Wheel-rail Wear Research Articles

Simulation of curving at low speed under high traction for passive steering hauling locomotives

The traction control in modern electric and diesel electric locomotives has allowed rail operators to utilise high traction adhesion levels without undue risk of damage from uncontrolled wheel spin. At the same time, some locomotive manufacturers have developed passive steering locomotive bogies to reduce wheel rail wear and further improve locomotive adhesion performance on curves. High locomotive traction loads in curving are known to cause the loss of steering performance in passive steering bogies. At present there are few publications on the curving performance of locomotive steering with linkage bogies. The most extreme traction curving cases of low speed and high adhesion for hauling locomotives have not been fully investigated, with effects of coupler forces and cant excess being generally ignored. This paper presents a simulation study for three axle bogie locomotives in pusher and pulling train positions on tight curves. The simulation study uses moderate and high traction adhesion levels of 16.6% and 37% for various rail friction conditions. Curving performance is assessed, showing forced steering bogies to have considerable advantages over self steering bogies. Likewise it is shown that self steering bogies are significantly better than yaw relaxation bogies at improving steering under traction. As the required traction adhesion approaches the rail friction coefficient, steering performance of all bogies degrades and yaw of the bogie frame relative to the track increases. Operation with excess cant and tensile coupler forces are both found to be detrimental to the wear performance of all locomotive bogies, increasing the bogie frame yaw angles. Bogie frame pitching is also found to have significant effect on steering, causing increased performance differences between bogie designs.

Wear rate estimation of train wheels using dynamic simulations and field measurements

Wheel–rail wear is one of the important problems in the railway industry, especially from the point of safety, maintenance, and replacement cost. To investigate this phenomenon, it is necessary to simulate the wheel–rail interaction. The simulation results and in particular the wear number is not tangible enough to explain the wear condition of the system. For one set of simulation performed on two different railway systems one could obtain the same wear numbers, of say 100, while having two completely different wear rates. In order to have a better understanding of the wear condition, it is proposed to convert the wear numbers to wear rates. In doing so by measuring the wear rate, one determines the rate at which the wheel flange thickness is reduced. In this research, a new approach has been proposed to determine the wheel wear rate through multi-body dynamic analysis and simulation and the field measurements carried out on the fleet of one of Tehran's subway lines. This procedure could also be expanded to determine a wear criterion for specific lines and their fleets. Having this wear criterion would provide a better understanding of the simulation results either prior to the construction of railway lines or for the presently used ones. In other words, designers can simulate a railway line, not being constructed yet, and with a good approximation determine the critical points along the line with high wear rates, and make necessary modifications to decrease the wear.

CONTROL ALTERNATIVES FOR YAW ACTUATED FORCE STEERED BOGIES

A new design for actively steered bogies (Simson S., 2007) has been proposed for tractive rollingstock to improve not only wheel rail wear and rolling contact fatigue but to also improve wheel rail adhesion. The new bogie design features forced steering with active yaw control of the secondary suspension.The control alternatives for the new bogie design are limited by the need for the control to act independently to wheel rail creep forces. Two control alternatives are presented, a full active method where the control is applied based on known track alignment and the vehicles position. And a semi active method where the track curvature is estimated from gyroscope inputs with no prior knowledge of the track and a target alignment is estimated.

1106 車輪～レール間の摩耗接触特性評価システムの開発(機械要素のトライボロジー,一般講演)

It is indispensable to grasp characteristics of contact point between wheel and rail geometrically to analyze the characteristics of vehicle dynamics. However, there was not an analytical method to be able to calculate simply and easily characteristics of contact point, which was formed by actual shapes of both tread wears of rail and wheel Therefore we developed an analytical system by which we could calculate variations of wheel radius and angle of attack each corresponding to lateral displacement of wheel set for a combination of wheel wear tread and rail wear tread Thus equivalent conicity could be obtained based on the results of calculation.

