Q.Y. Liu

Adhesion Experiment on a Wheel/Rail System and Its Numerical Analysis

Abstract The experiment on the adhesion coefficient of a wheel-rail system has been carried out by means of a full-scale test facility under the condition of different axle loads and rolling speeds. The effects of the condition of the wheel-rail contact surfaces, such as a clean and dry surface, water and oil contamination and slip, on the adhesion coefficient have been investigated in the experiment. The experimental results show that, when the rolling speed of the wheelset increases, the adhesion coefficient decreases under the condition of the constant creepage and water contamination on the contact surfaces, but it increases for oil contamination. Using the data obtained by statistics and analysis of the experimental results and Kalkers rolling contact theory with Hertzian form modified by the present authors, a numerical analysis concerning the effect of wheelset rolling speed on the adhesion coefficient and the distribution of the stick-slip area in the contact area has been made. The numerical results are in good agreement with those obtained by experiment. They are very useful in designing the traction power of a locomotive at higher speeds.

Investigation on rolling contact fatigue and wear properties of railway rails

Abstract The rolling wear tests of rail material were conducted under unlubricated condition using a JD-1 wheel/rail simulation facility. The fatigue damage and wear behaviours of rail rollers were investigated in detail by examining the microhardness, wear volume, and wear scars using optical microscopy and scanning electronic microscopy. The results indicate that wear volume of a rail roller increases rapidly with the increase of axle load and decrease of curve radius. Wear volume of U71Mn rail is bigger than that of PD3 rail. It is observed that PD3 rail roller has some fatigue microcracks on the surface of wear scar. Furthermore, the microcrack propagates along depth direction with an angle of 15–30°. By comparison, U71Mn material has better fatigue resistance performance. The results indicate when the wear is serious, the fatigue damage is relatively slight. The relationship between fatigue crack damage and wear seems as competitive and restrictive coupling mechanisms.

Effect of laser quenching on wear and damage of heavy-haul wheel/rail materials

In order to alleviate the wear of heavy-haul wheel/rail materials, the wear experiments of wheel/rail rollers undergoing laser quenching were carried out using rolling-sliding testing apparatus. The results indicate that laser quenching produces a hard martensite layer with a certain depth. The improvement of wear resistance of materials resulting from laser quenching markedly decreases the wear volume of wheel/rail rollers. The maximal decrease rate of wear volume of wheel and rail materials is about 92.9% and 89.5%, respectively. Furthermore, the worn surfaces of wheel/rail rollers present different surface morphology and damage mechanisms due to difference of hardness matching. When the surface hardness of wheel/rail rollers undergoing laser quenching is high, the spalling damage and adhesion wear are dominating. When a single wheel or rail roller undergoes laser quenching, the damage mechanism of wheel and rail rollers are significantly different. According to the severe wear region of the heavy-haul wheel/rail, it is proposed that the rail side and wheel flange may undergo laser quenching treatment for alleviating wear of heavy-haul wheel/rail materials. However, further work should be carried out for clarifying the fatigue characteristic of wheel/rail with laser quenching.

Experimental research on noise emanating from concrete box-girder bridges on intercity railway lines

Simply supported pre-stressed concrete box-girder bridges are the most common bridge type found on high-speed railway and urban rail transit lines in China. A field experiment has been conducted on the Pixian Viaduct of the Chengdu–Dujiangyan Intercity Railway, where two kinds of simply supported pre-stressed concrete box-girder bridges with a standard span of 32 m are used, one single track and the other double track. Characteristics of the noise underneath the box-girder, far from the bridge, and near the bridge gap were measured and analyzed in the time and frequency domains during high-speed train passage, as was the vibration of the box-girder’s bottom plate. The variations of noise with distance and train speed at locations 1.5 and 9 m above ground level were measured and fitted using mathematical formulae. A simplified formula to predict near-field bridge-borne noise was proposed and verified. The peak bridge-borne noise frequency and its tonal characteristic at 50 and 63 Hz for the double-track and single-track box-girders, respectively, were interpreted in terms of bridge vibration and sound radiation efficiency, respectively. The vibration/noise transfer function and coherence were evaluated, showing that vibration resonance is more significant than acoustic coincidence and that the former is more important in terms of noise reduction.

