J. Guo

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.

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.

Optimal design of rail grinding patterns based on a rail grinding target profile

Based on the grinding target profile of the rail and the grinding capacity of a single grinding stone, a numerical calculation method for rail grinding patterns that includes grinding angle and grinding power of each grinding stone of the GMC96 rail grinding train was designed and established. By means of this numerical method, the grinding pattern of each grinding pass was optimized and the rail head profile after grinding was calculated. Furthermore, a method for the evaluation of the grinding quality is provided. The results indicate that in multipass rail grinding, a sequence of grinding passes – where the greatest grinding effort is applied on the earlier passes, with the last pass applying reducing levels of grinding effort – produces the highest conformance to the target grinding profile. For example, when rail grinding is planned for two passes, applying 60% of the total grinding effort on the first pass and 40% on the second pass decreases the final grinding error by 7.3%.

Experimental study on wear and spalling behaviors of railway wheel

The current researches of the wear and spalling behaviors of wheel/rail materials focus on the field investigation rather than the mechanism. However, it is necessary and significant for clarifying the mechanism and relationship between the wear and spalling damage of railway wheel to test and reproduce the wheel damages in laboratory. The objective of this paper is to investigate the wear and spalling damage behaviors of railway wheel using a JD-1 wheel/rail simulation facility, which consists of a small wheel serving as rolling stock wheel, and a larger wheel serving as rail. The damage process of wheel roller is explored in terms of the creep ratio, axle load, and carbon content by means of various microscopic examinations. The experimental results show that the wear volume growth of wheel roller is proved to be proportional to the increase of the creep ratio and normal load between simulating wheel and rail. The increase of carbon content of wheel material causes a linear reduction in the wear volume. The microscopic examinations indicate that the rolling wear mechanism transfers from abrasive wear to adhesive and fatigue wear with an increase of tangential friction force, which results in the initiation of fatigue crack, and then aggravates spalling damage on the wheel roller surface. The surface hardness of material depends strongly upon its carbon content. The decrease of the carbon content of wheel material may alleviate spalling damage, but can cause a significant growth in the wear volume of wheel roller. Therefore, there is a competitive relationship between the wear and spalling damage of wheel material. This research proposes an important measure for alleviating or preventing the wear and spalling damage of railway wheel material.

An Investigation Into Effect of Train Curving on Wear and Contact Stresses of Wheel and Rail

Some important papers concerning the studies on rail wear and wheel/rail contact stresses are reviewed. The present paper utilizes a numerical method to analyze the effect of railway vehicle curving on the wear and contact stresses of wheel/rail. The numerical method considers a combination of Kalker’s non-Hertzian rolling contact theory, a material wear model and a vertical and lateral coupling dynamics model of a half vehicle and a curved track. The present analysis investigates the influence of the curving speed, the curved track super-elevation and the rail cant on the wear and the contact stresses. Through the detailed numerical analysis, it is found that the maximum contact stress depends greatly not only on the curving speed but also on the profiles of the wheel/rail. The curving speed increasing leads to increase the normal load of the wheel rolling over the high curved rail, but, decrease the normal contact stress level under the condition of the optimum match of wheel/rail profiles. The track super elevation increasing efficiently lowers the contact stresses and the wear at a constant curving speed. The rail cant has a great influence on the low rail wear of the curved track. Increasing the rail cant leads to the great growth of the low curved rail wear, the reduction in the high rail wear. The results are very useful in the maintenance of the track.Copyright

Influence of granularity of grinding stone on grinding force and material removal in the rail grinding process

The objective of this study is to explore the influence of grinding stone granularity on the grinding force and rail material removal behaviors using a rail grinding friction machine. The results indicate that with the increase in granularity, the grinding force, and friction coefficient in the grinding interface obviously increase, which brings about a rise in the hardness and grinding temperature-rise of rail specimens. The increase in the grinding stone granularity causes a fall in the grinding volume and surface roughness of rail materials and brings about stronger vibration in the grinding interface owing to different material removal mechanisms. In view of the experimental results, the optimization of grinding stone granularity is significant for improving the rail grinding efficiency and surface quality.

Study on Friction and Wear Behavior of GCr15/1045 Steel under Nano-Particle Additive Conditions

The aim of this study was to investigate the friction and wear behavior of GCr15/1045 steel under different nano-particle additive conditions using a reciprocating horizontal tribometer. The results indicate that the nano-particle additives could decrease friction coefficient of CGr15/1045 steel and reduce the wear of material compared with the dry condition. Nano-particles play an important role of polishing the micro-gibbosity of contact surfaces during the friction process. The nano-particles of Ca10(PO4)6, TiO2 and TiN can form the self-repairing film on the worn surface of 1045 steel. The analysis indicates that the self-repairing effect of nano-particle of TiN is best and the self-repairing effect of nano-particle of TiO2 is worst.

Effect of Non-Steady State Loading on Rolling-Sliding Contact Stress

The stresses, strains, and deformations produced by repeated, two-dimensional non-steady state rolling-sliding contact were analyzed using an elastic-plastic finite element model. An advanced cyclic plasticity model was used. The non-steady state rolling contact was restricted to a harmonic variation of the normal Herztian contact pressure. Repeated rolling and sliding were simulated by multiple translations of a set of varying normal and tangential surface tractions across an elastic-plastic semi-infinite half space. The non-steady state loading considered results in a wavy contact surface profile. The surface displacements and wave depth of the wavy deformation increase with increasing rolling passes, but the increases in wave depth per rolling pass (ratchetting rate) decay. The residual stresses and strains near the wave trough of the residual wavy deformation are higher than those near the wave crest. The results are in agreement with the experimental observations. The tangential force has a greater influence on the residual strains than on the residual stresses.

Study on Rolling Contact Behaviors of Three Kinds of Railway Wheel Treads

The rolling contact behaviors between LMA, S1002 and XP55 wheelset and track in static rolling contact are analyzed using the rolling contact theory of three-dimensional elastic bodies with non-Hertz form and numerical program of CONTACT. The numerical results indicate that three kinds of wheel treads have different difference of rolling radius and equivalent taper. The rolling contact behaviors between three kinds of wheel treads and CHN60 rail have obvious difference. The comprehensive analysis indicates that the matching effect of LAM wheel tread and CHN60 rail is relatively superior. Furthermore, it is suggested that new wheel tread should be designed and optimized for the high-speed railway.