Evolution of ultrasonic inspection techniques on railway axles

摘要

Considering solid and hollow railway axles, reliable non-destructive inspection techniques and procedures are required in order to guarantee the structural integrity during service. Axles are periodically inspected by the ultrasonic method (UT) during maintenance interruptions in first level workshops without need to be disassembled, while the magnetic particles test is carried out in second level workshops after wheelset disassembly. UT inspections of solid axles can be performed by a rotating probe applied to the ends of solid axles, whilst hollow axles can be tested with boreprobes roto-traslating along the longitudinal bore. In terms of inspection reliability, great developments have been introduced over the last years, especially focusing the aim to improve the capability of instruments to prevent human errors (a very sensible topic always present in EU technical discussions) thanks to automatic instrumentations and guided procedures. From this point of view, the present paper aims to present and discuss such developments, considering the evolution of the rotating probe and boreprobe inspection instrumentations: starting from their origin in the analogic era through the introduction of digital applications, the experimental and numerical characterization of their capabilities and performance, the present status and, finally, near future developments and improvements.