In this work the influence of considering wheel-rail contact creepages on fatigue crack growth rates due to Rolling Contact Fatigue (RCF) is studied. For this purpose, the FASTSIM algorithm, which considers the moving complex pressure distribution with slipping and adhesion zones of the wheel-rail contact patch, has been implemented in Abaqus using FORTRAN code subroutines. The developed methodology has been validated with a 60E1 rail profile model which uses XFEM, by comparing the obtained Stress Intensity Factors (SIFs) and sub-surface shear stresses with numerical results available in the literature. Finally, the RCF crack propagation analysis of a 60E1 rail profile with different contact conditions has been performed using the XFEM. The obtained results justify the necessity of considering contact creepages on contact shear stresses for crack growth analysis.

Rolling contact fatigue (RCF) is a common cause of rail failure due to repeated stresses at the wheel-rail contact. This phenomenon is a real problem that greatly affects the safety of train operation. Preventive and corrective maintenance tasks have a big impact on the Life Cycle Cost (LCC) of railway assets, and therefore cutting-edge strategies based on predictive functionalities are needed to reduce it. A methodology based on physical models is proposed to predict the degradation of railway tracks due to RCF. This work merges a crack initiation and a crack growth model along with a fully nonlinear multibody model. From a multibody assessment of the vehicle-track interaction, an energy dissipation method is used to identify points where cracks are expected to appear. At these points, crack propagation is calculated considering the contact conditions as a function of crack depth. The proposed methodology has been validated with field measurements, conducted using Eddy Currents provided by the infrastructure manager Network Rail. Validation results show that RCF behavior can be predicted for track sections with different characteristics without the necessity of previous on-track measurements.

Rail vehicles negotiating curves or in crosswinds are subjected to high lateral forces which provoke high displacements of the lateral suspension. As these displacements need to be limited due to gauging restrictions these forces cause the lateral suspension to reach the bumpstops and consequently the passenger comfort is significantly jeopardized. The paper presents the design of a pneumatic system that allows limiting the lateral displacement during curve negotiation (hold-off device). It describes the different phases of the design process starting from the definition of requirements to be fulfilled. The main components and the effect of their characteristics on the overall performance of the centring system are studied, and completed with an experimental analysis of the centring system. Finally, the described methodology is applied to a typical high speed rail vehicle. The results prove that the concept of a centring system which uses the same technology and components that are used in rail vehicles for the pneumatic height control system of secondary suspensions is possible. This fact is particularly interesting as the market offers this kind of components and has proven their reliability during many hours of service therefore the new hold-off system will be based on in-service validated components.

A multiaxial fatigue criterion recently developed by the authors for 2D conditions is extended here to 3D situations and applied to predict fatigue damage in rail welded joints with the help of an explicit finite element model. Contact theory and axle box acceleration response in frequency domain are used to validate the finite element model. The influence of depth and length of the welded joints is analyzed. It is found that fatigue damage is more severe with shorter and deeper welded joints. When the length of the welded joints is less than 150 mm, fatigue damage is greatly increased with the increasing of the depth. When the depth is less than 0.1 mm, fatigue damage is not relevant, regardless of the length. When the depth is greater than 0.3 mm, fatigue damage increases significantly with the decreasing of the joint length, especially when the length is less than 150 mm. When the welded joints are long enough, the depth restriction can be relaxed. This work can provide guidance and theoretical support for maintenance and repair of rail welded joints.

This paper presents a theoretical study of the parameters that influence sandwich-type constrained layer damper design. Although there are different ways to reduce the noise generated by a railway wheel, most devices are based on the mechanism of increasing wheel damping. Sandwich-type constrained layer dampers can be designed so their resonance frequencies coincide with the wheel's resonant vibration frequencies, and thus the damping effect can be concentrated within the frequency ranges of interest. However, the influence of design parameters has not yet been studied. Based on a number of numerical simulations, this paper provides recommendations for the design stages of sandwich-type constrained layer dampers.

