Active learning approach to enhance rotor dynamics understanding: A classroom demonstration

In the last decades, novel teaching strategies have been increasingly adopted to improve and enhance the students learning process by promoting their involvement and engagement during classes. In this context, this work presents a laboratory experience proposed to the third-year bachelor students of the course of ‘Mechanics of Vibrations’, held at the faculty of mechanical engineering of Politecnico di Milano. The experience consisted in the presentation of a rotor test bench specifically designed for educational purposes. Main concepts of rotor dynamics were analysed and showed, together with a critical discussion on the discrepancies between the Jeffcott–Laval model and experimental results. This project, that is one of the outcomes of an educational project for post-covid teaching promoted by Politecnico di Milano, involved almost 200 students in total. An anonymous evaluation survey proposed to students revealed a general appreciation of the experience, especially for the possibility of visualising important theoretical concepts. Given the positive feedback, the demonstration will be repeated in the next academic year, with some changes according to students’ suggestions

A study of the influence of aerodynamic loads on the forces exchanged in a twistlock corner casting connection of flat-wagons

In this paper cross-wind effects on freight wagons are studied. A mathematical model of a freight train made up of a flat-car and one or two containers has been built defining the dynamical characteristics of the connection (twistlock-corner casting). Wind tunnel tests on a scaled model are then used to define the aerodynamic coefficients of the wagon, both in loaded and unloaded conditions, considering different trainset layouts. Wind forces are finally applied separately to the container and the flat-car in order to define the CWC of the wagon and to verify the maximum forces exchanged through the twistlock-corner casting connection. The results of the analysis showed that severe conditions with respect to the risk of rollover can be found as a result of a succession of empty and loaded wagons

A study of the factors affecting flange-climb derailment in railway vehicles

Avoiding flange climb derailment is one main issue with ensuring the running safety of railway vehicles. This paper discusses the different causes that can lead to the derailment of a railway wheel, particularly in the light of different derailment criteria used by the standards or proposed by various researchers. Furthermore the paper presents two case studies, one for a vehicle with solid axles and one for a bogie with independently rotating wheels, reporting a description of the derailment case and discussing the causes that led to derailment, by making combined use of measurements and numerical simulation. Based on these exemplary cases, some conclusions are drawn concerning the validity of the derailment criteria presently used by the standards in force

Acceleration-based condition monitoring of track longitudinal level using multiple regression models

In this paper, a condition monitoring system for railway track geometry is presented. The methodology has been designed for high-speed application, where the train travels at the maximum allowed speed for most of the trip. The system is designed to rely on acceleration data recorded by in-service vehicles to provide estimations of the track longitudinal level, based on pre-built regression models. It exploits synthetic indicators sampled over predefined track sections 100 m long. Different predictors are considered, computed both from acceleration data and from track geometry measured by the diagnostic train. The proposed modelling strategy allows distinguishing between isolated and distributed defects that populate the railway track as well as reproducing the evolution over time of the maximum longitudinal level registered in the considered track section; moreover, also accurate predictions of the defect amplitude are made. The results have been validated against track geometry data recorded by the diagnostic train during a monitoring period of 2 years. It is proven that the proposed system could support current maintenance strategies, providing a continuous flow of data to monitor the track infrastructure

A Methodology for Continuous Monitoring of Rail Corrugation on Subway Lines Based on Axlebox Acceleration Measurements

Rail corrugation is a degradation phenomenon that manifests as a quasi-periodic irregularity on the running surface of the rail. It is a critical problem for urban railway lines because it induces ground-borne vibrations transmitted to the buildings near the infrastructure, causing complaints from the inhabitants. A typical treatment to mitigate the rail corrugation problem is the periodic grinding of the rails, performed by dedicated vehicles. The scheduling of rail maintenance is particularly critical because it can be performed only when the service is interrupted. A procedure for the continuous monitoring of rail corrugation is proposed, based on axlebox acceleration measurements. The rail irregularity is estimated from the measured acceleration by means of a frequency domain model of vertical dynamics of the wheel–rail interaction. The results obtained by using two different methods (a state-of-the-art method and a new one) are compared. Finally, the study of the evolution of the power content of the rail irregularity enables the identification of the track sections where corrugation is developing and rail grinding is necessary

