Fatigue problems and challenges in railway industry under real-world context

Fatigue failures in railway assets (e.g. infrastructures, rolling stocks, electrification and signalling systems) have been a root cause for regular operational downtimes, service cancellation, and occasionally train derailments. This presentation will address two key prevailing fatigue challenges in railway industry.

(i) Rail rolling contact fatigue (RCF) and resulting rail squats are defined by the growth of any cracks that have grown longitudinally through the rail subsurface and some of the cracks propagating to the bottom of rails transversely have branched from initial longitudinal cracks with a depression of rail surface. The rail defects are commonly referred to as ‘squats’ when they were initiated from damage caused by rolling contact fatigue, and as ‘studs’ when they were associated with white etching layer caused by the transform from pearlitic steel due to friction heat generated by wheel sliding or excessive traction. This fatigue problem has caused major unplanned rerailing programs, resulting in significant cost and operational downtime. We will address the recent progress in using data-driven technology to diagnose the complex parameters contributing to the wide spread of the RCFs and rail squats globally.

(ii) Railway concrete sleepers are safety-critical components that inevitably face complex loading conditions and hostile environments in real life. Their constituent materials are cementitious composites (i.e. concrete predominantly) and high-strength steels. The structural capacity is born through the composite bonding between concrete and steels through surface frictions. Prestressing concept has been applied to enhance serviceability and durability of the components. In addition, complex tensor redistributions can be identified due to the non-uniform topology of the components. This presentation will showcase the challenges and progress in fatigue life estimation of railway concrete sleepers. True fatigue characteristics of the components cannot simply be assessed by European standard EN 13230. On this basis, this presentation will discuss fatigue life assessment approaches and the progress to evaluate fatigue life and remaining life of the components. We will then highlight new insights into the use of stress life approach (i.e. S-N curves) for fatigue life estimation of real-scale railway sleepers in real-world context. In addition, we will address the recent progress in using artificial intelligence to enable real-time assessment and monitoring in practice.