Paul Hyde

Investigating fluid penetration of rolling contact fatigue cracks in rails using a newly developed full-scale test facility

Abstract Fluid penetration of surface breaking rolling contact fatigue cracks in rails is believed to be a key factor in their growth to dangerous lengths. Fluid entry has been proved for surface breaking cracks in laboratory twin disc contact simulations, but the authors are not aware of direct evidence for fluid penetration of cracks in full-scale rail-wheel contacts. There is, however, a widely held view that the behaviour observed in the laboratory will translate to full-scale cases. To investigate fluid penetration of cracks in full-scale rail-wheel contacts, cracked rails with a range of rolling contact fatigue severity were removed from mainline railway track and re-installed at a newly developed test facility. Investigation was undertaken using two different water-based marker fluids, and the rails subjected to over 1000 wheel passes with a locomotive. The rails were subsequently removed and selected crack faces broken open for observation by placing the rail in four-point bending. Ultra-violet and visible light were used to assess the degree to which the marker fluids had entered the surface breaking cracks. Good evidence of fluid penetration was found for one of the marker fluids, but the second fluid was not observed inside the cracks. The possible reasons behind this difference in behaviour are discussed.

Growth of multiple rolling contact fatigue cracks driven by rail bending modelled using a boundary element technique

Abstract Examination of rails on which large rolling contact fatigue cracks have developed, either at the gauge corner or on the rail head, typically reveals that the cracks have not developed in isolation but occur at intervals along a length of track. Individual cracks are typically separated from one another by a few millimetres, although the reasons for this spacing between the cracks are not yet understood. This paper presents an investigation into the interaction between adjacent long cracks (tens of millimetres) that are at the beginning of their bending-stress-driven propagation phase. Results are presented as plots of stress intensity factor around crack fronts for single- and multiple-crack situations, for which crack growth rates are predicted. The work focuses particularly on the degree to which single-crack models may be misleading when dealing with a rail containing multiple cracks. The work has application in improving the modelling of crack growth in rails, leading to improved asset management and risk assessment.

Railway Applications for Monitoring and Tracking Systems

Recent developments in different types of technologies enabled the development of new performant systems that can successfully be employed for various applications and subsequent functions related to railway operations, including safety and security aspects. Functions such as real-time monitoring, tracking and tracing of railway vehicles can improve the overall rail system reliability and provide better harmonised traffic for freight and passenger trains. These would also contribute to the improvement of interoperability, by enabling the use of the captured data in real time. Furthermore, the potential benefits of GNSS applications in the rail sector are examined alongside past attempts and recent new rail research in relation to the implementation of a GNSS system for security purposes.