motion, is quite interesting from both an industrial and academic point of view. Such systems, with which the loading conditions of a wide population of running vehicles can be verified, are very important from a safety and maintenance perspective. The evaluation of the axle load conditions is fundamental especially for freight wagons, more likely to be subjected at risk of unbalanced loads that may be extremely dangerous both for the vehicle running safety and the infrastructure integrity. In this way, potentially dangerous overloads or defect of rolling surfaces could be easily identified: in case of measured overloads, the axle could be identified and monitored with non-destructive controls to prevent the propagation of potentially dangerous fatigue cracks. Also peaks on the measured contact forces could be caused by wheel flats or other kinds of damages of the rolling surfaces which could be early identified saving both vehicle and railway line from the dangerous consequence of a prolonged exposure to irregular loads. As a consequence the WIM system could be used both as Prognostic and Diagnostic tool thanks to its capability of early identifying a minor fault condition which could cause, if ignored, potentially catastrophic events. The development, the simulation and the validation of the innovative WIM algorithm aimed at estimating the axle loads of railway vehicles will be presented in this paper. The innovative algorithm have been preliminary validated using experimental data provided by Ansaldo STS and further trained on FEM simulation results. Obtained results are quite encouraging considering that experimental results have been optained with an experimental layout optimized for a different WIM algorithm previously developed by Ansaldo STS which, after the comparison, turned out to be inferior both in terms of performances and reliability.

Tilting pad journal bearings (TPJBs) are crucial elements in turbomachinery applications providing stiffness and damping characteristics that determine rotor system dynamic behavior. Hence, a correct design and an accurate dynamic properties prediction is fundamental for the successful industrial operation of rotating machinery. Current design trends in turbomachinery aiming at higher efficiency and power through weight optimization and higher operating speeds determine the development of large flexible rotors that are particularly important from the rotordynamic standpoint. The dynamic feasibility of this type of machine relies on bearing stiffness and damping characteristics that must be predicted with a certain level of confidence in order to increase the accuracy of the expected rotordynamic behaviour and avoid unpredicted vibration issues when rotors are operated. Furthermore, large centrifugal compressors commonly used in Liquified Natural Gas (LNG) applications make the beari...

An accurate dynamic estimation of the axle loads of running railway vehicles and an estimation of the position of the vehicle center of mass are fundamental and represent an important topic in the railway safety and traffic management. Weigh-in-Motion (WIM) systems [1] are aimed at the dynamic weighing of railway vehicles (without stopping the vehicles), making use of different measurement stations localized along the track. The goal of the proposed work is the development of an innovative WIM estimation algorithm, able to estimate the axle and wheel loads and the position of the center of mass of a generic train composition by means of track measurements. The proposed solution is capable of manage different types of experimental and simulated input data (rail shear, rail bending, vertical forces on the sleepers) and to perform the estimation at high vehicle speeds. The WIM algorithm processes the set of experimental physical quantities chosen as track inputs by means of estimation ...

The accurate estimation of the axle loads and the correct detection of overloads and imbalances, represent a primary concern for railways management companies, since they are strictly related to traffic safety and maintenance planning of the track. Weigh in Motion (WIM) systems aim at the dynamic weighing of railway vehicles through a reasonable number of measurement stations placed along the track. Such systems may overcome disadvantages in terms of costs and traffic management exhibited by conventional static weighing systems. In this paper the authors present an innovative algorithm for high speed WIM applications to estimate the wheel loads of trains by means of indirect track measurements. The formulation of the algorithm is quite general and it can be customized for several track measurements; consequently it can be employed in different typologies of measurement stations. The WIM algorithm processes the set of experimental physical quantities chosen as track inputs by means o...

The accurate three-dimensional (3D) modelling of the dynamical phenomena characterizing rotating machines plays a fundamental role in rotordynamics and turbomachinery to ensure system stability, to obtain safe operating conditions and to minimize the costs (design, testing installation and maintenance). A generic rotating machine (see Fig. 1) usually comprises four main structures: rotors, bearings, casings and foundation. In the last decades the research mainly focused on the 2D and 3D analysis of the single previous parts without considering the whole mechanical system [1][2]; however this kind of approach could only lead to partial results. In the last years it has become evident that global 3D models, comprising all the system parts, are required to reach the desired goals in terms of accuracy, stability, safety and costs [3][4]. At the same time high numerical efficiency and memory consumption are needed to get a satisfying compromise between accuracy and numerical efficiency. ...

In railway applications, the wear estimation at the wheel-rail contact is an important field of study, mainly correlated to the planning of maintenance interventions, vehicle stability and the possibility to carry out specific strategies for the wheel profile optimization. In this work the Authors present a model for the evaluation of the wheel and rail profile evolution due to wear specially developed for complex railway networks. The model layout is made up of two mutually interactive but separate units: a vehicle model (composed by the multibody model and the global contact model) for the dynamical analysis and a model for the wear evaluation (composed by the local contact model, the wear evaluation procedure and the profile update strategy). To study complex railway lines the Authors also proposed a new statistical approach for the railway track description in order to achieve general significant accuracy results in a reasonable time: in fact the exhaustive simulation of the veh...

topic of coupled lateral-torsional vibration in rotors is due to its general topology. Multi-rotor linking elements (such as couplings) modelled with different levels of detail may be used and non-standard elements may be also adopted for describing particular rotor components, such as rotor with distributed inertias or complex connections. The model is based on a finite element (FE) formulation with 6 degrees of freedom (dofs) for each node and it is therefore suitable to fully coupled studies, in which the existing dependency among longitudinal, lateral and torsional dynamics can be evaluated. Thanks to its numerical efficiency, the proposed model represents a good compromise between accuracy and computational effort, thus it may be used to perform rotordynamical investigation commonly used in rotating machinery design. The investigated rotor test-case is a dynamometric flywheel test bench for railway brakes that is characterised by a complex geometry formed of several rotors with complex topology (distributed inertias). The effectiveness of the presented model in predicting the critical behaviour of the considered test-case has been tested by means of experimental vibration data. The experimental data are the results of dedicated vibration tests campaign, performed in collaboration with Politecnico di Milano, Italcertifer (FS) and Simpro S.p.A to assess the vibration behaviour of the machine.

The reduction of wear due to wheel–rail interaction is a fundamental aspect in the railway field, mainly correlated to safety, maintenance interventions and costs. In this work, the authors present an innovative wheel profile optimisation procedure, specifically designed with the aim of improving the wear and stability behaviour of the standard ORE S1002 wheel profile matched with the UIC60 rail profile canted at 1/20 rad, which represents the wheel–rail combination adopted in Italian railway line; this matching shows poor wear performance due to the non-conformal contact. A new wheel profile, conventionally named DR2, has been developed by the authors in collaboration with Trenitalia S.p.A. The DR2 wheel profile is designed to guarantee the same kinematic characteristics of the matching formed by ORE S1002 wheel profile and UIC60 rail profile with inclination angle p equal to 1/40 rad, widely common in European railways and characterised by good performances in both wear and kinema...