Improving the reliability of aluminothermic rail welds under high axle load conditions

Aluminothermic rail welding is widely used as an in-track welding process due to its low cost, fast installation time and equipment portability. Despite these operational advantages, aluminothermic welds may exhibit variable weld quality, including defects which are the result of its cast-like process. As a consequence, the probability of aluminothermic service failures may be higher than the parent rail, particularly under high axle load conditions. This paper addresses the risk of weld failure though the development of an analytical approach to assessing the fatigue behaviour of aluminothermic welds, and the implementation of an enhanced welder training and competency program which has contributed to a significant decrease in defective welds under heavy haul conditions. The bending behavior of an aluminothermic weld type used in these applications was investigated in terms of the two most important failure modes for heavy haul operation: horizontal split web (HSW) and straight break. Due to the cyclic nature of the applied loads, these failure modes are overseen in the context of fatigue crack analysis which involves fatigue crack initiation and propagation assessments. However, it is believed that the material distress as a result of wheel-rail contact stresses, bending, weld residual and seasonally-dependent thermal stresses, as well as the geometry of the weld collar would influence the failure initiation sites and the life to crack initiation of the weld. In order to investigate the weld material distress, a thermo-structural finite element model of the welded rail section has been developed; the model incorporates the track stiffness behavior to enable the seasonal thermal effects to be superimposed on those due to local bending and contact stresses. The effect of some heavy haul parameters such as contact patch lateral movement due to curving or hunting with various traction coefficients was also investigated. The simulation results show a good consistency between the bending behavior of the weld and fatigue crack initiation probability based on the in-service behaviour of this weld type. The current study forms the basis for a comprehensive fatigue crack initiation analysis as the next stage of the project.

Media Info

  • Pagination: 9p.
  • Monograph Title: Rejuvenation and renaissance: CORE 2010: conference on railway engineering, 12-15 September 2010, Wellington, New Zealand

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Filing Info

  • Accession Number: 01517103
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ATRI
  • Created Date: Mar 4 2014 8:08PM