Failure analysis of draw gear and screw coupling of railway vehicles as a factor of safety and trains break risk

U cilju poboljšanja bezbednosti i efikasnosti železničkog saobraćaja u eksploataciji, potrebno je redukovati učestanost raskinuća vozova, kao jedne od vrsta nesreća i nezgoda koje se mogu javiti u železničkom saobraćaju. Istraživanju uzroka raskinuća se često daje mali značaj, što ima za posledicu ponavljanje pojava raskinuća i dovodi do povećanja neplaniranih troškova u eksploataciji, koji bi inače mogli biti izbegnuti. Kako u stručnoj literaturi, pored analize pojedinačnih slučajeva raskinuća, ne postoji sveobuhvatna i sistematska analiza uzroka raskinuća, ovo istraživanje je aktuelno u domaćim uslovima eksploatacije, gde je prosečan broj raskinuća teretnih vozova u prethodnih 15 godina oko 40 slučajeva godišnje. Primenom metode konačnih elemenata (MKE) modela izabranih elemenata vučnih uređaja i opterećenja koja se mogu očekivati u eksploataciji verifikovano je stanje elemenata utvrđeno ispitivanjem. Utvrđivanjem glavnih uzroka raskinuća voza predložene su odgovarajuće preventivne mere radi smanjenja ove štetne pojave, čime se direktno utiče na povećanje bezbednosti i sigurnosti u železničkom saobraćaju, i na smanjenje troškova u slučaju raskinuća u eksploataciji. Ovo istraživanje predstavlja značajan doprinos nauci s obzirom da ne postoji sistematsko istraživanje u ovoj oblasti. Naučni doprinos ovog istraživanja se ogleda u kvantifikaciji parametara koji utiču na pojavu raskinuća i procenu nastanka raskinuća pri poznatim uslovima eksploatacije i stanja vučnih uređaja. Praktični značaj ove disertacije ogleda se u mogućnosti da se u određenoj meri unaprede postojeći postupci dijagnostike i opravke vučnih uređaja, na osnovu saznanja dobijenih analizom otkaza, čime bi se unapredilo održavanje i smanjili otkazi vučnih uređaja.In order to improve the safety and efficiency of railway traffic in operation, it is necessary to reduce the frequency of train breaking, as one of the types of accidents and incidents that can occur in railway traffic. Research the causes of breaking is often of little importance, resulting in recurrences of breaking and leading to an increase of unplanned operating costs, which could otherwise have been avoided. In the railway literature, despite the analysis of individual cases of breaking of train, there is no comprehensive and systematic analysis of the causes of breaking, this research is authentic in domestic operating conditions, where the average number of breaking of freight trains in the previous 15 years is about 40 cases per year. By applying Finite Element Method (FEM) on coupling system and loads that can be expected in operation, the condition of the elements determined by testing was verified. By determining the main causes of breaking of train, appropriate preventive measures have been proposed in order to reduce this occurrence, which directly affects the safety and security in railway traffic, and the can lead to reduction of costs in case of breaking of train in operation. This research represents a significant contribution to science as there is no systematic research in this area. The scientific contribution of this research is in the quantification of parameters that affect the breaking of train and the assessment of the breaking under known operating conditions and the condition of coupling system. The practical significance of this dissertation is in the possibility to improve, to some extent, the existing procedures for diagnostics and repair of coupling systems, based on the findings of failure analysis, that would improve the maintenance and reduce failures of coupling system

Breaking of coupling of trains on the Serbian Railways

This paper proposes an analysis of breaking of train coupling which occurred on the Serbian Railways (ŽS) in the period since 2007. by 2011. The problem of longitudinal dynamic forces, especially in freight trains, is most evident in the Serbian Railways, and for the reference period breaking of coupling of freight train occurred on a total of 201 cases (an average of 40.2 cases per year). Analysis of breaking of freight train coupling will be done based on number and place of breaks relative to the length of the freight trains, driving regime of trains, speed before breaking of coupling, damaged parts, causes of train breaks, etc. This analysis will identify the main factors that affect more frequent emerge of freight trains breaking of coupling, in order to prevent accidents and improve safety in freight railway traffic

Risk assessment of coupling system failure on train in current maintenance system

Development of new management approaches on the railway, based on risk management, with the adoption of standards EN 50126-1 and EN 50126-2 provide safety management processes for railway applications. Risk factors can be determined using different risk assessment methods like FMEA, FMECA, FTA etc. or their combination. The permissible risk values based on accepted values and defined preventive measures are designed on the current maintenance plan for freight wagons. Preventive measures are established for revision maintenance which is carried out every 4-6 years. Risk analysis of coupling system failure can be different depending on the time of analysis (regulations, exploitation conditions) and the applied maintenance practice. FMEC analysis applied to train coupling systems based on regulation shows different permissible risk values that don't match exploitation data

The trend of train coupling failure on Serbian railways in 10 year period

This paper presents an analysis of train coupling failure on the Serbian Railways and displays a trend of characteristics over 10 year period. The impact of changes in the organization of exploitation and maintenance and led by the introduction of Entity in Charge of Maintenance (ECM) and reconstruction of Serbian railway company into 3 separate entities as well as some differences and aging in rolling stock induce certain changes in the parameters of train coupling failure. The analysis is done based on parameters of train configuration and driving specifications. Only freight trains with single traction locomotives are considered. The distribution of coupling failure along the train, driving regime and velocity is comparatively discussed related to the values from the previous period. Load status, as well as the length and mass of the trains in the extended collection, correspond to a certain distribution. Causes of failure and damages to coupling and draw gear indicate specific conditions leading to failure. Analysis significance helps the systematization of failure features and sets the ground for defining the parameters that impact failure and determining their quantification

