Detectability of Rail Defects by Magnetic Flux Leakage Method

Abstract

The ability of the Magnetic Flux Leakage (MFL) method to detect flaws in railway rails in two different ways has been studied. First, a three-dimensional computer simulation of the leakage of magnetic flux around a transverse crack in the rail head was carried out to determine the relationship between the main characteristics (size and depth) of the defect and the magnetic sensor signal. Second, signals were analyzed from more than 600 actually confirmed defects of the rail track, enabling statistically determined conclusions on the detectability of various types of flaws by magnetic and ultrasonic methods. It has been established that the MFL method detects rail head defects with the critical size at a depth of up to 20 mm under the upper rail edge. In general, the revealed defects constitute more than 90% of hazardous damage to rail head; this confirms the high efficiency of the MFL method in comparison with acoustic methods, which are also traditionally used in rail non-destructive testing.