FEA to assess railhead material damage with a reference to nylon endpost material of insulated rail joints

Railhead material becomes severely stressed due to localised wheel/rail contact loadings. The stress situation is more critical in the vicinity of the endpost of an insulated rail joint (IRJ). As the contact point moves towards the endpost, the wheel loading peak pressure increases sharply, not following the well-known Hertzian Contact Theory (HTC). Fibre-glass (fg) is used as the endpost material in IRJs in Australia. With a view to finding a more suitable endpost material to reduce impact force and damage of railhead material, a Nylon 66 (ny) endpost has previously been considered for contact force distributions and stresses near the ny endpost, not focussed on railhead damage. However, for designing a longer service life rail joint, it is essential to minimise damage of railhead and endpost materials and limit the extent of the plastic zone in the sub-surface in the vicinity of the endpost.This paper presents a 3D finite element analysis targeting damage and stress distributions in the railhead material near a Nylon 66 endpost. The following design parameters are considered: 5mm endpost thickness in a 6-bolt IRJ centrally suspended between two sleepers as per Australian Standard AS 1085.12, 2002. A non-linear isotropic and kinematic material hardening model is used to represent elastic-plastic behaviour. 2000 loading cycles in the form of wheel pressure using the amplitude function in ABAQUS are applied for this analysis. Critical strain and stress components are determined to quantify railhead damage. The effects of both fg and ny endpost material on the mechanical behaviour of IRJs are analysed to find the best design. In this regard, PEEQ and von-Mises stresses are considered to determine plastic deformation and material degradation of the railhead material.