Gilardoni RDG-4000 TR: residual stress in railway wheels

Gilardoni is an Italian maker of X-ray and ultrasonic equipment for non-destructive testing. The RDG-4000 TR assesses the internal stress state of monolithic railway wheels. An instrument like this is only as good as its software: acquiring the signal, showing it clearly and producing a record the inspector can trust.

• EMAT probes that need no coupling agent: two identical transducers send shear waves polarised at right angles, one parallel and one perpendicular to the rolling surface.
• Acoustic birefringence: the flight time of each wave to the first echo from the bottom wall gives the speed difference between the two planes.
• A mechanical probe, positioned magnetically, that moves along the radius of the wheel and measures at different points.
• Software, controlled from a PC, that moves the probe, acquires the data and calculates the stress from the speed difference and the material's acoustoelastic coefficient.

We wrote the instrument's software and co-designed the algorithm that measures the residual stress. The detector gives the average circumferential stress across the thickness of the wheel rim, at different points along the radius.

The residual stress of a railway wheel is measured with a contact-free probe and calculated by the algorithm we co-designed, in software we wrote.