The acoustic reductions achieved with the current damping solutions for railway wheels that appear in the state of the art were obtained with different railway wheel designs, under different measurement scenarios (laboratory and on track), under different testing conditions, making it impossible to compare these damping solutions in a straightforward manner. The aim of this paper is to analyse, measure and estimate the behaviour of damping solutions installed on the same railway wheel and under the same testing conditions. Experimental measurements were carried out in the laboratory on wheels that are currently in use in metro lines. Damping solutions that were evaluated are ring damper, friction damper and sandwich-type constrained layer damper. Results show that ring and friction dampers are dependent on the applied preload and that they can only dissipate energy at high frequencies. Sandwich-type constrained layer dampers are the only damping solution that can add damping at low frequencies, but it is essential that they be properly designed in order to significantly increase the final wheel damping.

This paper presents the modelling and design of a constrained layer damper to eliminate squeal noise in a particular tram. Even though resilient wheels are installed in every bogie, squeal noise is generated at the frequency of 780-800 Hz due to the small radius curves that the tram has to draw. Tuned constrained layer dampers provide a solution to this particular problem. Butyl rubber is chosen as the viscoelastic material for the damper, and conventional steel is used for the metallic sheets. The modelling approach and the final design of the damper are presented, together with evaluation of its performance in a real application. Experimental measurements on track have demonstrated that the constrained layer damper is properly tuned to the squealing frequency and that there is a significant reduction in noise when the proposed damper is attached to the wheels.

This paper presents a procedure for predicting the damping added to a railway wheel when sandwich-type dampers are installed. Although there are different ways to reduce the noise generated by a railway wheel, most devices are based on the mechanism of increasing wheel damping. This is why modal damping ratios are a clear indicator of the efficiency of the damping device and essential when a vibro-acoustic study of a railway wheel is carried out. Based on a number of output variables extracted from the wheel and damper models, the strategy explained herein provides the final damping ratios of the damped wheel. Several different configurations are designed and experimentally tested. Theoretical and experimental results agree adequately, and it is demonstrated that this procedure is a good tool for qualitative comparison between different solutions in the design stages.

Rubber elements are widely used in the railway industry in order to achieve vibration transmission requirements. Although they are critical components in railway vehicles, their modelling in the dynamic models of railway vehicles is usually relatively simple: it is usual to characterise them using a simple linear model formed by a spring and a viscous dashpot in parallel. In this paper the behaviour of typical rubber elements is analysed and a model that allows more accurately the prediction of its behaviour is proposed. The methodology to implement this model in railway simulation programs is also discussed.

This paper presents and validates an appropriate physical damper model to predict the dynamic behaviour of a railway damper for frequencies of up to 200 Hz. The model is computationally efficient and, therefore, appropriate for implementation in NVH-CAE models used to study the transmission of vibration paths to the train body. The model parameters are related to the physical characteristics of the damper (volume of the chambers, piston rod sections, characteristics of the valves, etc.). However, it is shown that in the absence of internal constructive information, which is most often the case, the model parameters can be fitted from a few tests carried out at low frequency (0-20 Hz), based on its theoretical background.

Rubber suspension elements suffer from oxidative ageing, resulting in a change of their mechanical behaviour. For the particular case of suspension elements of vehicles, ageing mainly increases the quasi-static and dynamic stiffness of the bushings. This influences the dynamic behaviour of the vehicle throughout its operational life, so being able to predict the changes in stiffness becomes of paramount importance. This investigation studies the influence of oxidative ageing on the mechanical properties of two natural rubber compounds that are commonly used to manufacture suspension bushings. Quasi-static and dynamic tests are conducted in tensile and compression specimens, both in non-aged and aged conditions, assessing the changes in the quasi-static stress/strain curves and in the dynamic Young's modulus. Samples are introduced in the oven for different time spans and five ageing temperatures. Accelerated thermal-ageing test results are afterwards extrapolated by using the Arrhenius approach.

Filled rubber is a hghly non-linear material. Nevertheless, frequency domain simulations enforce the use of linear models. When rubber is subjected to a harmonic excitation, the linearization of the models is straightforward, but when it is subjected to a random one this is not so evident. This paper presents a methodology for the linearization fo rubber models, in order to accurately simulate in frequency domain the response of a rubber component subjected to a random excitation.