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Vo K.D.,University of Wollongong | Vo K.D.,Cooperative Research Center Cooperative Research Center for Rail Innovation | Tieu A.K.,University of Wollongong | Tieu A.K.,Cooperative Research Center Cooperative Research Center for Rail Innovation | And 3 more authors.
Wear | Year: 2015

In wheel-rail contact, the locomotive adhesion variable characterizes the capability of the locomotive to convert available friction into traction at the interface. Recently developed AC (Alternating Current) drive induces a higher adhesion level compared to DC (Direct Current) drive. This can significantly affect the wheel-rail contact conditions such as high contact temperature due to the frictional rolling, wear and damage initiation of the rails. The aims of this paper are to determine the temperature rise due to high adhesion contact and the thermal influence on the wear and rail life. Three-dimensional (3D) elasto-plastic finite element model was applied to evaluate the growth of temperature, residual stress and strain. The numerical model employed the moving heat source code developed by Goldak within ANSYS/LS-DYNA. The mechanical and thermal properties of the rail material were governed by temperature. The influence of multi-passes from multiple wheels attached to the locomotives on one point of the rail was also taken into account. The results indicated that after six wheel passes, the temperature due to the high adhesion condition was sufficiently high (723. °C) to form the white etching layer (WEL) known to be associated to the rolling contact fatigue (RCF) on the rail surface. Moreover the rail material would be softened by high temperature, which resulted in the acceleration of wear process. Finally the results of thermal stress and strain from FE model were used as input to Kapoor's ratcheting model to determine the number of wheel rolling cycles leading to rail damage. © 2015 Elsevier B.V. Source


Vo K.D.,University of Wollongong | Vo K.D.,Cooperative Research Center Cooperative Research Center for Rail Innovation | Zhu H.T.,University of Wollongong | Zhu H.T.,Cooperative Research Center Cooperative Research Center for Rail Innovation | And 3 more authors.
Wear | Year: 2015

In wheel/rail contact, rolling phenomenon on the curved track can be much more complicated than that on the straight track, especially on a sharp curved track. Due to the influences of super-elevation (also called track cant), angle of attack (AOA) and rail cant, stress states on the high rail are significantly different from that on the low rail. Therefore, the appearances of damages on the low and high rails are different as well. These damages can result in the rail failures, subsequently leading to the vehicle derailments. In this paper, a realistic finite element model using Australian wheel/rail profiles (ANZR1 wheel and 60. kg rail) was developed to investigate the wheel/rail contact on the low and high rail of a curved track under high adhesion condition. Based on the datum of contact stress states, surface damage mechanisms of the rail in curved track was determined. The new and worn profiles were utilized in the simulation to examine different contact situations: new wheel/new rail, new wheel/worn rail, and worn wheel/worn rail contacts. The obtained results showed that the two-point contact might appear on the high rail of the curved track and the stress distributions at each contact location were varied depending on the contact location and AOA. Moreover, the response of material at the rail head was predicted to be ratchetting. Regarding the damage predictions, the rail corrugation tended to be formed on the low rail rather than the high rail; and the fatigue defects could be easier developed on the standard carbon rail compared with hardened rail. © 2014 Elsevier B.V. Source

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