[6A5] Verification of phased array ultrasonic and eddy current measurements of near-surface cracks in railheads with rail slicing
Rayendra Anandika and Jan Lundberg Division of Operation and Maintenance, Department of Civil, Environmental, and Natural Resources Engineering, Lulea University of Technology, Sweden
High accuracy of measurement result of near-surface cracks in railheads with non-destructive testing (NDT) is very important since the measured cracks are located inside the railheads, thus cannot directly be seen by human eye. The measurement accuracy can be verified by destructing the railheads and measuring the cracks size. In this study, measurement results of near-surface cracks in railheads with two non-destructive methods, phased array ultrasonic testing (PAUT) and eddy current testing (ECT), were verified by rail slicing. A number of typical surface-breaking cracks were selected for this study. After being inspected by the testing, the cracked regions were sliced into 0.65-mm thick pieces by 0.35-mm thick electrical discharge wire (EDW). From the pieces, the cracks were measured to verify the testing results. The crack networks were also reconstructed based on the crack profile from the pieces. By comparing the crack images and the testing results, accuracy of the testing could be delivered. PAUT could deliver 8-18% error accuracy of 3.5-mm crack depth. PAUT could also observe the crack profiles with high accuracy. While, ECT showed an unclear correlation between crack depth and area with electrical signals from measurements. Besides showing a way to verify NDT results, this study evaluates the commonly-used non-destructive testing methods to be considered by inspection engineers when they inspect defects with these methods especially for defects in railheads.
