DMTI

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.

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...

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...