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Carbody hunting stability has attracted more and more attention due to its great influence on the dynamic performance of a railway vehicle. To fully understand the correlation between the wheel–rail contact relationship and the carbody hunting stability of an electric locomotive, the wheel–rail contact geometry analysis and the multi-body dynamics simulation are carried out in this work. The focus is on the influences of track parameters (including rail profile, rail cant and track gauge) on wheel–rail contact relationships and carbody hunting stability. A group of rail profiles are obtained by interpolating between the standard CHN60 profile and the worn rail profiles. The nominal equivalent conicity, the effective equivalent conicity and the wheel–rail contact bandwidth for a wheelset lateral displacement of ±6 mm are used to evaluate the wheel–rail contact relationship, while the lateral continuous comfort index is used to evaluate the carbody hunting stability. The simulation results show that keeping the rail cant at about 1/40 and reducing the track gauge and the wear depth at the gauge corner of rail can improve the carbody hunting stability of the electric locomotive. Furthermore, the effective equivalent conicity is a good choice to establish the relationship between the wheel–rail contact geometry and the carbody hunting stability.

In this work, a new wheel steel named 40SiCr, which containing 0.4 wt.% C, 1.33 wt.% Si, 0.84 wt.% Mn and 1.07 wt.% Cr, was designed and prepared. The steel was subjected to isothermal heat treatment process, which consisted of austenitizing at 860 °C followed by duration holding at 650, 633, 613, and 593 °C, respectively, and was called 40SiCr-650, 40SiCr-633, 40SiCr-613, and 40SiCr-593. Tempering was performed at 540 °C for 2 h. With decreasing isothermal temperature, all of the volume fraction of ferrites, the pearlite colony size and the interlamellar spacing decreased, the prior austenite grain size remained unchanged, and the cementite lamellae fragmented gradually and changed into cementite spheroids, since the synergy of the increase in nucleation rate, the decrease in carbon diffusivity and the effect of Cr element. The fragmenting of cementite lamellae led to the improvement of hardness and strength but the deterioration in ductility of the steel, thus optimizing the wear resistance. The 40SiCr steels isothermally treated at 633 °C possessed a perfect combination of strength and ductility and therefore superior wear resistance.

Two types of high power alternating current (AC) locomotive in China are prone to serious high-order polygonal wear, which has significant negative effects on the operation of locomotives. This study investigates factors influencing polygonal wear in locomotive wheels and determines methods of minimizing operation damage. We designed experiments to analyze the process of polygonization formation of wheels to identify the key influencing factors, finding that natural vibration of wheelsets is the central inherent factor of wheel polygonization and that these vibrations can be easily stimulated by wheel or rail irregularities. We found that poor re-profiling quality is the key external factor in these irregularities. The wheelset bending resonance is activated when the remaining wheel polygonal wear has a wavelength of 200 mm in the 1/3 octave band, in turn leading to significant increases of wheel polygonal wear. In this study, we review a new wheelset design that can mitigate and/or eliminate the polygonal wheel wear due to increased stiffness in wheel bending. We evaluate the potential capacity of the newly designed wheelset and propose two proven effective measures to further improve the wheel re-profiling quality for polygonal wear.

Metro trains often encounter the problem of wheel flange wear when they pass through sharp curves, especially for the poor wheel–rail profile matching or lack of lubrication, evidently increasing t...

A long-term tracking test was performed on a newly designed high-speed train with the nominal speed of 250 km/h. The wheel roughness and structural vibration were both recorded during two re-profil...

High-order polygonal wear wheels have been detected on metro express train operating on one metro line in China, which cause fatigue failures of steel coil springs in the primary suspension. A seri...

Discrete irregularities are a common issue occurring on locomotive wheels. The wheel roughness measured in the field sites indicates that some wheels suffer from discrete wheel irregularities, such...

This paper developed an online estimation of fatigue damage of bogie frame based on the axle box accelerations. In this method, the 3-axis accelerations of axle box and dynamic stress of concerned hotspot in the bogie frame are taken as inputs and outputs to determine the transfer function. This permits us to calculate the power spectra density (PSD) of dynamic stress in the frequency domain based on the axle box acceleration PSD. Subsequently, the frequency-domain fatigue life estimation method is employed to determine the real-time damage based on the obtained stress PSDs. This is expected to facilitate the development of condition-based maintenance or damage-based maintenance.

