Real time measurement of dynamic wheel-rail contacts using ultrasonic reflectometry

The contact condition between the wheel and the rail is paramount to the lifespan, safety, and smooth operation of any rail network. The wheel/rail contact condition has been estimated, calculated, and simulated successfully for years, but accurate dynamic measurement has still not been achieved. Methods using pressure-sensitive films and controlled air flow have been employed, but both are limited. The work described in this paper has enabled, for the first time, the measurement of a dynamic wheel/rail contact patch using an array of 64 ultrasonic elements mounted in the rail. Previous work has successfully proved the effectiveness of ultrasonic reflectometry for static wheel/rail contact determination. The dynamic real-time measurement is based on previous work, but now each element of an array is individually pulsed in sequence to build up a linear measurement of the interface. These cross-sectional, line measurements are then processed and collated resulting in a two-dimensional contact patch. This approach is able to provide not only a contact patch, but more importantly, a detailed and relatively high-resolution pressure distribution plot of the contact. Predictions using finite element methods (FEM) have also been carried out for validation. Work is now underway to increase the speed of the measurement.