Qi Yue Liu

An experimental study of rail corrugation

Abstract This paper presents experimental study of rail corrugation using a JD-1 wheel/rail simulate facility, which mainly consists of a big wheel serving as the rail, and a small wheel serving as the locomotive or rolling stock wheel. The power delivered to each testing wheel can be accurately controlled. The traction or braking force can be obtained by the power applied to the small wheel during continuous test operation. In order to understand the mechanism of the wear, the wear corrugations on the scars of small wheel were examined by optical and scanning electron microscopy. Preliminary results can be drawn as follows: the corrugation depends on the tangential force and vertical oscillation between the rail and wheel of test machine. The tangential force enhanced the wear of contact surface, and the fluctuating force between two contact surfaces could induce asymmetry wear, which could produce original corrugation on the rolling wheel. When the original corrugation initiated, the uneven surface would lead to a rapid growth of the corrugation.

Effect of displacement amplitude in oil-lubricated fretting

Fretting behaviour have been investigated in oil lubrication, covering a large range of amplitude from 2 to 400 μm. Two types of oil and contact pair on fretting behaviour were studied. A significant reduction in the coefficient of friction occurred above critical displacement amplitude. Analysis of fretting condition in combination with fretting mark examinations reveal that, at an early stage, fretting behaviour depended upon oil boundary lubrication, and was later closely associated with the degree of oxygen access and penetration of oil into the interface. Compared to dry conditions, a great difference in fretting regime behaviour and contact wear was observed.

Effect of tangential force on wear behaviour of steels in reciprocating rolling and rolling–sliding contact

Abstract A new rolling testing apparatus was developed on a tension–compression hydraulic machine with a high precision. The aim of this paper is to study the transition of wear mechanisms of steels with the increase of tangential friction force between contact surfaces in rolling. The wear modes were particularly analyzed during the passage from rolling to mixed rolling–sliding contact.

Influence of Different Application of Lubricants on Wear and Pre-existing Rolling Contact Fatigue Cracks of Rail Materials

Rolling contact fatigue (RCF) of rail can be a significant problem affecting safety and maintenance. Rail materials have been optimized to reduce it, but not enough is known about how friction management products applied to the rail affect crack growth. This study presents experimental results carried out to explore the influence of different lubricants and application orders on wear and pre-existing RCF cracks in rail materials. The results indicate that the types or properties of lubricants have a vital role in the wear rate and fatigue crack growth characteristics of rail materials after conditioning with 5000 dry cycles to initiate cracks. Using a different application order of two lubricants has a significant influence on the crack growth angles in the rail rollers.

The Effect of Rail Material on Wear Behavior of Wheel and Rail

This study investigates the effect of rail material on their wear behavior of rail-wheel system by using MMS-2A twin-disc abrasion tester. When one type of wheel matches with different types of steel rail, the worn lose of the steel rail decreases with the increasing hardness, and the abrade wear of wheel increases. The trend showed by the SEM micrograph of the wear scar was consistent with the results of the worn lose.

Study on Using Numerical Method to Predict Wear Volume of Rail

This paper describes an numerical method and simulation experiment investigation on the rail wear affected by the curve radius and axle load etc. the effects of curve radius and axle load on The effects of axle load and curve radius on total slippage of contact particles and friction work of wheel/rail are investigated with numerical methods are analyzed by kalker’s program CONTACT. The effect of curve radius and axle load on rolling wear behaviour of rail is investigated by simulation experiment. It is indicated that axle load and curve radius are important factors to effect rolling contact wear of wheel-rail, and there is a linear relationship between wear volume of rail and friction work of wheel/rail; The preliminary empirical formula between wear volume of rail sample and friction work is given by analysis the experimental and calculation results, the formula offers a certain reference value for researching wear of wheel-rail and predicting wear volume of rail.

Numerical and Experiment Analysis of Rail Wear

The rolling contact wear is a severe problem and meets with much widespread interest in the world. This paper describes an numerical method and simulation experiment investigation on the rail wear affected by the curve radius and axle load etc. The creep force ,stick/slip areas of contact particles, and friction work of wheel/rail in static condition are analyzed by kalker’s program CONTACT. The effect of curve radius and axle load on rolling wear behaviour of rail is investigated by simulation experiment. The results of numerical and experiment indicates that with the decreasing of curve radius and the increasing of axle load, the wear value of rail increase nonlinearly, especially in the condition of the curve radius is less than 1200m,the wear value of rail increase rapidly. And with the decrease of curve radius, the maximum slippage decrease gradually, and the stick areas decrease while the slip areas increase. The growth speed of friction work of wheel/rail in the condition of smaller curve radius and heavier axle load is faster than in the condition of larger curve radius (straigth line) and lighter axle load.

An Experimental Investigation on Railway Adhesion Properties under Water Medium and Dry Condition Respectively

The effect of wheel speed, axle load and track curve radius on wheel/rail adhesion properties under dry and water medium condition was investigated in this paper using JD-1 wheel/rail simulation facilities with Hertz simulation method, and then testing method of “four horizontals and three factors” was adopted to analyze the influence degree of speed, axle load and track curve radius on wheel/rail adhesion. Results from the experiment are that: The adhesion coefficient reached maximum at creep ratio of 1.5% under dry condition, and 1% under wet condition respectively; the adhesion coefficient under water medium condition occupy about a proportion of 32%-50% of that under dry condition. adhesion coefficient would reduce with speed increasing, axle load increasing and track curve radius decreasing under dry condition, and reduce with speed increasing, axle load decreasing and track curve radius decreasing under water medium condition; As far as influence degree of three testing factors which have effect on adhesion coefficient is concerned, axle load is the first one, then speed, finally track curve radius under dry condition, and speed is the first one, then axle load, finally track curve radius under water medium condition.

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.