Severe rail roughness leads to a series of problems in metro systems, particularly the vehicle noise problem. To ensure a better acoustic environment, rail roughness control is therefore one of the main concerns for the metro operators. But the existing roughness acceptance criteria are not suitable for metro interior noise control. It is an appropriate method to determine the rail roughness limit based on interior noise. A rail roughness acceptance criterion based on metro interior noise is accordingly proposed in this paper. The relationship between rail roughness and interior noise can be derived with wheel–rail noise as link. With this objective, a combined test and simulation method is adopted. A validated wheel–rail noise prediction model is thus established to determine the relationship between rail roughness and wheel–rail noise. Moreover, the transfer function of wheel–rail noise to interior noise is developed based on extensive field test. Using this method, the noise sensitivity to roughness wavelength and acceptance criteria at different speeds and track structures are investigated. Finally, an eclectic rail corrugation acceptance criterion on curved track is suggested in consideration of practical application.

A transient FE model of wheelset-rail rolling contact has been developed with ANSYS/Ls-dyna to simulate the high speed running of a free wheelset on a slab track. Applying vertical, lateral and longitudinal vibrations at the passing frequencies of typical short pitch corrugation to the wheelset with no initial lateral shift, it is found that the vertical and lateral wheel-rail interactions are coupled to a large extent, while the longitudinal relatively independent under rolling-sliding and dependent when approaching full-sliding. The resulting irregular wear calculated with implemented wear models of Archard, Tγ and Zobory increases in amplitude with the friction exploitation level, whereas its phase keeps rather stable under rolling-sliding. As full-sliding is approached, the phase shifts greatly in the presence of the vertical or lateral vibration, but not of the longitudinal vibration. Consequently, corrugation initiation from the vertical and lateral vibrations becomes harder if both full- and rolling-sliding wheels pass over.

Affected by the traction/braking, creep control and wheel-rail interface environment, wheel wear of locomotives is more complicated than that of other rolling stock. A locomotive wheel wear simulation model is developed, which includes a 3D locomotive track coupling dynamics model, a rolling contact model for rail traction vehicles based on Kalker's simplified theory, a PI-based creep control model and a wheel material wear model based on frictional power. The advantages of the dynamics model built in this paper are evaluated through two typical simulation cases. The effects of traction/braking and creep control on wheel wear are comprehensively investigated. The results indicate that the natural vibration characteristics of the locomotive/track system can be well reflected, and their influence on wheel wear can be taken into account. Traction and braking have a great influence on wheel wear, which should be considered for locomotive wheel wear simulation. It is a better way to control creep by using a control mode with variable creep threshold value.

The objective of this paper is to ascertain the wheel–rail low adhesion mechanism using a high-speed wheel–rail rolling contact test rig under different interfacial contaminations. Based on the experimental results, a numerical method was proposed to investigate the wheel–rail wear and rolling contact fatigue due to low adhesion issues. The experimental results indicated that the wheel–rail low adhesion phenomena can happen under interfacial liquid contaminations, especially at high-speed running condition. Preliminary numerical investigations showed that the low adhesion condition can easily lead to sliding hence serious wear, especially at the speed between 160 km/h and 200 km/h. The temperature rise within the contact patch can be significantly more severe once wheel and rail are in full slip, causing rolling contact fatigue due to material softening.

Optimisation of railhead profiles using improved non-uniform rational B-Splines (NURBS) and measured profiles is presented for curved tracks to minimise wear. Measured geometry of rail profiles have been parameterised for the NURBS model. These parameters have then been decomposed as constants and variables to represent any other generalised rail profile. The variable parameters have been defined as design variables for the optimisation modeling method that minimises wear of the railhead profile suitable for curved rail track. A genetic algorithm optimisation method was formulated incorporating the parameters of the measured rail profiles with improved NURBS curves described as genes for high and low rails in curved tracks and combined them as chromosomes. The method can handle optimisation of any unique rail profile, although examples given in this paper refer to only the 60 kg/m Chinese Rail CH60. Optimal rail profiles are shown to mitigate wear of wheel-rail contact under the operation of a vehicle passing through a curved track. The optimal shape was shown to minimise contact stresses, increase rolling radius difference and conicity for improved passenger comfort and vehicle safety.