Comparison of Wheel-Rail Contact Modelling in Multibody System Online Simulation

The wheel-rail contact modelling is always an interesting topic in rail vehicle system dynamics simulation. Many contact models have been developed for different purposes, and each model has its own pros and cons for different applications. In multibody system (MBS) simulation of rail vehicles, the efficiency and accuracy of the wheel-rail contact model are of importance. It is the aim of this paper to compare in MBS online simulation one classical approach (Hertz theory+FASTSIM), one approximated non-Hertzian approach and the ‘exact’ solver CONTACT and show the influences of the contact modelling on the results of vehicle dynamics simulations

Derailment risk and dynamics of railway vehicles in curved tracks: Analysis of the effect of failed fasteners

[EN] The effect of the fastener s failure in a railway track on the dynamic forces produced in the wheel-rail contact is studied using the simulation software VAMPIRE to assess the derailment risk of two different vehicles in two curves with distinct characteristics. First, a 3D-FEM model of a real track is constructed, paying special attention to fasteners, and calibrated with displacement data obtained experimentally during a train passage. This numerical model is subsequently used to determine the track vertical and lateral stiffness. This study evidences that although the track can practically lose its lateral stiffness as a consequence of the failure of 7 consecutive fasteners, the vehicle stability would not be necessarily compromised in the flawed zone. Moreover, the results reveal that the uncompensated acceleration and the distance along which the fasteners are failed play an important role in the dynamic behavior of the vehicle-track system, influencing strongly the risk of derailmentMorales-Ivorra, S.; Real Herráiz, JI.; Hernández Gracia, C.; Montalbán-Domingo, L. (2016). Derailment risk and dynamics of railway vehicles in curved tracks: Analysis of the effect of failed fasteners. Journal of Modern Transportation. 24(1):38-47. doi:10.1007/s40534-015-0093-zS3847241Iwnicki S (2006) Handbook of railway vehicle dynamics.CRC Press, Boca RatónJin XS, Wen ZF, Wang KY, Zhou ZR, Liu QY, Li CH (2006) Three-dimensional train-track model for study of rail corrugation. J Sound Vib 293:830–855Jin X, Wen Z, Xiao X (2007) A numerical method for prediction of curved rail wear. Multibody Sys Dyn 18:531–557Li W, Xiao G, Wen Z, Xiao X, Jin X (2011) Plastic deformation of curved rail at rail weld caused by train-track dynamic interaction. Wear 271:311–318Jin X, Wen Z (2008) Effect of discrete track support by sleepers on rail corrugation at a curved track. J Sound Vib 315:279–300Di Gialleonardo E, Bruni S, True H (2014) Analysis of the nonlinear dynamics of a 2-axle freight wagon in curves. Veh Syst Dyn 52(1):125–141Wang K, Liu P (2012) Lateral stability analysis of heavy-haul vehicle on curved track based on wheel/rail coupled dynamics. J Transp Technol 2:150–157Kurzeck B, Hecht M (2010) Dynamic simulation of friction-induced vibrations in a light railway bogie while curving compared with measurement results. Veh Syst Dyn 48:121–138Chen P, Gao L, Hao J (2007) Simulation study on parameters influencing wheel/rail wear in railway curve. China Railway Science 5Sun Y, Cole C, Boyd P (2011) A numerical method using VAMPIRE modelling for prediction of turnout curve wheel-rail wear. Wear 271(1–2):482–491Brabie D (2007) On derailment-worthiness in railway vehicle design. Analysis of vehicle features influencing derailment processes and consequences, PhD Thesis, Royal Institute of Technology, StockholmMatsumoto A, Sato Y, Ohno H, Shimizu M, Kurihara J, Saitou T, Michitsuji Y, Matsui R, Tanimoto M, Mizuno M (2014) Actual states of wheel/rail