Fracture mechanics analysis of rail-end bolt hole crack and effects of different parameters on fatigue crack growth rate

Bolted rail joints are one of sensitive components in railway tracks which is used in signaling and broken rail identification systems. Rail joints are the most vulnerable spots in the track structure and many man-hours are spent on their maintenance. A common mode of failure in bolted rail joints is fatigue crack initiation and growth from the bolt holes at the end of the rail. Nowadays, fatigue and fracture of railway track components has been a critical problem. Consequently it caused high cost of maintenance and it threatened the safety of mobility. On the other hand, in addition to casualties and financial loss, this occurrence could have serious consequences. The fatigue failure around rail-end bolt holes is particularly dangerous since it leads to derailment of trains and consequently occurs inevitable accidents. However, researchers have not treated the crack growth in much detail. Therefore, this research will focus on fracture mechanics analysis of the rail-end bolt hole crack. Firstly, a 3D finite element model of rail joint has been provided using commercially available software Abaqus/CAE. In this study, FE models analyzed quasi-statically. After the verification of model and checking the condition of LEFM, fracture mechanics analysis of cracks were carried out. In this stage, considering the stress intensity factor of cracks, the effects of variation of axle load, train speed and the rail support stiffness was determined on the equivalent stress intensity factor and the ratio of KI to KII. In addition, step by step fatigue crack growth analysis has been conducted based on Paris law and Maximum Tangential Stress (MTS) criterion. As a result, the estimation of cracks path and cracks growth rate were obtained.