Rail corrugation is a common railway defect that involves diverse and complex factors. Rail grinding is also the most commonly used method to address corrugations. Through numerous irregularity tests and one-third octave frequency spectrum analyses, this study determined the characteristics and development process for rail corrugation on high-speed rail tracks. The vibration transmission properties of the grinding train were tested using the force hammer impacting method. Thereafter, using a simulation, the influence of the vertical vibration behavior of the grinding stone and the stiffness of the hydraulics were determined. Through a series of field tests and numerical simulations, this study revealed a clear correlation between rail corrugation and rail grinding and confirmed that the technical operation of rail grinding is closely associated with regular grinding marks at a wavelength of approximately 60 mm on rail surfaces. The combination of the natural vibration of the grinding stone (frequency of 60 Hz) and an inappropriate operational process can aggravate the grinding marks on the rail surfaces, thereby forming an initial excitation of rail corrugation. Although a large number of irregularity tests are performed after rail grinding, these wavelength-fixing grinding marks can cause the formation and development of rail corrugation. Suggestions for improving the high-speed rail-grinding technology are also provided.

Based on the measured spectra of rail roughness and track structures longitudinal roughness, the rail grinding limit is studied with the help of an established coupled dynamic metro vehicle–track model and a rolling contact fatigue model. The results indicate that metro rail grinding control should be regulated according to corrugation wavelength range and operating speed. Based on the rolling contact fatigue model, longer wavelength of rail corrugation has less influence on the wheel rolling contact fatigue. For the metro lines with a maximum operating speed of 80 km/h, the average levels of rail corrugation in the wavelength ranges of 30–65 mm, 65–125 mm, and 125–250 mm should be less than 5.4, 24.8, and 33.8 dB re 1 μm, respectively; for the ones with the operating speed of 80–120 km/h, the corresponding average corrugation levels in the three wavelength ranges should be less than 4.4, 9.8, and 29.8 dB re 1 μm, respectively.

In a field test, three corrugation profiles of rails and their corresponding vibrations were measured, and the wavelengths and frequencies of rail corrugations were obtained. In the model prediction, finite-element models of the self-excited vibrations corresponding to three different wheelset–track systems were established. The corrugation frequencies of these models were predicted, and a comparison between the measured and the predicted corrugation frequencies showed that they are in good agreement. It can be concluded that the self-excited vibration of a wheelset–track system can cause rail corrugation. A benchmark condition for the validation of rail corrugation models is proposed.

Wheel flange wear often occurs on metro trains when they negotiate sharp curves, especially for the poor matching of wheel and rail profiles or lack of lubrication, which evidently increases the maintenance and replacement costs of the wheelsets and rails. The reason for severe flange wear of the original wheel profile on one metro line in China is investigated through field experiments and numerical simulations. An optimal wheel profile is presented based on the rolling radius difference (RRD) to improve curving performance of the vehicle and mitigate flange wear. A wheel wear prediction model, coupling a metro vehicle dynamics model considering multipoint contact with a long-term wear simulation model, is developed, which is validated using field measurement results. The capability of the optimal wheel profile is numerically evaluated. The results show that the improper wheel-rail profile matching of the original wheel profile is responsible for wheel flange wear. The large proportion of sharp curves and the abnormal rail cant also contribute to flange wear. The optimal wheel profile proves to work fine in terms of wheel/rail contact geometry and wear performance. The wheel flange wear of the optimal wheel profile is decreased by over 60% compared with that of S1002 profile.

Wheel polygonisation is a wavy wear on wheel’s circumference, which aggravates the wheel-rail interaction and prematurely invalidates or damages the components of vehicle-track system. This paper presents an investigation into the formation mechanism of high-order polygonal wear of metro train wheels through field experiments and numerical simulations. Some necessary field experiments are conducted to obtain the characteristics of the irregular wear of the wheels and the dynamics responses of the vehicle components. The numerical modal analysis of vehicle’s key components is performed. Furthermore, a long-term wheel wear model is built including a vehicle-track dynamics model coupled with a local wear model. The metro vehicle-track coupled dynamics model considers the flexibilities of the wheelset and track, where the wheelset and track are modelled using finite element method. The effects of elastic deformation of the wheelsets and rails on creepages, creep forces and wheel wear can be considered in the model. The investigation results indicate that the dominating order of wheel polygonal wear is 11–16, corresponding to wavelengths of 165–240 mm. The formation mechanism of high-order wheel polygonal wear is the P2 resonance of some types of track structure, and the first bending resonance of the wheelset can accelerate the development of wheel polygonal wear.