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The concept of managing and adjustment of friction between the wheel and rail has a long history within the operation of railways systems. In the past, adjustment/management has been limited to gauge face lubrication and the use of sanding equipment. The introduction of the top of rail (TOR) friction modifier (FM) over the last 20 years now allows for the modification of the friction at the top of...
In order to simulate the rail profiles evolution in the switch panel of a railway turnout, the simulation of vehicle–turnout dynamic interaction, the wheel–rail rolling contact model and rail material wear model are integrated as a numerical simulation tool for rail wear of the switch panel in this paper. A multi-body dynamical model of the CRH2 Chinese high speed vehicle is created using Simpack...
Wheel treads are subject to different types of damage such as wear, rolling contact fatigue (RCF), thermal cracks, plastic deformation and flats caused by wheel sliding. These types of damage cause changes in the tread profile of the wheel, which necessitates frequent wheel reprofiling in order to maintain the ride comfort of the vehicle.In this study, a series of full-scale tread braking experiments,...
Stress- and strain-controlled tests of heat treated high-strength rail steel (Australian Standard AS1085.1) have been performed in order to improve the characterisation of the said material׳s ratcheting and fatigue wear behaviour. The hardness of the rail head material has also been studied and it has been found that hardness reduces considerably below four-millimetres from the rail top surface. Historically,...
Low adhesion presents a major concern for many rail operators. Railway vehicles under these circumstances can experience a serious loss of braking capability giving rise to dangerous situations such as platform overruns and signals passed at danger. One cause of adhesion loss is autumn leaf fall, Fulford C.R. (2004) [1]. Leaves are run over by the wheels of a train and a chemical reaction occurs between...
This work investigates the power dissipation in a wheel/rail system through friction work modeling. In order to identify the effect of the friction coefficient on the power dissipation in the wheel/rail contact, several simulations were performed using a three-dimensional multibody model of a railway vehicle implemented in the software package VI-Rail Adams. The power dissipation and wear rates of...
Wheel/rail contact modelling is essential in railway vehicle dynamic simulation, wheel/rail wear and fatigue. For this purpose, the tiny contact area at wheel/rail interface needs to be carefully investigated. In this paper a Partition Model (P_M) method is proposed to solve the wheel/rail normal contact problem. In the model, the contact region is divided into zones according to different curvature...
A novel wheel–rail contact model is proposed to be implemented for multi-body dynamics simulation, in order to facilitate accurate online calculation of damage phenomena such as wear and rolling contact fatigue. The normal contact, i.e. contact patch and pressure distribution, is calculated using a fast non-elliptic algorithm called ANALYN. The tangential contact, i.e. tangential stress distribution,...
The paper investigates gradient effects, which relate to how highly stressed regions should be dealt with in fatigue design analyses. In particular stress gradients in rolling contact are investigated with a focus on differences in response between full and partial slip conditions. To this end the multiaxial state of stress beneath a wheel–rail contact featuring full or partial slip is quantified...
Assessments of the severity of wheels tread defects under rolling contact fatigue conditions are in general very uncertain when based on theoretical concepts supported only by small scale material characterization and without the possibility of a full scale validation. In real service conditions, the tread surface and subsurface defects are subject to a number of variable mechanical loading conditions...
This paper presents the progress of an attempt to identify wheel/rail contact geometry parameters related to vehicle behaviour. A so called “nonlinearity parameter” has recently been proposed with the aim to extend the commonly used characterisation of wheel/rail contact geometry by one equivalent conicity value. New investigations on a large amount of measured wheel and rail profiles show the typical...
Thermal damage of rails can occur through brake lock-up, or traction control system failure to prevent wheel spin. In most cases the damage produced is shallow and takes the form of a “white etching layer”, usually thought to have a martensitic structure, formed as the steel is heated above its eutectoid temperature and then rapidly cooled as the wheel moves away. In many cases such layers are benign,...
There has been a ballooning of demand on the Chinese railway system which has brought about a need to maximize the availability of vehicles. This has, in turn, led to a need to optimize reprofiling intervals for wheels. Ideally, these intervals should be based on operational benefits and effects of worn profiles on the running behavior of vehicles. Chinese high speed railway system started to develop...
Head Check is a major rolling contact fatigue (RCF) defect initiated after cyclic wheel/rail contacts by severe plastic deformation of the rail head surface. A field analysis campaign has been conducted on a site affected by Head Checking. The aim of this study is to increase understanding of the relationship between RCF cracking and plastic deformation of the pearlitic microstructure. Investigations...
Rail corrugation is a significant problem in railway engineering, manifesting as an oscillatory wear pattern on the rail head. These profile variations induce unwanted vibrations, excessive noise and other associated problems. Constant train speed for consecutive train passes has been shown to accelerate corrugation growth while widening the probabilistic speed distribution can be shown to mitigate...
Laser cladding has been considered as a method for improving the wear and RCF performance of standard grade rail. This paper presents results of small scale tests carried out to assess the wear and RCF performance of rail which had been laser clad. Using the laser cladding process premium metals can be deposited on to the working surface of standard rail with the aim of enhancing the wear and RCF...
A three-dimensional numerical model of wheel/rail in rolling contact is established to study the adhesion characteristics under interfacial contamination considering surface roughness at high speed. The thermal partial elastohydrodynamic lubrication (EHL) theory in elliptical contact is used in the model. The numerical model is successfully solved by applying the iterative algorithm between the pressure...
Energy saving achieved by application of top of rail (TOR) friction modifier (FM) in heavy haul are modeled, and the effects of curve radius and rail profile on the energy saving are discussed. A vehicle model for a C70 freight car running on the track of a heavy haul line was established. The coefficient of friction and Kalker coefficient were adjusted to simulate the creepage/force relationship...
The development of premium heat treated rail steels with hardness levels of 400HB and above, and the application of these under high axle load conditions, has provided substantial improvements in rail lives. An additional benefit is the potential to increase the intervals between consecutive grinding cycles, where rail grinding is used to control rolling contact fatigue damage. Increased grinding...
A model which can predict the length of the surface crack and crack depth in rails was developed in a previous study by the authors B. Dirks, R. Enblom, A. Ekberg, M. Berg (2015) [1]. In the present study, verification of this crack prediction model in combination with a wear prediction model was done against wheel measurements. For a period of 15 months, the wheels of three units of a Stockholm commuter...
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