TIE-PLATE CRACKING ON WOOD/COMPOSITE TIES: A PARAMETRIC STUDY

摘要

Composite ties are commonly used as a replacement for wood ties because of many advantages. For example, composite ties show higher decay and corrosion resistance, greater compatibility with available fastening methods, and the ability to be inter-mixed with wood ties. However, recently, premature fatigue failures of tie plates installed on composite ties have been found at the TTCI test facility, while no failures had been found in tie plates installed on wood ties. This paper presents an investigation of tie plate failures using finite element analysis. A full-scale finite element model of the involved components-consisting of axle, wheel, rail, tie plate, and tie-is developed with an application of vertical and lateral loads on the axle. Three contact interfaces-between wheel-rail, rail-tie plate, and tie plate-tie, are defined to simulate actual operational configuration. To investigate the bending stresses in tie plates as a result of wheel-rail rolling contact, a parametric study of the elastic modulus of the ties, and the applied vertical and lateral wheel loads is examined. Results show that 1) given typical vertical and lateral loads, the decrease of tie's elastic modulus increases transverse (bending) stresses at the base of the tie plate; thus, promoting high-cycle fatigue failures, and 2) in addition to the vertical load, the lateral loads also have a significant effect on the bending stress in the tie plate, 3) spike-hole cracking is the dominant mode of failure in composite ties operated under all simulated load cases, while edge failure is dominant in wood ties operated under a large lateral load.