Investigation on Wear Resistance and Fatigue Damage of Laser Cladding Coating on Wheel and Rail Materials under the Oil Lubrication Condition

ABSTRACT The aim of this study is to investigate the wear resistance and fatigue spalling damage of wheel and rail materials with and without laser cladding coating under oil lubrication using a rolling–sliding machine. It illustrates that the laser cladding Co-based alloy coating improves the wear resistance of wheel and rail rollers. Serious spalling is dominant for untreated wheel and rail rollers. The wheel or rail roller undergoing laser cladding treatment takes on slight abrasive wear and visible ploughing. Furthermore, there are no cracks on the contact surface and subsurface. The laser cladding Co-based alloy coating exhibits outstanding resistance to wear and fatigue spalling damage due to its microstructure in the coating under oil lubrication.

Numerical and experimental investigation on adhesion characteristic of wheel/rail under the third body condition

A numerical model of wheel and rail lubricated by a third body was established using the partial elasto-hydrodynamic lubrication theory and multi-grid method. The effects of rolling speed, surface roughness, contact load, wheel diameter, and viscosity of third body on adhesion coefficient are explored. The results show that the rolling speed, surface roughness, and the viscosity of third body have a significant influence on adhesion coefficient when the wheel/rail interface is lubricated under oil and water conditions. Furthermore, to verify the precision of the numerical calculating results, some experiments were carried out by means of a JD-1 wheel/rail simulation facility. The results show that there is same changing trend and almost same adhesion coefficient between the curves of numerical and experimental results. The relative difference between the numerical and experimental results is less than 10%. This numerical method can be used to explore the adhesion coefficient of wheel/rail under the third body condition.

Complex Eigenvalue Analysis of Railway Curve Squeal

A finite element complex eigenvalue analysis of curve squeal is carried out. Two models for the wheel tread/rail top contact and the wheel flange root/rail gauge corner contact are established. In the both models, the contact between the wheel and rail is simulated with a spring. The friction force is considered as the contact spring force multiplied by a coefficient of friction. The rail is supported by vertical and lateral springs at each sleeper. The simulation result shows that the coefficient of friction, contact point positions and stiffness of the rail support spring all have distinct influences on the curve squeal occurrence. Appropriate stiffness of the rail support spring can suppress or eliminate curve squeal.

Investigation on adhesion characteristic of wheel/rail under the magnetic field condition:

The aim of this study is to explore the influence of magnetic field and surface roughness on the adhesion coefficient of wheel/rail using a JD-1 wheel/rail simulation facility. The results indicate that the magnetic field has a significant influence on the adhesion coefficient under the water and oil conditions by means of magnetic force on the wheel/rail contact zone. The use of magnetic field is beneficial to increase the adhesion coefficient of wheel/rail interface. The speed has no visible effect on adhesion coefficient under the magnetic field condition. Increasing surface roughness improves the adhesion level of wheel/rail interface under the water and oil conditions.

Investigation between rolling contact fatigue and wear of high speed and heavy haul railway

Abstract Rolling contact fatigue and wear are inevitable problems for the infrastructure of modern railways. The rolling tests of railway rails were performed using a JD-1 wheel/rail simulation facility without any lubricant. The failure behaviour of rail rollers with different materials, axle loads and curve radius was investigated in detail by examining wear volume and wear scar using optical microscopy and SEM. The results indicate that the crack propagation is more significant, and fatigue damage is more severe at high speeds. However, the wear volume of rail rollers becomes large in heavy haul railways. The results show that there is a mutual competitive relationship between wear and surface fatigue cracks. A high wear rate can reduce rolling contact fatigue damage by removing constantly surface cracks.

Preliminary Analysis on Effect of Sleeper Pitch on Rail Corrugation at a Curved Track

This paper investigates the effect of sleeper pitch on the initiation and development of rail corrugation at a curved track when a railway vehicle passes through the curved track using a numerical method. The numerical method considers a combination of Kalker’s rolling contact theory with non-Hertzian form, a linear frictional work model and a dynamics model of a half railway vehicle coupled with the curved track. The numerical analysis examines in detail the variations of wheel/rail normal loads, the creepages, and the rail wear volume. The numerical results show that the discrete track supports cause fluctuations in the normal loads and the creepages at different frequencies. These frequencies encapsulate the sleeper passing frequency and the track resonant frequencies higher than the sleeper passing frequency. Consequently rail corrugation with several wavelengths initiates and develops. Also the results show that the contact vibrating frequencies of the four wheels of the same bogie and the rails are different. The rail corrugations caused by the four wheels of the same bogie present different wavelengths and wave depth.