Wheel–rail wear simulation

This paper declares the method for the computation of the wheel–rail surface degradation in a curve where the major surface degradation phenomenon is a combination of wear and plastic deformation. Simulating the form change of the wheel–rail contacts help to identify the risk of severe or catastrophic wear resulting from increased train speeds and axle loads and can help in determining more efficient maintenance schedules for track and rolling stock. The method was previously used to simulate the form change in a two-roller contact. The progress is made in the terms of general geometry modelling, which makes differences in the various contact configurations. The normal contact problem is analysed using the modified Winkler method and calibrated using the results from FEM modelling of the wheel–rail contact with elastic–plastic material model. A piecewise approach and stick-slip analysis of the rolling–sliding contact solves the tangential problem. A linear wear law is used in the wear computation. The form change for a typical two-point contact in a low radius curve was analysed and discussed.

Study on dynamic curving behavior of tilting passenger cars

By using tilting carbodies, train can negotiate at a higher speed without reducing the passenger's ride quality.This is a good method to allow a significant increase in speed at existing track to improve the railway transportation capa-bility, and to enhance the competition ability of railways with other transportation systems. With the increase of the curvenegotiation speed, the wheel-rail lateral forces and wheel-rail wear of the tilting train will increase. The self-steering radialbogie is an effective way to solve the problem. The dynamic model of the tilting passenger car with self-steering bogies isestablished in detail, and the curving performance of the car is investigated.

A model of an actively controlled roller rig for tests on full-size railway wheelsets

A mathematical model of a roller rig for full size tests on a railway wheelset is proposed. The model is used in order to allow optimal utilization of the testing facility and is expected to give important insights into wheel-rail contact modelling and wear mechanisms, through comparison between numerical results and experimental ones performed in a controlled and stable environment. The mathematical model includes a description of the mechanical system, of the hydraulic actuators and of the electric servomotors used to control the motion of the wheelset. Comparisons between measurements performed on the roller rig and numerical results provided by the model are reported and briefly discussed.

Simulation Of Severe Wheel-rail Wear

Wear is inherent to wheel-rail system. Severe wear is a problem for heavy haul railways. Based on experimental results, knowledge in vehicle-track system dynamics and advances in rolling contact mechanics, computer aided wheel-rail wear simulation is possible. It provides a fast and cheap means for prediction of wear life, optimal profile design and more realistic vehicle-track dynamical analysis. In this paper, a method for the simulation of severe wheel-rail wear by non-Hertz contact is presented, it is fast and robust. Combining it with vehicle dynamical simulation is desired.

Tribological interrelationship of seasonal fluctuations of freight car wheel wear, contact fatigue shelling and composition brakeshoe consumption

This paper proposes a novel theory which explains the strong linkage between brakeshoe metal pick-up and a corresponding increase in wheel tread wear and shelling during the wet winter months. The model suggests that pick-up metal forms through the tribo-reduction of oxidized wheel-rail wear debris. The presence of abundant carbonaceous residues and moisture is thought to promote this reaction. The consequent removal of carbon and wear debris from the wheel-rail interface increases friction during the dry periods to the range 0.4-0.6. This exacerbates wheel-rail wear and shelling. It is concluded that the most effective way to alleviate seasonal increases in wheel shelling and wear is to control friction in the range 0.2-0.4. This can be accomplished by inhibiting carbon depletion associated with metal pick-up or by applying commercial friction reducers.

A Laboratory Investigation of Threshold Stress in Wheel/Rail Interaction for Heavy Axle Loads

