ASSESSMENT OF DEGRADATION OF RAILROAD RAILS: FINITE ELEMENT ANALYSIS OF INSULATED JOINTS AND UNSUPPORTED SLEEPERS

摘要

This research investigates the response of rail material using an elastic-plastic finite-element framework. The implications of unsupported sleepers and insulated rail joints which represent sources of stiffness discontinuity in railroad lines were included. The nonlinear response of wheel-rail material was considered. The developed finite-element model has been supported by an analytical method to assess the onset of fatigue cracks in rails. Deflections, strains, stresses, and crack initiation parameters were obtained. The results showed good compatibility with the field observations, Hertz's theory, and equivalent studies. The findings showed the high sensitivity of plastic flow and rail material fatigue to the value of rail deflection which on the contrary has a meagre impact on the magnitudes of stresses. In addition, insulated rail joints due to stress singularity have a hurtful influence on the quantities of stresses, plastic deformation, and fatigue life. However, this effect plummets with increasing depth. For all cases, cracks initiate at the rail's surface knowing that the simulated friction coefficient between wheel and rail is 0.35 and the applied wheel load is 110 kN. Additionally, 15 mm depth is enough to study the nonlinear characteristics of rail materials. And finally, unsupported sleepers accelerate the electrical failure, which causes troublesome traffic disturbances, at insulated rail joints.