Cracks - Rail defects

Cracks - Rail defects

Figure 1: Magnetic particle inspection of the rail cross section at the start of the VLS section (image courtesy of Serco Rail Technical Services).

Defect name: Cracks
Record No.: 2668
Type of defect (Internal/Surface): Internal
Defect classification: Rail defects
Steel name: Steel
Steel composition in weight %: No data.
Note: The report of the metallurgical analysis of the rail fragments stated that some of the crack surfaces showed signs of corrosion, indicating that they had been exposed to the air. The report stated that this was likely to have occurred over a period of several months, indicating that the VLS crack had broken through the surface of the rail several months before the derailment. The analysis found that the RCF and VLS cracks were independent (Figure 1) and found no evidence of the VLS crack growing up into the area of RCF cracking near the rail head, but the crack had broken through the upper fillet radius in several places. The crack surfaces were smooth, showing that the pieces of rail each side of the crack had rubbed against each other, smoothing off the crack surface. This relative movement could only occur if the rail was loaded in bending after the crack had formed, showing that the crack had been in the rail for some time. On the basis of the corrosion that had occurred to some of the fracture faces, it is possible that the crack had broken through the surface before the inspections by the asset engineer, section manager (track) and ultrasonic team in July 2014.
Reference: Not shown in this demonstration version.