Ratchetting damage of railhead material of gapped rail joints with reference to free rail end effects

Free ends of insulated rail joints (IRJs) occur because gaps between the rails and endposts can be created due to pull-apart problems as the rails contract longitudinally in winter and by degradation of railhead material. Dynamic behaviour of gapped rail joints (GRJs) changes adversely compared to that of IRJs. Thus, material degradation and damage of GRJ components such as rail ends, joint bars, etc are accelerated. Only limited literature are available addressing the free end of rail effects at rail joints, targeting stress and pressure distributions in the vicinity of the rail joints. To understand clearly the material degradation and delamination process of GRJs, a thorough analysis of failure of both IRJs and GRJs and subsequent damage of the railhead material is necessary to improve the service life of these joints. A new 3D finite element analysis (FEA) is carried out in this paper to assess damage to railhead material when GRJs form. Both narrow (5mm) and wide (10mm) gaps are considered, using a peak vertical pressure load of 2500MPa applied cyclically at one rail end, forming vertical impacts. Stress distributions and plastic deformations in the vicinity of GRJs are quantified using FEA data and compared with that of the IRJs to show the effects of free rail ends. Residual stress and strain distributions indicate the damage to the railhead material. Equivalent plastic strain (PEEQ) quantifies the progressive damage to the railhead material at the rail ends. The free end of rail effects can be further illustrated by comparing PEEQ for IRJs and GRJs. The railhead material of 5mm and 10mm GRJs is more sensitive to permanent deformation compared to that of the corresponding IRJs. Therefore, free rail end joints pose an increased potential threat to rail operations in relation to crack initiation, damage and premature failure of railhead material.