Analysis of coupling system failures on freight trains

This paper presents an analysis of train coupling failure that led to trains break apart on the Serbian Railways over 10 years period. Train coupling failure of freight trains with single locomotives was considered. The analysis was done based on accident data combine with FMECA risk assessment. As a result distribution of failure along the train, driving regime and velocity were obtained, as well as the frequency of failure concerning the length and mass of the trains, load status, etc. The systematization of coupling failure helped to establish conditions leading to failure and to define the parameters causing it. Risk factors for coupling failure were determined using FMECA risk assessment. Preventive measures are recommended for the revision of maintenance. Risk analysis of coupling system failure can be different depending on the time of analysis (regulations, exploitation conditions) and the applied maintenance practice. FMECA analysis applied to train coupling systems based on regulation shows different permissible risk values that don't match exploitation data

Comparation of brake performance of freight vagons with classic brake and compact freight car brake

Contemporary design of the freight wagons requires lightweight and compact design of all subassemblies and components (e.g. bogies, brake systems etc.). Because of that several manufacturers of railway brake systems have developed a compact brake system having all major components located within bogie. This system despite the more complex construction than standard have more advantages (lower mass, reduced air consumption, higher efficiency of brake rigging etc.) This paper presents results and conclusions obtained by testing of two freight wagons of the same type equipped with classic brake system and compact freight car brake system (CFCB). The testing included brake performance test i.e. stationary test and slip brake test

Experimental research of mechanical characteristics of railway vehicles safety coupling components

The coupling system provides a mechanical connection between European railway vehicles. Screw couplings are designed as a safety device in railway vehicles with coupling links and screw as two main components intended to break. Failure of these components is necessary when the load between vehicles is exceeded, otherwise more significant draw gear elements will fracture. The analysis of train break cases shows that the failure of the links occurs only in an approx. 6% of cases. Therefore, the links taken from exploitation after more than 30 years in operation were tested to determine their mechanical characteristics. Tensile testing was performed according to the ISO 6892-1 standard with a continual force and a minimal and maximal test speed prescribed by ISO 6892-1. The values of mechanical characteristics of coupling links are substantially improved during production after heat treatment by hardening and tempering. However, test results of mechanical characteristics didn’t meet all prescribed limits for the minimum requirements according to UIC 826. The current regulations of mechanical characteristics were not in force in time of link production. Examination of the tested links showed a ductile fracture and the cross-sectional area shows the planar stress state

Dynamics of train composition as a discrete non-homogeneous chain system

The longitudinal train dynamics which included movement and oscillations of coupled railway vehicles only in the direction of the track (longitudinal) is analyzed. The one direction motion of the train, as well as the relative motions between vehicles, is presumed. The assumption of exclusion of movements of the vehicles in the vertical direction is taken in accordance with the real low values of these displacements components. Model of train is generally present as a discrete non-homogeneous chain system with viscoelastic non-linear frictional elements. This model simulates railway vehicles equipped with conventional pneumatic brake system and brake blocks. In the presented research, for the developed train model, a general solution of the system of ordinary differential equations, which described eigen and forced vibrations of a non-homogeneous chain under the external one frequency excitation, is obtained and analyzed. The methods and procedures used for solving the described task are explained in detail. The presented theoretical simulation model and real dynamics of train composition are compared and conclusions about the suitability and accuracy of the developed model are discussed

Modal analysis of the hydro turbine shaft with cracks

The design process for the elements which are the parts of the structures and equipment in power industry includes both of stress and strain state calculations, as well as an analysis of natural mode shapes and frequencies. During operation of the machine elements and systems, periodic vibration measurement in unloaded and loaded state is essential for high level of availability of the equipment operation. This is especially important after the reparation of particular elements of mechanical systems, when the vibration monitoring is source of the information necessary for their proper and safe use. Therefore, the previous numerical calculations of the eigen frequency and modal analysis give the necessary information for appropriate operation loading. In this paper the dynamics of the Kaplan turbine shaft is analyzed in accordance with these preferences. The Finite Element Analysis is used for numerical simulations and calculations. The real case of the shaft failure is chosen and the analyses are performed for the shaft before and after damage appearance. The cracks of different depth are modeled at the shaft to flange transition zone, in accordance with the real damages. Also, the model of the shaft with the shape and dimensions after the reparations is analyzed in order to compare the shaft dynamics with changed transition radius. Conclusions and discussion about the obtained results are given in comparison with the real operation conditions for the analyzed case study

Simulation of the kinematic hardening of AISI 316 steel by nonlinear finite element analysis

The coupled non-linear transient calculation is performed and explained in order to simulate the kinematic hardening behavior of AISI 316 steel and the Finite Element Method (FEM) is used for presented simulation. The material non-linear models features in Finite Element Analysis (FEA) are explained with special attention in non-linear kinematic hardening material models. For simulating of non-linear kinematic hardening and ratcheting effects of AISI 316 steel the Chaboche constitutive material model is used. The Finite Element Model of rectangular block modeled for material behavior simulation is shown. Definition of constraints and input stresses is explained in detail. The results obtained after six cycles of input stresses give the excellent superposition with theoretical results of other authors. The created diagrams show the ratcheting phenomenon of research material. Therefore, the FEM model developed for non-linear kinematic hardening research is verified and could be used for wide research of different materials under different input loads