contact forces and friction on sharp curves—continuous monitoring from in-service trains and numerical simulations. Wear 314:189–197Wang L, Huang A, Liu G (2013) Analysis on curve negotiation ability of the rail vehicle based on SIMPACK. Adv Mater Res 721:551–555Eom BG, Lee H (2010) Assessment of running safety of railway vehicles using multibody dynamics. Int J Precis Eng Manuf 11(2):315–320Zhou L, Shen Z (2013) Dynamic analysis of a high-speed train operating on a curved track with failed fasteners. J Zhejiang Univ Sci A 14(6):447–458Xiao X, Jin X, Wen Z (2007) Effect of disabled fastening systems and ballast on vehicle derailment. J Vib Acoust 129:217–229Shi W, Cai C (2011) Influence of slab track fastener failure on track dynamic performance. In: Advances in environmental vibration-proceedings of the 5th international symposium on environmental vibration, Chengdu, pp 686–692Xiao X, Jin X, Deng Y, Zhou Z (2008) Effect of curved track support failure on vehicle derailment. Veh Syst Dyn 46(11):1029–1059Zakeri J, Fakhari M, Mirfattahi B (2012) Lateral resistance of railway track with frictional sleepers. Proc Inst Civ Eng Transp 165(2):151–155Gibert X, Patel V, Chellappa R (2015) Robust fastener detection for autonomous visual railway track inspection. In: IEEE Winter Conference on Applications of Computer Vision, Waikoloa Beach Hawai, pp 694–701Thompson D, Hemsworth B, Vincent N (1996) Experimental validation of the TWINS prediction program for rolling noise, part 1: description of the model and method. J Sound Vib 193(1):123–135Zakeri JA (2012) Lateral resistance of railway track. In: Perpinya DX (ed) Reliability and safety in railway. InTech Europe, Rijeka, pp 357–374Kernes RG, Edwards JR, Dersh MS, Lange DA, Barkan CP (2011) Investigation of the dynamic frictional properties of a concrete crosstie rail seat and pad and its effect on rail seat deterioration (RSD). Transportation Research Board 91st annual meeting. Railtec, Chicago, IllinoisCarrascal-Vaquero I (2006) Optimization and analysis of the behavior of fastener systems for Spanish high-speed railways. PhD Thesis, University of Cantabria, Santander (In Spanish)Sany J (1996) Another look at the single wheel derailment criteria. In: Proceedings of the IEEE/ASME Joint Railroad Conference, pp 17–22Koo J, Oh H (2014) A new derailment coefficient considering dynamic and geometrical effects of a single wheelset. J Mech Sci Technol 28(9):3483–3498UIC-Leaflet-518 (2009) Testing and approval of railway vehicles from the point of view of their dynamic behaviour-safety-track fatigue-ride quality. 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Carotid Plaque Imaging with SPECT/CT and PET/CT

A major contributor to the occurrence of ischemic stroke is the existence of carotid atherosclerosis. A vulnerable carotid atherosclerotic plaque may rupture or erode, thus causing a thrombotic event. Currently, clinical decision-making with regard to carotid endarterectomy or stenting is still primarily based on the extent of luminal stenosis, estimated with CT angiography and/or (duplex) ultrasonography. However, there is growing evidence that the anatomic impact of stenosis alone has limited value in predicting the exact consequences of plaque vulnerability. Various molecular processes have, independently of degree of stenosis, shown to be importantly associated with the plaque's capability to cause thrombotic events. These molecular processes can be visualized with nuclear medicine techniques allowing the identification of vulnerable patients by non-invasive in vivo SPECT(/CT) and PET(/CT) imaging. This chapter provides an overview of SPECT(/CT) and PET(/CT) imaging with specific radiotracers that have been evaluated for the detection of plaques together with a future perspective in this field of imaging.</p