A 3-D numerical simulation of fatigue crack growth in an alumino thermite welded UIC60 rail joint under different loading conditions

Abstract

In this article, a UIC60 rail AT weldment with appropriate rail and weld geometry on two-parent rail tracks as per Indian Railways is analysed separately under vertical and lateral loads, applying FEM. Stresses in an alumino-thermite welded rail is measured using finite element analysis. The results of operating condition on the development of fatigue cracks in rail welds are investigated. A 3-D elastoplastic material basis analysis has performed on a CAD assembly model for this purpose. A wheel-rail track model is used to simulate for the allocation of high stresses field in the weldment on the rail under intense service conditions for the welded straight track. Damage mechanics approaches are also used to assess the stress allocation on weld and wheel interaction along with the influence on fatigue lifecycle. The crack's variables like of displacement and stress intensity factors (SIFs) are calculated at crack tip in finite element model to measure crack propagation patterns and the rate of growth, considering two crack and its comparison for different modes. Also the trapped fluid condition due to weather and its influence on crack has been discussed. As friction rate of the contact area between rail weld and wheels increases, formation of crack 1 initiates, and the growth of crack-2 accelerates. Friction of contact patch and the fracture surface have opposite effects on fatigue life. Wet-lubrication are useful for crack friction reduction and can be used as a catalytic factor for SIF on mode II, but this liquid may flow into crack-1 and creates wedge effect. The SIF of opening mode in crack-1 abruptly rises as a result the crack's spread-up, and the fracture becomes deeper. Increasing friction force reduces slip on the fracture crack surfaces, thus reduction in crack propagation. Fracture mechanics fundamentals are used to find the growth of fatigue cracks in weld zone. To measure the progress rate of fatigue crack and SIFs, updated Paris model is used with ANSYS academic.