Monitoring Dynamic Properties of Railway Tracks Using Train-borne Vibrometer Measurement

Characterization and Mitigation of Speckle Noise in Laser Doppler Vibrometer on Moving Platforms (LDVom)

Laser Doppler vibrometer (LDV) is a vibration-detecting instrument for noncontact and non-destructive measurement. It is superior to classic contact transducers in terms of the wide frequency range and high measurement resolution. LDV on moving platforms (LDVom) is one of the LDV measurement technology to one-way scan the vibrating surface, so...

Vibration-based railway track condition monitoring: A physics-based digital twin approach

This thesis transforms the way we understand and monitor rail infrastructure with a digital twin that merges measurement data and physics-based models to deliver instant insights. This thesis will be of particular interest to professionals in the rail industry seeking to answer the following questions: What are the key features in the...

Mechanisms and mitigation of short pitch rail corrugation

Short pitch corrugation is a (quasi-) periodic rail surface defect with shiny crests and dark valleys. It primarily occurs on tangent tracks or gentle curves with a typical wavelength in the range of 20-80 mm. Short pitch corrugation excites high-frequency wheel-rail dynamic contact forces and generates a high level of noise, which is a nuisance...

Mechanisms of short pitch rail corrugation

Short pitch corrugation is a (quasi-) sinusoidal rail vertical defect on rail surface, and it was first found more than one century ago. The wavelength of short pitch corrugation is 20-80 mm, and its amplitude can be up to 100 µm. It mainly develops on straight tracks or at gentle curves with comparatively light axle loads. Due to short pitch...

Influence of Microstructure on Mechanical Properties and Damage Initiation of Bainitic Steels in Railway Applications

In this PhD thesis, we investigated possible steel candidates for use in railway crossings in order to reduce the damage in them. Pearlitic R350HT together with Bainitic grades including CrB, B1400 and carbide free B360 were investigated for their mechanical properties such as ultimate strength, yield strength, ductility and hardness. The...

An investigation into the formation of squats in rails: modelling, characterization and testing

Rolling contact fatigue (RCF) is an important form of damage in wheels and rails that typically has surface and subsurface cracks. Squats are one of the major RCF defects that occur in the running band of rails and can create high dynamic forces and cause rail fracture if they are not detected and treated in time. In the current research, three...

Intelligent rail maintenance decision support system using KPIs

Key Performance Indicators (KPIs) enable the infrastructure manager to keep the performance quality of the infrastructure at an acceptable level. A KPI must include specific features of the infrastructure such as functionality and criticality. The KPIs can be classified into three performance levels: (1) technical level KPIs; (2) tactical level...

Finite Element Solution of Rolling Contact and Analysis of Squats Formation

One goal of this thesis is to study the performance and accuracy of an explicit finite element (FE) method for frictional rolling contact in a wider-range of conditions. The other goal is to reveal the physical phenomena of squats and the mechanisms behind, such as cracking mechanisms and development process. The first part studies the...

Numerical Modelling of Wheel-rail Dynamic Interactions with an Explicit Finite Element Method

The modelling of wheel-rail dynamic interactions is crucial for accurately predicting wheel/track deterioration and dynamic behaviour. A reliable wheel-rail dynamic interaction model requires a careful treatment of wheel-rail frictional rolling contact and a proper consideration of dynamic effects related to the contact. Since the wheel-rail...

Modelling and Monitoring of Dynamic Wheel-Rail Interaction at Railway Crossing

This dissertation aims to gain a better understanding of the dynamic wheel-rail interaction at crossings, including characterizing the wheel-rail contact behavior, evaluating the performance of crossings under traffic loads and monitoring the health condition of the structure. The first part of this dissertation focuses on an in-depth analysis...

The Wheel-Rail Contact Problem in Vehicle Dynamic Simulation: Modeling of Train-Turnout Interaction

One of the major costs incurred by railway companies is the maintenance of turnouts.This situation occurs because the large dynamic forces between the wheels of a train and the rails of a turnout cause excessive wear, rolling contact fatigue and rapid degradation of other components. A thorough understanding of the dynamic interaction between a...

Detection of early squats by axle box acceleration

This thesis discusses a new method for detection of short track irregularities, particularly squats, with axle box acceleration (ABA) measurements. A squat is a surface initiated short track defect, associated with high frequency vibrations of the wheel-rail system. High stresses in the contact patch at squats cause accumulation of plastic...

Dynamic Wheel/Rail Rolling Contact at Singular Defects with Application to Squats

Squats, as a kind of short wavelength rail surface defects, have become one of the main rolling contact fatigue problems in railways worldwide. The purpose of this work is to better understand the squatting phenomenon, contribute to reduction and even prevention of squat occurrence, and thereby reduce the related costs. To such an end, a new...

Low Adhesion in the Wheel-Rail Contact

Adhesion, or adhesion coefficient, is given by the ratio of the longitudinal tangential (i.e., braking or traction) force over the normal force at the wheel-rail contact. The tangential force that a braking or tractive railway wheel can exert on a rail is limited by the friction coefficient available between the surfaces in contact for a given...