The influence of track stiffness on rail crack occurrence
To predict crack growth in railway rails, measurements of track characteristics have been post-processed. Potential correlation between track parameters (e.g. longitudinal level, deflection and track stiffness), and defect positions as detected by ultrasonic testing of rails has been investigated. Although no straightforward correlation was found there were indications of stiffness variations in connection to detected cracks.
A deeper investigation was realized regarding measured track stiffness and deflections around detected defects. Deviations of these parameters at detected defect locations were found. However not all defects could be linked to significant deviations (and vice versa).
A further study was carried out on the influence of hanging sleepers. These will cause track stiffness variations, which will increase the bending moment in the rail and may promote growth of rail cracks. Results of the studies carried out specify a distance over which the bending moment is increased. This affected length surrounding hanging sleepers should be investigated during maintenance operations to detect potential rail cracks and thereby avoid subsequent rail breaks.
Finally, the report outlines a procedure for how measured track stiffness can be included in an analysis of resulting rail bending moments. Thereby track sections with an increased risk of rail crack growth may be detected and mitigated.