STUDY OF THE LONG TERM EVOLUTION OF LOW-RCF WHEEL PROFILES FOR LKAB IRON-ORE WAGONS

SUMMARY The Swedish iron-ore company LKAB is using three-piece bogies with 30 tones axle load to transport pellets from the mines in Kiruna and Malmberget to the ports in Lulea and Narvik. LKAB provided a new wheel profile that is expected to perform better with regard to rolling contact fatigue and results in a longer wheel life than the currently used WP4 profile (RCF). A simulation model of the freight wagon has been built at KTH using the multibody simulation code GENSYS. However, in order to study the long-term stability of the new profile, monitoring the evolution of the shape of the wheel profile is inevitable: there is a risk that the optimised profile might wear in an unfavourable way and, after a while, cause even higher RCF or wear than the original one. The current study predicts the wheel profile evolution as function of running distance using the uniform wear prediction tool developed at KTH, see e.g., Jendel and Berg [1]. It includes an analysis of when, during the wheel life, the highest RCF probability occurs. The procedure contains of a number of so-called wear steps with a set of time-domain simulations reflecting the actual rail network. As the wagons are equipped with pneumatically actuated tread brakes, the influence of braking on material removal is also estimated via the calculation of the braking force for each simulation case; this is, considering the topography of the line, the amount of braking by the locomotives and the running resistance from curving, aerodynamics and mechanical resistance. The calculation is first performed for the current wagon wheel profiles, and the results are compared with field measurements in order to validate the simulation procedure. There is a great potential of saving time and money if an optimal wheel-rail profile combination can be selected with the help of computer simulation. The results did not show any major difference between the wear of WP4 and WPX profiles. Although the WPX profile produces less RCF on the tread, it may be at a risk of developing RCF at the flange area. Since there are no major differences observed in the simulation results, LKAB has not yet decided if they use the suggested WPX profile. A field test with the new profiles on wagons would be beneficial to verify the simulation results. This work has been performed and continuously validated in the Malmbanan Wheel-Rail group to try to solve the RCF problems with the wagons and loco wheels.