Laboratory Tests of Inspection Feasibility of Internal Material Defects in Rails at Speeds up to 120 km/h

Non-destructive in situ assessment of the emerging defects in the rail material structure is a critical issue due to the demanding safety requirements. The speed and accuracy of inspection are crucial for maintaining the traffic uninterrupted and safe. In this paper, a patented ultrasonic measuring head is demonstrated to be able to perform defect identification at moving speeds up to 120 km/h. In the laboratory experiments, the “defects” were prefabricated in the rotating test wheel in the form of orifices, as follows: Ø6 mm radial orifice and flat bottom axial orifices of diameters Ø6 mm, Ø8 mm, Ø10 mm, and Ø12 mm. The rotational speed of the test wheel, 800 rpm, corresponded with the relative movement between the sensor and the rail at ca. 130 km/h. Statistical analysis confirmed the accuracy of material defect identification with a random error of ±2.0 %FSH (full screen height) for static amplitude. Finally, the uncertainty of measurement for the amplitude drop was ±1.5 dB, which can be considered a very high accuracy for the ultrasonic material defect inspection.