This study is a continuation of earlier investigations to determine acceptable upper bound of contact stresses (threshold stress) for new wheel and rail under heavy axle load conditions. Using sharply increased wear rate (as initial maximum contact stress increases) under free rolling conditions as an indicator of threshold stress, laboratory investigations of wheel-rail rolling contact wear, simulating the 125-ton car wheel load, were conducted. Tangent track conditions with clean and dry surfaces were tested on two facilities; one of one-quarter scale and the other of one-fifteenth scale wheel-rail simulation. The earlier experiments conducted in the IIT Railroad Engineering Laboratory to investigate threshold stress used a varying load with the same wheel-rail profiles, the present study used constant load with varying wheel-rail profiles to determine whether the above increase in wear rate phenomenon will still be observed. While the results of the small (1/15th) scale facility were not considered quantitatively conclusive because of small size, qualitatively they indicated the presence of threshold stress phenomenon. The results of the one-quarter scale test facility very clearly confirmed that there is indeed a threshold stress above which the rolling contact wear rates increased sharply. The value of this stress, found to be approximately the same as reported in the earlier study, was nearly 200 ksi (for standard carbon steel rail). From the earlier and the present investigations of threshold stress, it is clearly concluded that the increased wear rates are primarily due to the increased initial contact stresses and 200 ksi is the value of threshold stress for standard carbon steel rail. Initial wheel-rail contact stresses for new wheel-rail should not be allowed to exceed this value to reduce damage to rail for heavy axle loads. It is recommended that new wheel-rail profiles should be developed to achieve stresses at or below this threshold stress level. Benefits of improved rail life with this approach are also discussed.

Wheel-Rail Wear and Adhesion With and Without Sand for a North American Locomotive

A systematic laboratory investigation, of the effect of sanding on wheel/rail wear and adhesion, is reported. The tests were conducted on the IIT-GMEMD Wheel Rail Simulation Facility, using Hertzian simulation of the conditions for a typical North American locomotive wheel. Experiments at adhesion coefficients of 0.24, 0.35 and 0.5, with and without sand application on a clean dry rail, show that ratios of terminal and average wear rates, for the two categories of tests, range approximately from 10 to 100. Archard wear coefficients for the two categories are in the range 10 × 10−5 to 50 × 10−5 for tests without sand and in the range 130 × 10−5 to 520 × 10−5 for tests with sand. The ratios of wear coefficients, for tests with and without sand, range from 5 to 30. Adhesion creepage characteristics of a locomotive wheel simulation under different contaminants, such as water, sand, diesel fuel, lubricating oil, sand after oil and oil after sand, are also reported. It was observed that the liquid contaminants decreased adhesion levels and increased creepage. Sand application reduces the high creepage due to liquid contaminants, simultaneously increasing the attainable adhesion levels. Contrary to earlier findings, it was observed that the degree of sanding does influence the adhesion creepage characteristics, low sanding rates resulting in higher adhesion levels and lower creepage as compared to medium/high sanding rates. The wear and adhesion studies indicate that the beneficial effects of sanding in improving adhesion are more than offset by the increased wear rates. This increase is one to two orders of magnitude, compared to no sanding condition, depending on levels of traction. It is concluded that application of sand should be avoided as far as possible and high adhesion should be achieved by other means in order to minimize wear and the resulting track and equipment costs.

The Use of Steering AXLE Suspensions to Reduce Wheel and Rail Wear in Curves

This paper reviews a number of methods of improving railway vehicle suspensions in order to overcome problems of excessive wheel flange and rail wear in sharp curves. Means of implementing such ideas are discussed for a variety of railway operations, including freight and rapid transit systems. It is shown that this approach is an attractive alternative to the traditional remedy of flange/rail lubrication in a wide range of practical situations.

573. Progress in methods of weighing under vacuum: Th Gast, Vakuum Techn, 14(2), March 1965, 41–44, (in German)

A new design for actively steered bogies (Simson S., 2007) has been proposed for tractive rollingstock to improve not only wheel rail wear and rolling contact fatigue but to also improve wheel rail adhesion. The new bogie design features forced steering with active yaw control of the secondary suspension.The control alternatives for the new bogie design are limited by the need for the control to act independently to wheel rail creep forces. Two control alternatives are presented, a full active method where the control is applied based on known track alignment and the vehicles position. And a semi active method where the track curvature is estimated from gyroscope inputs with no prior knowledge of the track and a target alignment is estimated.