SWORD – Simulation of wheel on rail deterioration phenomena

SWORD

Researchers

Background

Deterioration of the wheel-rail interface is a major cost driver in maintenance of wheels and rails. Improvements in understanding pertinent phenomena and the ability to predict the behaviour are essential to the involved parties as railway operators, track owners, and manufacturers.

The aim of closely related previous research project has been to improve the knowledge of how wheel and rail profiles change over time due to wear and develop numerical prediction procedures.

Objective

The intention with this project is to take the prediction technology a step further, extending it with rolling contact fatigue models and address the trade-off between wear and fatigue.

Rail wear
Railway wheel profile showing slight hollow wear and some fatigue cracking.

Research Direction

The research focus is on damage prediction in the wheel-rail interface. The contact patch is small and subjected to high stresses and wear. Two common modes of deterioration, causing significant maintenance costs, are wear and fatigue. In addition, the vehicle-track interaction may be influenced in the direction of decreasing dynamic performance. The prevailing mode of deterioration is determined by load and operating conditions. The challenge is to develop and integrate methods for prediction of wear and rolling contact fatigue (RCF) – in reality mutually dependent phenomena. Initiated cracks may be worn away and the contact geometry may be altered, changing the rate of crack propagation.

The objective is to create a model for prediction of the total expected life of wheels or rails with respect to both fatigue cracking and wear, practically applicable and resting on a firm scientific foundation. For model validation, access to results in terms of real damage investigations and laboratory tests, mainly carried out by other research projects or the industry, is anticipated.

The prediction methodology is based on recent achievements in wear and RCF modelling. Multi-body simulations (MBS) of the interaction between vehicle and track by using commercially available software provide input to the tribological models. The real operation conditions are emulated by defining an adequate set of simulations.

Wear depth
Calculated wear depth over the contact patch for two different vehicles in the same curve. The adhesion zone with no wear, a portion of the slip zone with mild wear, and the rear part of the slip zone with severe wear can be clearly recognised.

For a successful simulation of the wear – fatigue trade-off it is believed that adequate models for contact stress, local slip, material loss, fatigue damage, and possibly plastic material flow are needed.

  • In the area of interface modelling the starting point is investigation and improvement of available wear and RCF prediction models.
  • For material loss modelling, the path forward may be further development and validation of the Archard approach with emphasis on lubricated contacts and poor adhesion conditions.
  • For assessing the fatigue damage, a quantitative damage accumulation rate is needed. Calibration of a Wöhler-like approach is intended using measured crack patterns.
  • The purpose is to determine the prevailing damage mechanism for actual contact conditions.
  • If found critical, some model for plastic material relocation should be considered.
  • Validation of the trade-off model will be done by recording wear and RCF development at two different vehicle types running on the same network.

Publications

  •  Dirks B and Enblom R: Prediction model for wheel profile wear and rolling contact fatigue. Wear 271, issues 1-2, pp. 210-217, May 2011. (Available online October 16, 2010)
  • Enblom R and Stichel S: Industrial implementation of novel procedures for prediction of railway wheel surface deterioration. Wear 271, issues 1-2, pp. 203-209, May 2011. (Available online October 12, 2010)
  • Dirks B and Enblom R: Prediction of wheel profile wear and rolling contact fatigue for the Stockholm commuter train. Proceedings of the 16th International Wheelset Congress, Cape Town, March 14-19, 2010.
  • Enblom R: Getting to the root of wheel wear. Railway Gazette, March 2010.
  • Dirks B and Enblom R: Prediction model for wheel profile wear and rolling contact fatigue. Proceedings of the 8th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Florence, September 15-18, 2009.
  • Iwnicki S, Björklund S and Enblom R: Wheel-rail contact mechanics. Chapter 3 in Wheel-rail interface handbook, Woodhead Publishing Ltd, Cambridge, England, 2009.